Wikipedia talk:WikiProject Mathematics/Archive/2019

Jan 2019

Repairing recursions at Harmonic number

I posted details of my problem at the TP there, but additionally take the freedom to submit this here to a broader public:

Please, could someone more dignified than I am take care about adding either missing or more reasonable base cases in the recurrence relations in this article? Both my efforts to either generally have as the base case some $H_{0}=0,$ not particularly coined as one of the harmonic numbers, or to specifically introduce it at places in specific need, were promptly reverted, ignoring that $H_{0}=0$ is already in use at the end of this section. Thanks for taking in consideration. Purgy (talk) 10:31, 10 January 2019 (UTC)

Errors in Alhazen's problem article

Hello

Sorry, I don't speak english, so be kind when you read me.

There is an error in Alhazen's problem article and also in Ibn al-Haytham article: we can read "This (i.e Alhazen's problem) eventually led Alhazen to derive a formula for the sum of fourth powers". There is a lot of treatises written by Ibn al-Haytham. In the The book of Optics, we can find the Alhazen' problem. Its solution has nothing to do with sum of the fourth powers (See A.I. Sabra, Ibn al-Haytham' lemas for solving Alhazen's Problem). The sum of four power is in an another treatise ( fi misahat al-mujassam al-mukafi On the Measurement of the paraboloid). You can read the source (Victor J. Katz (1995), "Ideas of Calculus in Islam and India). The banned contributor Jagged 85 made this mistake in june 2007[1].

He added also a second error "Mathematicians were not able to find an algebraic solution to the problem until the end of the 20th century" It is non sens because before 20th, people knows already that intersection of two conics led to a quartic equation. (see Paul Bode (1892),«Die Alhazensche Spiegel-Aufgabe in ihrer historischen Entwicklung nebst einer analytischen Lösung des verallgemeinerten Problems to see all the solutions (algebraic, trigonometric, geometric...). p. 86 you can see an equation of the Huygens' hyperbole.

Can you fix these two errors ? Thank's. HB (talk) 21:10, 12 January 2019 (UTC)

Yet more links to DAB pages

I have collected yet another, but this time very small, batch of articles which include mathematics-related links to DAB pages. Expert attention in solving these puzzles would be welcome. If you solve any of them, remove the {{dn}} tag from the article and post {{done}} here.

• Uniformizable space  Done
• Termial  Done
• Hybrid number  Done

Thanks in advance, Narky Blert (talk) 04:05, 20 January 2019 (UTC)

Exponentiation

Totally unproductive sniping -- discussion should be at Talk:Exponentiation. Other editors are invited to participate there. --JBL (talk) 15:35, 20 January 2019 (UTC)
The following discussion has been closed. Please do not modify it.
User:Jasper Deng seems to think that explicitly mentioning the exceptions to a supposed "mathematical identity" is somehow inferior than just saying the equation holds "in general". I made some changes which he objected to for the use of elementary logical quantification, which I have now removed. He continues to revert for no apparent reason. He's also made some wildly wrong statements like "The convention in mathematics is to use intensional definitions" and has confused the logical negation of an equality with a quantified inequality. Stemdude (talk) 02:05, 20 January 2019 (UTC) @Stemdude: insists on an arcane interpretation of the ≠ symbol that is contrary to literally every textbook I've seen. I'm already at WP:3RR. I'd like someone with more experience in formal logic to chime in, however, I believe that his concerns are unfounded. Please leave any comments you may have on that article's talk page.--Jasper Deng (talk) 02:41, 20 January 2019 (UTC) Both of you get a trout for a ridiculously childish edit war. The discussion on the article talk page has only been open for a couple of hours, and the first comment by a third party (me) was just added to the conversation. Give the undo button a rest and wait for other editors to weigh in. Perhaps while you're waiting you could try to find some reliable sources on which to base the relevant parts of the article. --JBL (talk) 03:02, 20 January 2019 (UTC) All I'm trying to do is prevent Wikipedia containing obviously incorrect statements i.e. claiming that a mathematical identity can only hold "in general" rather than being true by definition. I'm disappointed that such an obvious fact seems to elude so many Wikipedians. But I'm not going to be bullied off this project because an admin wants to win a foolish edit war. Stemdude (talk) 09:13, 20 January 2019 (UTC) In case it wasn't clear, the crux of the issue is that you interpret $f(x)\neq g(x)$ as $\forall xf(x)\neq g(x)$. This is not at all the most common interpretation of the $\neq$ sign and is absurd when comparing the two functions as objects in their own right, since $f(x)\neq g(x)$ is perfectly valid as an inequality of sets. @Stemdude: I'd trust User:Joel B. Lewis who is a professional mathematician. Definitely not a "deranged undergraduate". By the way, I spoke with some graduate student friends of mine and they also do not support your view. Most importantly, if independent reliable sources have not corroborated your interpretation of that sign, then we cannot accept it. See WP:EXPERT.--Jasper Deng (talk) 09:45, 20 January 2019 (UTC) This has NOTHING to do with my edit to Exponentiation whatsoever. You seem to want to argue about irrelevant issues rather than talking about improving the article in question and have gone off on a wild tangent. And I never called JBL a "deranged undergraduate"; I was referring to you but I decided to revert that comment in the interests of keeping things calm. I'm amazed that an admin is behaving so childishly. Stemdude (talk) 09:56, 20 January 2019 (UTC) And if we need any more proof that Jasper Deng has no idea what he is talking about, check out this [this|https://en.wikipedia.org/w/index.php?title=Talk:Euler%27s_formula&diff=877389352&oldid=877387501] comment in which he confuses (complex) exponentiation with logarithm. ix isn't multivalued! Stemdude (talk) 10:09, 20 January 2019 (UTC) @Stemdude: okay, then it's time to ask for your qualifications because $i^{x}$ by its most conventional definition very much is, and I in particular am not the first one to state that there. What I said above most definitely does have everything to do with your edit, because your edit concerns a statement of that form. Don't be so self-righteous, especially when you have shown no evidence of consulting external resources to support your claim. You're wasting your breath without citing reliable sources in any case.--Jasper Deng (talk) 10:18, 20 January 2019 (UTC)

Polygons

Hi

1) It is César R. K. Stradiotto again.
2) To avoid any problems, now I just consulted the video tutorial to post complains about wikipedia pages. thanks.
3) The last post I did was about this page [List of two-dimensional geometric shapes][2], where the section

Polygons with specific numbers of sides -Quadrilaterals --Trapezus

were pointing to a Wikipedia "Pornhub"-about page.

4) I just saw the link were changed, but still not corrected: Now the link on Trapezus is pointing to a geographic place: Trabzon [3] (Just look for Wikipedia Trabzon, on Google).

That´s it.

Cordially

César R. K. Stradiotto — Preceding unsigned comment added by 189.85.185.93 (talk) 15:27, 21 January 2019 (UTC)

As far as I understand, there is no such polygon (and there is such geographic place). Thus I delete it from the list of two-dimensional geometric shapes. If anyone saw such polygon, correct me. Boris Tsirelson (talk) 15:50, 21 January 2019 (UTC)

"Trapezus" could be a misspelling of "trapezoid", "trapezius", "Trabzon", or "Trapezus (Arcadia)". JRSpriggs (talk) 09:20, 22 January 2019 (UTC)

Invalid variants of mathematical theorems

Look at the history of Lagrange's four-square theorem. I added a section revealing an invalid variant of the theorem. This means a variant of what the theorem says that would make it false. Three times, however, someone reverted me. Interestingly enough, there's an article, Beal's conjecture, which has a similar section that no one objected to. We need some kind of discussion on what the best rule for how articles on mathematical theorems should deal with sections like this. Georgia guy (talk) 15:50, 22 January 2019 (UTC)

I think you both are correct: the material can be included but not in the form you gave it. It would probabably be helpful if you framed this in the context of what is the algorithmic complexity of finding the four squares; then you could mention that greedy doesn't work, but something else (properly sourced) does. Another problem with your edit is that you did not provide a source for greedy not working, so it ends up looking like original research. You could try {{cite OEIS|A006892}} (Sloane, N. J. A. (ed.). "Sequence A006892". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation.). That would also give you an alternative method of framing this in terms of the growth pattern of this sequence. I don't see a need for a general rule to handle this sort of case. —David Eppstein (talk) 16:08, 22 January 2019 (UTC)

Please show me a better form. Georgia guy (talk) 16:16, 22 January 2019 (UTC)

It involves doing some literature research. I don't have time for that this morning. —David Eppstein (talk) 16:32, 22 January 2019 (UTC)

As a general question, we certainly don't want to open the door to adding random text of the form "proposition P is true, but this stronger proposition Q that I just made up is false". There needs to be a reason to mention Q. The best sort of reason would be that multiple sources consider Q a natural thing to mention, but if we all agree that Q is an easy misunderstanding of the statement of P I might be willing to look the other way.

In this case, though, I just don't see it at all. There's nothing in the statement of four-squares that invites considering the greedy algorithm. And if you do wonder about it, it's trivial to convince yourself that the greedy algorithm gives unboundedly long sequences of squares, since you if you have a number that gives N squares, then just add a really big square number to that, and now you've got N+1. --Trovatore (talk) 17:14, 22 January 2019 (UTC)

I disagree. I think it is very natural to go from a statement that a number can be represented using few members of some set, to the question of how few members the greedy algorithm uses. I have a publication on exactly those issues (not suitable as a reference here because it doesn't mention sums of squares). There are many sequences in OEIS based on this principle of greedy representations as sums from some set, and published literature going back to Pillai in 1930. And as you point out sequences of natural density 0 (such as squares) never have a finite bound on the lengths of their greedy sums. The big problem with the proposed addition was not its interestingness or naturalness or triviality, but (as you point out) that it was totally unsourced and therefore appeared to be original research. You undercut that issue by pointing out how simple the calculation is, though. —David Eppstein (talk) 20:48, 22 January 2019 (UTC)

Well, it's not an unnatural direction to go, I suppose. But it's not directly suggested by the statement. Contrast with the section GG is referring to in Beal conjecture, where the "variants" section seems to be a (slightly clumsy) attempt to explain why some clauses in the theorem's hypothesis are necessary. That directly implicates Grice's maxim of relevance; this doesn't. --Trovatore (talk) 21:26, 22 January 2019 (UTC)

Maybe it's my background, but to me the question "how do we find it" is directly suggested by any existence theorem, and "does the most obvious method of trying to find it work" is not far behind. —David Eppstein (talk) 00:47, 23 January 2019 (UTC)

Category: Mathematical object

Jamgoodman adds systematically Category:Mathematical objects to many mathematical articles. As almost all mathematical articles could belong to this category, I have open a deletion discussion at Wikipedia:Categories for discussion/Log/2019 January 23#Category:Mathematical objects. D.Lazard (talk) 15:36, 23 January 2019 (UTC)

Please also see the discussion on my talk page. The category is a perfectly good category, but generally articles should belong to its subcategories rather than directly to it. It is a useful distinction e.g. from the category "Areas of mathematics" and should not be deleted. --JBL (talk) 16:35, 23 January 2019 (UTC)

Documenta Mathematica

Is this the same thing as Journal der Deutschen Mathematiker-Vereinigung? Or Jahresbericht der Deutschen Mathematiker-Vereinigung?

Mostly asking to see if redirecting to German Mathematical Society would be appropriate. Headbomb {t · c · p · b} 20:39, 24 January 2019 (UTC)

It's also published by the DMV but it has a different ISSN than JDMV (ISSN 1431-0635 for Doc. Math., ISSN 0012-0456 for JDMV) and is indexed separately from JDMV in MathSciNet, with both of them publishing at the same time. So I'm pretty sure it's not the same thing. Nevertheless, if we don't have an article on Doc. Math., and it's mentioned in the DMV article, a redirect might make sense. I don't think there is a "Journal of the..."; I've only seen it as Jber. —David Eppstein (talk) 21:42, 24 January 2019 (UTC)

Created the redirect. According to the [4], 'Journal der Deutschen Mathematiker-Vereinigung' is a subtitle. Headbomb {t · c · p · b} 03:02, 25 January 2019 (UTC)

List of constants

In case anyone's looking for something to do, I just stumbled upon List of mathematical constants, which is in fairly rough shape. The table is somewhat broken, and perhaps has some columns that could simply be removed. It's a bigger project than I have time for right now, so I thought I'd mention here. –Deacon Vorbis (carbon • videos) 15:07, 30 January 2019 (UTC)

Wow. --JBL (talk) 15:15, 30 January 2019 (UTC)

Similar issues at List of mathematical symbols and List of mathematical symbols by subject. Not only some columns could be removed, but also many entries should be removed: those that are far to be standard, and must be defined before being used (such as $\bullet ,$ ↯, ⨳, and many others).

Also Mathematical symbol redirects to List of mathematical symbols, while it deserves to have a regular article. D.Lazard (talk) 16:14, 30 January 2019 (UTC)

Feb 2019

Numerical modelling

Is numerical modelling the same as mathematical modelling? --Redrose64 🌹 (talk) 19:50, 31 January 2019 (UTC)

What is the context? In general, no. Mathematical models can be at the level of algebraic or analytic equations or even logical models, with no necessity for reduction to numbers. --{{u|Mark viking}} {Talk} 20:13, 31 January 2019 (UTC)

It's at Emily Shuckburgh which uses the term "numerical modeller" twice. I want to link it, because a previous editor removed the significant word "numerical", which could imply that Shuckburgh makes small-scale ships, trains or aircraft. --Redrose64 🌹 (talk) 20:28, 31 January 2019 (UTC)

I would say that numerical modeling is a sub-area of mathematical modeling. --JBL (talk) 22:06, 31 January 2019 (UTC)

Ah, I see. As a climate scientist, she uses mathematical models of the climate by simulating or solving those models on a computer (computational modeling or computer experimentation). The results of a simulation are numbers--e.g., temperature profiles over a region and across time. From my physics perspective, I would probably call her a "theoretician, computational modeller, and observational scientist." --{{u|Mark viking}} {Talk} 22:15, 31 January 2019 (UTC)

The source says that she does numerical modelling but it seems to be in the specific context of a climate model, possibly using numerical techniques to solve a box model. Certes (talk) 22:39, 31 January 2019 (UTC)

Thanks guys. Having found Numerical weather prediction, Category:Scientific modeling and its many subcats, I'm even more confused, so I've stuck with numerical modeller. Edit if you see fit, I just don't want the word "numerical" to be removed again, or it to be left without a link. --Redrose64 🌹 (talk) 14:09, 2 February 2019 (UTC)

Correspondence vs. binary relation

Currently, we have two articles: correspondence (mathematics) and binary relations. Set-theoretically speaking, there is no essential difference. Wikipedia insists a correspondence is an ordered triple (A, B, f) where f is a subset of $A\times B$, while a relation is just f or rather what f determines. While I can (a sort of) understand the difference, I don't think the distinction is enough for separate articles; basically the difference is like a difference between a function and the graph of a function (in fact, "binary relation" seems to be a bit confused about whether it wants to discuss a correspondence or a relation; see Binary relation#Is a relation more than its graph?). So, I'm inclined to just merge the two into one, except algebraic geometry bit in "correspondence (mathematics)" feels quite out of a place at "binary relation" and best to split off to correspondence (algebraic geometry). Thoughts? -- Taku (talk) 21:02, 30 January 2019 (UTC)

I'm not a huge fan of articles grouping together vaguely related things that share the same name. Maybe the bullet points could be merged into a glossary somewhere, with the specific content in the various fields merged into the articles on the individual fields? Or something?

I suppose having them all in one place could be useful to someone trying to read mathematical content who comes across the word "correspondence" and isn't sure what it means in context. I guess I don't object to that too much, as long as it doesn't try to abstract some commonality from them in an original-researchy sort of way. --Trovatore (talk) 05:45, 31 January 2019 (UTC)

Inspired by this comment (as well as the above thread), I have started Glossary of mathematics; I think it makes sense since some mathematical terms like correspondence are used across areas of mathematics. This at least gives us a merger target...

I will be splitting off the algebraic-geometry bit to correspondence (algebraic geometry), as I doubt there is an objection. -- Taku (talk) 00:45, 1 February 2019 (UTC)

In fact, Category of relations uses the term “binary relation” to mean a correspondence (so, it appears, Wikipedia actually doesn’t want to make this distinction). —- Taku (talk) 14:54, 3 February 2019 (UTC)

Amnon Pazy

Would someone from this WikiProject mind taking a look at this article and assessing it? It was created by someone hired by Pazy's family and it was not submitted for review via WP:AFC. I've done a bit of minor clean up, but there's still some issues that need sorting, particularly with respect to the sourcing (it seems that most of them are to documents, etc. uploaded to Commons). I'm assuming the subject meets WP:ACADEMIC and is notable for an article to be written, but some serious trimming/rewriting might be needed to bring the article more inline with current policies and guidelines. -- Marchjuly (talk) 13:06, 4 February 2019 (UTC)

Map (mathematics)

There is a dispute as to whether map (mathematics) should be a disambiguation page or not; i.e., should redirect to map (disambiguation). Note the content of the page has already merged with function (mathematics). To resolve the conflict, inputs from more editors are needed; the main objection is from an editor who claims “a function is not a morphism in the category of sets.” —- Taku (talk) 18:20, 1 February 2019 (UTC)

Wait, if a function is not a morphism in the category of sets, then what is? I hope this isn't some quibble about whether a function is just a set of ordered pairs versus also knowing its domain and codomain. --Trovatore (talk) 20:24, 1 February 2019 (UTC)

You nailed it. People (not me) believe two separate articles are needed (in part) because of this quibble... (the same problem for correspondence vs binary relation) —- Taku (talk) 20:34, 1 February 2019 (UTC)

Whatever happens with this proposed merge, do not make Map (mathematics) a redirect to Map (disambiguation), without first making sure that no articles link to it, since links to disambiguation pages are (generally) considered errors. Please see User talk:BD2412#Map (mathematics). Paul August ☎ 18:31, 1 February 2019 (UTC)

I think it's important that, in general-audience mathematics articles, the term "map" be linked to a useful article on functions or mappings that clearly explains the intended meaning of the term (the purpose of having an actual article as the target for Map (mathematics)). This is much more important than helping editors find the right link to add when they see the term "map" in a mathematics article but don't understand which kind of map is intended (the purpose of having a disambiguation page as target). Whether there is a separate article on maps and mappings or whether Map (mathematics) redirects to Function (mathematics) is less critical. I would lean to having a separate article, though, just because a redirect is going to entail a messy hatnote on the function article for all those other meanings of mappings. —David Eppstein (talk) 18:57, 1 February 2019 (UTC)

To add some context, I guess I just don’t see a point of an article explaining *terminology* as opposed to *concept* in Wikipedia. Wikipedia is a place to explain concepts, at least when math is concerned; terminology note is important, sure, but is of a secondary importance. For me, thus, this page is a disambig page in an effective sense since the concepts of a map are already discussed at other places like function (mathematics), morphism (category theory), homomorphism, etc. It doesn’t help that those “terminology” articles tend to be of low quality and low information (#Correspondence vs. binary relation above is another instance). Not to mention, our readers often complain about those article... —- Taku (talk) 19:33, 1 February 2019 (UTC)

See also: Talk:Map_(mathematics)#Suggestion to dedicate this article to the use of Map as a concept in mathematics when it is not a synonym of function. -- Taku (talk) 23:54, 2 February 2019 (UTC)

I’m probably sounding repetitive but here, a very similar type of an article: embedding. While there is a certainly a general concept of embedding, I don’t think it’s useful to use a “single article” to cover embedding in topology as well as those in other fields. Is there any benefit of doing (instead of having separate articles) that I’m not seeing? —- Taku (talk) 20:59, 4 February 2019 (UTC)

Are unedited drafts and disambiguations somehow related? Purgy (talk) 07:55, 5 February 2019 (UTC)

I was just saying it seems better to have "embedding (topology and geometry)" as a separate article instead of a single article. In fact, maybe I will split-off the topology-geometry stuff; the topic should be important enough for an standalone article. -- Taku (talk) 08:54, 5 February 2019 (UTC)

In the main embedding article, would you have a short summary for "Topology and geometry" with a "See also" pointing to the new article? The summary would be almost the same as the article in that case. Alternatively, if you made the main article a disambiguation pointing to several smaller articles then the other pages like embedding (algebra) or embedding (metric spaces) would be quite short! How would you structure the relationship between the "embedding" page and the "embedding (topology and geometry)" page?

On a barely-related point, why should it be written "Topology and geometry" rather than an alphabetized "Geometry and topology"? — MarkH21 (talk) 09:29, 5 February 2019 (UTC)

I didn't mean to propose that embedding be a disambig page. Also, "The summary would be almost the same as the article in that case" I don't think that need to be the case; there are so much embedding stuff in geometry and topology. (I didn't have any particular reason to write "Topology and geometry" instead of "geometry and topology". That was not a conscious choice and didn't mean to imply topology comes before geometry, for instance). -- Taku (talk) 10:28, 5 February 2019 (UTC)

I think the point was that there's very little content there now. And so the natural thing to do would be to add content in the current location, until such time as there is enough that the split can be done with a short summary section that doesn't duplicate the entire content of the new article.

For the question of what is the benefit of having several things in the same article, the answer is that it's easier to navigate: for example, the (not closely analogous, just illustrative) situation described here is one in which it can be hard to find the information one is looking for. --JBL (talk) 13:44, 5 February 2019 (UTC)

Ah, got it. My impression is that there was just going to be a split of the section as it is now into a new article. — MarkH21 (talk) 18:56, 5 February 2019 (UTC)

Possibly Taku was suggesting that; I was hoping that Taku would take my comment as a suggestion for a way to proceed with low likelihood of causing consternation. --JBL (talk) 19:56, 5 February 2019 (UTC)

First to JBL, I actually don't buy the navigation argument. Hypothetically, imagine there was an embedding (geometry and topology) and I proposed to merge it with embedding, to make it easier to navigate. I doubt there will be much support. So, the current setup is probably a historical artifact, rather than something out of the logical reason. So, for me, "geometry and topology" can be split off as is. Of course, you can do splitting-off after more content is added. But the topology section already has stuff beyond the typical summary (e.g., "proper embedding"). So, for me, it's time to split the section; replace it with a shorter summary; the rest of the sections will be untouched. Sounds like a plan? But yes I understand changes need to be implemented incrementally; so I will not do anything in an immediate future. -- Taku (talk) 20:21, 5 February 2019 (UTC)

You asked for a benefit; I have identified one. I have certainly experienced frustrations navigating Wikipedia articles on mathematics because of over-fragmentation before, so I'm not sure what there is to not buy. Moreover, I think that your hypothetical is just restating your views rather than adding anything new: I would certainly support the proposed merge you've described, given that the combined article is of such reasonable size. In fact, I don't really see that you've identified any benefit to splitting: two related-but-not-exactly-the-same ideas are covered in the same article, and that's bad because ... why, exactly? Given the nice size of the current article, anyone looking for an embedding is going to be able to find it easily. If you eventually manage to add so much material to the article that the geometry section overwhelms the rest (and so, for example, it becomes hard to find embeddings in category theory buried under sub-sub-sub-sections on geometry), then there would be a reason to split. But at present the article is nowhere near that, and the two half-articles would be very short. (FWIW, the chance of my intervening in any way more substantial than this conversation is 0.) --JBL (talk) 22:26, 5 February 2019 (UTC)

It didn't occur to me the fragmentation causes a navigation difficulty. I thought having focused articles is a preferred style here; in fact, easier to navigate, no distraction from unrelated topics. But, ok, I understand you see this differently. "Nice size" depends on one's position. For example, I imagine anonymous users will find discouraged to expand the geometry and topology section because of the size. Splitting-off the section gives a room for more growth. In any case, this comes down to personal preferences; I like big fancy rooms. I will however not be demanding that (got no right, obviously). Thank you for answering the my original question: yes, there is indeed some advantage (combining stuff). -- Taku (talk) 23:09, 5 February 2019 (UTC)

Map (mathematics) 2

User:Trovatore, yes, functions are not defined as the arrows of **Set**. Functions are defined, and then **Set** is defined as an emergent concept. This shouldn't be news to anyone. Now, the other thing that happens is that there are two types of references: (1) Those that (modulo wording) define functions as correspondences (<- beware User:TakuyaMurata has been vandalizing this page too.) with the 'unique image property' and (2) Those authors who define (modulo wording, although in this case they tend to be more explicit) functions as relations with the 'unique image property'. There is a third in which they explicitly state (2) and then hand-waving-ly add the codomain to the function. Those are essentially in (1). As a result, reliable sources have two positions, one in which there is a function for each arrow of **Set** and one for which there are many. It looks like it has to be reminded, specially to User:TakuyaMurata, that Wikipedia works by presenting what is contained in reliable sources, not what random editors imagine the concepts should be in Mathematics. Cactus0192837465 (talk) 13:23, 5 February 2019 (UTC)

+1 for relying solely on WP:RS. Paul August ☎ 13:34, 5 February 2019 (UTC)

@Cactus0192837465: I don't think the term "vandalism" applies here, I think you should strike it. Paul August ☎ 13:59, 5 February 2019 (UTC)

Vandalism? The definition of a relation in terms of a graph in the old version was not in a reference and so I simply replaced one in the reliable sources. How is it not an improvement? —- Taku (talk) 13:53, 5 February 2019 (UTC)

Again I have acknowledged a difference; we have merely chosen the most standard one and you’re advocating for a non-standard one, which will result in a function not being a morphism in the category of sets. —- Taku (talk) 13:56, 5 February 2019 (UTC)

User:TakuyaMurata, the very first reference in the article correspondences, which you have turned from an independent article into a redirect link, contains explicitly and precisely a definition for relation, and a definition for correspondence. I added links to screenshots in the talk page of that article for those who don't have access to the references and are literally pulling definitions out of what they can find online, in forums, or their imagination. Yes, you are pushing an agenda of smudging the boundaries of these concepts well beyond of what they are already done in the literature. Cactus0192837465 (talk) 16:51, 5 February 2019 (UTC)

Another thing. I am not advocating for any other definition. Actually, when I teach it, I use the definition of function as a correspondence (triple of domain, codomain, and relation). The vandalism is that you are trying to turn the article of correspondences into a redirect to relations. they are two different concepts. Very important, when consulting the literature, one must take into account that sometimes the word correspondence, just like mapping (as a verb), are sometimes used just as a common word, and not as a word loaded with concept. Cactus0192837465 (talk) 17:12, 5 February 2019 (UTC)

Again this is the difference between whether a function is a triple or a subset; what you call a map and a correspondence are also called a function and a relation by other authors (so a function is a triple). That’s just that. For example, Jacobson Basic Algebra defines a correspondence as a subset not as a triple (and Jacobson gives it as a proper definition). Sloopy? But I don’t have a strong reason to go again Jacobson and you need to know how reliable Jacobson is. Please also see category of relations where morphisms are correspondences in your usage but are called binary relations. So a binary relation is also a correspondence in your terminology. It shows even Wikipedia uses the terms “binary relation” and “correspondence” interchangeably: I know you want to make terminologic distinction; the fact is that your language is not universally adopted.

I do acknowledge the difference; in fact, binary relation has very explicit example showing why codomain matters. It only makes sense to have a redirect to a page where there is a discussion of this. —- Taku (talk) 17:24, 5 February 2019 (UTC)

This is similar to the situation that the terms "map" and "function" are frequently used interchangeably, you like it or not. We cannot claim your distinction is universally adopted one. That's ok if you are teaching, but saying that in Wikipedia is misleading (and in fact wrong as Wikipedia has to take a neutral stand). And, both in function (mathematics) and binary relation, we clearly indicate variations on the usage. -- Taku (talk) 21:02, 5 February 2019 (UTC)

To other editors, we (Cactus and I) need a tie-breaker for [5]. Please note we have Correspondence (algebraic geometry) and the rest in binary relation; my edit thus doesn’t mean any information loss. -- Taku (talk) 17:31, 5 February 2019 (UTC)

If I understand well the subject of the dispute is the following: for Cactus0192837465 a relation is a subset R of a direct product $A\times B$ of sets, while a correspondence is the triple $A,B,R.$ As, for Cactus0192837465, these are different concepts, two different articles are needed. My opinion is that the only situation where it is useful to distinguish between the two definitions is when using a proof assistant. So, there is only one concept and two slightly different formalizations of it. Cactus0192837465 provides a source that makes a distinction, but omits that most reliable sources do not care with such a distinction, and when they distinguish between the two definitions and/or between the two terms, it is not necessary done as presented by Cactus0192837465. So, presenting these two definition a different concepts with different named different articles, is not only confusing for the reader, this is also a biased presentation of the common mathematical usage.

So my opinion is that we must redirect Correspondence (mathematics) to Binary relation, as taku did. D.Lazard (talk) 23:24, 5 February 2019 (UTC)

Root 2 and Root two redirects

Root 2 and Root two are currently redirects to Square root of 2 and List of numbers respectively. They have been nominated for deletion at Wikipedia:Redirects for discussion/Log/2019 February 8#Root two where your comments are invited. Thryduulf (talk) 19:59, 8 February 2019 (UTC)

Is there a list of crap mathematics journals somewhere?

I'm currently expanding WP:CRAPWATCH (a project to detected predatory/unreliable sources) with various sources that document unreliable journals in various fields of research. Are there any such list mathematics for mathematics? Preferably externally sourced to reliable people, rather than personal opinion. Headbomb {t · c · p · b} 09:41, 5 February 2019 (UTC)

My preference for testing whether a math journal is crap is whether it is not listed in MathSciNet. But that isn't so good for finding a listing of all of the crap ones. —David Eppstein (talk) 19:13, 5 February 2019 (UTC)

Yeah, we need a list of crap stuff, not a list of good stuff. There's Beall's List in general, and medicine has Quackwatch's list for instance, just wondering if there is something similar for mathematics (even a blog post by a reliable person would be fine). I know about some weird math people like Florentin Smarandache and his Smarandache Notions Journal, but I really don't know enough about mathematics at this level to be able to be build a case-by-case list myself. If someone here wants to build it, and the math project agrees with the list, I could easily incoporate it in the crapwatch. Headbomb {t · c · p · b} 17:59, 6 February 2019 (UTC)

Why not build a whitelist first? "Not whitelisted journals" could be part of the report and then you can work either on blacklisting those or whitelisting those. --Izno (talk) 19:37, 6 February 2019 (UTC)

Mostly because a "not in MathSciNet" or whatever math whitelist you want to use would mean reporting a lot of non-mathematical journals as potential crap. And that's not really a workable solution. Headbomb {t · c · p · b} 20:33, 6 February 2019 (UTC)

I mean, there should be a general whitelist... --Izno (talk) 23:24, 6 February 2019 (UTC)

I think Google Scholar and Google Scholar Metrics take care of the problem. In math, if something is cited over and over, it is OK. Otherwise using these criteria of "where is it published" rather than "how cited it is", we would end up excluding people like Grigory Perelman and the greatest results of the past 120 years --Borel, Groethendieck, etc. Mathematics is much more robust than other sciences. Limit-theorem (talk) 01:55, 7 February 2019 (UTC)

True, but the idea isn't to have a YES/NO are publication always crap/always good, but rather YES/NO are there redflags about certain publications, e.g. pay-to-publish journals or journals edited by pseudo-mathematicians. For instance arXiv is a serious venue, but viXra is not. Doesn't mean you can't publish crap on arXiv, or good stuff on viXra, but the odds are if someone has cited viXra, they've cited crap. Headbomb {t · c · p · b} 04:33, 7 February 2019 (UTC)

Your statement about odds does not seem very well founded to me. It could almost be simultaneously true for vixra articles that being cited by a Wikipedia article implies that they are almost certainly non-crap, and that it also implies that they are almost certainly crap; see vacuous truth. However, currently there are at least some citations to vixra on Friedwardt Winterberg; I'm not sure whether they are crap. There is also at least one citation on Lebesgue's universal covering problem that is definitely not crap, and could go to vixra, but uses a different link instead. —David Eppstein (talk) 04:50, 7 February 2019 (UTC)

viXra is an unmoderated repository of preprints. That leads to things like this being very, very common on viXra. For something a bit less ridiculous, see [6], picked at completely random in the topology subgroup. Now I don't understand topology one bit, but I can't fathom that any person would consider this a solid source. Also the reason why only the Winterberg page has viXra links at the moment is because I removed most of the others a few months back. It is simply not a reliable source, generally speaking, although exceptions may certainly exist. Headbomb {t · c · p · b} 06:20, 7 February 2019 (UTC)

The moderation on arXiv consists only of checking whether the preprints are on-topic and (for some but not all classifications) whether they are not total crankery. So arXiv preprints should also not be considered to be reliable sources unless either the author is a known expert on the topic (WP:SPS) or they have been properly peer-reviewed and published elsewhere. In that sense, I don't see a qualitative difference from vixra in how we should treat them here. In particular, your "arXiv is a serious venue, but viXra is not" is either meaningless (seriousness is irrelevant for our standards on sourcing) or wrong (you are treating arXiv sources as being inherently reliable and you should not be doing that). —David Eppstein (talk) 23:31, 7 February 2019 (UTC)

And, by far and large, those posting stuff on the arXiv are published experts. The nonsense tends to get re-classified to [physics.gen-ph]. So yes, arxiv shouldn't be treated better than WP:SPS, the difference is that if you roll a dice and pick a random preprint on the arxiv, chances are it will be by a published expert. If you do the same on vixra, chances are you'll end up on a nonsense paper from a quack. Headbomb {t · c · p · b} 23:37, 7 February 2019 (UTC)

Certainly, arXiv should not generally be a fully reliable source but nowadays it is close to one when published by experts. However, viXra is not even close! Many serious academics will reference arXiv preprints in peer-reviewed published papers but very very few will reference viXra (I can't say that I've ever seen one). Of course, there are very bad preprints in both so neither can satisfy WP:RS and any citation of either can only really be used as a primary source (which means that they should both be on crapwatch based on its definition). Even Perelman's proof of the Poincaré conjecture, posted on arXiv, is only significant in conjunction with its recognition by the mathematical community. — MarkH21 (talk) 10:56, 10 February 2019 (UTC)

SPA

Assistance handling an WP:SPA at k shortest path routing and a related talk would be helpful. Johnuniq (talk) 09:16, 11 February 2019 (UTC)

I tend to agree with David Eppstein that this is probably the same obsessed sockpuppeteer. (Although maybe their English has improved over the last few months?) --JBL (talk) 02:15, 12 February 2019 (UTC)

Mathematics Wikiproject:probability and statistics at Wikipedia:WikiProject Statistics

Wikipedia:WikiProject Statistics includes a table of articles tagged as probability and statistics with the {{maths rating}} template. But the table shows no articles. Can someone here take a look and fix it? Thank you.--76.14.38.58 (talk) 22:01, 15 February 2019 (UTC)

It looks as if the table is transcluded from User:WP 1.0 bot/Tables/Custom/Mathematics-Probability. That page is updated by WP 1.0 bot, which removed the content in late 2017. More help may be available at Wikipedia talk:Version 1.0 Editorial Team/Index. Certes (talk) 00:35, 16 February 2019 (UTC)

Our article titled Wishart distribution needs some work!

Here I need to point out a conspicuous elephant in a room, but maybe that particular room doesn't get a lot of attention. Our article titled Wishart distribution contains this assertion:

[I]f n ≥ p, X has a Wishart distribution with n degrees of freedom if it has the probability density function

$f_{\mathbf {X} }(\mathbf {x} )={\frac {1}{2^{np/2}\left|{\mathbf {V} }\right|^{n/2}\Gamma _{p}\left({\frac {n}{2}}\right)}}{\left|\mathbf {x} \right|}^{(n-p-1)/2}e^{-(1/2)\operatorname {tr} ({\mathbf {V} }^{-1}\mathbf {x} )}$

where $\left|{\mathbf {x} }\right|$ is the determinant of $\mathbf {x}$ and Γ_p is the multivariate gamma function defined as

$\Gamma _{p}\left({\frac {n}{2}}\right)=\pi ^{p(p-1)/4}\prod _{j=1}^{p}\Gamma \left({\frac {n}{2}}-{\frac {j-1}{2}}\right).$

Anyone who wants to understand that or make any use of it or do anything at all with it will instantly wonder how in Hell we're supposed to integrate a thing like that, i.e. with respect to which measure is this a density, or to put it another way, with respect to which variables over which set are we integrating? Observe that the argument ${\textstyle \mathbf {x} }$ is a ${\textstyle p\times p}$ positive-definite matrix and we may denote its entries by ${\textstyle x_{ij}}$ for ${\textstyle i,j\in \{1,\ldots ,p\}}$. So a naive guess is we're talking about

$\int f(\mathbf {x} )\,\prod _{i,j}dx_{ij},$

so it would be just Lebesgue measure. But that raises question: since ${\textstyle \mathbf {x} }$ is symmetric, should we have $\displaystyle \prod _{i,j\,:\,i\,\leq \,j}$ or the like? So Lebesgue measure on a space of dimension ${\textstyle p(p+1)/2{\text{?}}}$ And what are the bounds of integration? The bounds may seem messy, but I think I may know a way to deal with that neatly. But is that what is meant, or is there some standard measure on the space of positive-definite symmetric matrices that anyone who knows about it would expect to be used here, or what? In any case, answers to these questions ought to be in the article.

Same problem in Inverse-Wishart distribution.

So maybe tomorrow I'll go to the library and look some things up, but maybe someone here knows something off the top of their head. Michael Hardy (talk) 18:47, 10 February 2019 (UTC)

Not a probability theorist nor a statistician, but there is a Lebesgue measure on positive definite matrices (corresponding to the Haar measure on the additive group). — MarkH21 (talk) 03:53, 11 February 2019 (UTC)

@MarkH21: The additive group? The set of positive-definite matrices is not a group under addition. Is the measure you have in mind the same as ${\textstyle \prod _{i,j\,:\,i\,\leq \,j}dx_{i,j},}$ as suggested in some of the other postings below? Michael Hardy (talk) 21:59, 11 February 2019 (UTC)

Whoops, ignore that - I think I had symmetric matrices in mind. So yes it should be that. — MarkH21 (talk) 00:44, 12 February 2019 (UTC)

I also think that you had symmetric matrices in mind. (The domain is another story.) On this (vector) space, the Haar measure is defined only up to a coefficient. By the way, on the plane $\mathbb {R} ^{2},$ the line $\{(x,y)\mid x=y\}$ is a one-dim Euclidean space, and carries its Lebesgue measure; but then, the segment from the origin to (1,1) has measure ${\sqrt {2}},$ while integrating $dx$ on it we rather get $1.$ This is the problem of the coefficient...

The Haar measure on a non-compact group is defined only up to a coefficient, this is the problem...

Indeed, most sources are silent on this point. But one (maybe not very reliable) is not silent; see here, equation (2.4) on page 8; is says:

For symmetric matrices, we are only concerned with the $p(p+1)/2$ independent elements of the symmetric matrix, thus $|d\Omega |=\prod _{k,l=1;k\leq l}^{p}\mathrm {d} \omega _{kl}.$

Boris Tsirelson (talk) 06:39, 11 February 2019 (UTC)

And now the same in the most reliable source, Wishart 1928 (ref 1 in our article); page 38 eq (8):

$\left|{\begin{array}{ccc}a&h&g\\h&b&f\\g&f&c\end{array}}\right|^{\frac {N-5}{2}}da\,db\,dc\,df\,dg\,dh$

in particular, and in general on page 38 eq (9): $da_{11}\,da_{12}\dots da_{nn}.$ Boris Tsirelson (talk) 07:09, 11 February 2019 (UTC)

And surely, the domain of integration is the set of all positive-definite matrices, a semialgebraic (see Sylvester's criterion), therefore Jordan measurable, open set in the dimension $p(p+1)/2;$ or equivalently, its closure, the (Jordan measurable closed) set of all positive semi-definite matrices (or any set in between of these two). Riemann integration applies (and Lebesgue integration as well, of course). Boris Tsirelson (talk) 07:15, 11 February 2019 (UTC)

Now added to the article. Boris Tsirelson (talk) 06:05, 17 February 2019 (UTC)

Draft:Oaxaca-Blinder decomposition

User:Legacypac was wondering if this draft is "useful/fixable" (I have no idea). So, is it useful? already covered in mainspace? -- Taku (talk) 00:41, 14 February 2019 (UTC)

Blinder–Oaxaca decomposition seems to cover it. Certes (talk) 01:03, 14 February 2019 (UTC)

Yep, the draft looks redundant with the existing article. XOR'easter (talk) 16:11, 14 February 2019 (UTC)

I've created a redirect at Oaxaca–Blinder decomposition (but not Oaxaca-Blinder decomposition) and thrown square brackets at a couple of relevant articles to create incoming links. Certes (talk) 16:37, 14 February 2019 (UTC)

(but not Oaxaca-Blinder decomposition) I do not know anyone who types en-dashes into search bars rather than hyphens. So I will create the other redirect. --JBL (talk) 17:15, 14 February 2019 (UTC)

@Joel B. Lewis: I often put en-dashes within search terms here. Michael Hardy (talk) 19:19, 14 February 2019 (UTC)

Wow... How do you put them? I do not see them on my keyboard. Boris Tsirelson (talk) 20:24, 14 February 2019 (UTC)

@Boris Tsirelson: They're not on my keyboard either. But when I click on "edit" I see a list of symbols right below the editing window:

– — ° ′ ″ ≈ ≠ ≤ ≥ ± − × ÷ ← → · §

The first one is the en-dash. You can also write &ndash; and when you save the article or click on "show preview" you'll see an en-dash. You can then copy that en-dash and paste it into the article, although that's not striclty necessary. Note that the minus sign is also there, and that differs from the en-dash. And from the hyphen, but that's obvious. Michael Hardy (talk) 06:37, 17 February 2019 (UTC)

I understand why do this fuss when editing articles. But in search bar?.. Moreover, when I search, I usually have nothing to edit yet; and I am reluctant to click "edit" without good reason. Boris Tsirelson (talk) 06:51, 17 February 2019 (UTC)

An en-dash takes me only one more keypress than a hyphen so I am likely to type it when appropriate, just out of habit, even when a hyphen would work. And also, keep in mind that it is pretty common to copy and paste into search bars. —David Eppstein (talk) 22:11, 17 February 2019 (UTC)

I see... probably I should develop the habit. Boris Tsirelson (talk) 07:03, 18 February 2019 (UTC)

WP:HTMD is useful for the dashophiles. --{{u|Mark viking}} {Talk} 20:33, 14 February 2019 (UTC)

Thank you for creating the hyphen redirect. I wondered whether it might seem rude when there was a draft of that name but you're right: it's more useful. By the way, I'm one of the rare people who do type en-dashes with ⇪ Caps Lock - - ., having repurposed my otherwise useless Caps Lock button as a compose key. Certes (talk) 21:08, 14 February 2019 (UTC)

When you huys are done merging please redirect the draft I found to tje mainspace page. Thanks. Legacypac (talk) 22:09, 14 February 2019 (UTC)

As I said at User talk:Michael Hardy, beware of time-traveling proofreaders accompanied by 5-meter ruminants. Robert McClenon (talk) 02:35, 15 February 2019 (UTC)

Where to request assessment

I've significantly expanded numerical linear algebra. Where can I request an assessment of it to revise its Stub Class label? - Astrophobe (talk) 22:05, 17 February 2019 (UTC)

@Apostrophe: I did a bit of copy-editing on it. I can't help wondering why you would write \underset_{\delta \to 0} {\lim} instead of \lim_{\delta \to 0} in a displayed (as opposed to inline) context. Michael Hardy (talk) 00:43, 20 February 2019 (UTC)

A TeX anomaly

In our system of mathematical notation coding, which is not LaTeX although people call it that, and is not actually TeX either, I found this in Barnes G-function:

${\begin{aligned}&z\log \Gamma (z)-\log G(1+z)=-z\log \left({\frac {1}{\Gamma (z)}}\right)-\log G(1+z)\\[5pt]={}&-z\left[\log z+\gamma z+\sum _{k=1}^{\infty }{\Bigg \{}\log \left(1+{\frac {z}{k}}\right)-{\frac {z}{k}}{\Bigg \}}\right]\\[5pt]&{}-\left[{\frac {z}{2}}\log 2\pi -{\frac {z}{2}}-{\frac {z^{2}}{2}}-{\frac {z^{2}\gamma }{2}}+\sum _{k=1}^{\infty }{\Bigg \{}k\log \left(1+{\frac {z}{k}}\right)+{\frac {z^{2}}{2k}}-z{\Bigg \}}\right]\end{aligned}}$

I changed it so that it says this:

${\begin{aligned}&z\log \Gamma (z)-\log G(1+z)=-z\log \left({\frac {1}{\Gamma (z)}}\right)-\log G(1+z)\\[5pt]={}&{-z}\left[\log z+\gamma z+\sum _{k=1}^{\infty }{\Bigg \{}\log \left(1+{\frac {z}{k}}\right)-{\frac {z}{k}}{\Bigg \}}\right]\\[5pt]&{}-\left[{\frac {z}{2}}\log 2\pi -{\frac {z}{2}}-{\frac {z^{2}}{2}}-{\frac {z^{2}\gamma }{2}}+\sum _{k=1}^{\infty }{\Bigg \{}k\log \left(1+{\frac {z}{k}}\right)+{\frac {z^{2}}{2k}}-z{\Bigg \}}\right]\end{aligned}}$

You see the difference on the second line: in the first version, the space between the minus sign and the z is what is normally followed when the minus sign is used as a binary operation symbol, rather the smaller amount of space that normally appears when it's a unary operation, thus:

${\begin{array}{r}5-3\\-3\end{array}}$

I tried the same code in genuine LaTeX and (as expected) this problem of incorrect spacing did not occur. The way I fixed the problem is that I changed this line of code:

= {} & -z \left[ \log z+\gamma z +\sum_{k=1}^\infty \Bigg\{ \log\left(1+\frac{z}{k} \right) -\frac{z}{k} \Bigg\} \right] \\[5pt]

to the following:

= {} & {-z} \left[ \log z+\gamma z +\sum_{k=1}^\infty \Bigg\{ \log\left(1+\frac{z}{k} \right) -\frac{z}{k} \Bigg\} \right] \\[5pt]

I found three instances of the same bug in the same section of that article and fixed them all the same way.

I don't recall that I've noticed this bug before. I'd hate to think that I'd encountered it without noticing, it, but such unpleasantenss can actually happen. How long has this been with us? Michael Hardy (talk) 20:24, 21 February 2019 (UTC)

Interesting. In the LaTeX world, this bug can be triggered in the amsmath multi-line environment.[7] Perhaps this only happens at WP in that environment? $=-z$ looks OK to me. --{{u|Mark viking}} {Talk} 22:34, 21 February 2019 (UTC)

RIP PlanetMath?

Our WP entry for the site describes it as inactive and apparently they moved their content last year to GitHub with the original website currently somewhere between dysfunctional and not maintained (and I suspect it being ditched in the future). Does anybody have any background on PlanethMath's exact status and planned future? We still have that collaboration project listed on our project page, but that seems to be inactive/dead for years now as well. Should we remove that? Do we still have an overlap of active editors or anybody doing work on the collaboration?--Kmhkmh (talk) 02:01, 18 February 2019 (UTC)

Planet Math restructured their website a few years ago and that left some of our external links not going to the right place. So far there are fewer than 250 pages which still use the obsolete {{PlanetMath reference}} template and I have replaced a few of them with the new one. For example, at Axiom of regularity, I replaced:

• {{planetmath reference|id=3485|title=Axiom of Foundation}}

with

• {{PlanetMath|urlname=axiomoffoundation|title="Axiom of foundation"}}.

This conversion still has to be done for the rest of the 250, which I hope to get to eventually. As to the continued importance of linking to Planet Math, probably that can be decided for each individual page. At Fano plane, the Planet Math link goes to a lengthy article and appears useful, but elsewhere some of the entries are very short. Those of our articles that actually use content taken from Planet Math need to keep whatever attribution template they currently have. EdJohnston (talk) 06:11, 18 February 2019 (UTC)

Thanks for the update on that, I completely forgot about the template in articles in my posting above. My question about removal however did not refer to the templates in articles but the whether we should still link Wikipedia:WikiProject Mathematics/PlanetMath Exchange on our project page or remove that link due inactivity/project having ended.

As far as the the templates in articles are concerned. Are we talking about the same change at PlanetMath? A few years back (2013) PlanetMath restructured its page and software (which probably requires older links to be adjusted). But I was talking about a more recent change seemingly from last year, when they moved their content to Github and seem to plan to shutdown/end their website completely (or maybe just to reorganize it again over a longer time frame). The information given on their website itself about this last change is scant and so is the activity on the related Github pages, hence i'm not really clear what's likely to happen there. For the templates/links currently existing in Wikipedia a possible fix might be to link them to archive.org, which seems to host a lot of former PlanetMath entries (probably all that were linked within Wikipedia).--Kmhkmh (talk) 09:36, 18 February 2019 (UTC)

Agree that the planetmath.org website does not seem to be updated very much and it's unclear whether anyone is home. Unsure that we would need to update our links to that site so long as it remains online. I'm leaving a ping for the people listed at WP:WikiProject Mathematics/PlanetMath Exchange#Participants who are still active on Wikipedia in case they want to comment: @Oleg Alexandrov, Paul August, Arthur Rubin, Tompw, and Rich Farmbrough: If it is correct that nothing much is happening, it may be time to remove the link to the WikiProject from the main page of WP:WPM. EdJohnston (talk) 16:35, 18 February 2019 (UTC)

I haven't contributed to our PlanetMath Exchange project in a very long time, and as far as I know the exchange project is moribund. Paul August ☎ 16:51, 18 February 2019 (UTC)

I haven't even looked at PlanetMath lately. No idea if there is anything there (any more) worth bringing here. — Arthur Rubin (talk) 10:17, 19 February 2019 (UTC)

Like Paul August, I haven't done anything relating to that project in a loooong time. It's a shame the site is inactive, but I agree any references should be replaced. Tompw (talk) 16:48, 19 February 2019 (UTC)

Concur. All the best: Rich Farmbrough, 09:27, 22 February 2019 (UTC).

Based on the discussion so far I removed PlanetMath from the project page now. As for the PlanethMath-Links in articles it might be best as suggested above to handle them individually on an article basis. Links that for now still works (at least most of the time) may be kept for now and those that hsve become completely dysfunctional/unavailable can be removed or replaced by copies on archive.org.--Kmhkmh (talk) 10:57, 22 February 2019 (UTC)

Discussion at Wikipedia:Village pump (idea lab)#Attention WikiProjects

 You are invited to join the discussion at Wikipedia:Village pump (idea lab)#Attention WikiProjects. We are designing a bot script to perform a few article assessment–related tasks and would appreciate your feedback. Qzekrom (talk) 08:56, 23 February 2019 (UTC)

Law of tangents

I've done approximately this same reversion three times, and I wonder if the user who added this stuff may persist. Michael Hardy (talk) 19:16, 21 February 2019 (UTC)

I've placed a warning on both IPs' user talk pages. — MarkH21 (talk) 23:12, 21 February 2019 (UTC)

Hi, Michael Hardy! The section IP users insert/restore into the article has been added 12 years ago (this edit Special:Diff/71696394 from 25 August 2006) by another anonymous user 202.135.111.2 and the same day hidden into a comment by yourself (Special:Diff/71730540). Good to see it deleted finally. :) CiaPan (talk) 07:42, 22 February 2019 (UTC)

Presumably, as an administrator, you (MH) have the ability to perform a short-term semi-protection of the article if disruption continues. --JBL (talk) 17:03, 23 February 2019 (UTC)

Gadi Moran is an AfD

Deletion of a new article titled Gadi Moran has been proposed at Wikipedia:Articles for deletion/Gadi Moran. Opinions can be posted on the latter page. Michael Hardy (talk) 17:52, 23 February 2019 (UTC)

Geometry of roots of real polynomials AFD

Geometry of roots of real polynomials is not a new article it as been proposed for deletion for the second time at Wikipedia:Articles for deletion/Geometry of roots of real polynomials. Opinion of editors that are competent in mathematics would be useful there. D.Lazard (talk) 20:45, 23 February 2019 (UTC)

Inclusion of Infobox mathematical statement in FLT

If you would like to contribute to reaching a consensus on whether Infobox mathematical statement should be included in Fermat's Last Theorem, please see this talk. — MarkH21 (talk) 05:09, 24 February 2019 (UTC)

Now nominated for deletion here by Deacon Vorbis (talk · contribs). — MarkH21 (talk) 05:31, 24 February 2019 (UTC)

WP 1.0 Bot Beta

Hello! Your WikiProject has been selected to participate in the WP 1.0 Bot rewrite beta. This means that, starting in the next few days or weeks, your assessment tables will be updated using code in the new bot, codenamed Lucky. You can read more about this change on the Wikipedia 1.0 Editorial team page. Thanks! audiodude (talk) 06:48, 27 February 2019 (UTC)

Portals added to math articles

New portals have been added in the "see also" section of several of our articles such as in e (mathematical constant), algebra, circles. There are more than twenty such automatically created portals. Please, participate to the discussion at Wikipedia:Village pump (proposals)#Hiatus on mass creation of Portals. Should we nominate for deletion all these portals that are related to mathematics? D.Lazard (talk) 15:49, 27 February 2019 (UTC)

• At the Portal:Burger King MfD an editor made some interesting points about pulling in barely related content, much like D.Lazard's points at the RFC. These things are based on Nav boxes but without the context of Nav boxes.

When WP:ENDPORTALS happened there were almost 1700 portals. Since then 4500 new portals have been created, about 3500 by one editor. Legacypac (talk) 16:23, 27 February 2019 (UTC)

• If you look closely at these portals, you see how terrible they are. I just nominated Portal:Circles for MfD. —Kusma (t·c) 17:07, 27 February 2019 (UTC)

Even the most advanced automated content creation is dangerous.User:Legacypac|Legacypac]] (talk) 18:27, 27 February 2019 (UTC)

References

• D.Lazard, are you suggesting deleting all math-related portals, or just the newly created ones? I think Portal:Set theory should stay. I would think all the "major branches" should probably have a portal — Algebra, Analysis, Geometry and Topology, Mathematical Logic, Number Theory. I haven't checked how many of these already exist or are newly created, but I saw algebra mentioned above among the newly created. --Trovatore (talk) 18:44, 27 February 2019 (UTC)

OK, Portal:Algebra is not new, although it has been widely edited by one of the creators of the new portals. About which portals should be delete, I have not a clear opinion. Otherwise, I would have been bold, by nominating them for deletion. D.Lazard (talk) 20:18, 27 February 2019 (UTC)

• I've seen the portals almost die over a long period, I've quite recently seen them revived by one(?) serious activist, I've seen dubious followers, and now I see mass-spamming. Maybe I am ametropic, maybe we should prepare to lean back and meditate while watching the AI-agents fighting their edit wars, installing infoboxes, partaking in RfAs, running the sanctions, ... I'd reduce the number of portals to just befor their near deletion, and watch their growth, before allowing for new portals. Purgy (talk) 19:29, 27 February 2019 (UTC)

Infobox mathematical statement

There is a sparsity of mathematical infoboxes and I think that one for mathematical statements (broadly construed, e.g. theorems, conjectures, propositions, lemmas, etc.) could be very useful on many particularly important mathematical articles. I've drafted a very simple one. Would other editors here welcome such a infobox? Feedback on its usage as well as its implementation (e.g. possible additional fields) would be very welcome as this is my first attempt at an infobox template! MarkH21 (talk) 06:17, 5 February 2019 (UTC)

I for one think that the sparsity is a good thing, and that adding more of them would be filling a much-needed gap. Infoboxes are inane. They're fine for filling out the details of inane subjects, like the teams a footballer has played on, but they are inherently a way of reducing material to a 5-second soundbite for readers who don't even have the attention span for a single full sentence at the start of the article. That's a bad fit for articles on technical topics in mathematics. —David Eppstein (talk) 06:31, 5 February 2019 (UTC)

Sure, I don't disagree with those statements! However, I do think that this would be a neat way of packaging a lot of the info for some major mathematical topics. Also, many of the articles for these problems are indeed technical and this would be a way to package basic information to a curious non-mathematician without requiring them to read through the history or current status. I'm sure many non-specialist readers look at articles about RH or P=NP precisely to get this kind of information quickly! MarkH21 (talk) 06:47, 5 February 2019 (UTC)

And indeed for important problems like P vs. NP you may find the Unsolved Problems box being used. --JBL (talk) 13:47, 5 February 2019 (UTC)

I've never seen that box used where the field given is mathematics (and in this case it's "Unsolved problem in computer science"). This is also an extension of that box, so if that merits use then shouldn't this? — MarkH21 (talk) 18:09, 5 February 2019 (UTC)

If you look at this you can see everywhere it is used, and find a bunch of math articles that way. For example, from the first 50 (and disregarding theoretical CS questions whose solutions will necessarily be mathematical in nature) uses I find these ten or so about mathematics: Sophie Germain prime, Hilbert's third problem, Sierpinski number, Collatz conjecture, Twin prime, Catalan's constant, Magic square, Catalan's conjecture, Mersenne prime, Perfect number. If that percentage is representative, then there are perhaps 50 or 60 total uses for mathematics. I was surprised to find it not used on RH, actually. --JBL (talk) 20:02, 5 February 2019 (UTC)

I see, although this is still not very widespread usage even for major problems (e.g. all 6 of the other Millenium Problems). Regardless, I see this infobox as an extension of the "Unsolved problem" box. Justification for the latter's existence and usage is pretty much also justification for the former's. — MarkH21 (talk) 19:56, 6 February 2019 (UTC)

Historically this Project has not been terribly enthusiastic about infoboxes, nav templates, and similar things, which can easily get spammy/crufty. That said, yours is plausible, and the RH example looks pretty good.

The "open question" field could get pretty controversial in some cases. Is the continuum hypothesis open, for example? Admittedly that particular problem is mostly concentrated in logic articles, and your format allows for explanation of the situation. But it might be good to explain that a problem being "open" doesn't necessarily mean the question is particularly in doubt (it would be shocking if, say, the Goldbach conjecture were false). Where one would explain that, I'm not sure. --Trovatore (talk) 06:38, 5 February 2019 (UTC)

Note that I just changed a few of the parameters and I changed the example since my first comment here. Sure, it could be controversial, in which case one could use something like Contested or just omit the field altogether until consensus is reached. A non-logic example would be the abc conjecture. I'm not sure evidence for/against validity would be a viable infobox field though.

Do note that many of the parameters are included for flexibility and that are optional. The example in the documentation includes all of them just for demonstration. MarkH21 (talk) 06:42, 5 February 2019 (UTC)

Heaven's blessings on the sparsity! Any single creation of such a box creates additional pressure an degrading substantial articles on math topics by stuffing real estate with boxes full of trivia, instead of structural content. I agree to the realm given above where these boxes may find a useful application, and I assume that there is nothing I can say beyond all the arguments already stated in the raging war against these infoboxes in serious articles. Maybe time has come where WP wants to degrade to trivia in boxes, I won't comment this. Diotimalives, Cassandra is dead. Purgy (talk) 07:51, 5 February 2019 (UTC)

I am in total agreement with David Eppstein and Purgy; the fewer of these things I see, the better. The kind of information that can be put into these sound bites is generally trivia, and while this may be useful in those articles where readers may be interested in trivia and trivialization of the subject, this just doesn't work in mathematical articles, not if you are trying to be intellectually honest. We work very hard, although not always successfully, at trying to make the lead accessible to a general reader and these infoboxes represent a repeat of that function in a highly formalized and abbreviated way. I don't think that this can be successfully carried out due to the inherent structural difficulties.--Bill Cherowitzo (talk) 16:49, 5 February 2019 (UTC)

I agree in general! But I do think that this particular usage would be helpful. I personally have looked up mathematical problems before just to remember who and/or when certain problems were posed and/or proven and the "simple answer" is not always obvious from the lead. I think that this particular usage would involve very little real estate and maintenance.

When the instance may not be "intellectually honest", then it can be expressed that way, the parameter can be omitted, or the infobox not used at all. — MarkH21 (talk) 18:09, 5 February 2019 (UTC)

I'm a bit late, and I'm not sure if I'm replying to anyone directly, but here goes anyway. I don't think I share quite the same level of disdain for infoboxes as some of the commenters above, but I do think that this one goes too far. They're good for examples of mathematical objects which have some standard bits of associated data – I think ones like {{Infobox probability distribution}} and {{Infobox graph}} work well. But for theorems, conjectures, etc., it mostly seems to be for information that's usually already in the article lead anyway, so I'm not sure much is really gained by having this. –Deacon Vorbis (carbon • videos) 19:17, 5 February 2019 (UTC)

Perhaps would the new "implied by", "generalizations", and "implications" parameters (that I just added be) useful as logical connectors between different theorems, axioms, etc.? I do think that such an infobox here could be revised to be appealing to most. — MarkH21 (talk) 19:31, 5 February 2019 (UTC)

I've thought about this some more, and I'd like to respond to the points brought up. The heart of the opposition seems to be that any infobox is a trivialization of the subject. However, the infobox neither detracts from the material of the articles for the knowledgeable nor expert reader, who may glance past the infobox just as one would for any biographical article. Meanwhile, the majority of articles on mathematical statements are too technical for the general reader (or even knowledgeable reader) to whom we should strive to make the articles more accessible. In particular, while basic details such as its history and its logical connections to other statements perhaps should be easily accessible in the lead (although I disagree for many cases), the fact of the matter is that they usually are not.

An implementation of the template, in great moderation and keeping the MOS purpose in mind, should add value to these articles – particularly for the general reader casually looking up math on Wikipedia. — MarkH21 (talk) 10:34, 10 February 2019 (UTC)

Bumping thread for 21 days. Referred to in a TfD listing –Deacon Vorbis (carbon • videos) 05:41, 24 February 2019 (UTC)

Mar 2019

Wikipedia:Miscellany for deletion/Draft:Bredon cohomology (2nd nomination)

There is a long-standing dispute flaring up again over a short, one-sentence-fragment draft at Draft:Bredon cohomology which needs input from editors familiar with mathematics topics. The crux of the issue is that the only editor interested in keeping the draft has not worked on it in five years, and nobody else who has interacted with this has the knowledge to edit topics of this complexity. If someone could help us work out what this draft is and where it should go, your efforts will be greatly appreciated. Thanks. Ivanvector (^Talk/_Edits) 16:29, 1 March 2019 (UTC)

I've removed some more spill-over from that debate. The page has been worked on enough that it's been promoted to an article, but it's a very short stub. More help there is still appreciated. Ivanvector (^Talk/_Edits) 17:18, 1 March 2019 (UTC)

Glitch prime?

I just stumbled on this video by Numberphile talking about a thing he called "glitch prime". I was surprised to see we don't have an article on that (or at least a redirect to an equivalent concept. Basically they're numbers, when expressed in a base, are an odd number of digits where all the digits is the maximum number in the base, and the middle digit is one less (e.g. 11011 in binary, 22222122222 in ternary, 99899 in base ten and so on), which also happen to be primes. I could be explaining this wrong, but that was my takeaway.

Not really sure if that passes any sort of WP:N standards, of if it's a 'thing' in math, but I was surprised not to have an article on them. Headbomb {t · c · p · b} 13:37, 5 March 2019 (UTC)

@Headbomb: I looked around briefly, but found very little. These are listed at oeis:A265383, but there's not much fanout in terms of what they link to. I'm not 100% sure, but my suspicion is that there just isn't enough out there to clear WP:N and sustain an article. –Deacon Vorbis (carbon • videos) 14:41, 5 March 2019 (UTC)

I don't see notability for their own article. They are a form of List of prime numbers#Palindromic wing primes which are a form of near-repdigit primes. Neither has an article. If they did (notatibility is very questionable) then "glitch prime" could have been mentioned there. PrimeHunter (talk) 15:49, 5 March 2019 (UTC)

Would a redirect to that make sense then? Or worth having a subsection in that list article? Headbomb {t · c · p · b} 19:02, 5 March 2019 (UTC)

I don't think they are notable enough for List of prime numbers. OEIS has thousands of prime number sequences. A redirect makes no sense if the target gives no indication of the meaning. PrimeHunter (talk) 10:30, 6 March 2019 (UTC)

Also, this is WP:OR, as the author of the video does not cite any source. So, this does not belong to WP. D.Lazard (talk) 12:31, 6 March 2019 (UTC)

@D.Lazard: The OR policy forbids an author from publishing their original research in Wikipedia. It absolutely does not forbid referencing a source that is itself engaged in original research. (Otherwise it would be forbidden to cite published mathematics research papers in WP.) --JBL (talk) 17:46, 6 March 2019 (UTC)

In WP:OR, original research is defined as The phrase "original research" (OR) is used on Wikipedia to refer to material—such as facts, allegations, and ideas—for which no reliable, published sources exist. This is precisely the case of "glitch primes". D.Lazard (talk) 18:07, 6 March 2019 (UTC)

The Numberphile video is a published source; possibly you believe that it is not reliable, but that is a totally separate issue from WP:OR. --JBL (talk) 18:11, 6 March 2019 (UTC)

In WP:OR: Self-published material, whether on paper or online, is generally not regarded as reliable. In WP:SPS: Self-published expert sources may be considered reliable when produced by an established expert on the subject matter, whose work in the relevant field has previously been published by reliable third-party publications. An anonymous blogger, such as nunberphile, cannot fit this definition of a self-published expert. So, the fact that this source is not reliable is the result of Wikipedia's definition of "reliable". It is not a belief nor an opinion. D.Lazard (talk) 18:53, 6 March 2019 (UTC)

Numberphile is not an 'anonymous blogger', and neither is Simon Pampena [8]. Headbomb {t · c · p · b} 18:56, 6 March 2019 (UTC)

Is Ngo best described as "Vietnamese-French" or "Vietnamese" in the lead?

Please see the discussion here. --173.79.47.7 (talk) 23:01, 6 March 2019 (UTC)

old Drafts found

Draft:Robust geometric computation Legacypac (talk) 03:19, 6 March 2019 (UTC)

Draft:Proto-value Functions. Robert McClenon (talk) 22:39, 6 March 2019 (UTC)

We already have an article on Proto-value functions, created in 2011. (This is the same topic but with different capitalization of the title). Both the draft and the article were created by User:GNrun. The article looks keepable; the draft should be disposed of in whatever way is correct. EdJohnston (talk) 23:06, 6 March 2019 (UTC)

I have tagged Draft:Proto-value Functions as a duplicate of an article. It will be available for comparison against the article for six months and then will self-destruct. See G13 rather than Mission Impossible. Robert McClenon (talk) 19:07, 7 March 2019 (UTC)

I have added these two drafts to Wikipedia:WikiProject Mathematics/List of math draft pages. -- Taku (talk) 23:18, 6 March 2019 (UTC)

I am interested to see that there is a list of drafts. I will occasionally add the name of a draft here to permit the updating of the list by someone whose math knowledge is a little better than mine, which consists of having forgotten all of the higher math that I learned in college and still remembering first-year calculus because I learned it in high school. Robert McClenon (talk) 19:07, 7 March 2019 (UTC)

I have moved Proto-value functions to Proto-value function. I left it as an orphaned article, i.e. no other articles link to it. I don't know which other topics should link to it. Michael Hardy (talk) 16:41, 9 March 2019 (UTC)

New Draft Found

Please categorize Draft:M* search algorithm Robert McClenon (talk) 01:37, 8 March 2019 (UTC)

The list was Taku's excellent idea. If other wikiprojects did this more good drafts could be improved. Legacypac (talk) 06:51, 8 March 2019 (UTC)

Entropy influence conjecture

If the new article titled Entropy influence conjecture should be kept, then it needs work. In particular, it's not all that clearly stated, and no other articles link to it. Michael Hardy (talk) 16:55, 2 March 2019 (UTC)

It almost makes sense to me, but since when does a "Boolean" function map to {-1, 1}? — Arthur Rubin (talk) 03:27, 3 March 2019 (UTC)

This conjecture showed up on Terrence Tao's blog, where it is explained much better. This article might be usefully merged into the section Analysis_of_Boolean_functions#Basic_results, with associated results. --{{u|Mark viking}} {Talk} 03:39, 3 March 2019 (UTC)

The value of a Boolean function could be any two things, but as I understand it it's pretty standard for those two things to be -1 and 1 instead of 0 and 1 when you're going to do Fourier analysis on the function. —David Eppstein (talk) 06:58, 3 March 2019 (UTC)

That the codomain is {0,1} is the convention that I know, but (1) it's still into a set of just two values and (2) it makes it possible to write ${\textstyle \prod _{i=1}^{n}x_{i}}$ instead of the more complicated ${\textstyle \prod _{i=1}^{n}(2x_{i}-1).}$ Michael Hardy (talk) 21:46, 3 March 2019 (UTC)

I've cleaned the article up a bit and linked the article from one of its originators (Gil Kalai) so that it's at least not an orphan anymore. Unsure if the article meets notability standards as it's not a terribly well-known problem but it should be a bit better now at least. It could certainly be merged into Analysis of Boolean functions as suggested by Mark viking (talk · contribs) (I would support that). — MarkH21 (talk) 07:38, 12 March 2019 (UTC)

Draft:Color and mathematics

So I don't know what should be done with this draft. The article title seems too vague, which is of course fixable and the topic itself seems legitimate (but I don't have a background to review the article itself myself). -- Taku (talk) 01:44, 15 March 2019 (UTC)

It looks like original research to me. Some of its content may of course have been published somewhere, but if you find those publications and turn that content into an article meeting Wikipedia standards, you'll have something so different from the draft that it will be effectively a completely different article.

That said, I see no urgency to delete these. --Trovatore (talk) 02:43, 15 March 2019 (UTC)

A vector space for color vision is not itself Original Research, but this draft probably needs revision to make clear what's derived from what. XOR'easter (talk) 02:50, 15 March 2019 (UTC)

"Original research" is of course a term of art here; it doesn't mean that it's particularly original or makes any research contribution. The content seems pretty simple and I don't see anything obviously wrong (not that I've been over it with a fine-tooth comb), so it's quite likely that any particular statement in it is more-or-less sourceable. But it's not clear that the exposition as a whole corresponds to anything in sources. --Trovatore (talk) 18:07, 15 March 2019 (UTC)

As far as I understand, this draft may be viewed as a tentative for describing the mathematical background of color space. So, the draft could be merged in color space, for making a section called "mathematical background" or "mathematical definition". But, for that, a lot of work is needed on the draft as well as on the target article. D.Lazard (talk) 10:09, 15 March 2019 (UTC)

(Thank you all for the responses). Following D.Lazard’s suggestion, I have put a merger tag; and, *hopefully*, someone knowledgeable can take care of the draft. Yes, the content looks fine; but I’m just not well equipped with the knowledge (or will power) to judge the content so simply moving it to mainspace seems wrong. —- Taku (talk) 09:14, 18 March 2019 (UTC)

The article "Compositional data"

This article doesn't seem to have much content to me. Is this not just giving examples where all data points lie on a simplex? It also happens to be almost entirely contained in Aitchison geometry (which seems to just define some operations on the simplex and a few isomorphisms, although perhaps their significance in statistics is greater than I can tell).

Seems to me like at least one of the two articles should be merged into the other or to Simplex#Applications (which itself needs some work). See the talk page discussion at compositional data and talk page discussion at Aitchison geometry that I just started. — MarkH21 (talk) 06:21, 12 March 2019 (UTC)

Compositional data is currently a very very stubby article. It currently has _nothing_ on the normal distribution of logits, along with their variance matrices and singular-value decompositions of them, etc. Obviously if one is to be merged into the other then Compositional data is the one that should survive. Michael Hardy (talk) 05:50, 13 March 2019 (UTC)

It is also obvious that if two of these are merged, then Aitchison geometry would be merged into Compositional data and not into Simplex, since analysis of compositional data is the purpose of Aitchison's work. Michael Hardy (talk) 17:03, 14 March 2019 (UTC)

Got it, thanks for the help! I may go ahead and do that if there is no objection. Would you be able to add the content that you mentioned? — MarkH21 (talk) 22:27, 14 March 2019 (UTC)

@MarkH21: I'm not sure the article titled Aitchison geometry shouldn't exist. Possibly when Wikipedia's coverage of the topic of compositional data analysis becomes somewhat complete it will be obvious that it should. Michael Hardy (talk) 05:48, 15 March 2019 (UTC)

My understanding is that Aitchison geometry is a set of transformations and a structure on a simplex used to study data that lies on a simplex (i.e. compositional data), right? It's the sample space of compositional data and seems to be better served as a section of the article on compositional data. It doesn't seem like the article compositional data (which is 15 years old!) and Aitchison geometry will each be expanded so greatly in the near future that Aitchison geometry should be a standalone article. But when it does, we could split Aitchison geometry into its own article?

This is just my (non-expert) opinion, but I think both article would be improved in their current (and foreseeable) state if we made Aitchison geometry a section of compositional data. — MarkH21 (talk) 18:49, 15 March 2019 (UTC)

For now that's probably the best way. But if the article gets expanded a lot later then a separate article may make more sense. Michael Hardy (talk) 17:38, 18 March 2019 (UTC)

Thanks for your input! I've done the merge now, made some other revisions to the writing, and added some links to the article / pointing at the article. — MarkH21 (talk) 07:04, 19 March 2019 (UTC)

Sieve of Eratosthenes and sieve theory

There's a dispute and discussion ongoing at Talk:Sieve of Eratosthenes over whether the lead of the article should mention sieve theory. Please participate with your opinions. —David Eppstein (talk) 16:06, 19 March 2019 (UTC)

Notice of RfC on Infobox inclusion at FLT

Apologies for bringing up an old issue. Just posting a notice that an official RfC has been posted for the FLT infobox debate: Talk:Fermat's Last Theorem#Request for comment (RfC) on inclusion of Infobox mathematical statement. Hopefully this can lead to the debate being effectively and peacefully closed in either direction. — MarkH21 (talk) 07:32, 19 March 2019 (UTC)

Re "peacefully", if no one gets stabbed as a result of this issue, I will be very disappointed ;). --JBL (talk) 16:10, 19 March 2019 (UTC)

Karen Uhlenbeck

Regarding Karen Uhlenbeck's win of the Abel prize, Coffeeandcrumbs wrote on Wikipedia talk:WikiProject Women in Red that "This article has the opportunity to appear at ITN today. Please help improve the article. We need to expand the Research section to explain why she won the Abel Prize. Please help!". My feeling is that this project is more likely than WIR to include people who understand her research well enough to help, so I am copying the message here. —David Eppstein (talk) 19:57, 19 March 2019 (UTC)

I've added some details to her work on minimal surfaces and Yang–Mills theory. I'm not an expert in the field though but it could certainly be expanded further by any passing geometric analyst. — MarkH21 (talk) 20:35, 19 March 2019 (UTC)

There's quite a bit more than can be added; in particular, the Donaldson survey has quite a bit of information that can improve the Research section. I don't have time to do this now, but perhaps someone else may find themselves up to the task. — MarkH21 (talk) 01:26, 20 March 2019 (UTC)

Infobox edits (thankfully not about FLT)

I am about to run off to work so can't deal with this properly, but attention is definitely needed with respect to the edits to mathematician infoboxes by this user: Debaditya2000 (talk · contribs · deleted contribs · logs · filter log · block user · block log). There have been some reversions (e.g. by D.Lazard at Paul Erdos and by me at Andrey Markov and Alexander Grothendieck), but there are many more. Courtesy ping: @Debaditya2000:. --JBL (talk) 13:26, 18 March 2019 (UTC)

The same editor has also created Kolmogorov's theory of 1941, which deserves clearly to be nominated for AfD. It would better to be nominated by an editor who knows turbulence theory. D.Lazard (talk) 14:14, 18 March 2019 (UTC)

PS: this article has been made a redirect to Turbulence by another editor, while I was writing my previous post. D.Lazard (talk) 14:18, 18 March 2019 (UTC)

All infoboxes edits by this user have now been reverted. D.Lazard (talk) 15:56, 18 March 2019 (UTC)

Hello, many of you reverted my edits for as one of you said, because I didn't summarize, I consider my goal is not only to summarize but also to unify as much information as possible on the main page with the associated pages, but also to keep it comprehensive, i.e. "summarized". As far as my conception of "known for" is concerned, I don't have a narrow minded approach towards the concept of 'known for" that I presume one of you have, a mathematically ignorant person may or may not "know" a person or his name because of his direct "contributions" to knowledge. Also, to back up my argument, I'll also mention you 3 few "good","protected" and a "featured" article that have the same format of representation of "known for" field that I tried to edit in my editing of Paul Erdős' article. Please have a look at the following articles: Richard Feynman, John von Neumann and Paul Dirac. The 3 aforementioned articles are rated "featured, "good" and "semi-protected" respectively also have a lengthy collapsible list. Also, to avoid super-lengthy infoboxes, I added collapsible lists, as it'd hence, be intuitively understandable to the reader that the associated field may contain long/medium sized information. My request to you people would be not to revert the articles and to allow my previous edits, as it'll both unify and summarize the articles' infoboxes. Debaditya2000 (talk • contribs) 1:47 pm, Today (UTC−4)

I'm afraid there is a general consensus that collapsible lists are not appropriate in articles. If you want to try to override that consensus in the articles you are editing, work on those articles' talk pages. I haven't checked your edits, and haven't analysed your comment here to see if there are other things you want which are contrary to established consensus. — Arthur Rubin (talk) 05:20, 19 March 2019 (UTC)

If there is a general consensus, then it should apply to every list and if, there is a general consensus on something which is contradictory of the established well written articles' (as I gave a few references earlier) formats then I think it is plausible that having collapsible lists are no violation, of Wikipedia policies, rather it's fundamentally within it, which is sharing as much information as possible. I repeat, when there is an inclusion of a collapsible list, it is intuitively understandable to the reader that the associated field may contain long/medium sized information. However, the list itself doesn't make the infobox too long, as there is an option to shorten or open a list, which is absent in general, non-collapsible ones. I think I have provided enough justification, so I shall continue to do what I think is needed to for the article for it's betterment, in accordance to Wikipedia policies with reference to "Good/Featured/Protected" articles. Thank you.Debaditya2000 —Preceding undated comment added 07:53, 19 March 2019 (UTC)

The question set by Debaditya2000 is about the style of the field "known for" in infoboxes of mathematicians. Debaditya2000 edits consist of providing a field containing only <show>, which allows display a long list that seems copied from articles titled "List of things named after ...". IMO, this breaks the purpose of infoboxes, which is to provide a synthetic view. For people with many important contributions, giving a short synthetic summary of them is very difficult, but a long indiscriminate list is certainly not the right solution. This needs a discussion here. Until reaching a consensus here, Debaditya2000 must not pushing his personal ideas by editing again infoboxes. D.Lazard (talk) 10:06, 19 March 2019 (UTC)

I don't agree,D.Lazard with providing a "synthetic view" which seems rather "insincere"/"superfluous" for view in infoboxes, rather to provide an informative yet, summarized view and I repeat for the 3rd time "intuitively understandable for the reader" type of a view. Just like in these articles: Richard Feynman, John von Neumann or Paul Dirac, which have used the same formats that I tried to present in my editing. Which seem again to have copied from List of things named after Richard Feynman, List of things named after John von Neumann and List of things named after Paul Dirac. And all these articles are rated. Hence, it doesn't matter whether it is copied or not, it matters whether the information provided thus forth is correct or incorrect. So, rather than to continue this long and unproductive discussion, I think my allowance should be granted ASAP. — Preceding unsigned comment added by Debaditya2000 (talk • contribs)

Infoboxers seem to be after the ultimate IB: the recursive one! The whole WP is to be turned into one, clearly laid out IB, making it easy for third parties, superficial readers, common-sense afficionados, ... This is to where indiscriminate use of IBs will lead.

Seriously, I think that an IB-entry "known for", allowing for more than three items should not be contained within an IB. I am strictly against "granting allowance" alongside these intentions. Purgy (talk) 13:51, 20 March 2019 (UTC)

Merely a wrong aspect ratio, or something else?

This picture is plainly wrong, and is used in the article titled Voronoi pole. Is this simply a result of using the wrong aspect ratio? Michael Hardy (talk) 20:43, 21 March 2019 (UTC)

I'm not sure we have to diagnose how it was broken to agree that it is a bad image and should not be used. —David Eppstein (talk) 21:17, 21 March 2019 (UTC)

Merge of double torus and triple torus to n-torus?

I just noticed that there are the stubs Genus-two surface and Genus-three surface which would probably be better suited as redirects to the section n-dimensional torus of Torus. The articles don't say much and have few links pointing towards them. Respective proposals: genus two and genus three. — MarkH21 (talk) 19:37, 25 March 2019 (UTC)

A more appropriate section is Torus § Genus g surface – a 2-torus is a regular (genus 1) torus, and a 3-torus is a 3-manifold ($S^{1}\times S^{1}\times S^{1}$). I'd generally think it would be preferable to merge the genus 2 and 3 surface articles into a single Genus g surface (or whatever-named) article (maybe there's already something like this? I haven't really looked yet), with a {{Main article}} pointer from the "Genus g surface" section of the Torus page. –Deacon Vorbis (carbon • videos) 20:25, 25 March 2019 (UTC)

Oops! Yes, thanks for pointing that out (that was the section I meant)! Sure, I can do that. Similarly, the same should perhaps be done for Three-torus and the dimension n torus section.— MarkH21 (talk) 22:20, 25 March 2019 (UTC)

Nomination of Portal:Areas of mathematics for deletion

A discussion is taking place as to whether Portal:Areas of mathematics is suitable for inclusion in Wikipedia according to Wikipedia's policies and guidelines or whether it should be deleted.

The page will be discussed at Wikipedia:Miscellany for deletion/Portal:Areas of mathematics until a consensus is reached, and anyone is welcome to contribute to the discussion. The nomination will explain the policies and guidelines which are of concern. The discussion focuses on high-quality evidence and our policies and guidelines.

Users may edit the page during the discussion, including to improve the page to address concerns raised in the discussion. However, do not remove the deletion notice from the top of the page. North America¹⁰⁰⁰ 12:38, 26 March 2019 (UTC)

Postmodern mathematics

Folks here might be interested in WT:WPP#Postmodern mathematics about some concerns I had on this article. –Deacon Vorbis (carbon • videos) 14:07, 27 March 2019 (UTC)

It does look rather OR-ish and essay-like. The brute-force solution would be to redirect it to Philosophy of mathematics, which is not great, but is better. XOR'easter (talk) 00:05, 28 March 2019 (UTC)

See (and discuss there) Wikipedia:WikiProject Deletion sorting/Mathematics#Postmodern mathematics. D.Lazard (talk) 04:13, 28 March 2019 (UTC)

More permanent link — MarkH21 (talk) 05:03, 28 March 2019 (UTC)

(Inappropriate) postnominals again

Everyone remember this fun from last year (continued here)? This time it started on Claude Shannon (talk page discussion for masochists) and seems to have progressed to ridiculousness -- note the inclusion on Paul Erdős again (which I have reverted). Some assistance dealing with this would be welcome. --JBL (talk) 23:13, 27 March 2019 (UTC)

"Progressed to ridiculousness", indeed! I'd support a massive rollback (I presume there's some admin tool that can do this). XOR'easter (talk) 23:54, 27 March 2019 (UTC)

I ended up doing it by hand (not so hard, actually, since he stopped after "only" 100 or so disruptions) -- there is now a discussion at ANI (perm) in case anyone cares. --JBL (talk) 12:58, 28 March 2019 (UTC)

Notation malfunction

I found this in an article:

Pr(X ∈ g⁻¹(F))

It is coded as follows:

Pr(''X'' ∈ <span style="text-decoration:overline">''g''⁻¹(''F'')</span>)

Obviously this was intended to look like this:

$\Pr(X\in {\overline {g^{-1}(F)}})$

Often one avoids inline "TeX" because of bizarre mismatches in font size and alignment. Nowadays we have the following sort of thing:

<math display="inline"> 2+2=4 </math>

Just how well that works is a matter on which I am not ready to opine, although some instances look good to me. So one could reasonably replace what I found, maybe. But still it would seem a good idea to fix the "overline" text-decoration feature, if possible. Michael Hardy (talk) 19:14, 30 March 2019 (UTC)

I prefer TeX myself, but for a CSS approach, span style="padding-top: 4px; border-top:1px solid" will give a better result:

Pr(X ∈ g⁻¹(F))

--{{u|Mark viking}} {Talk} 20:05, 30 March 2019 (UTC)

AfD on a mathematician needs attention from independent editors

The AfD on Rick Norwood (a mathematician and comics publisher) has drawn attention from editors who personally know him due to a Facebook post by the subject Rick Norwood (talk · contribs) (courtesy ping). Any reviews from independent editors would be greatly appreciated. — MarkH21 (talk) 00:23, 31 March 2019 (UTC)

These two AfDs connected to the subject (although not about math) have also been affected: Wikipedia:Articles for deletion/Manuscript Press (his publishing company) and Wikipedia:Articles for deletion/John Blair Moore (an article he created). — MarkH21 (talk) 00:40, 31 March 2019 (UTC)

I asked for help in the form of citations of reliable sources which have reviewed or commented on my work. MarkH21 has informed me that this is against Wikipedia policy. I've been editing Wikipedia for 14 years, and had not come across this rule before, but I apologize for breaking it, and will heed MarkH21's advice. Rick Norwood (talk) 01:31, 31 March 2019 (UTC)

I tend to agree that this is not against the rules, although I haven't asked for it during the 6 times Arthur Rubin has been nominated for deletion. — Arthur Rubin (talk) 04:09, 31 March 2019 (UTC)

Good for you. There are more than three hundred living topologists who have articles on Facebook, and I don't know how many mathematicians, and I doubt more than ten percent meet the stringent requirements that MarkH21 wants to apply. However, I am basing my defense less on my mathematics than on my expertise, writing, and publishing in the area of comic strips, where I really am one of the top people in that field. Rick Norwood (talk) 12:36, 31 March 2019 (UTC)

Poorly written sentence

I'm trying to fix a poorly written sentence in the topology article. It includes multiple uses of "we". But another editor is reverting my improvement. Also, the key terms in the section containing the sentence should be wikilinked (which I did, but the other user reverted). Could someone please take a look at the article? Jrheller1 (talk) 00:32, 27 March 2019 (UTC)

Your concerns about this sentence are valid, but as other editors have pointed out, your "fixes" have had problems. I have suggested a fix that does not distort the underlying concept, perhaps this will suffice. --Bill Cherowitzo (talk) 18:17, 27 March 2019 (UTC)

"The definition of an open set determines the nature of continuous functions, compact sets, and connected sets" is the cleanest version of the sentence. What exactly is incorrect about this version of the sentence? Also, how is it helpful to readers to remove the wikilinks to the key concepts from that section? Jrheller1 (talk) 22:44, 27 March 2019 (UTC)

A better wording might reflect that the definitions of continuity, compactness, etc. are based on/use the open sets. To be annoyingly precise, it is not really the definition that determines those sets. If you switch one definition with an equivalent one (but not "the same"), then the other sets don't change. — MarkH21 (talk) 23:00, 27 March 2019 (UTC)

What exactly is incorrect about this version of the sentence? I personally wouldn't say that it's incorrect, just that it's not at all clear what the meaning of that string of words is supposed to be. What does "the definition of an open set" mean? What is "the nature of" continuous functions, etc., and how is it "determined"? (Honestly though I'm not sure such a sentence is needed there at all.) --JBL (talk) 23:08, 27 March 2019 (UTC)

Multiple people have complained about "nature of", so maybe "The definition of an open set completely determines the continuous functions, the compact sets, and the connected sets" would be better. I don't understand what is unclear about "definition" and "determines". But as JBL stated, the sentence might not even be necessary. Jrheller1 (talk) 04:45, 28 March 2019 (UTC)

So I changed two sentences to:

The definition of an open set completely determines the continuous functions, the compact sets, and the connected sets. A choice of open subsets is called a topology.

Another user changed it back to this version:

If the collection of subsets that are designated as open is changed, then this affects which functions are continuous, as well as which sets are compact and which sets are connected. A choice of subsets to be called open is a topology.

Which of these two versions is better? Jrheller1 (talk) 15:07, 31 March 2019 (UTC)

This does not belongs to this page but to Talk:Topology. Nevertheless the second version is slightly better, as the singular in "the definition of an open set" is confusing. Nevertheless both formulations are badly written. I'll propose a better version by editing the article. D.Lazard (talk) 15:16, 31 March 2019 (UTC)

Apr 2019

Math Portals

Which of these approx 30 Portals does the math project provide support to or are you interested in managing? From Category:Mathematics_portals.

1. Portal:Contents/Mathematics and logic
2. Portal:Algebra
3. Portal:Analysis
4. Portal:Angles
5. Portal:Applied mathematics
6. Portal:Areas of mathematics
7. Portal:Arithmetic
8. Portal:Category theory
9. Portal:Cryptography
10. Portal:Differential equations
11. Portal:Discrete geometry
12. Portal:Discrete mathematics
13. Portal:Equations
14. Portal:Functional analysis
15. Portal:Game theory
16. Portal:Geometry
17. Portal:Infinity
18. Portal:Information theory
19. Portal:Integrals
20. Portal:Irrational numbers
21. Portal:Knot theory
22. Portal:Mathematical optimization
23. Portal:Mathematics
24. Portal:Metallic means
25. Portal:Number theory
26. Portal:Probability distributions
27. Portal:Set theory
28. Portal:Tensors
29. Portal:Topology
30. Portal:Volume

Legacypac (talk) 22:45, 2 April 2019 (UTC)

Most of them seem reasonable, particularly those on specific areas of mathematics. I don't understand the purpose of 1 (same as Portal:Mathematics?), and the portals on 4, 13, 17, 19, 20, 24, 28 (which is a little broken), and 30 seem hyper-specific. They look like they are portals for essentially one article or about a topic that's not really cohesive (e.g. Portal:Equations is about any equation???). — MarkH21 (talk) 23:07, 2 April 2019 (UTC)

Name order for Chinese mathematicians

There is a move discussion at Talk:Tian Gang, with a disagreement about whether we should treat all mathematicians the same or all Chinese people the same in terms of their names. More input would be welcome. —Kusma (t·c) 07:33, 6 April 2019 (UTC)

Links to DAB pages

I have collected another batch of math(s)-related articles which contain links to DAB pages, where expert attention would be welcome. Search for 'disam' in read mode, or for '{{d' in edit mode; and if you solve one of these puzzles, post {{done}} here.

• Hybrid number  Done
• Metatheory  Done
• Separable algebra  Done
• Performance effects  Done
• Coulomb constant  Done

Thanks in advance, Narky Blert (talk) 01:19, 7 April 2019 (UTC)

Wow, performance effects is thick with management-speak. XOR'easter (talk) 15:34, 7 April 2019 (UTC)

Yes; but anyway, "sum of squares" there is just that... Boris Tsirelson (talk) 18:21, 7 April 2019 (UTC)

Another Portal

Wikipedia:Miscellany for deletion/Portal:Percentages Legacypac (talk) 06:39, 8 April 2019 (UTC)

Problems resulting from software that generates TeX code

A few years ago some software packages appeared on the web somewhere that generates TeX code for those who don't know how to do that by hand. I don't know what any of them are called, nor where or how they are found. But at first some of them generated code that looked as if it was written by someone with a major psychosis. That problem may have subsided. But we find things like this:

\dim\Sigma{\,>\,}4

I just fixed a whole bunch of things like that in the article titled Topological geometry.

Apparently one of these packages encloses binary operation symbols and binary relation symbols within {curly braces}, writing

a{+}b

instead of

a+b

and that affects what the reader sees, as follows:

${\begin{aligned}&a{+}b\qquad {\text{instead of}}\\&a+b\end{aligned}}$

(There are compelling reasons why TeX was designed to work that way, and I have found that some people don't know about those reasons.)

I suspect somebody sees that and "corrects" it by manually adding spaces, changing

a{+}b to a{\,+\,}b.

At any rate, multiple instances of the latter usage were in the Topological geometry article until I fixed them a moment ago.

Is there something that can be done to prevent this problem? Michael Hardy (talk) 18:23, 7 April 2019 (UTC)

@Michael Hardy: That notation has been present in the article from its very first version Special:PermaLink/812407777. However, its author Rboedi seems no longer active, so I doubt you'll manage to find out the reasons for it. --CiaPan (talk) 09:44, 8 April 2019 (UTC)

Here are more examples of backslash-comma-rightcurlybrace sequences (it uses a regular expression for the contents sought and an insource: magic word to search in the articles' definition instead of their rendered version) :

https://en.wikipedia.org/w/index.php?search=insource%3A%2F%5C%5C%2C%5C%7D%2F&title=Special%3ASearch&profile=advanced&fulltext=1&advancedSearch-current=%7B%7D&ns0=1

I have no idea of any solution to prevent such notation. --CiaPan (talk) 09:48, 8 April 2019 (UTC)

@CiaPan: I wonder if you missed the point. Not all instances of \,} are objectionable. The one I mentioned is objectionable for the reasons that I explained. Michael Hardy (talk) 19:46, 8 April 2019 (UTC)

@Michael Hardy: The above was kind of a proof of concept for my third approach to finding problematic math typesetting – and the first one going somehow towards useful results. I realize it was neither general enough nor specific enough – but it was just a try. If you don't like it, just forget it. I won't cry. And if you do, hopefully you'll be able to translate your objections' criteria to the language of regular expressions more precisely. --CiaPan (talk) 21:04, 8 April 2019 (UTC)

There is a chance that an Wikipedia:Edit filter could detect the syntax and give a warning. These are a little expensive so we really need to see how frequent it is to be worth the CPU time. Salix alba (talk): 21:55, 8 April 2019 (UTC)

Group theory: an oddly written sentence

See my remarks at Talk:Sims conjecture. Maybe someone here knows how to clean this up. Michael Hardy (talk) 17:40, 9 April 2019 (UTC)

Good news regarding the List of unsolved problems in mathematics

Every item in the List of unsolved problems in mathematics now has a bluelink, a reference or both. There's still an "other" section whose items could stand a proper classifying, if anyone feels like tackling that. XOR'easter (talk) 16:52, 7 April 2019 (UTC)

Invariant subspace problem is Functional analysis. Boris Tsirelson (talk) 18:24, 7 April 2019 (UTC)

Kaplansky's conjectures: the first (on group rings) is Algebra, the second (on Banach algebras) is Functional analysis. Boris Tsirelson (talk) 18:28, 7 April 2019 (UTC)

Erdős–Ulam problem and Scholz conjecture are Number theory.

Rendezvous problem is Game theory. Boris Tsirelson (talk) 07:38, 8 April 2019 (UTC)

Generalized star height problem is Formal language theory.

Kung–Traub conjecture is Numerical analysis. Boris Tsirelson (talk) 18:54, 8 April 2019 (UTC)

Thanks! I think all the sorting is done now. Work remains to be done on providing blurbs and copy-editing those that are currently there. XOR'easter (talk) 22:13, 8 April 2019 (UTC)

The current redlinks in the list: Taniyama's problems, Unsolved Problems on Mathematics for the 21st Century, DARPA's math challenges, Hartshorne conjectures, MNOP conjecture, Zariski multiplicity conjecture, Kung–Traub conjecture, Closed curve problem, Calluna's Pit, Birkhoff conjecture, Quantum unique ergodicity conjecture, Guralnick–Thompson conjecture, density hypothesis, Keating–Snaith conjecture, and Mazur's conjectures. In the "solved since 1995" list, we have Erdős sumset conjecture, Babai's problem, Anderson conjecture, Beck's 3-permutations conjecture, Kauffman–Harary conjecture, Normal scalar curvature conjecture, Böttcher–Wenzel Conjecture, Nirenberg–Treves conjecture, Alon–Friedgut conjecture, Kirillov's conjecture, Kouchnirenko’s conjecture, Deligne's conjecture on 1-motives, Erdős–Stewart conjecture and Harary's conjecture. Some of these could be articles, and some could conceivably be redirects to (sections of) existing pages, while perhaps some should be trimmed completely. XOR'easter (talk) 22:49, 9 April 2019 (UTC)

Replacing 2D renders with 3D models for solids

As some of you may know, a couple months back, Commons added the feature of uploading .stl 3D models. When opened, these files can be interacted with: zoom in, pan around, etc (see the 3D model on the right). I think they would be a great addition to articles about shapes and solids, such as Cube and Mobius strip. I've already replaced some of the lead images with 3D versions, and I hope to add more.

There are some issues to note though: The 3D models aren't interactive on mobile, and smooth surfaces aren't well replicated (Wikipedia's 3D file viewer doesn't smooth things). – XYZt (talk  |  contribs) – 05:58, 31 March 2019 (UTC)

I reverted those changes. They are black and white and inferior quality, and not interactive within an article. Tom Ruen (talk) 05:43, 10 April 2019 (UTC)

A new newsletter directory is out!

A new Newsletter directory has been created to replace the old, out-of-date one. If your WikiProject and its taskforces have newsletters (even inactive ones), or if you know of a missing newsletter (including from sister projects like WikiSpecies), please include it in the directory! The template can be a bit tricky, so if you need help, just post the newsletter on the template's talk page and someone will add it for you.

– Sent on behalf of Headbomb. 03:11, 11 April 2019 (UTC)

Draft:Quantile

Any use? If not just ignore it and it will go away. Thanks. Legacypac (talk) 06:53, 11 April 2019 (UTC)

• I doubt that this is even remotely useful. Reyk _YO! 09:05, 11 April 2019 (UTC)

New article assistance

Hi. Dimension of a scheme was just created. While I can check for structure, sourcing and copyvio stuff, would appreciate someone with more knowledge on the subject to take a look and make sure it's notable, and well, correct. Onel5969 ^{TT me} 14:51, 16 April 2019 (UTC)

To editor Onel5969: The stub is correct, and the subject notable. However, I am not sure whether it deserves having a stand alone article, as the definition is a trivial generalization of the dimension of an algebraic variety, and AFIK, anything that can be said on this topic results immediately from the second and third definition/properties listed in the linked article. Thus we must consider merging the new article as a section of the older one. D.Lazard (talk) 15:23, 16 April 2019 (UTC)

Thank you for your feedback, D.Lazard. Since I'm not up to snuff to discuss a merger, I'll leave that to you good folks over here at this project. Onel5969 ^{TT me} 15:44, 16 April 2019 (UTC)

I think it's conceptually better to have a separate article. Of course, the notion is a generalization of dimension of an algebraic variety. But already stuff like codimenion do not have a counterpart in the variety case. It's similar to the way we have scheme (mathematics) or morphism of schemes as separate articles from variety ones. Note the article is more than a definition. -- Taku (talk) 05:05, 17 April 2019 (UTC)

"Where triangle's area is triangle's area"

Seeing a recent note about "well-intended vandals" I recall an anecdotal case from my childhood. Our guest asked me a geometric problem; I solved it and wrote for him a solution. He read loudly: "...where triangle's area is triangle's area" and asked me menacingly: what's this? I asked: where? He showed me a line: "...where $S$ is triangle's area". After a moment of confusion, I realized that for him "$S$" means "triangle's area" and is read "triangle's area" by an eternal global indestructible convention. And, looking at him, I realized that he would aggressively defend this position. Being just a teenager (not a professor yet) I preferred to escape.

Back to Wiki. I think many (non-mathematicians) believe that all mathematical notations are an eternal global indestructible convention. Seeing a formula slightly different from their textbook they just "fix the error". I see no way to solve this problem. Do you?

By the way, I guess, many think (likewise) that words of different languages are related by the canonical bijective correspondence. But this is not our problem. :-) Boris Tsirelson (talk) 05:30, 18 April 2019 (UTC)

No, there is no way to solve this problem. (If you want to feel depressed, the article binary tree is a particularly hopeless case.) But I like your anecdote! --JBL (talk) 11:18, 18 April 2019 (UTC)

Template:Did you know nominations/Xiuxiong Chen

Please take a look at Template:Did you know nominations/Xiuxiong Chen. Thanks! Dennui (talk) 04:19, 13 April 2019 (UTC)

• @David Eppstein and Michael Hardy:

Sounds like something that could be appropriate for WP:ITN (although maybe not of wide enough interest), although they both look like they are eligible for WP:DYK. — MarkH21 (talk) 04:22, 13 April 2019 (UTC)

• Could be interesting for DYK, but I refuse to review DYKs that do not already have their full complement of QPQs. That's just laziness and I don't want to enable it. —David Eppstein (talk) 05:27, 16 April 2019 (UTC)

What are QPQs? Thanks. Dennui (talk) 15:16, 18 April 2019 (UTC)

See WP:QPQ and Quid pro quo.

I can do it. Dennui (talk) 15:58, 19 April 2019 (UTC)

Article product rule

Hello! In a book by Ivan Niven there is a proof which is probably the best proof of the product rule for beginners. It's not presented there. I would like to show it on the page, but English is not my native language, and I don't know how to paraphrase it very well. Would anyone be interested in adding it to the article? (for the benefit of the freshmen!). Dennui (talk) 19:26, 3 April 2019 (UTC)

Another think... In a book by Vladimir Arnold he shows a geometric interpretation of the product rule (with a rectangle... you know that image?...), which makes it "obvious". Dennui (talk) 19:27, 3 April 2019 (UTC)

Comments about a specific article belongs on that article's talk page. So please raise this issue instead at Talk:Product rule. Better yet, add the proof yourself, with citation, and let a more proficient English speaker clean up your text. Mgnbar (talk) 19:41, 3 April 2019 (UTC)

Thank you. I will do that. I just need to get some time (lots of exams already, on ring theory, calculus III, differential equations, etc... xD) Thanks again! Dennui (talk) 19:43, 3 April 2019 (UTC)

Which is the best proof for beginners made depend on which kind of beginner it is. I like this one: side of a rectangle moves while remaining parallel to where it was, thus causing the sides that it meets to grow or shrink. Now let two sides move. And then: The length of the side times the rate at which it moves equals the rate at which the area grows, but it's two sides. The lengths are ƒ; and g; the rate of growth of the side of length ƒ is g′ and the rate of growth of the side of length g is ƒ′. Michael Hardy (talk) 17:41, 4 April 2019 (UTC)

The length of the side times the rate at which it moves equals the rate at which the area grows should be "The length of the side times the rate at which it moves in the direction away from the other side and perpendicular to itself equals the rate at which the area grows." — MarkH21 (talk) 19:42, 4 April 2019 (UTC)

@MarkH21: It can move toward the other side, and then we would say that its rate of motion is negative. Michael Hardy (talk) 21:37, 5 April 2019 (UTC)

Yes, but my point was that movement parallel to the side won't change the area! Unimportant pedantry though. — MarkH21 (talk) 04:51, 6 April 2019 (UTC)

@Michael Hardy: That's essentially Arnol'd argument! Dennui (talk) 16:13, 19 April 2019 (UTC)

By the way, Niven's is more algebraic and is better than the ones presented. A guy named Howard Levi presents an algebraic one in his unusual calculus textbook. Dennui (talk) 16:14, 19 April 2019 (UTC)

Markov chain central limit theorem

I have created a new article titled Markov chain central limit theorem. It could use more work. In particular

• cited references
• So far just three articles link to it.
• Possibly a proof.
• Categories? I've included a bunch of these, but might I have missed some that will be obvious to others?

Michael Hardy (talk) 19:22, 20 April 2019 (UTC)

MathGenealogy link

I swapped the link in the {{mathgenealogy}} template (widely used in our biographies of mathematicians) from NDSU to AMS; please discuss this change at Template talk:MathGenealogy. —David Eppstein (talk) 20:08, 20 April 2019 (UTC)

Proposed restructuring on articles on plane curves

There is a discussion on the overlap and naming of the articles: algebraic curve, plane curve, curve, and differential geometry of curves (especially the first two). Much of the discussion is about the focus on plane curves in algebraic curve and curve. Some restructuring needs to be done because of the overlaps and redirects. — MarkH21 (talk) 05:06, 15 April 2019 (UTC)

(The discussion has been moved to the above link.) -- Taku (talk) 23:21, 20 April 2019 (UTC)

Conglomerate (set theory)

Here is an AfD that could use additional attention from those with expertise in mathematics and set theory. Eozhik (talk) 14:57, 21 April 2019 (UTC)

• Opinions of our experts in logic/set theory are very welcome there. Boris Tsirelson (talk) 05:34, 25 April 2019 (UTC)

Original research and examples in math articles

I'm pondering a rewrite of Discrete logarithm based on eight reliable sources that I've assembled at Talk:Discrete logarithm#Reliable sources. The rewrite raises some questions for me about what constitutes original research and plagiarism in math articles. Here are a few:

1. There is no mathematical reason to restrict the group to be finite, but all of the reliable sources (that I can find) do, so we must as well?
2. Therefore we cannot use the example G = {..., 1/100, 1/10, 1, 10, 100, ...}, which would otherwise be a very accessible example (because the discrete log there is just the common logarithm)?
3. Nor can we use the example of rational points on an elliptic curve? (Reliable sources do elliptic curves over finite fields.)
4. Reliable sources do examples in GF(2^4) and GF(3^2) but not GF(2^2), GF(2^3), etc. Can we do an example in GF(2^3), or would that be original research?
5. If we must pull our GF(p^k) example from GF(2^4) or GF(3^2), then must we use exactly the same instance of the problem? Or can we use a different base, for example?
6. If we must do exactly the same instance of the problem, then is there a danger of plagiarism?

I'm raising the issue here, because similar questions apply to many math articles, and I can't find specific policy. Mgnbar (talk) 14:20, 23 April 2019 (UTC)

Here you could apply WP:Common sense and WP:Be bold: if your new version is much better than the old one, you will not be reverted, or if you will, a compromise version could improve the article further. If your edit if controversial but can be modified for being an improvement, the discussion on the talk page, the precess WP:BRD can converge to a good result.

To answer to your specific questions and for getting an article that is not too technical, you must recall that for any element a of a group G denoted multiplicatively, the map $n\to a^{n}$ is a group homomorphism from $\mathbb {Z}$ to $G$ that induces an isomorphism from some $\mathbb {Z} /k\mathbb {Z}$ to some subgroup H of G. The discrete log is the inverse isomorphism. The two first examples of the article are the case where G is the group of positive real numbers. In this case, the discrete logarithm is simply a restriction of the usual logarithm of base a, and therefore does not deserve to be further studied. All what precedes is certainly not WP:OR, even if we are not able to source it exactly. So there is no reason for avoiding such examples. The example of $\mathbb {Z} /8\mathbb {Z}$ is also worth to be given, as the image H of the homomorphism has at most two elements, so the discrete logarithm is trivial. This explains why discrete logarithm is generally considered only when H is G or a large subgroup of it.

An other reason for which only finite groups are generally considered, is that the study of discrete logarithms is motivated by cryptography. So a large part of the study consists of searching for which finite groups the discrete logarithm is difficult to compute. So, it can be useful to give examples for which the discrete logarithm is not difficult to compute. D.Lazard (talk) 16:01, 23 April 2019 (UTC)

Another more trivial reason is that it should be a "discrete" logarithm, not just a logarithm in the usual sense from continuous mathematics. —David Eppstein (talk) 16:09, 23 April 2019 (UTC)

If the content you are adding is just a modest generalisation of well-documented material where the correctness of filling-in steps you make will be easily seen by mathematically well-informed editors, then I think this should be considered far from what Wikipedia intends original research to mean and furthermore not in need of additional sourcing. User:D.Lazard is right to reference WP:Common sense. I'm not clear just how far you want to go with your generalising, though

Wikipedia is meant to be a tertiary source; plagiarism is a non-issue.

A question in general: do we consider Wolfram MathWorld to be a reliable source? — Charles Stewart (talk) 19:06, 23 April 2019 (UTC)

It is widely used as a reference for at least certain kinds of articles. In my opinion this is not-so-good and it would be better to use better sources. The only time it's ever come up on WP:RSN seems to be this week, in a discussion of whether Wolfram Alpha is reliable. --JBL (talk) 19:18, 23 April 2019 (UTC)

I think there's a general sense that merely having an article on MathWorld isn't enough to merit a stand-alone article on Wikipedia (example). Nor is their choice of terminology always seen as reliable (example). XOR'easter (talk) 19:40, 23 April 2019 (UTC)

See WP:SCG, in particular the section Examples, derivations and restatements. It recommends that editors be given quite a lot of leeway. Jheald (talk) 21:40, 23 April 2019 (UTC)

Thanks, everyone. Special thanks to Jheald, whose link to WP:SCG is specifically what I wanted. Mgnbar (talk) 13:03, 25 April 2019 (UTC)

Be rash!

We are told to "Be bold" in editing. Not knowing algebraic geometry, I created a page called Kodaira map, redirecting it to Kodaira–Spencer map. If it needs further work, probably someone here knows what should be done. Michael Hardy (talk) 17:08, 18 April 2019 (UTC)

The redirect should be appropriate; I don't think there is a meaning of "Kodaira map" other than "Kodaira–Spencer" one. -- Taku (talk) 22:50, 20 April 2019 (UTC)

Sorry, I stand corrected. "Kodaira map" there means a map determined by a linear system. Authors in complex algebraic geometry use this terminology presumably motivated by Kodaira embedding while authors such as Hartshorne do not (I have therefore changed the redirect). -- Taku (talk) 23:38, 26 April 2019 (UTC)

Quasi-coherent sheaf on an algebraic stack

Another new article. Could use the eyes of you good folks here at this project. Thanks for taking the time.Onel5969 ^{TT me} 01:16, 27 April 2019 (UTC)

Versor

Versor (physics) has been proposed for deletion since April 18, and will probably be deleted (if nothing changes) today or tomorrow. Anyone want to save it? —David Eppstein (talk) 00:10, 25 April 2019 (UTC)

Surely "normalized vector" and "unit vector" are more common terms. I don't recall seeing "versor" being used to mean ${\hat {r}}={\vec {r}}/|{\vec {r}}|$ before. I'd suggest just making versor (physics) into a redirect to unit vector, but I doubt it's a common search query. XOR'easter (talk) 20:02, 25 April 2019 (UTC)

Someone removed the prod notice with the rationale that it survived AfD in 2016. I can't find this AfD. Rather than going through the whole rigmarole in order to delete an article that we don't need but which won't go away, I'm going to make it a redirect into unit vector. XOR'easter (talk) 16:29, 27 April 2019 (UTC)

Please do so. I don’t see how this is different from a unit vector. Also Scott Burley (talk · contribs) may have been looking at the talk page which seems to indicate that a user was planning on nominating the article for AfD without ever doing so. — MarkH21 (talk) 19:47, 27 April 2019 (UTC)

Talk:String theory#Semi-protected edit request on 29 March 2019

Hi! String theory is within this project's scope, so I was hoping somebody would have a look at the above edit request and implement/deny it as required. I understand pretty much nothing the abstract for the source is saying. Thanks in advance, NiciVampireHeart 22:36, 27 April 2019 (UTC)

I've weighed in (against), but I don't feel confident enough to close. — Arthur Rubin (talk) 23:36, 27 April 2019 (UTC)

(But string theory is't exactly math; it *uses* math but not math. -- Taku (talk) 01:10, 28 April 2019 (UTC))

That's why I didn't feel confident enough to close. The article says "perhaps" twice in the sentence in the body; essentially that the larger number may be the number of parameter sets, which may have associated vacuums (vacuua?). — Arthur Rubin (talk) 03:22, 28 April 2019 (UTC)

May 2019

Placing the Iterated function and Tetration pages on more solid mathematical ground

Folks, please check out my recent edits on the Iterated_function and Tetration pages as well as my comments at Talk:Tetration#Moving_towards_a_verifiable_article. Both pages suffer from liberal edits including non-attributable and nonverifiable mathematical content that have never been peer reviewed or published. I have five-year-old comments asking for people to fix their entries that have never been responded to. The content of the pages is ruled by politics, not Wikipedia policy. I would like to hear of better options than what I have offered. Thanks.

Daniel Geisler (talk) 19:04, 30 April 2019 (UTC)

Please disregard. Wikipedia is not the appropriate place for me to benefit people.

Daniel Geisler (talk) 08:10, 2 May 2019 (UTC)

Two-dimensional graph

This article is linked to in Curve (mathematics). I came to it because its title does not indicate what is the subject. The first sentence is "A two-dimensional graph is a set of points in two-dimensional space". For me, a set of points in two-dimensional space is called a plane figure. The content and the figures suggest that it what is intended by this title. The article does not contain any reference, and is tagged as such. What should be done with this article? My opinion is that it should be either deleted or redirected to graph of a function. But other advices would be useful. D.Lazard (talk) 17:00, 30 April 2019 (UTC)

It sounds both vague and non-standard. "Two-dimensional graph" could refer to a plane curve, a planar graph, a 2D plot, etc. In the absence of a uniquely good redirect, and without evidence that it is a common search term, I'd be inclined to delete it. XOR'easter (talk) 18:03, 30 April 2019 (UTC)

I second the deletion suggestion. Currently too ambiguous. — MarkH21 (talk) 18:25, 30 April 2019 (UTC)

I have prodded the article. D.Lazard (talk) 08:41, 2 May 2019 (UTC)

How about turning it into a disambig page? For me, the issue seems that the term can be ambiguous without context. -- Taku (talk) 23:53, 2 May 2019 (UTC)

Taku's suggestion done. D.Lazard (talk) 09:37, 3 May 2019 (UTC)

RD: Goro Shimura

Goro Shimura just passed away yesterday, so I have updated the article and made an RD nomination at ITN/Candidates. Comments and article improvements would be most welcome! — MarkH21 (talk) 10:45, 4 May 2019 (UTC)

Geometry of an algebraic curve

(Note there is Wikipedia:Articles for deletion/Geometry of an algebraic curve.) I have split-off some of content to separate articles (Severi variety (Hilbert scheme) and Hurwitz scheme) and merged the rest into Draft:Complete algebraic curve and its talkpage. This should solve the issue that the page looks too unfocused and for me, this seems like the most constructive steps instead of arguing about the page. I just sincerely hope we focus on the discussion and development of the content (not the history or the procedure). —- Taku (talk) 13:19, 22 April 2019 (UTC)

I never saw this article before it was deleted, so I cannot judge on what was there, but I find it alarming that some other editors seem to be ganging up on Taku and being mean to him. Taku's one of ur finest math editors, he's been here for over a decade, his work is top-notch, and I find it disturbing that some editors, who have never-ever contributed to any math articles, can just pop up and commit these kinds of drive-by vandalism-by-deletion. I don't like this, I don't like it at all. I think its deeply and fundamentally wrong. 67.198.37.16 (talk) 18:09, 4 May 2019 (UTC)

A typesetting software bug

In Nowhere-zero flow we find this code:

0&nbsp;<&nbsp;|''φ''(''e'')|&nbsp;<&nbsp;''k''

With a certain window geometry, one sees this:

0 < |

φ(e)| < k

To say the least, the line-break is in a very very bad place. But "&nbsp;" is supposed to prevent that. Michael Hardy (talk) 18:29, 5 May 2019 (UTC)

@Michael Hardy: not at all – “|” is a punctuation mark, that is, line break is allowed after it. Unfortunately, some faction of en.Wikipedians persists with the use of bare text as mathematical formulas. Such thing could be acceptable for certain special kinds of notation—such as A ∨ ¬A—but leads to misery for common mathematics. For the latter, importantly, sans-serif fonts are ill-advised. Incnis Mrsi (talk) 21:57, 5 May 2019 (UTC)

@Incnis Mrsi: What do you take to be the pros and cons of A ∨ ¬A versus ${\textstyle A\vee \lnot A}$? Michael Hardy (talk) 00:59, 6 May 2019 (UTC)

“A” and “A” and “$A$” have not much difference between each other. But, while both “ln x” and “$\ln x$” look more or less good, “ln x” is strikingly unprofessional, not only with ugly letters but overextended whitespace also. Modern students perhaps are more accommodated to illegible letters, than myself, because developers of Beamer supplied the class with sans font—by default—for some bizarre reason. Incnis Mrsi (talk) 05:54, 6 May 2019 (UTC)

Your third capital A looks a lot bigger than the other two. Michael Hardy (talk) 23:13, 6 May 2019 (UTC)

You could possibly try surronding the whole expressions in {{Nowrap}}. You will need to use {{abs}} or {{pipe}} to replace the verticle bars. Using the {{abs}} template might work without the nowrap as the remplate adds some hair-spaces which might prevent line breaking. --Salix alba (talk): 14:21, 6 May 2019 (UTC)

Alternatively to escaping the vertical bars one could use {{nowrap begin}} and {{nowrap end}} directly. – Tea2min (talk) 14:58, 6 May 2019 (UTC)

An “expert” on spinors and tensor algebra

Hi.
Wrote a wall of text on talk:Spin group #Incorrect use of “⊗” while their notation is clearly wrong. Incnis Mrsi (talk) 18:18, 3 May 2019 (UTC)

I wrote a wall of text since, apparently, you do not actually know how to construct a quotient algebra of a tensor algebra. I really do not want to get into a hostile argument over this stuff -- there are plenty of published textbooks in representation theory that explain this -- and also pretty much any text that explains how to construct the symmetric algebra or the exterior algebra or the clifford algebra, etc. out of the tensor algebra. This is quite wide-spread, and foundational for lots of math/physics applications. 67.198.37.16 (talk) 20:37, 3 May 2019 (UTC)

Whether do I know how to make quotient stuff is irrelevant. The point is that a mathematician reading allegations that e₁ ⊗ e₂ = −e₂ ⊗ e₁ is somewhere a true statement becomes confused. Should a student learn what does “⊗” mean to subsequently solve such quizzes? Incnis Mrsi (talk) 20:55, 3 May 2019 (UTC)

See talk page. It's been removed. For a long-term solution, I think a low-brow article on the construction of quotients of tensor algebras is in order; lets continue conversation at Talk:Spin group. 67.198.37.16 (talk) 18:13, 4 May 2019 (UTC)

I'm not sure about "low-brow" but we certainly lack an algebra-version of presentation of a group and presentation of a module, which should probably be called a presentation of an algebra. -- Taku (talk) 23:43, 4 May 2019 (UTC)

@TakuyaMurata: I don’t think that anything like free presentation would be helpful to explain how to construct an associative algebra (such as Clifford algebra) off tensor algebra as a quotient. My proposal is to render references to “quotient algebra” as a link to quotient ring for the time being. Writing a new article for the case grazes the domain of original research, whereas quotient algebra considers a way abstract stuff having little in common with quotient over ideals. Incnis Mrsi (talk) 16:39, 5 May 2019 (UTC)

Constructing an algebra out of generators and relations is definitely not an original research; I do agree with User 67.'s assessment that Wikipedia seems to lack an article on the subject. A separate article is appropriate just as presentation of a group is not part of quotient group. Maybe a better article title is "algebra defined by generators and relations" (and we're allowed to rename it as we like).

About quotient algebra: I don't believe "quotient algebra" in the sense in universal algebra is a primary topic and therefore the page should be redirected to quotient ring (and the current article be moved to quotient algebra (universal algebra).) -- Taku (talk) 22:59, 5 May 2019 (UTC)

A disambiguation page on “quotient algebra”, perhaps? Incnis Mrsi (talk) 05:54, 6 May 2019 (UTC)

A disambig page is fine too but I just did a Google search and very few instances of the use in universal algebra came up and that suggests a redirect is better. -- Taku (talk) 23:05, 6 May 2019 (UTC)

We do have algebra extension, which is closely related but is a still *somehow different* notion (different, in the same way, we distinguish between group presentation and group extension) -- Taku (talk) 00:46, 5 May 2019 (UTC)

Please can an expert disambiguate the incoming links to the new disambiguation page Quotient algebra? As the meanings are easily confused, I'd rather not guess. Thanks, Certes (talk) 11:25, 8 May 2019 (UTC)

 Done I have disambiguated all these links. Not surprisingly (for me), when the links was intended to quotient (universal algebra), I had generally to further edit the article for fixing some errors, such as "the kernel of a homomorphism" is a subalgebra. D.Lazard (talk) 14:40, 8 May 2019 (UTC)

RfC, of a sort

Smarandache came up at Talk:Jean-Pierre Petit2021/December#Request for comment (which came to my attention here), so it may be of interest to the community here. XOR'easter (talk) 17:57, 8 May 2019 (UTC)

"of a sort", indeed! --JBL (talk) 18:58, 8 May 2019 (UTC)

I tried to come up with a more precise description, but nothing quite did it justice.

There may also be WP:BLP issues with that article, with claims and counter-claims about academic misconduct cited to unreliable primary sources. This isn't a good week for me to put time into sorting out a mess like that, though. XOR'easter (talk) 20:44, 8 May 2019 (UTC)

Unknown Symbol

Hey, WikiProject Math,

I was reading an article and came across a mathematical symbol that looks like a fork or trident, placed on its side like an "E". Can anyone tell me what this is? I wasn't even sure where to look for an explanation and the article didn't explain what it meant. Thanks, anyone. Liz ^{Read! Talk!} 03:01, 9 May 2019 (UTC)

Never mind. I found it at Table of mathematical symbols and it has to do with set membership (although that doesn't explain the equation I read). Liz ^{Read! Talk!} 03:10, 9 May 2019 (UTC)

Either copy the symbol over here (in context) or link to the article in which it appeared and tell us the section and line number. JRSpriggs (talk) 03:14, 9 May 2019 (UTC)

Watch out for the mob of angry villagers with $\pitchfork$ s! –Deacon Vorbis (carbon • videos) 03:28, 9 May 2019 (UTC)

@Liz: Presumably this is about the symbol $\in$ (indicating that an element is a member of a set)? (As opposed to $\subseteq$, indicating that one set is contained in another, or the Greek letter $\epsilon$, sometimes rendered less trident-like as $\varepsilon$.) Often it is easy to replace that symbol in context with English words. Can you point out the article where you found it? --JBL (talk) 11:42, 9 May 2019 (UTC)

What is a curve?

See Talk:Curve#What is a curve? for a discussion that concerns several articles.

See also Talk:Plane curve#Merge with algebraic curve? and Talk:Curve#Sections on differentiable curves for recent related discussions]]. D.Lazard (talk) 15:31, 9 May 2019 (UTC)

Interior solution

Members of this project may be able to assist at WP:Redirects for discussion/Log/2019 May 9#Interior solution. Certes (talk) 21:40, 9 May 2019 (UTC)

"Ramanujan prime corollary", possible OR

A few months ago, I had a brief exchange here with Reddwarf2956 about this addition to the article Prime gap, about something Reddwarf2956 calls the Ramanujan prime corollary. In addition to not understanding how their response answers my question (and so not being clear on the mathematical validity), I am worried about original research and self-promotion: the attribution at Ramanujan prime says The Ramanujan Prime Corollary is due to John Nicholson (uncited), and Reddwarf2956 signs their talkpage posts as "John W. Nicholson". I would be grateful if another editor could take a look to determine whether this content (at both Prime gap and Ramanujan prime) is meaningful, and whether it belongs in Wikipedia. (I have not tried to assess whether similar remarks have been added elsewhere.) --JBL (talk) 12:24, 14 May 2019 (UTC)

Reddwarf2956 has responded to this post by removing the cn and clarify tags at Prime gap -- more eyes would be welcome. --JBL (talk) 14:05, 14 May 2019 (UTC)

It does look like COI. But even disregarding COI, this "Ramanujan Prime Corollary" is not something mentioned anywhere except in this paper (with John W. Nicholson as co-author, plus note the email name). I haven't found anything about it anywhere else in mathematical literature so does not really belong here unless other evidence from RS can be given. I went and removed the content from both articles. — MarkH21 (talk) 02:59, 15 May 2019 (UTC)

Ok, thanks. (Maybe at some point Reddwarf2956 will discuss this so it will be easier to tell if there's any merit to inclusion.) --JBL (talk) 11:22, 15 May 2019 (UTC)

Voronoi pole

The article Voronoi pole is in dire need of attention from an expert, preferably in computational geometry.  --Lambiam 22:06, 16 May 2019 (UTC)

In particular, the illustration in that article is an atrocity. The problem resulted only from an incorrect aspect ratio. This is obviously one of those occasions when it's important to hvae the right aspect ratio. Michael Hardy (talk) 18:41, 17 May 2019 (UTC)

It should be rescaled with the horizontal scale reduced to about 42%. Since it is an svg image, that shouldn't be particularly hard. But there are other serious issues; please have a look at the talk page.  --Lambiam 20:18, 17 May 2019 (UTC)

Nested radicals

Possibly this anonymous editor is trying to say something, but obviously what was added is unsuitable for anything to be kept in its present form. Can someone who knows what Euler did with nested radicals decipher it and possibly clean it up? Michael Hardy (talk) 17:08, 13 May 2019 (UTC)

The assertion seems to be: If a and b are integers, then there exists rational numbers x and y such that ${\sqrt {a+{\sqrt {b}}}}={\sqrt {x}}+{\sqrt {y}}$ if and only if $a^{2}-b$ is a square. This is true; a proof follows. Nevertheless, I have not verified whether Euler gave a proof (in one direction my proof could certainly be given by Euler, but in the other direction, I uses Galois theory, which was unknown by him). In any case, this result is misplaced in the section about Landau's algorithm.

Proof: If x and y exist, then the left-hand side belongs to the field F generated by ${\sqrt {x}}$ and ${\sqrt {y}},$ which is a Galois extension. It follows that the conjugate ${\sqrt {a-{\sqrt {b}}}}$ belongs to the same field, and satisfies ${\sqrt {a-{\sqrt {b}}}}=\pm {\sqrt {x}}\pm {\sqrt {y}}$, since the automorphisms of F are obtained by simply changing the signs of one or two square roots. Then ${\sqrt {a+{\sqrt {b}}}}\;{\sqrt {a-{\sqrt {b}}}}={\sqrt {a^{2}-b}}=\pm (x^{2}-y^{2}).$ This shows that $a-b^{2}$ is a square. Conversely, ${\sqrt {a+{\sqrt {b}}}}$ is a root of $(x^{2}-a)^{2}-b=x^{4}-2ax^{2}+(a^{2}-b).$ If $a^{2}-b=d^{2},$ the polynomial may be rewritten $(x^{2}+d)^{2}-2x^{2}(a+d)=\left(x^{2}+d+x{\sqrt {2(a+d)}}\right)\left(x^{2}+d-x{\sqrt {2(a+d)}}\right).$ As the discriminant of both factors is $2(a-d)$ is follows that one can take ${\tfrac {a+d}{2}}$ and ${\tfrac {a-d}{2}}$ for x and y. D.Lazard (talk) 10:46, 14 May 2019 (UTC)

In fact, the easy part was already in the article, but needed also some deciphering. I have edited the article for making a specific section for the case of two nested square roots. D.Lazard (talk) 14:05, 14 May 2019 (UTC)

The assertion above and its "proof" are both wrong. Try a=0, b=1, x=0, y=1. 157.131.141.41 (talk) 14:16, 14 May 2019 (UTC)

Should be clear from context that a and b are both nonzero. This case is trivial. Reyk _YO! 14:20, 14 May 2019 (UTC)

Try a=3, b=1, x= 2(typo: should be 4), y=0. 157.131.141.41 (talk) 14:32, 14 May 2019 (UTC)

Um, that doesn't work. You mean x=4. And stop trying to pass off trivial cases where one of the numbers is zero as a counterexample. It's clear from context those aren't being considered. Reyk _YO! 14:42, 14 May 2019 (UTC)

a=3, b=1, x=1, y=1.157.131.141.41 (talk) 14:46, 14 May 2019 (UTC)

Huh, interesting. In fact, if a+sqrt(b)=4k^2 then x=y=k^2 will do. 31, 25,9,9 for instance. Or I wonder if there are counterexamples with irrational left and right hand sides. Reyk _YO! 15:26, 14 May 2019 (UTC)

It is implicit in D.Lazard’s argument that b is not a rational square (so that we really are dealing with a nested radical). —JBL (talk) 15:32, 14 May 2019 (UTC)

Euler argues (§672) that $x+y+2{\sqrt {xy}}=5+2{\sqrt {6}}\implies x+y=5$ and $2{\sqrt {xy}}=2{\sqrt {6}}$, because the rational parts must be equal and so must the irrational parts. This could probably be made rigorous but its later application relies on ${\sqrt {b}}$ to make the final terms irrational, which (as Reyk just said) fails when b is a square. Certes (talk) 16:05, 14 May 2019 (UTC)

@D.Lazard: I believe the proof is incorrect. We have that $a=7,b=2,c=6,x=6,y=1$ is a solution to ${\sqrt {a+b{\sqrt {c}}}}={\sqrt {x}}+{\sqrt {y}}$, but $5={\sqrt {a^{2}-b^{2}c}}\neq x^{2}-y^{2}=35$. Perhaps we could use an elementary proof: Assuming $c$ is not square, then $a+b{\sqrt {c}}=x+y\pm 2{\sqrt {xy}}$ implies that $a=x+y$ and $b^{2}c=4xy$, so $a^{2}-b^{2}c=(x-y)^{2}$. Pbroks13 (talk) 15:38, 17 May 2019 (UTC)

You are right, I'll fix the proof in the article. D.Lazard (talk) 16:17, 17 May 2019 (UTC)

Fixed and sourced to Euler. D.Lazard (talk) 17:17, 17 May 2019 (UTC)

I have completely rewritten the proof: no need of separate proofs for the "if" and the "only if" implications. This follows Euler's argument, although, for a rigorous proof I need some field theory, namely that 1 and ${\sqrt {c}}$ boom a basis of the $\mathbb {Q}$-vector space $\mathbb {Q} ({\sqrt {c}}).$ D.Lazard (talk) 12:24, 18 May 2019 (UTC)

Absolute number

The redirect Absolute number, which currently targets Absolute value, has been nominated for deletion at RFD. You are invited to join the discussion at Wikipedia:Redirects for discussion/Log/2019 May 19#Absolute number. Thryduulf (talk) 11:20, 19 May 2019 (UTC)

A possible Science/STEM User Group

There's a discussion about a possible User Group for STEM over at Meta:Talk:STEM_Wiki_User_Group. The idea would be to help coordinate, collaborate and network cross-subject, cross-wiki and cross-language to share experience and resources that may be valuable to the relevant wikiprojects. Current discussion includes preferred scope and structure. T.Shafee(Evo&Evo)^talk 02:55, 26 May 2019 (UTC)

Nomination of Portal:Number theory for deletion

A discussion is taking place as to whether Portal:Number theory is suitable for inclusion in Wikipedia according to Wikipedia's policies and guidelines or whether it should be deleted.

The page will be discussed at Wikipedia:Miscellany for deletion/Portal:Number theory until a consensus is reached, and anyone is welcome to contribute to the discussion. The nomination will explain the policies and guidelines which are of concern. The discussion focuses on high-quality evidence and our policies and guidelines.

Users may edit the page during the discussion, including to improve the page to address concerns raised in the discussion. However, do not remove the deletion notice from the top of the page. North America¹⁰⁰⁰ 21:11, 26 May 2019 (UTC)

Category problem

I was looking at a draft article with the {{Maths banner}} on it. I clicked on the Drafts link and was sent to Category:Draft-Class mathematics articles, which to my surprise was empty. I dug around and found the article at Category:Draft-Class mathematics pages. Is there a way that the banner can be changed? The "articles" category appears to be the standard page (for {{category class}} as well) but for some reason it gets sent to the "pages" category.--Auric talk 16:08, 26 May 2019 (UTC)

@Auric: I was excited to see a post about categories, but then became sad when I realized it was about categories. But seriously, I don't see why that would be a problem; I'm unsure what's actually going on from a technical standpoint. I can try to take a look around if you want, but I'm not really an expert with this stuff. –Deacon Vorbis (carbon • videos) 16:41, 26 May 2019 (UTC)

This sounds like a simple matter of changing |ASSESSMENT_CAT = mathematics pages to |ASSESSMENT_CAT = mathematics articles in {{Maths banner}} but I'm not sure what else that might affect. The only other page that would obviously need editing is WP:WikiProject Mathematics/List of math draft pages. Certes (talk) 16:59, 26 May 2019 (UTC)

Thanks. I don't know how I missed that.--Auric talk 22:16, 27 May 2019 (UTC)

An edit to Gamma function

I am suspicious of this edit. I cleaned up the formatting and added a "citation needed" tag. The editor is User:Lewisbrito; the alleged fact added is attributed to "Hamilton Brito", and Google finds this page belonging to "Hamilton Brito (Lewis)". Is this "OR"? And is the mathematics correct? (I haven't yet even reached the point of looking closely at what it says yet.) Michael Hardy (talk) 18:40, 28 May 2019 (UTC)

• I played around a bit with this on Wofram Alpha and as far as I can tell it is correct. I can't find a source for it though and, even though it's a pretty result, I'm not sure how important it is. Reyk _YO! 19:11, 28 May 2019 (UTC)

COI edit request 29-MAY-2019

There is currently an edit request from an editor with a conflict of interest pending in the Gray code article which requires a math background, in particular, a knowledge of the reflected binary code used in that numeral system. Any editors who might be able to review this request would be most appreciated.  Spintendo  01:04, 30 May 2019 (UTC)

Jun 2019

Nail H. Ibragimov

A new article on mathematician Nail H. Ibragimov has been nominated for deletion. Feel free to weigh in with your opinions at the AfD, but I have a different request. In the current version of the article, at the bottom in the "Further reading" section, there is a link to a three-page biography of Ibragimov, in Russian, published for his 70th birthday. I think it would be useful in expanding the text of our article, but I don't read Russian and (as an image of a printed document rather than web text) it's inconvenient to run through an automatic translator. Would someone who does read Russian like to give it a try? —David Eppstein (talk) 20:59, 1 June 2019 (UTC)

You may be able to run the images of Russian text through OCR software, either locally or online. I tried onlineocr.net which normally works well but it failed to give any useful results from these images. Certes (talk) 22:01, 1 June 2019 (UTC)

Update: the images are PNG, which onlineocr.net doesn't handle. Converting them to JPG then putting them through onlineocr.net produces Russian text almost ready for automatic translation, though it could do with being cleaned up by a Russian speaker first. Other OCR tools may handle PNG directly. Certes (talk) 22:26, 1 June 2019 (UTC)

If so, please make the text (in Russian or English) available (on that talk page, or otherwise); then I should be able to clean it up. Though, it is 3 pages long. What really do we want there? By the way, the corresponding article in Russian wikipedia is short. Boris Tsirelson (talk) 22:29, 1 June 2019 (UTC)

Something about his career after he finished his Dr.sci. might be helpful. E.g. how did he end up in South Africa and why did he move from there to Sweden? Also, is Rustem Khamitov his step-son? —David Eppstein (talk) 22:46, 1 June 2019 (UTC)

I see.

Wow, no need in OCR! The PDF file is available for download on the same cite; I just copied its text to our talk page. Boris Tsirelson (talk) 04:13, 2 June 2019 (UTC) English translation added. But I am not guilty if David's questions remain unanswered.   :-)   Boris Tsirelson (talk) 05:54, 2 June 2019 (UTC)

Nomination of Portal:Geometry for deletion

A discussion is taking place as to whether Portal:Geometry is suitable for inclusion in Wikipedia according to Wikipedia's policies and guidelines or whether it should be deleted.

The page will be discussed at Wikipedia:Miscellany for deletion/Portal:Geometry until a consensus is reached, and anyone is welcome to contribute to the discussion. The nomination will explain the policies and guidelines which are of concern. The discussion focuses on high-quality evidence and our policies and guidelines.

Users may edit the page during the discussion, including to improve the page to address concerns raised in the discussion. However, do not remove the deletion notice from the top of the page. North America¹⁰⁰⁰ 23:25, 2 June 2019 (UTC)

Covering lemma and Core model

Should the article covering lemma and core model be merged? Neither has enough context that I can be sure I understand them, and both seem to make little sense without the other. I am a set theory expert, but am not good with large cardinals.... — Arthur Rubin (talk) 16:45, 3 June 2019 (UTC)

No, I don't think they should be merged. The core model K, as I understand it, is a slightly imprecisely defined term in the most general case. It becomes well-defined when you have some smallness assumption on the universe. For example, if 0# does not exist, then the core model is just L. If there is no measurable cardinal, then the core model is the original Dodd–Jensen core model, obtained by starting with L[U] and iterating the measurable up out of the top of the universe. And on and on, adding a smallness assumption that says large cardinals just beyond the ones you're studying don't exist.

With no smallness assumption, I've never managed to get the folks who understand this stuff to completely nail themselves down on whether the notion is precisely defined, but they throw around terms like "the union of all L[E] models where E is an extender sequence".

In any case, the core model is a notion of an inner model that fills out everything you can fill out just by adding large cardinals.

The covering lemma, on the other hand, is a flexible name for a theorem, which is quite a different thing from a flexible name for a model. The original covering lemma is the one that applies to L if 0# does not exist. I don't think you would want to merge that with the article on L, would you? So merging the general name with the general article on K doesn't seem to make sense either. --Trovatore (talk) 20:00, 3 June 2019 (UTC)

Math community group

Anyone interested in an international math community group https://meta.wikimedia.org/wiki/Wikimedia_Community_User_Group_Math ? --Physikerwelt (talk) 21:41, 4 June 2019 (UTC)

A proposal for WikiJournals to become a new sister project

Over the last few years, the WikiJournal User Group has been building and testing a set of peer reviewed academic journals on a mediawiki platform. The main types of articles are:

• Existing Wikipedia articles submitted for external review and feedback (example)
• From-scratch articles that, after review, are imported to Wikipedia (example)
• Original research articles that are not imported to Wikipedia (example)

Proposal: WikiJournals as a new sister project

From a Wikipedian point of view, this is a complementary system to Featured article review, but bridging the gap with external experts, implementing established scholarly practices, and generating citable, doi-linked publications.

Please take a look and support/oppose/comment! T.Shafee(Evo&Evo)^talk 11:09, 5 June 2019 (UTC)

For us mathematicians, two mathematical examples (out of two existing, do not blame me for the choice): Spaces in mathematics (external review and feedback); Can each number be specified by a finite text? (explanatory essay, submitted, not to be imported to Wikipedia). Boris Tsirelson (talk) 17:34, 5 June 2019 (UTC)

English versus European terminology

Several years ago there was a lengthy argument between myself (under my old username "SharkD") and another user (User:Ag2gaeh) over the usage of terminology related to 3D projection and descriptive geometry, especially the terms "Axonometry" and "Axonometric projection". However there seems to be a difference in English sources versus European sources. For instance, I did two brief surveys of English language sources (#1, #2), but the European literature seems to differ in many ways. I was wondering if someone could take a look into the topic. There also seems to be a language issue, in that the original author of Axonometry is not fluent in English, so I'm not clear exactly on how the literature differs, except that "axonometry" in Europe seems to include all types of parallel projection, not just a few types as is common (but not universal) in English sources. In general I am wondering if we should switch over to the European terminology. ➧datumizer  ☎  09:32, 29 May 2019 (UTC)

Some specific questions:

• Are parallel projection and axonometry/axonometric projection synonymous?
• Do the terms isometric, dimetric and trimetric apply equally to oblique projections?
• Do the terms orthographic and orthogonal refer to the angle between the viewing direction and the projection plane, or to the angle between the principal faces of an object (for instance a cube) and the projection plane?

Thanks. ➧datumizer  ☎  09:58, 29 May 2019 (UTC)

@Datumizer: A minor note about 'steps' order dependency' in Axonometry#Principle of axonometry: the clause refers to three bulleted sub-steps inside the step 3, not to steps 1 through 4 – started from zero-zero you can go by x in the X direction, then by y in the Y direction or the other way, and you'll get to the same (x, y) point. Similarly you can make the Z step before, between or after X & Y steps and finally get to the same (x, y, z). --CiaPan (talk) 10:29, 29 May 2019 (UTC)

I have renamed sub-steps. :) CiaPan (talk) 10:34, 29 May 2019 (UTC)

As far as I know, the terms "axonometry" and "axonometric" are no more in use in mathematics, except for describing applications to graphics. Presently these are terms specific to graphical representation, typically in architecture and industrial design. So, for the most usual meanings to the terms, you must consider sources in specialized areas. In mathematics, the reliable (for this question) sources that you can find are probably more 100 years old, and thus not reliable for a modern encyclopedia.

About your first specific question: Translated in modern mathematics language, Axonometry#Principle of axonometry defines axonometry as an affine mapping of the 3D-space onto a plane. Pohlke's theorem means that these affine mappings are the composition of a parallel projection and a similarity (this is explicitly said on this article. This answers your first question, by no. Similarity must not be forgiven, as the graphical representation of a building cannot be the result of a parallel projection (at least because of the respective sized of the building and the paper sheet). — Preceding unsigned comment added by D.Lazard (talk • contribs) 12:01, 29 May 2019 (UTC)

So, are you saying that parallel projections can include representations of objects that are dissimilar? Or, that parallel projections are never scaled up or down and are always 1:1 representations of objects? Which is greater in scope? ➧datumizer  ☎  03:20, 30 May 2019 (UTC)

A parallel projection of a sphere is a circle of the same radius. As buildings contain generally sphere of large radius, a parallel projection of a building cannot fit in a paper sheet without being scaled, and scaling is a similarity. In summary, Pohlke's theorem asserts that "axonometry", "affine map from 3D to 2D", and "composition of a parallel projection and a similarity" are three synonyms. On the other hand two non-similar plane figures may have the same image by axonometry: clearly a plane figure and its image by a parallel projection have the same image by the same parallel projection; they are similar if and only if the plane of the figure is perpendicular to the direction of projection in general, they are not similar if the planes of the figure and its image are not parallel. D.Lazard (talk) 09:35, 30 May 2019 (UTC)

@D.Lazard: Is it assumed the projecting rays are perpendicular to the projection plane? Because if they needn't, then your last sentence is false: an arbitrary planar figure will be similar (actually: congruent) to its parallel projection if (but not only if, in special cases) the figure plane is parallel to the projection plane, for arbitrary projection direction (not parallel to the plane, of course). --CiaPan (talk) 09:46, 30 May 2019 (UTC)

You are right, I have been too fast by writing my post. I have corrected it. About the "only if": It is clear that the projection of a line is always similar to it. I guess (I have not checked the details) that "if and only if" is true for bounded plane figures that are not contained in a line. D.Lazard (talk) 10:27, 30 May 2019 (UTC)

If you look at the illustrations in Axonometry, the three projected coordinate axes may generally go in any direction, and be scaled (foreshortened) to any length. This is not possible if the two planes must always be parallel. (In fact, there is a name for when the planes are not parallel: Oblique projection, a sub-class of axonometric projection according to European literature.) ➧datumizer  ☎  06:38, 1 June 2019 (UTC)

Anyway, it seems parallel projection amounts to a specific case of axonometric projection (if we agree that coincidence is a type of similarity), and that the latter has greater scope than the former. That clears things up for me, thanks. However, if we look at my survey of English sources (#1, #2) there is little agreement with this taxonomy. And this is also the case currently with English Wikipedia. What should we do? Should we just ignore the problem? ➧datumizer  ☎  06:46, 1 June 2019 (UTC)

• Parallel projection is defined without coordinate axes and coordinates. It includes orthogonal (normal) and oblique projections.

In German textbooks

• Axonometrie is a centuries old procedure generating a picture of a 3D-object using coordinate axes and coordinates. The latter are usually given implicitely by a pair of "zugeordnete Risse" ("Grundriss, Aufriss", which are connected orthogonal projections). The result of the axonometric procedure is a parallel projection + a uniform scaling (Pohlke's theorem). The so generated parallel projection is oblique or orthogonal. If one wants to generate an orthogonal projection, only the images of the coordinate axes can be prescribed (and not the foreshortenings !) , see the German article on orthogonale Axonometrie)

In English textbooks an axonometric projection seems to be always an orthographic (orthogonal)) projection.

• Mehrtafelprojektion (multiview projection ?) means 3 or more "zugeordnete Risse" ("Grundriss, Aufriss, Kreuzriss, ..."). If one deals with "Grundriss" and a connected "Aufriss" one calls it "Zweitafelprojektion". --Ag2gaeh (talk) 08:08, 1 June 2019 (UTC)

Addendum: An essential practical improvement of the procedure Axonometrie is the "Einschneideverfahren" (or "Schnellriss"), which is due to the Austrian mathematican Ludwig Eckhart. It omits determining single coordinates and their foreshortenings and facilitates marking image points.--Ag2gaeh (talk) 14:16, 1 June 2019 (UTC)

So, how should we proceed from here? ➧datumizer  ☎  21:04, 6 June 2019 (UTC)

It seems to me (see list of Your excerpts, above), that there are no clear definitions on axonometry in English literature. As I have no English text books to check and compare terms, I refrain from further editing on this subject.--Ag2gaeh (talk) 11:20, 7 June 2019 (UTC)

Wikipedia:WPM listed at Redirects for discussion

An editor has asked for a discussion to address the redirect Wikipedia:WPM. Please participate in the redirect discussion if you wish to do so. Steel1943 (talk) 15:37, 13 June 2019 (UTC)

Formulas in captions

I've started a discussion at WT:Manual of Style/Captions#Formulas in captions that may be of interest to folks here. –Deacon Vorbis (carbon • videos) 01:58, 17 June 2019 (UTC)

On a certain bug in our not-actually-LaTeX software

I found this in the article titled Random variable:

$\mathrm {ess} \sup _{\omega }|X(\omega )-Y(\omega )|$

It was coded like this:

\mathrm{ess } \sup_\omega|X(\omega)-Y(\omega)|

$\mathrm {ess} \sup _{\omega }|X(\omega )-Y(\omega )|$

I changed the code to this:

\operatorname{ess} \sup_\omega|X(\omega)-Y(\omega)|

But ideally, one would like to see this:

\operatorname*{ess sup}_\omega|X(\omega)-Y(\omega)|

This works in LaTeX, but it doesn't work here, in this software that people sometimes incorrectly call "LaTeX":

$\operatorname {*} {esssup}_{\omega }|X(\omega )-Y(\omega )|$

That same code, in genuine LaTeX, would yield something about like this:

${\underset {\omega }{\operatorname {ess} \sup }}|X(\omega )-Y(\omega )|$

But here we have to code that as follows:

\underset \omega {\operatorname{ess} \sup} |X(\omega)-Y(\omega)|

I don't like doing that in lots of Wikipedia articles because some day this bug may be fixed and in fact people do learn how to code these things by looking at code that they find here.

I think this has been reported (I seem to recall having reported it a couple of years ago), and that means some time before the 29th century developers may get to it, or may not. Can anything be done to get this attended to besides hoping that developers who don't understand the need understand the need? Michael Hardy (talk) 21:14, 15 June 2019 (UTC)

I've noted this, and probably reported it as well, but kind of lost hope with respect to math rendering stuff getting improved, or even fixed. –Deacon Vorbis (carbon • videos) 01:57, 17 June 2019 (UTC)

I think this is T185552. There are some workarounds on the bug page.

The long term solution is to remove the texvc system completely, but this is a complex task. There has been progress towards this via T195861. We have now sanitized the syntax removing all deprecate syntax on almost all wikis. This allows texvc to be removed without breaking anything. --Salix alba (talk): 06:45, 17 June 2019 (UTC)

@Michael Hardy: You can achieve this:

$\operatorname {\underset {\omega }{ess\ sup}} |X(\omega )-Y(\omega )|$

with:

\operatorname{\underset \omega {ess\ sup}} |X(\omega)-Y(\omega)|

(based on a workaround description Help:Displaying a formula#Starred operatorname \operatorname*). --CiaPan (talk) 10:29, 17 June 2019 (UTC)

≘

The redirect ≘ (U+2258 CORRESPONDS TO) which currently targets Binary relation has been nominated for deletion at Wikipedia:Redirects for discussion/Log/2019 June 18#≘, your comments in that discussion would be appreciated. Thryduulf (talk) 17:11, 18 June 2019 (UTC)

Mathematical formalism

Please can someone review the few remaining links to dab Mathematical formalism and divert them to relevant articles or unlink? Thanks, Certes (talk) 15:11, 17 June 2019 (UTC)

• Domain of discourse: done. Boris Tsirelson (talk) 16:09, 17 June 2019 (UTC)
• Informal mathematics: done. Boris Tsirelson (talk) 16:15, 17 June 2019 (UTC)

Thanks! We have a similar problem with Correspondence (mathematics), which discusses specific types of correspondence and has now been tagged as a dab. Certes (talk) 15:42, 18 June 2019 (UTC)

I have edited Correspondence (mathematics) for using the standard style of dab pages. By the way, I have added 1:1 correspondence, and linked the entries that were tagged.

I have also disambiguated some links; a few by unlinking, when they refer to the common English meaning; those that appeared in a "See also" section, by removing the entry; the remainder ones by linking either to multi-valued function or to correspondence (algebraic geometry). Hoping that this summary can help those who will continue to dab the incoming links. D.Lazard (talk) 18:02, 18 June 2019 (UTC)

Thank you. We're now down to about a dozen links. I have boldly merged the incomplete disambiguation into Correspondence per WP:PARTIALDAB, and created a new redirect for the von Neumann meaning. Certes (talk) 18:57, 18 June 2019 (UTC)

Gap-Hamming problem

There is a new page titled Gap-Hamming problem. On the theory that "gap" is being used here as a common noun, I set the initial in lower case. If it's actually someone's name, then the article should say who that is and the hyphen in "gap-Hamming" should become an en-dash. I found no links to this article at all and added one to the "See also" section of Hamming distance.

So further work is needed. Michael Hardy (talk) 16:30, 24 June 2019 (UTC)

Sadly the original paper mentions neither gap nor Hamming. The other references are split between Gap and gap, often mixing them in the same paper, so I doubt that we are dealing with a Dr. Gap here. My first thought was that it might mean the "gap" between the strings, a vague and colloquial synonym for Hamming distance, but that would be tautologous, so I think it must refer to the communication gap which limits how much information Alice can share with Bob. I think we need a hyphen or even a space: "gap Hamming problem", i.e. the problem of estimating the Hamming distance over a gap, as used here and here. (That article can link in once we confirm the title.) Certes (talk) 17:19, 24 June 2019 (UTC)

That is entirely fair. The reference is not to a given name, but rather to the fact that there is an "allowable gap" in distance (of size roughly ${\sqrt {n}}$) where the answer can be indeterminate. So, the correct spelling should, indeed, be "gap-Hamming" following most English conventions, but as proper nouns are capitalized (and "Gap-Hamming" appears to have become its own term for an important problem in the field), I opted for capitalizing the G. I also added the dash (not an en-dash) as it appears to be customary in the field, but I agree with Certes that a space is likely the best possibility (though it is not standard when naming the problem in most papers).

Additionally, apologies, I'm not quite sure how to "properly" edit a talk page, so this might not be quite right :) Guilleunofficial (talk) 18:28, 24 June 2019 (UTC)

Zero divisors

Our article on Zero divisors may have some WP:NPOV problems, taking Bourbaki's choice to include 0 as a zero divisor as the "right" one, and being dismissive of those references that exclude it. In fact, in the four textbooks I checked (Gallian, Fraleigh, Rotman, and Dummit & Foote), every one of them excluded 0 in their definitions of zero divisors. I'm not sure of the best way to proceed, so I'll just leave this here, and anyone interested can take a whack at it. –Deacon Vorbis (carbon • videos) 17:36, 26 June 2019 (UTC)

Any ring element—0 included—is a divisor of itself, albeit a trivial divisor. Deacon Vorbis makes a project-wide problem off a linguistic nonce. Incnis Mrsi (talk) 18:19, 26 June 2019 (UTC)

The problem is that our article takes a WP:POV through its tone and its favoring of one source over others. This is not a problem that I created, but one that has existed at this article for some time. I posted here in order to seek assistance from other editors. If you have nothing constructive to offer, then please just keep it to yourself. –Deacon Vorbis (carbon • videos) 18:58, 26 June 2019 (UTC)

In Divisor#Definition, zero is not a zero divisor. On the other hand, in Regular sequence#Definition, zero is not a non-zero-divisor (and it is thus a zero divisor). D.Lazard (talk) 19:12, 26 June 2019 (UTC)

Jul 2019

Deletion

Wikipedia:Articles for deletion/ProofWiki got relisted and now deleted seemingly without any/much input from the math community. I just post that here in case anybody thinks it might be worth to revisit that deletion. Peronally I would have preferred to keep the article, although it could be hard to convince non-mathematics editors on the base of Wikipedia:GNG.--Kmhkmh (talk) 18:08, 4 July 2019 (UTC)

Footnotes request

I recently created an article: Hasse–Schmidt derivation. Boleyn insists that the article, which in my opinion has completely acceptable references, needs more footnotes. Any opinions on such a situation? Jakob.scholbach (talk) 20:44, 30 June 2019 (UTC)

It does have inline references, in a perfectly acceptable (parenthetical) style, in the lead and in two of its other sections. It is only the definition section that is missing inline references. —David Eppstein (talk) 20:47, 30 June 2019 (UTC)

I tend to agree that for very short, non-controversial (science) article based on a very few sources it is sufficient to simply add/list those source at the end of the article. Unfortunately there others which disagree with that, in particular there are "formalists" who need to see footnotes (inline references) for footnotes' sake. This imho partially tool driven, which autamically find/mark any new article not having footnotes, usually by editors having no relation or knowledge of the content.

I personally find this footnote formalism annoying, but it might not be worth to pick a fight about it and potentially waste time a lot of (frustrating) time on it. If you transform your sources into footnotes (even if that is hardly an imprivement), they usually move on to the next target and leave you alone.--Kmhkmh (talk) 18:00, 4 July 2019 (UTC)

You are missing the point. The article did have inline sources. They were merely in a different format than footnotes. WP:CITEVAR explicitly states that one should not be required to convert to a different sourcing format. —David Eppstein (talk) 19:26, 4 July 2019 (UTC)

Degrees of TeX literacy among Wikipedian mathematicians

In LaTeX, one finds \wedge and \bigwedge. The latter looks different in a "displayed" context from the way it appears in an "inline" context, not only in that it is somewhat smaller, but also in that any subscripts and superscripts appear to the right rather than directly above and below the symbol. Thus three forms, here exemplified:

$\omega =\sum _{i_{1}<\cdots <i_{k}}\omega _{i_{1}\cdots i_{k}}\,dy^{i_{1}}\wedge \cdots \wedge dy^{i_{k}},$

In full generality, let ${\textstyle \bigwedge ^{k}(df)^{*}}$ denote the kth exterior power of the dual map to the differential.

Following Dieudonne, there is a unique

$\sigma _{x}\in \bigwedge ^{m-n}T_{x}^{*}(f^{-1}(y))$

which may be thought of as the fibral part of ω_x with respect to η_y.

This afternoon I did a fairly large number of edits to Differential form, where I found quite a large number of occurrences of \wedge where \bigwedge should appear.

Is it possible that

• There are mathematicians who are not aware of these typographical distinctions? or
• There are mathematicians who do not know that LaTeX can routinely handle these things, and they should expect that so can the not-actually-LaTeX system used here? or
• There are mathematicians who don't know that by googling "latex symbols" you can find out how to type these things? or
• There are mathematicians who don't care about such things?

ok, So clearly such things are possible, but would one expect to encounter such things as frequently as one does here? Michael Hardy (talk) 20:59, 4 July 2019 (UTC)

I suspect that there is an element of truth in each of these statements, but the root cause I believe lies in the way that most of us learn LaTeX in the first place. Much like our students, we pick up just enough of the basics to write respectable (if not correct) math in our own fields and expand on this by looking at examples that we come across in our work. Few if any read manuals or guides, except when the need for a reference arises. This leads to a very spotty coverage of the language and, if you are writing outside of your specialty, you are likely to not be aware of the niceties. --Bill Cherowitzo (talk) 04:54, 5 July 2019 (UTC)

"except when the need for a reference arise." If this is not an obvious case of such a need arising, I wonder what is? Is it really possible to be unaware of the difference? Michael Hardy (talk) 05:26, 5 July 2019 (UTC)

Yes, knowledge of LaTeX is spotty. Also, most of the population (any population) lacks your attention to detail. Particularly on wikis, I find an attitude of "let's the content up there and let someone else clean it up". Further, I think that this attitude is productive. It's the avoidance of "perfect is the enemy of good". Cheers. Mgnbar (talk) 07:32, 5 July 2019 (UTC)

As far as I remember, I have never seen the notation $\bigwedge ^{m-n},$ always ${\textstyle \bigwedge ^{m-n}}.$ How should we proceed for having the second notation in the right size in display style? $\bigwedge {}^{m-n}$ is clearly to avoid, although I prefer it to $\bigwedge ^{m-n}.$ D.Lazard (talk) 09:35, 5 July 2019 (UTC)

In fact, it seems that $\bigwedge _{i=1}^{m-n}e_{i}$ is correct when the e_i are vectors, but $\bigwedge ^{m-n}E$ is incorrect, when E is a space, as it is the case in your (third) example. In any case, even if it may be correct, this is certainly confusing, as, for a non-expert, it is unclear whether the second and the third examples refer to the same concept. D.Lazard (talk) 09:57, 5 July 2019 (UTC)

The answer to my above question is ${\bigwedge }^{m-n}.$ I guess that this use of { } is not natural for most editors. D.Lazard (talk) 10:04, 5 July 2019 (UTC)

To editor Michael Hardy: I have fixed your changes in Differential form. If you have done similar changes in other articles, please fix them yourself. As this is notation for exterior algebra, I had a look to this article. It appears that this article uses \Lambda ($\Lambda$) instead of \bigwedge. It is unclear for me whether \Lambda must be changed into \bigwedge there or \bigwedge must be changed in \bigwedge in Differential form. This deserves a discussion. D.Lazard (talk) 10:36, 5 July 2019 (UTC)

Streamline upwind Petrov–Galerkin pressure-stabilizing Petrov–Galerkin formulation for incompressible Navier–Stokes equations

"Streamline upwind Petrov–Galerkin pressure-stabilizing Petrov–Galerkin formulation for incompressible Navier–Stokes equations" may be the most unusual article title I've seen. No other articles link to it. Probably if it ought to exist, it needs attention. Michael Hardy (talk) 02:07, 6 July 2019 (UTC)

All horses are the same color

A source would be ideal, but I think Staszek Lem (talk · contribs) is in the wrong here. More comments would be appreciated.--Jasper Deng (talk) 20:12, 7 July 2019 (UTC)

Η-pseudolinearity

The redirect Η-pseudolinearity, which currently targets Pseudoconvex function (where pseudolinearity also redirects) has been nominated for deletion at Wikipedia:Redirects for discussion/Log/2019 July 10#Η-pseudolinearity. The discussion needs attention from editors with relevant subject knowledge. Please leave your comments there. Thryduulf (talk) 20:58, 15 July 2019 (UTC)

This is terminology from optimization with which I’m not familiar but I chipped in based on what I could gather on Google. — MarkH21 (talk) 22:07, 15 July 2019 (UTC)

Unchecked erratas

Category:Articles unintentionally citing publications with errata has 3 articles with erratas that need to be double-checked to make sure the material cited still matches what the paper concludes. They're all the same publication article, I believe. Headbomb {t · c · p · b} 14:15, 17 July 2019 (UTC)

 Done The claim in question is much disputed; I replaced all three citations with a historical survey article that should still be useful even if the problem is one day resolved. XOR'easter (talk) 15:22, 17 July 2019 (UTC)

Two grammatical numbers:

This erratum is....

These errata are....

The word "errata" is plural. I've never seen "erratas" before. Michael Hardy (talk) 19:50, 17 July 2019 (UTC)

False position method

Should False position method be moved to Method of false position (the latter currently redirects to the former)? See Talk:False position method#Name of article. Johnuniq (talk) 04:00, 19 July 2019 (UTC)

Wikipedia:Meetup/Providence/NonlinearAlgebra 2018/ICERM

An attention should be paid to some of drafts created (and deleted) at this meetup. -— Taku (talk) 05:15, 19 July 2019 (UTC)

Template:Infobox mathematical constant

plz no mor infobox

Looing at articles in Category:Mathematical constants, many (like Apéry's constant) have ad hoc pseudo infoboxes. I think someone should create a Template:Infobox mathematical constant to standardize use (like {{Infobox mathematical statement}} and {{Infobox mathematics function}} ). – Finnusertop (talk ⋅ contribs) 17:42, 19 July 2019 (UTC)

Sounds reasonable. There has been much debate about mathematics-related infoboxes (infoboxen?) in the past, due largely I think to the fact that mathematics can be squishy and hard to summarize. The statement of who first posed a conjecture, for example, can become surprisingly subtle when the conjecture was made more precise over time, and that can be hard to express within the confines of an infobox. But basic information about mathematical constants can be codified pretty well, I suspect, and if ad-hoc infoboxes already exist, it would be better to standardize them. XOR'easter (talk) 18:10, 19 July 2019 (UTC)

(edit conflict) Infoboxes make the kitty sad. Please, think of the kitty. But seriously, the only ones I could find are some of the ones listed in the irrational number template. These should probably just be removed. It's hard to see why having the value in binary or hex is useful, and continued fractions aren't unique (unless in standard form, but other forms often exhibit nicer patterns and are more sought). Infoboxes have their place, but not here (or for mathematical statements). –Deacon Vorbis (carbon • videos) 18:17, 19 July 2019 (UTC)

The mathematical constant article is problematic from the very first sentence. No, a constant doesn't have to be "interesting in some way". All it has to be is constant. The definition is sourced to MathWorld, which is a decent source for mathematics, but a terrible one for naming. --Trovatore (talk) 18:19, 19 July 2019 (UTC)

I took a stab at rewriting that introductory sentence. XOR'easter (talk) 18:37, 19 July 2019 (UTC)

I like it a little better; at least "interesting" is gone. But who says a constant has to be definable? --Trovatore (talk) 19:28, 19 July 2019 (UTC)

But wait; who says that "a constant" is a well-defined mathematical notion? I doubt it. I suspect this is an informal idea, context-dependent term, which is why sometimes it is required (or not) to be notable, definable, etc. Boris Tsirelson (talk) 19:54, 19 July 2019 (UTC)

Exactly. That's why it shouldn't have a Wikipedia article. --Trovatore (talk) 20:14, 19 July 2019 (UTC)

Let me modify that a little bit. I could live with it as a list article — perhaps list of named mathematical constants or some such. My objection is trying to abstract out some underlying concept from them, to write a (non-list) article about. It's not that there's no concept there; it's that I don't think any such concept has a sufficiently standard treatment to write an article about. --Trovatore (talk) 20:25, 19 July 2019 (UTC)

For example, compare two phrases: "$\pi$ is an important mathematical constant" and "in this inequality, $C$ is an absolute constant". Do they use the same idea of "constant"? Boris Tsirelson (talk) 19:57, 19 July 2019 (UTC)

See above. --Trovatore (talk) 20:14, 19 July 2019 (UTC)

Another cynical question: what about "1 if ZFC is consistent and 0 otherwise"? Is this a mathematical constant? Boris Tsirelson (talk) 20:00, 19 July 2019 (UTC)

Yes. It's 1, which is constant, and mathematical. --Trovatore (talk) 20:15, 19 July 2019 (UTC)

If you still believe that "a constant" is a well-defined mathematical notion, please decide, which of the following statements are true: (a) "Every real number is a constant"; (b) "the class of all constants is a proper class (not a set)". And, how do you prove or disprove them? Boris Tsirelson (talk) 20:11, 19 July 2019 (UTC)

Not to mention that a reasonable fraction of the time people write that something is constant when they really mean that it is bounded (another thing that makes kitty sad). See e.g. constant time. —David Eppstein (talk) 21:50, 19 July 2019 (UTC)

N.B. We already have a List of mathematical constants. XOR'easter (talk) 21:59, 19 July 2019 (UTC)

Hmm, yeah, I think maybe mathematical constant should be merged into that article. In my opinion there is no abstract notion of "mathematical constant" for which there is a sufficiently standard body of knowledge to write a good Wikipedia article about. But the list article could be made a bit more expository, using some of the text from the existing mathematical constant article. --Trovatore (talk) 23:11, 19 July 2019 (UTC)

Also I would be much happier if the merged article were moved to list of named mathematical constants, to reflect the fact that what really sets them apart is that someone has given them names, not that they are in any clearly identifiable systematic way different from others not listed. --Trovatore (talk) 23:13, 19 July 2019 (UTC)

Style guide for parentheses for the argument of a function

Does anybody know an authoritative style guide? A user claims that there should be a “blank” between the function symbol and left parenthesis in f(x)—specifically, the user pushed for U+0020—although I suspect a mild trolling. Incnis Mrsi (talk) 13:56, 21 July 2019 (UTC)

What JRSpriggs wrote was Personally, I like to have a blank between the "ln" and the "(2)", but I would not have reverted you if that was the only change you made, which is expressing a personal preference in an obviously good-faith way, and which you seem to have intentionally misrepresented. If anyone is trolling here, it is you. --JBL (talk) 14:25, 21 July 2019 (UTC)

Here's what's standard and what's not:

$\underbrace {\ln 2\qquad \ln(2)} _{\text{standard in LaTeX}}\qquad \underbrace {{\text{ln}}2\qquad \ln \,(2)} _{\text{NOT standard in LaTeX}}$

If you write \ln 2 or \ln2 you get a space between ln and 2 that's the same in both cases, and if you write \ln(2) then the space to the right of ln is smaller. The third example among the four above is coded as \text{ln}2, and that does not have context-dependent spacing. The fourth example is coded as ln\,(2). The same thing happens with \exp and \sin and other things. Michael Hardy (talk) 05:03, 23 July 2019 (UTC)

There could reasonably be an italic correction (not a space) between the function and the paren in f(x), though, as without it they run into each other. —David Eppstein (talk) 06:59, 23 July 2019 (UTC)

@David Eppstein: I agree.

${\textstyle f(x)}$

The line above shows once again that Donald Knuth is one of the few people who have some common sense. Michael Hardy (talk) 15:40, 23 July 2019 (UTC)

New kind of references?

User:Jarble is adding a lot of URLs to our references ("adding links to references using Google Scholar"); and these URLs point to Google Book "digests" of occurrences of the given notion in the given book (rather than the whole book). Is it a good idea? Boris Tsirelson (talk) 19:04, 25 July 2019 (UTC)

I am not a fan of adding links to books.google, because one cannot access much of the content there. However, adding links such as this one seems a good idea to me. Jakob.scholbach (talk) 19:17, 25 July 2019 (UTC)

In a somewhat different direction, but related to references I would like to point out a tool which I recently started using: user:Citation bot allows to expand a tiny bit of a reference, such as

{{Citation|isbn=0521337798}}

into a (more) full-fledged citation template, in this example it produces

{{Citation|isbn=0521337798|title=Stone Spaces|last1=Johnstone|first1=Peter T.|year=1982}}.

The tool also seems to look for arxiv links, and works well with doi's, as well. Jakob.scholbach (talk) 19:17, 25 July 2019 (UTC)

@Tsirel and Jakob.scholbach: Full-text copies of the books are not always available online, but the links usually show some of the relevant pages in the books that were cited. These Google Books previews are commonly used throughout Wikipedia, so I recently added several more of them. Jarble (talk) 19:28, 25 July 2019 (UTC)

What I see absolutely no point in is adding a link to a google page showing the title page of the book, such as this edit of yours, for example. If you add a link to the particular page which is being referenced I see the benefit for our readers, but simply linking to the book as a whole is not a helpful edit, in my mind. Jakob.scholbach (talk) 20:06, 25 July 2019 (UTC)

Draft:Arnold Mathematical Journal

This journal is indexed in Scopus and zbMATH, which will be enough to pass WP:NJOURNALS usually. If someone would like to shepherd this to mainspace, see WP:JWG for how to expand the article up to our standards. The indexing information can be found at [9]. Headbomb {t · c · p · b} 19:52, 26 July 2019 (UTC)

Recently created article Codensity monad

I recently created Codensity monad which was quickly tagged by Domdeparis with some curation tags including "This article needs attention from an expert on the subject. The specific problem is: Verification of the sources and the content.". While I am not an expert in category theory, I would consider myself sufficiently qualified to simply remove the tag (because nothing, in my mind, is problematic about the verification here), but if someone else around would have a look, I would appreciate it. Thanks! Jakob.scholbach (talk) 20:55, 30 July 2019 (UTC)

Does anyone know about Kan extensions? If so, then (s)he should say in the article that the codensity monad is the right Kan extension of a functor along itself. Dually, the density comonad is the left Kan extension of a functor along itself, and perhaps the article should also give examples of density comonads. GeoffreyT2000 (talk) 21:07, 30 July 2019 (UTC)

Hi @Jakob.scholbach: please don't think that I am not assuming good faith or questioning your expertise but I specifically tagged it to request a second pair of eyes other than those of the article creator. New pages written by every editor, except those that are autopatrolled, go through new pages review and get screened. I am not competent enough to verify what is written and to say if it is in accordance with the sources. There are no footnotes (which by the way should be added) so I wouldn't know where to begin looking in the sources. Rather than just leaving it as unreviewed I have asked for an expert on the subject to help me review it. As you are not autopatrolled I am afraid I would object to the removal of the tag by you and would have to revert. I hope you understand. --Dom from Paris (talk) 21:26, 30 July 2019 (UTC) p.s. my apologies for not having posted this here myself, I should have done it. --Dom from Paris (talk) 21:28, 30 July 2019 (UTC)

Don't worry Domdeparis, I was in no way offended. However, the request that every statement should be sourced by a footnote (as opposed to an inline citation) is, IMO, not backed up by the regulations. As far as the sources are concerned, anyone with a minimum knowledge of category theory will be able to confirm that the sources cited in the article do say what I summarized in the article. Let's hope someone here does so.

@GeoffreyT2000: please add such statements if you are up to it. (I did plan to include the right Kan business, but did not yet make it). Jakob.scholbach (talk) 21:35, 30 July 2019 (UTC)

You are right about footnotes not being the only way to make an inline citation the other method is a parenthetical citation as as per WP:INCITE Inline citations are added using either footnotes (long or short) or parenthetical references.. Your references are not inline though but are General references. Inline citations are preferable to these as stated in WP:CITETYPE A general reference is a citation that supports content, but is not linked to any particular piece of material in the article through an inline citation. General references are usually listed at the end of the article in a References section. They are usually found in underdeveloped articles, especially when all article content is supported by a single source. They may also be listed in more developed articles as a supplement to inline citations.. I should have said that there are no inline citations in this article and they should be added.Hope this clears up the misunderstanding. --Dom from Paris (talk) 22:28, 30 July 2019 (UTC)

Re "Your references are not inline though but are General references": Really? I see five inline parenthetical citations in the current version of the article, a high density for an eight-line article. —David Eppstein (talk) 22:38, 30 July 2019 (UTC)

I've just checked and there were actually 2 when I tagged but I must admit I missed them because this is the first time I have come across the Harvard text citation without brackets and didn't roll my mouse over it first. Please accept my apologies and I shall trout myself! --Dom from Paris (talk) 00:16, 31 July 2019 (UTC)

Discussion about old AfD Wikipedia:Articles for deletion/Covariance mapping

Here (I only noticed because I was pinged). XOR'easter (talk) 14:21, 31 July 2019 (UTC)

Aug 2019

Draft:Artin-Tits groups

Someone might want to rescue Draft:Artin-Tits groups from languishing in draft state. It looks well-sourced and reasonably close to publishable to me (although the title should be Artin–Tits group with an en-dash and no plural, and it needs more wikilinks), but a request to publish it was declined by Theroadislong for the bogus reason of being "largely incomprehensible" (it is a technical subject that would not reasonably be expected to be comprehensible to non-mathematicians). —David Eppstein (talk) 21:13, 27 July 2019 (UTC)

Thank you for your input, I declined it because I didn't think there were sufficient sources, I merely commented that it was largely incomprehensible, I have added some Wiki linking and moved it to article space. It does need better sourcing and I am sure it could be written in a more accessible way as is Tits group. Theroadislong (talk) 21:44, 27 July 2019 (UTC)

How is this distinct from Artin group? XOR'easter (talk) 22:17, 27 July 2019 (UTC)

It's not. At first I thought the definition at Artin group only allowed for relations between consecutive generators, but I think that's just a quirk of how it was written and not actually what's intended. Otherwise, I guess we should just try to see if there's anything different enough in the new article worth merging in, and redirect to Artin group (with no opinion on what the actual ultimate name should be). –Deacon Vorbis (carbon • videos) 01:16, 28 July 2019 (UTC)

I moved it from Artin-Tits groups to Artin–Tits groups and then from there to Artin–Tits group. I am uncertain whether that last move is right.

So far no other articles link to this new article. Michael Hardy (talk) 13:49, 28 July 2019 (UTC)

Definitely needs to be merged with Artin group. This is just an alternate name. — MarkH21 (talk) 16:11, 28 July 2019 (UTC)

I am (enthusiastically) willing to work on merging "Artin groups" and "Artin-Tits groups", which by coincidence have been created almost simultaneously. I just need a few days, and I'll post a proposal. OK ? I am a specialist of this area of mathematics, and should be able to make something coherent. Patrick Dehornoy 15:11, 1 August 2019 (UTC)

PS. I enterely agree with the critics about the first draft of "Artin-Tits groups", of which I am the author. I am not yet very familiar with the editorial features of Wikipedia, but I should learn fast... Patrick Dehornoy 15:15, 1 August 2019 (UTC)

Yes, please do, and thank you beforehand! Boris Tsirelson (talk) 15:27, 1 August 2019 (UTC)

I now posted a tentative version of the new, completed page merging "Artin group" and "Artin-Tits group". Please check and criticize. Patrick Dehornoy 19:47, 3 August 2019 (UTC)

P.Aczel reference to Recursive definition

Please see Talk:Recursive definition#(Aczel 1978:740ff). --CiaPan (talk) 16:58, 4 August 2019 (UTC)

Opinions of an edit

Any opinions of this edit? I wonder if there's a third way of phrasing the thing that's better. Michael Hardy (talk) 03:18, 8 August 2019 (UTC)

I don't think the edit is an improvement; I suspect that that is the sort of sentence which can be tweaked all sorts of ways without making it much more or much less clear. XOR'easter (talk) 03:28, 8 August 2019 (UTC)

I took a red pen to the opening paragraph. I tried to make it somewhat better, but there's still plenty that could be done I'm sure. As I said in the edit summary, please feel free to revert or tweak further as you like. –Deacon Vorbis (carbon • videos) 03:42, 8 August 2019 (UTC)

I like your version better than what was there before, and further tweaked it. --JBL (talk) 13:20, 8 August 2019 (UTC)

More on Artin–Tits group

The original creator of the article titled Artin–Tits group has told me that he merged it into Artin group. After that I moved it to Artin–Tits group. So two questions arise:

• Is that the best title for the article?
• Was the merger done well, and what further work may be needed?

Michael Hardy (talk) 02:49, 6 August 2019 (UTC)

I did some minor cleanup, but I am not sure which is the more prevalent name. The article mostly consists of a list properties and results that does not seem entirely appropriate here too. Thoughts? — MarkH21 (talk) 03:24, 6 August 2019 (UTC)

Is there the right place to answer these questions? (I am an old mathematician, but a newcomer on Wikipedia...).

About the title, there is no obvious answer. Artin-Tits groups are a vast subject, and many people work on them. More importantly, there are several classes of such groups, and several specialized subcommunities. "Artin-Tits groups" is more common in recent references. But an important subcommity, those working on "Right Angled Artin-Tits groups" ("RAAGs") uniformly use "right-angled Artin groups", and not "right-angled Artin-Tits groups". Ideally, the two names should be possible. What is the better solution for this situation?

About the content, your comment "The article mostly consists of a list of properties and results that does not seem entirely appropriate here too" is very interesting. This is precisely what I aimed at doing: it seems to me that the paper, as it stands, would be all I expect to learn about these groups if I were a newcomer in the subject, namely the state-of-the-art results which are considered important (top journals references). But you are a hugely qualified Wiki author, and I would like to know your opinion: what would be typically missing, or useless? As I intend to invest myself in writing on several subject of my expertise area, I am much willing to understand what is the exact aim and philosophy of Wiki (as far as mathematical subjects are concerned). Thank you very much for any comment....

A minor point: your talk page is wonderfully structured, with a summarized "abstract" presenting you. How could I do the same for me? Patrick Dehornoy 17:30, 8 August 2019 (GMT)

Thanks for your contributions! Wikipedia has many idiosyncrasies, and I'm not sure anyone is completely familiar or comfortable with all of them, no matter how long they've been here. Discussing the article here is fine; another good venue is its Talk page, but it's possible that more people will notice your comments here than there. (Wikipedia has the handy feature known as the Watchlist, which is a list of pages that you select as important to you so that the software will automatically notify you when they are changed. Many more people "watch" this page than Artin–Tits group, so feedback may happen faster here.) Regarding the "list of properties and results" comment, I think the concern is a matter of prose style more than anything else. We like Wikipedia articles to be prose paragraphs, with a logical flow from one to the next, rather than bulleted lists, which too often read in a choppy way (like PowerPoint slides filled up with text). Perhaps the mathematics articles that have received the "Good article" stamp of approval may be of inspiration. XOR'easter (talk) 16:56, 8 August 2019 (UTC)

You can put the text "{{Talk header}}" at the top of your own Talk page to make a header. This is an example of a template, like the {{citation}} and {{cite journal}} templates you have already encountered. XOR'easter (talk) 17:01, 8 August 2019 (UTC)

Indeed, that is what my comment meant. Wikipedia articles should be well-written prose that introduces and describes domains of knowledge, rather than an academic reference or a large collection of bullet-point facts.

I am far from well-qualified WP editor, and I appreciate the compliments but your contributions here may be equally or more important than my own. As XOR'easter mentioned, the top of my talk page has the aforementioned talk header template. If you mean my user page itself, feel free to copy bits that you may want to include on your own. The procedure to write on it is the same as writing on any other Wikipedia page! — MarkH21 (talk) 18:00, 8 August 2019 (UTC)

Australian IP edit-wars in Quaternion

Insists that knows the only correct notation and the rest of the world the preceding version is “wrong”. Look at https://en.wikipedia.org/w/index.php?title=Quaternion&action=history&offset=2019081216&limit=9 and talk:Quaternion‎‎ #Exponential, logarithm, and power functions, please. Incnis Mrsi (talk) 15:42, 12 August 2019 (UTC)

Strange editor

Please look at these edits: Special:Contributions/Hanumantw; not vandalism, but... something strange? Boris Tsirelson (talk) 16:07, 11 August 2019 (UTC)

It may not be deliberate destruction motivated by hatred of the good, but damaging things as a result of carelessness or ignorance can be just as harmful. JRSpriggs (talk) 01:21, 12 August 2019 (UTC)

Now blocked indefinitely. Boris Tsirelson (talk) 08:15, 17 August 2019 (UTC)

Factorial and double exponential

See recent history of factorial. An editor there insists that the constant function f(x)=1 is an example of a double exponential function and on using that example to change the statement that the factorial grows "slower than double exponential functions" to the overly-pedantic "slower than many double exponential functions e.g. (example)". I don't think this is an improvement, but additional opinions might be more helpful than my repeated reversion of these edits. —David Eppstein (talk) 22:46, 17 August 2019 (UTC)

Very depressing bug in the editor

I was editing Talk:Axiom of union#Independence of the axiom of union. I had planned out what I wanted to say in my head and was rushing to get it committed to writing before I forgot it. As usual, there were times when I needed to look at another article to get the correct spelling or latex symbol. This time, I went to the Axiom of powerset to get the symbol for the powerset. I had to enter the editor to see the source of that article to get "\mathcal (P)". When I tried to back out of that edit and return to my original edit, it would not allow me to do so. Ultimately, I had to "resend" to escape and as a result I lost most of what I had already written. I cannot say in words just how discouraging this is. For several minutes I sat stunned, enervated, unable to do anything. Eventually, I forced myself to re-enter an approximation to what I had written before.

This is not the first time this has happened. It has happened several times before. But it is infrequent enough that I forget to take precautions against it. Is there some way to get this bug fixed? JRSpriggs (talk) 01:20, 13 August 2019 (UTC)

Which editor(s) are you using? It may make a difference. I haven't had problems except when my browser exceeded available memory on my machine and locked up.... 01:36, 13 August 2019 (UTC)

(edit conflict × how ironic) Not quite sure I'm following your steps exactly. Do you mean that from the edit window, you went directly to another article (maybe via the search bar), and then hit the back button on your browser only to find that it hadn't saved the state of what you were doing? If so, then that's not really a bug; there's no guarantee that a browser will keep the current state of what you're doing cached if you move forward to another page. Ideally it will try to, especially for simple stuff, but that's not something you can rely on. On the other hand, if you go browsing in another tab or window, then all should be fine, but if not, it's likely browser-related, not a Mediawiki issue. Or have I misunderstood what the problem is? –Deacon Vorbis (carbon • videos) 01:42, 13 August 2019 (UTC)

To Arthur Rubin: I was just using the normal editor provided by Wikipedia, the old one, not the visual editor.

To Deacon Vorbis: Yes, I think you got it right. My browser is Firefox. I was thinking that there are three things I might do to work around this: (1) copy the source of my edit into a file on my disk before going on such expeditions, just in case this happens; (2) do the search and cutting (before pasting) in another copy of Firefox; or (3) save my edit before I am really done and then edit again after I have done the search. What do you recommend? JRSpriggs (talk) 06:13, 13 August 2019 (UTC)

This depends on the browser, and even on the browser version. With Safari, non-saved edits are sometime lost, sometime not lost when one come back to a page with the back button. If one has left the page after clicking "show preview", edits are sometimes kept, but with the most recent versions they are kept only if one does almost nothing (no search in the page, no diff, no look to the source, ...) with the visited page(s). Therefore, I have now the habit to use another tab for navigation during an editing process, and, when searching or following a link from the edit window, to to it with the right button and "open the link in another tab". D.Lazard (talk) 07:51, 13 August 2019 (UTC)

That's more or less my habit as well. XOR'easter (talk) 15:22, 13 August 2019 (UTC)

To Lazard: Thanks for the suggestion. I will try the right-click on a link to get a separate tab method. JRSpriggs (talk) 01:29, 14 August 2019 (UTC)

I’m late but I can confirm I had the same type of (very disheartening) experiences before on multiple occasions; they may have been in Wikipedia or some other website. Since I couldn’t figure out the behavior (how unsubmitted text is handled), my habit has been to copy large text into the clipboard before hitting submit (if edits are small, I don’t bother). —- Taku (talk) 22:54, 17 August 2019 (UTC)

Puzzled by watchlist

This WPM talk page is on my watchlist, in the sense that I do see the corresponding blue star between "View history" and "More". And nevertheless it does not appear on my watchlist. This is a new phenomenon (the last week or two). Mostly, my watchlist looks as before; but some items are missing, I do not know why. If I click the blue star ("remove this page from your watchlist") and then click the (no more blue) start again (making it blue again), it helps; the page returns to my watchlist. But afterward it disappears again. Why so? Boris Tsirelson (talk) 06:51, 19 August 2019 (UTC)

Or maybe not quite so. I just tried to click twice the star on Talk:Normal distribution (edited by me yesterday, and by a bot today); it did not help. Boris Tsirelson (talk) 06:57, 19 August 2019 (UTC)

Empty square root

The empty square root ${\sqrt {\;}}$ generated as <math>\sqrt{\;}</math> is very badly aligned (I have found this in nth root). The reason seems that the alignment is done on the center of the argument and that the space character is viewed as a zero-height character placed at the bottom of the line. For having a normal alignment such as ${\sqrt {{~^{~}}^{~}\!\!}},$ I have used <math>\sqrt{{~^~}^~\!\!}</math>. Do someone know a less weird method for a similar result? D.Lazard (talk) 07:42, 19 August 2019 (UTC)

P.S. A similar result (${\sqrt {\color {white}{x}}}$) is obtained with <math>\sqrt{\color{white}{x}}</math>, but it is also semantically doubtful. D.Lazard (talk) 07:54, 19 August 2019 (UTC)

Try <math>\surd</math>, giving $\surd$. No horizontal bar, but it does better align it with the text. If WP handled real TeX, \sqrt{\phantom{x}} or \sqrt{\hspace{1em}} would be reasonable ways to create an empty square root.--{{u|Mark viking}} {Talk} 08:14, 19 August 2019 (UTC)

Convex hull lower bound

Please see Talk:Convex_hull_algorithms#Lower_bound_on_computational_complexity --GunterS (talk) 08:43, 21 August 2019 (UTC)

Already answered there. D.Lazard (talk) 09:21, 21 August 2019 (UTC)

Cocycle of a group action

It is a pity that cocycle of a group action is not treated; neither in "Cocycle", nor in "Group action (mathematics)". See Talk:Cocycle#Cocycle of a group action. Boris Tsirelson (talk) 08:22, 24 August 2019 (UTC)

Pollard algorithms

Are Pollard's rho algorithm for logarithms and Pollard's kangaroo algorithm about the same thing? Bubba73 ^{You talkin' to me?} 15:35, 24 August 2019 (UTC)

I am not acquainted with these; but in "Pollard's kangaroo algorithm" I read: "Pollard's kangaroo algorithm ... introduced ... in the same paper [1] as his better-known Pollard's rho algorithm"; if so, then they are two different algorithms "for solving the same problem". Boris Tsirelson (talk) 17:21, 24 August 2019 (UTC)

The way it seems to me is that Pollard's rho algorithm is for factoring numbers and the other two use a similar method for finding discrete logarithms. Bubba73 ^{You talkin' to me?} 18:09, 24 August 2019 (UTC)

Draft:Genus of a group

Is this a topic that deserves a separate article? Genus (mathematics)#Graph theory already covers the topic but a quick Google search shows the topic is of independent interest. (I admit I’m not a specialist on this area so the others might know better.) — Taku (talk) 22:52, 26 August 2019 (UTC)

No separate IMHO, but definitely as little as redirect to Cayley graph, especially because the article already mentions the genus of it (albeit without a wiki link). Incnis Mrsi (talk) 16:21, 27 August 2019 (UTC)

Where in Cayley graph is the genus of a Cayley graph discussed? --JBL (talk) 17:09, 27 August 2019 (UTC)

In fact, nowhere the genus of the graph (I suffered a glitch). Anyway the concept is defined via Cayley graphs and may deserve a section there. Incnis Mrsi (talk) 17:24, 27 August 2019 (UTC)

I'd start by writing about the concept at Cayley graph and then breaking it out into its own article if that material grows too big. XOR'easter (talk) 17:45, 27 August 2019 (UTC)

I agree that Cayley graph is a better initial home for such material than Genus (mathematics)#Graph theory. --JBL (talk) 18:46, 27 August 2019 (UTC)

Started! XOR'easter (talk) 19:18, 27 August 2019 (UTC)

Thank you for the works. I will now make the draft page a redirect. —- Taku (talk) 23:07, 27 August 2019 (UTC)

Sep 2019

Missing articles about Category:FEM elements

Serendipity element and Lagrange element are not created. --Sharouser (talk) 14:35, 1 September 2019 (UTC)

Punctuation epsilon–delta

Yet another occasion arises whose understanding requires one to realize that the "LaTeX" we use here is (many would say "obviously") not actual LaTeX.

${\begin{aligned}&\varepsilon -\delta \\&\varepsilon {-}\delta \\&\varepsilon {\text{-}}\delta \\&\varepsilon {\text{--}}\delta \end{aligned}}$

If the "LaTeX" code uses a hyphen, then the first form above is seen, with a minus sign rather than a hyphen.

The second form is with a minus sign enclosed in {curly braces} so the spacing appropriate when it is used as a binary operation symbol does not appear.

Thus: \varepsilon{-}\delta.

The third has this: \varepsilon\text{-}\delta. This causes an honest hyphen to appear.

The fourth has this: \varepsilon\text{--}\delta.

In our not-really-LaTeX system, this makes two hyphens appear. In genuine LaTeX, it would make an en-dash appear. In the non-TeX occurrences of this phrase in the article titled (ε, δ)-definition of limit, an en-dash is used.

Use of an actual en-dash in the not-really-LaTeX code results only in an error message.

Should we eschew our not-really-LaTeX software altogether for these occasions, or should we use one of the options above, or should we compromise and write

$\varepsilon$–$\delta$

or should we do something else? Michael Hardy (talk) 18:21, 31 August 2019 (UTC)

The solution is obvious: not to use the <math> tag when saying “ε–δ” which is essentially a human-language shorthand, not a scientific notation. But I know that many users stuck to LaTeX notation and call <math> on every imaginable pretext. Under a dire need to say “ε–δ” under LaTeX math mode one can say <math>\varepsilon\text{–}\delta</math> ↦ $\varepsilon {\text{–}}\delta$. Incnis Mrsi (talk) 18:49, 31 August 2019 (UTC)

@Incnis Mrsi: I could have sworn I hard tried \text{–} (with an actual en-dash) and that the result was an error message, but apparently it actually works. Michael Hardy (talk) 17:18, 2 September 2019 (UTC)

The solution that seems most obvious to me, to get an honest en-dash between the two symbols, is to go outside of math to do it. <math>\varepsilon</math>–<math>\delta</math> renders as $\varepsilon$–$\delta$. I don't see how that is in any way a compromise. —David Eppstein (talk) 17:22, 2 September 2019 (UTC)

I agree with David Eppstein (and this is also what I would do when actually writing a LaTeX document, i.e., I would type "... by the $\varepsilon$--$\delta$ definition ..."). The title of the article (ε, δ)-definition of limit suggests another (non-dash-based) resolution. --JBL (talk) 17:42, 2 September 2019 (UTC)

@Joel B. Lewis: That's exactly how I do it in actual LaTeX. I always hesitate to mix TeX with non-TeX notation in Wikipedia because of the many times they have failed to fit together well. Michael Hardy (talk) 21:01, 2 September 2019 (UTC)

$\varepsilon$--$\delta$ is probably what I'd do in an actual LaTeX document, too. XOR'easter (talk) 17:51, 2 September 2019 (UTC)

+1. Boris Tsirelson (talk) 18:33, 2 September 2019 (UTC)

A question about English grammar

The article titled Nonlocal operator begins like this:

In mathematics, a nonlocal operator is a mapping which maps functions on a topological space to functions, in such a way that the value of the output function at a given point cannot be determined solely from the values of the input function in any neighbourhood of any point. An example of a nonlocal operator is the Fourier transform.

Occasionally I think English-speaking mathematicians are not attentive enough to nuances of the use of the word any.

This function can take any number as an input.

is not quite the same as

This function can take every number as an input.

since in some contexts this might mean every number at the same time. But

Any function from R into whatever is blah blah blah.

means

Every function from R into whatever is blah blah blah.

Maybe this point is clearer if one thinks of the difference between

"Any member can preside over this meeting."

and

"Every member can preside over this meeting."

Now suppose you say

If it is the case that any function from R into whatever is blah blah blah then etc.etc.

That is in danger of being read as

If any function from R into whatever is blah blah blah then etc.etc.

and hence as

If there is any function from R into whatever is blah blah blah then etc.etc.

so that a universal quantifier in the writer's mind becomes an existential quantifier in the reader's mind. Merely writing "every" instead of "any" at the outset is all it takes to obviate this hazard.

Thus "any" can be universal in some contexts ("Anyone can do that.") and existential in others ("There isn't any." or "If anyone can run a 50 meters in three seconds, it's Usain Bolt.") The contexts in which it becomes existential seem to be these:

• Negative sentences: "I've never seen any examples of that."
• Questions: "Is there any money left?"
• Conditional clauses: "If there is any money left, donate it to Wikipedia."

How shall we apply this to the two occurrences of the word any in the passage quoted from Nonlocal operator? Michael Hardy (talk) 18:25, 27 August 2019 (UTC)

This topic is not in my expertise, but isn't there an extra quantification? Shouldn't the "of any" be changed to "the" or "the given"?

If you're asking/telling about the more general issue of imprecision in natural languages, then I'm not sure what the resolution is. Formal logic exists exactly to avoid that imprecision. Mgnbar (talk) 14:13, 3 September 2019 (UTC)

Square root of integers

The problem arose from WP:Articles for deletion/Square root of 10. What to do with the topic now, in light of the deletionist assault? Is a separate article warranted? If no separate, then my proposal, square root #Principal square roots of the positive integers, or something else? Incnis Mrsi (talk) 14:06, 3 September 2019 (UTC)

My knee-jerk reaction was, "This topic is basically (integers in) quadratic number fields, which are extremely important." But then I realized that we have Quadratic field for all that. What is the intended division of labor between the two articles? Is there a substantial body of knowledge specific to quadratic integers? The presence of reliable sources in that article suggests so, but I haven't examined them closely. Mgnbar (talk) 14:23, 3 September 2019 (UTC)

Properties like being Euclidean domain, being principal ideal domains, basis as free abelian group, and many others are more specific to quadratic integer rings than to quadratic fields, even if these properties are described in Quadratic field. D.Lazard (talk) 14:42, 3 September 2019 (UTC)

Integers are important far beyond ℚ[√D], if only due to such rings as Gauss ℤ[ i ], Eisenstein ℤ[³√1], and Dirichlet ℤ[ τ ] which is important for 5-fold rotational symmetry. Incnis Mrsi (talk) 14:51, 3 September 2019 (UTC)

@D.Lazard: what? Isn’t the usefulness of prime factorization to compute many of square roots of integers important? Incnis Mrsi (talk) 14:51, 3 September 2019 (UTC)

The computation of (approximations of) square roots of integers is not very different from that of real number, and belongs thus to Square root. Two things may belong to quadratic integers that are not there in any version: 1/ Computing the largest square-free factor of an integer (that is the smallest d generating a given $\mathbb {Q} ({\sqrt {d}})$). For that, no better algorithm is known than prime factorization. So a few lines in Quadratic integer suffices. 2/ Testing whether a quadratic integer is the square of a quadratic number, and, if yes, computing the square root. This is considered in Nested radical and would deserve to be linked here. D.Lazard (talk) 15:36, 3 September 2019 (UTC)

As “not very different from” – false, they are algebraic numbers and “integers”, after all. These facts are completely obscured after D.Lazard’s edits. Incnis Mrsi (talk) 16:06, 3 September 2019 (UTC)

Which edit(s) obscured anything? D.Lazard (talk) 16:54, 3 September 2019 (UTC)

Before the deletionist strike the topic redirected to that subsection. Now one can’t easily infer that square roots of integers are algebraic integers. Nor can the reader access √2, √3, √5, at least not in reasonable proximity of the request. The √10 thing is also removed, but it was not directly a D.’s fault. Incnis Mrsi (talk) 17:11, 3 September 2019 (UTC)

No redirect is needed for saying that the square roots of an integer are quadratic integers. I have added this to Square root. D.Lazard (talk) 18:19, 3 September 2019 (UTC)

What occasion could there be to write "square root of integers" rather than "square roots of integers" or "square root of an integer"? Michael Hardy (talk) 23:51, 4 September 2019 (UTC)

I followed the model of square root of negative numbers. For comparison, Special:PrefixIndex/square roots has nothing of the sort. Incnis Mrsi (talk) 04:44, 5 September 2019 (UTC)

So there exist more useless redirects from grammatically-faulty titles? Interesting, but not a good choice to use as a model. —David Eppstein (talk) 06:01, 5 September 2019 (UTC)

David Eppstein highly probably speaks English better than me by a large margin, hence WP:SOFIXIT. Incnis Mrsi (talk) 06:06, 5 September 2019 (UTC)

Math-related affiliate

Just a reminder about m:Wikimedia Community User Group Math, which any person who supports the group's goals is welcome to join. As of a few weeks ago, the group is one of the officially recognized m:affiliates of the Wikimedia Foundation. Whatamidoing (WMF) (talk) 00:29, 6 September 2019 (UTC)

Invariants and covariants

There is a problem with the disambiguation required for Michael Roberts (mathematician) in the previous thread: the link to a dab page is clearly intended to refer to covariants of invariant theory. The problem is that I have not found any mention of such a covariant in English Wikepedia. Do someone has an idea for solving the problem?

Here is what I remember on this subject: Let $f$ be a generic form in n variables (that is, its coefficients are indeterminates). The group GL(n) acts on the form by linear changes of variables. The discriminant of a form in two variables is an invariant. An invariant of GL(n) (or of a subgroup) is a polynomial in the coefficients of the form. A covariant is a form in the same variables, with coefficients polynomials in the coefficient of the given form, which is similarly invariant. For example, an invariant is a covariant of degree 0.

What precedes is clearly not sufficient, even for a stub. Again, any idea? D.Lazard (talk) 18:22, 9 September 2019 (UTC)

This is in fact about covariant transformations, or I miss something? Forms are tensors of special form. Incnis Mrsi (talk) 18:39, 9 September 2019 (UTC)

One possibility is to replace the phrase "covariants and invariants" with the phrase "invariant theory". (If there were a reference attached to this statement in the article then I would worry about accurately representing it, but since there is none ....) Also pinging the article author @Moonraker: to this discussion; possibly they can share some insight. --JBL (talk) 19:05, 9 September 2019 (UTC)

We do have the article “module of covariants”. — Taku (talk) 04:45, 10 September 2019 (UTC)

I have found two definitions of a covariant; one in Invariant of a binary form, and one in wikt:covariant, which is more general (not restricted to binary forms) and perfectly accurate. Therefore, I have created the redirect Covariant (invariant theory), I have disambiguated Michael Roberts (mathematician) by using this redirect, and added an entry in Covariance (disambiguation), that links to the redirect and contains a copy of dictionary definition. However, some questions deserve a further discussion;

• The new redirect is the only occurrence of the noun "covariant" in the dab page. This suggest creating a stub based on Wiktionary definition, called Covariant, and with a hatnote like "for the adjective uses, see Covariance (disambiguation)". What do you think?
• The fact that it vas so difficult to find this definition shows that a reorganization is needed for interlinking Invariant theory and all related articles. When this will be correctly done, it will probably appear that Invariant theory would need a complete rewrite, with possibly some merges and or splits.

D.Lazard (talk) 09:43, 10 September 2019 (UTC)

We already have definitions in a glossary; Glossary_of_invariant_theory has 42 uses of the term and and entry for covariant. --{{u|Mark viking}} {Talk} 17:27, 10 September 2019 (UTC)

The problem is that the definition given there is not understandable for most readers, and does not correspond to the usual definition (that of wikt:covariant and Invariant of a binary form). D.Lazard (talk) 18:10, 10 September 2019 (UTC)

I wouldn’t call a subminimal stub an article. See talk:Module_of_covariants #AG. Incnis Mrsi (talk) 18:20, 10 September 2019 (UTC)

(I have added an explanation on the notation as well as to a link to the article giving the definition. -- Taku (talk) 00:19, 11 September 2019 (UTC))

If I've opened up a smallish can of worms, I'm delighted. WP is full of holes where readers can't find easily, or can't find exactly, what they need, and every one filled is an improvement. Narky Blert (talk) 21:17, 10 September 2019 (UTC)

• First, as I recall, a covariant is something like a linear (multi-linear, polynomial) map that is invariant under the given group action. The basic idea is that you get more flexibility by working with maps not elements; i.e., you get more invariants to work with. (Module of covariants, I think, gives probably the most general definition of covariants.) So, given this, I don’t think redirecting covariant (invariant theory) to an invariant of a binary form is a good idea. I will make a library trip to find some refers (and do some edits).
• Generally speaking, Wikipedia is still weak in invariant theory topics (I don’t need to tell you why).
• Finally, yes, there is adjective “covariant” as in “covariant functor” and that has to be distinguished from. (So the disambig page is needed). — Taku (talk) 23:09, 10 September 2019 (UTC)

Thank you to JBL for pinging me. I am happy with what Taku says. Moonraker (talk) 21:43, 12 September 2019 (UTC)

Using a book that plagiarized Wikipedia as a Wikipedia source?

I've been editing trigonometry to address some of the problems it had in its GA review. In particular, much of it was unsourced or OR. I've been going through and deleting unsourced assertions and adding sources to everything else.

There was a section marked with 'more sources needed'. This sections was the 'applications' section, which has largely been unchanged since at least 2007: https://en.wikipedia.org/w/index.php?title=Trigonometry&oldid=122379664

I was going through and sourcing each 'application' one at a time, when I found a book that had all of them:

https://books.google.com/books?id=bENTBQAAQBAJ&pg=PA10&dq=trigonometry+audio+synthesis&hl=en&sa=X&ved=2ahUKEwjjtYeVgMzkAhUEt54KHXpECH4Q6AEwAHoECAYQAg#v=onepage&q=trigonometry%20audio%20synthesis&f=false

This is a Springer book where the authors have just copied and pasted the Wikipedia section, rearranging a few items.

I'm not too concerned that the authors have plagiarized this. My real question, though, is, would it be appropriate to use this book as a source for the whole list (as I've done for now), or would it be better to find sources that aren't plagiarized from Wikipedia itself?

Brirush (talk) 19:33, 12 September 2019 (UTC)

I think it's definitely better not to use sources that plagiarized from Wikipedia (or from elsewhere). XOR'easter (talk) 20:17, 12 September 2019 (UTC)

More definitively, Wikipedia policy prohibits using such sources. See WP:CIRCULAR. (Their preface credits Wikipedia, so this might count as properly-credited use of CC materials rather than straight-up plagiarism, but it makes no difference for its usability as a source.) —David Eppstein (talk) 20:18, 12 September 2019 (UTC)

It may also be worth adding {{Backwards copy}} to the articles, to prevent them being flagged as copy violation by Wikipedia. Certes (talk) 20:24, 12 September 2019 (UTC)

Thanks to both of you, this is very clear. Brirush (talk) 01:37, 13 September 2019 (UTC)

Articles with links to DAB pages

I have collected another batch of articles containing math(s)-related links to DAB pages which would benefit from expert attention. Search for 'disam' in read mode, and for '{{d' in edit mode; and if you solve one of these puzzles, post {{done}} here.

• Almost complex manifold  Done
• Chern's conjecture (affine geometry)  Done
• College Scholastic Ability Test  Done
• Color confinement  Done
• Complex manifold  Done
• Connectivism  Done
• Fractional quantum Hall effect  Done
• Geneviève Raugel  Done
• John W. Negele  Done
• Kummer surface  Done Jakob.scholbach (talk)
• Meta learning (computer science)  Done
• Michael Roberts (mathematician) → Covariant  Done (see next thread) D.Lazard (talk) 09:45, 10 September 2019 (UTC)
• n-sphere  Done
• Navier–Stokes equations → Stress tensor  Done
• Normal basis  Done Jakob.scholbach (talk)
• Polyvector field  Done Jakob.scholbach (talk)
• Random field  Done
• Transport coefficient → Stress tensor  Done
• Studentized range distribution  Done
• Two-dimensional electronic spectroscopy → Ensemble, Charge transfer  Done
• Variational multiscale method → Stress tensor  Done
• Whitehead's algorithm  Done (needed to create the redirect primitive element (free group), and to edit the linked dab page) D.Lazard (talk) 14:11, 9 September 2019 (UTC)
• Xiaohong Chen  Done

Thanks in advance, Narky Blert (talk) 02:58, 9 September 2019 (UTC)

I had to edit after a substandard fix in “almost complex manifold”. Please, look at a whole article, not only to narrow context. Don’t make job to earn green points. Incnis Mrsi (talk) 12:52, 9 September 2019 (UTC)

I'm going to stay polite, but please don't ask thanks for this rather aggressive pointing out of a perfectly correct (if maybe not optimal) edit that did not satisfy your opaque standards, and let me add that I have no idea what a green point is nor any desire to learn.

I'd also suggest you refrain from insulting people for petty motives. If you want to discuss math leave a message on the talk page of the article. jraimbau (talk) 11:15, 11 September 2019 (UTC)

The standards aren’t in fact “opaque”, it is MOS:LINKCLARITY. If Jean Raimbault wants to discuss my petty motives, then he can leave a message here, although it can become moot soon. Incnis Mrsi (talk) 11:51, 11 September 2019 (UTC)

Notice that Incnis Mrsi has been blocked for one month by Rschen7754 for incivility. JRSpriggs (talk) 03:06, 12 September 2019 (UTC)

Let us not escalate... Boris Tsirelson (talk) 04:45, 12 September 2019 (UTC)

Thanks for all your help and to Narky Blert for finding the problems. It looks as if the one unfixed link needs a physicist or engineer rather than a mathematician. Certes (talk) 12:22, 11 September 2019 (UTC)

Fixed the last one; it was referring to charge transfer in a CT complex --{{u|Mark viking}} {Talk} 07:37, 12 September 2019 (UTC)

I work on the assumption that mathematicians will be the people best-placed to determine the specific concepts which physicists, engineers, and the like have borrowed and misused.

(I'm an organic chemist. I'm allowed to say that sort of thing.) Narky Blert (talk) 19:37, 13 September 2019 (UTC)

Am engineer. Can agree, borrow and misuse math all the time. --Izno (talk) 20:20, 13 September 2019 (UTC)

What should an article for a branch of mathematics look like?

As I mentioned above, I've been reworking Trigonometry, focusing on organization and on removing OR and adding sources.

The page still looks skimpy, however, and I feel that more could be added (maybe separate sections on the properties of the graphs, on inverse functions, and perhaps fourier series/analysis?). I've been looking at other pages for inspiration, but I found to my surprise that no 'branch of mathematics' is currently a GA or a FA. Algebra, calculus, etc. are all below GA quality, and have some of the same problems that trigonometry has.

So I wanted to get some consensus before acting. What should 'big topic' articles like this cover? Is there any thing that you feel is necessary or standard for such articles? Is there any particularly good article in a related field that could be used as a template or inspiration? Brirush (talk) 02:42, 13 September 2019 (UTC)

You raise good questions. I think it is quite a challenge to be comprehensive, readable by non-experts and a reasonable length all at once for articles on general topics. One general article I like is Field (mathematics). It takes pains to be readable and concrete near the start of the article, but doesn't shy away from the more advanced topics later on. For trig, some ideas: I guess one of the first things to do is to figure out what goes in trigonometry and what goes in trigonometric functions. One might compare and contrast trigonometry, which is really about plane trigonometry, with spherical trigonometry, hyperbolic trigonometry and generalized trigonometry. Is there anything interesting about how trig has been or is currently taught? For applications, something more than just a long list of fields that use it might be good. Are there some particularly notable uses, maybe something from navigation or surveying? --{{u|Mark viking}} {Talk} 03:52, 13 September 2019 (UTC)

A detailed history section is a major plus! Edit: I see that trigonometry actually has a fairly well-developed one, with just a few citations that need to be added. — MarkH21 (talk) 07:03, 13 September 2019 (UTC)

Thanks for the work already done on Trigonometry. I completely agree with Mark viking's comments. A large part of my Wikipedia activity is devoted to improve in this way fundamental articles of Wikipedia (See my user talk for some of my main edits). IMO, we must distinguish articles about an area of mathematics, such as Trigonometry from articles about the fundamental concept(s) that are the basis of such an area, such as Trigonometric functions. Articles on areas must explain the motivations, the history, the limits of the area (when there is a consensus for that), and the relations with other areas. The objective is that a reader can gets an idea of the subject and find easily the related technical articles that he may need. An example of a very good such article is Number theory, although it needs many improvements (cosmetic, IMO) for being labeled GA. On the other hand, article on fundamental concepts must allow the reader to find the technical details that he needs, such as a formula that he has learnt and forgiven, or a related concept that he has heard about. This is in this spirit that I have recently edited Trigonometric functions (see [10]). In particular, other trigonometric functions than sine, cosine, and tangent are rarely used, except, maybe, in teaching; therefore, my edits limit the formulas given in the article to the most useful formulas relating sine, cosine, and tangent and refer to List of trigonometric identities for the less important formulas. However, the maintenance of such fundamental articles is a true problem, because of the numerous good faith editors who want to add their preferred minor aspect of the subject. For example, since my edits, a section on the expansion of trigonometric functions as infinite products has been added. IMO, such a section is confusing, and must be replaced by a simple link, as it gives too much emphasis on a non-fundamental result. D.Lazard (talk) 09:45, 13 September 2019 (UTC)

At the risk of putting words into D.Lazard's mouth, let me say it another way. Mathematical concepts have precise definitions. For example, a topology is a set of subsets satisfying certain axioms. However, mathematical disciplines are ill-defined and overlapping. For example, the discipline of topology heavily overlaps with geometry, analysis, algebra, etc. And Wikipedia should explain both concepts and disciplines. Mgnbar (talk) 12:16, 13 September 2019 (UTC)

I completely agree, and what I was saying is that rules for a good article (answer to the question in the heading) are different for disciplines and for concepts. D.Lazard (talk) 12:23, 13 September 2019 (UTC)

Agreed. And the citation process for the two is a bit different. For the concept of topology, one can cite the definition from Munkres' book Topology. For the discipline of topology, which topics can be included and excluded? If a topic appears in Munkres' Topology, then one can reasonably include it. If a topic does not appear, then one cannot reasonably exclude it. (The same problem exists for other sources and for combinations of sources.) So the discipline of topology has to be "defined" using examples. Mgnbar (talk) 16:34, 13 September 2019 (UTC)

This is maybe a bit of a quibble, but I don't think "concept" is the right word for topology in the sense of a collection of open sets, at least to distinguish it from topology as a discipline. Topology as a discipline is arguably still a concept. I think a better word would be "object" — the collection of open sets notion is a type of mathematical object, whereas the discipline is not (and indeed has no precise mathematical definition at all). --Trovatore (talk) 19:56, 13 September 2019 (UTC)

I've now completed my revision of Trigonometry. In the process, I've added several figures and tables, and almost doubled the size of the entry. I've tried to be careful and check for errors, but I would appreciate it if someone would look it over for mistakes, especially stray sentences from copy-and-paste or errors in the tables. If you feel any additions or removals are inappropriate, I can revert them. Thanks for the advice given above, it was extremely helpful.

Edit: The article itself isn't complete. As mentioned by someone else, it could use an overview of spherical/hyperbolic geometry. I'm not too familiar with spherical trigonometry, so I didn't attempt it.

Brirush (talk) 19:43, 13 September 2019 (UTC)

Trovatore: Topology is a class of mathematical objects, and topology (the discipline) is a sociological/anthropological object? Actually, I don't have strong opinions about the terminology. :) Mgnbar (talk) 20:44, 13 September 2019 (UTC)

I find that a useful proxy is whether you use a countable or uncountable noun. A topology (count noun) is a mathematical object, whereas topology (mass noun) is a discipline.

This is by the way the distinction we should use for a Boolean algebra (count noun, the structure) versus Boolean algebra (mass noun, the equational style). I fought the good fight on that point many years ago, with a somewhat unsatisfactory outcome, because of a participant with unusual foundational views. --Trovatore (talk) 21:29, 13 September 2019 (UTC)

​The page numbers in a lot of the references in trigonometry are given as the first half of a range. Surely this doesn't mean that the entire rest of the book after that page number is the relevant part. Would ff. work better? XOR'easter (talk) 18:40, 14 September 2019 (UTC)

Thank you, I was using https://reftag.appspot.com/ to convert google book links to Wikipedia citations. It had a few other idiosyncracies that I had to address (like using a non-existent 'coauthors' tag). I'll see if I can convert the page ranges to ff's! Brirush (talk) 22:53, 14 September 2019 (UTC)

Okay, I fixed it. I did not use ff after all, because I didn't realize it meant 'multiple pages', and when I found references, my technique was to find the exact page that had the quote I wanted, so it shouldn't need the subsequent pages. I changed it to single pages. Brirush (talk) 23:03, 14 September 2019 (UTC)

Thanks! I did some spot-checking and fixed a couple other glitches that were probably due to Google Books metadata weirdness. I'll try to check the page over more thoroughly soon. XOR'easter (talk) 23:58, 14 September 2019 (UTC)

Regarding the mathematics banner of the Category:Ordinal numbers

@Chongkian: See Category talk:Ordinal numbers. Chongkian (talk · contribs) removed the {{Maths banner}}. Apparently, he believes that {{WikiProject Numbers}} is sufficient. Is that appropriate?

I think that ordinals are relevant to Mathematics generally, not merely to the Numbers project. JRSpriggs (talk) 05:34, 15 September 2019 (UTC)

Sure! I've restored WPM there. Boris Tsirelson (talk) 09:21, 15 September 2019 (UTC)

From what I have found, generally there are WikiProject Mathematics ('math banner' or 'math rating'), WikiProject Statistics and WikiProject Numbers which are highly inter-related to each other. Whenever it is related to math in general, we shall use math banner or math rating, but if it is a more specific term of math (which is number or statistics), isnt that we should related it to its more 'specific' WikiProject category? 'Numbers' and 'statistics' are (and always be part of) 'mathematics'. That's the idea behind it for my reason. Same case like 'country', 'geography' or 'city'; 'geography' (or WikiProject Geography) shall be the default categorization first for all of administrative divisions (e.g. town, village, state, province), unless such particular article is about a country or city, then we shall put it under WikiProject Countries or WikiProject Cities respectively (because such WikiProjects do exist), and take out the 'parent' WikiProject which is WikiProject Geography. Villages shall be put under the general WikiProject Geography because up to this moment, there is no WikiProject Villages. Chongkian (talk) 10:03, 15 September 2019 (UTC)

It’s worth noting that WikiProject Numbers is only semi-active now. Also, statistics isn’t universally considered a branch of mathematics. — MarkH21 (talk) 10:18, 15 September 2019 (UTC)

Looking at WikiProject Numbers I fail to find there any interest to transfinite numbers. Thus, I'd say, it is THEIR decision, to treat "number" as "finite number". I just respect their (quite reasonable) decision. Boris Tsirelson (talk) 10:30, 15 September 2019 (UTC)

WikiProject Numbers has been concentrating on articles about integers by removing cruft (77 is the shirt number of Joe Minor-Leaguer), improving navigation templates and promoting their existence. Three years ago, 1 was the title of the article about the year AD 1. Certes (talk) 11:37, 15 September 2019 (UTC)

As a moderately active member of both projects, I don't remember any discussion of infinite numbers in the WikiProject Numbers page or notability guidelines. I don't believe 0.999... is tagged with WikiProject Numbers. — Arthur Rubin (talk) 17:30, 15 September 2019 (UTC)

The usual practice with project banners is to use all applicable ones, not to try to decide which is most applicable and use only that. —David Eppstein (talk) 17:56, 15 September 2019 (UTC)

I don't think WikiProject Numbers wants Ordinal number. As a fairly active member of both WPM and WPN, I don't think the charter of WPN includes infinite numbers. — Arthur Rubin (talk) 17:55, 16 September 2019 (UTC)

To Arthur: Then remove {{WikiProject Numbers}} from Category talk:Ordinal numbers and Category talk:Cardinal numbers. I do not feel qualified to do that since I am not a member of the numbers project. JRSpriggs (talk) 09:45, 17 September 2019 (UTC)

Hilbert's fourth problem article

Hi! The second sentence in this article in its current form seems to be somewhat mangled for me.

In one statement derived from the original, it was to find up to an isomorphism all geometries whose axioms system of the classical geometry (Euclidean, Hyperbolic and elliptic) if we drop the axioms of congruence involving the concept of the angle and add the systems with the `triangle inequality' regarded as an axiom.

Maybe this rewriting could be adequate:

In one statement derived from the original, it was to find up to an isomorphism all geometries that have an axiomatic system of classical geometry (Euclidean, Hyperbolic and elliptic), with those axioms of congruence that involve the concept of the angle dropped, and `triangle inequality', regarded as an axiom, added.

As I am not a professional, I would like to have an expert opinion before editing the article. Thank you in advance! --94.21.201.110 (talk) 11:17, 17 September 2019 (UTC)

Courtesy link: Hilbert's fourth problem. That is, indeed, incomprehensible. It used to be different, before a spate of edits by Vlasenko D in June. Probably those edits deserve some scrutiny (for English language usage at a minimum). --JBL (talk) 12:00, 17 September 2019 (UTC)

I agree. At least, the old version of the lead deserves to be immediately restored, although it could also be clarified. D.Lazard (talk) 13:49, 17 September 2019 (UTC)

Just why the initial letter in "hyperbolic" should be capital while that in "elliptic" is in lower case is unclear. Or to put it more bluntly, it shouldn't be. Michael Hardy (talk) 21:46, 18 September 2019 (UTC)

Portal:Mathematics

Proposal to delete all portals. The discussion is at Wikipedia:Village pump (proposals)#Proposal to delete Portal space. Voceditenore (talk) 08:55, 23 September 2019 (UTC)

Proposition of splitting Cubic function

I have opened a discussion on the suggestion of splitting Cubic function into Cubic function and Cubic equation. Feedback is welcome. D.Lazard (talk) 10:26, 24 September 2019 (UTC)

Pull the knotted part of the curve tight?

This discussion calls for experts, right? Boris Tsirelson (talk) 18:49, 19 September 2019 (UTC)

No, I don't think so: in the 2 years since the first comments were made, the caption has been changed and now does not suffer from the problem discussed there. --JBL (talk) 19:28, 19 September 2019 (UTC)

I see, thank you. Boris Tsirelson (talk) 19:49, 19 September 2019 (UTC)

(I agree with your comment there, incidentally -- Daqu was right about the error, the most recent comment looks wrong. But it is all moot as far as the article is concerned.) --JBL (talk) 20:47, 19 September 2019 (UTC)

Do you not need to require that the first (directional) derivative of the curve be continuous? I think that would be impossible if you just shrink it to a point. JRSpriggs (talk) 07:55, 20 September 2019 (UTC)

Feel free to find a verifiable source supporting your claims, if I am not to be considered as an expert. Quantum Knot (talk) 08:32, 20 September 2019 (UTC)

(to Quantum Knot) Such sources surely exist; can someone help to find them?

For now I've found this: This turns out to not be the correct notion of equivalence for knots - it would force all tame knots to be equivalent!. Boris Tsirelson (talk) 10:13, 20 September 2019 (UTC)

And this: For $m-n\leq 2$ this is not so: e.g., any knot $S^{1}\to \mathbb {R} ^{3}$ is PL isotopic to the unknot, but is not necessarily PL ambient isotopic to the unknot. Boris Tsirelson (talk) 10:24, 20 September 2019 (UTC)

And this: Secondly, surprisingly (and catastrophically), the way we have defined equivalence actually causes all knots to be equivalent to one another! “Gradually pulling the string tight” so that the knot shrinks to a point is a perfectly good continuous deformation between any knot and the unknot! (page 14)Boris Tsirelson (talk) 11:30, 20 September 2019 (UTC)

And this: The word "isotopy " refers to the deformation of the string. The word "ambient" refers to the fact that the string is being deformed through the three-dimensional space that it sits in. Note that in an ambient isotopy, we are not allowed to shrink a part of the knot down to a point, as in Figure 1.20, in order to be rid of the knot. (page 120) Boris Tsirelson (talk) 11:45, 20 September 2019 (UTC)

And this: Remark 1.5. All knots are trivial under continuous isotopy. (batchelor’s unknotting) Boris Tsirelson (talk) 11:52, 20 September 2019 (UTC)

Wow! The clue is the phrase "batchelor’s unknotting" (or "batchelor’s isotopy")! Google this, and you'll find easily a lot of required sources. So, I stop here; the problem is solved. (Should we create an article on this idea?) Boris Tsirelson (talk) 11:57, 20 September 2019 (UTC)

(to JRSpriggs) Sure, if we work in the space $\mathrm {Emb} ^{1}(S^{1},\mathbb {R} ^{3})$ of continuously differentiable embeddings, then the situation should be different. But differentiability is never mentioned in "Homotopy". Boris Tsirelson (talk) 10:02, 20 September 2019 (UTC)

Maybe "bachelor" rather than "batchelor"? Justin Roberts's discussion (your third link) is very nice. A less rigorous, more sociological explanation for why continuous deformations are the wrong idea is that no one would ever have introduced ambient isotopies into knot theory if continuous deformations sufficed. --JBL (talk) 20:13, 20 September 2019 (UTC)

I haven't tracked down an explicit reference, but this seems likely to be named after G. K. Batchelor, who studied knotted vortices in fluid dynamics. —David Eppstein (talk) 21:00, 20 September 2019 (UTC)

Huh, what do you know? --JBL (talk) 11:11, 24 September 2019 (UTC)

Minkowski fractal

(for context)

Image from "Fractal antenna"

Image from "Vicsek fractal"

See also: Talk:Fractal antenna/Archive 1 § Minkowski island/Vicsek fractal

There are currently redirects from Minkowski curve, Minkowski island, Minkowski sausage, and Minkowski fractal which lead to the article "Fractal antenna". An image given as an example of a fractal antenna design is labelled as a "Minkowski Island". Currently the term is in bold because the redirects indicate that it is a topic. However, an article about a subspecies of doves should probably redirect to an article about doves and not to an article about bird-shaped objects. It would be beneficial if an appropriate article was created to explain the Minkowski fractal, or if the redirects led to an article which explained the Minkowski fractal. The image is titled File:6452553 Vicsek Fractal Antenna.png, which implies that "Minkowski island" is an alternate name for the Vicsek fractal. "Vicsek fractal" does mention that the boundary is a variant of the Koch snowflake, and the "Koch snowflake" article contains a quadratic variant of the Koch curve labelled as the 'Minkowski Sausage', so one or both of the articles "Vicsek fractal" and "Koch snowflake" should probably contain the explanation. Hyacinth (talk) 04:08, 14 September 2019 (UTC)

See: Minkowski Sausage. Hyacinth (talk) 21:43, 24 September 2019 (UTC)

Not in Active WikiProjects category

I noticed that the Mathematics page doesn't appear on https://en.wikipedia.org/wiki/Category:Active_WikiProjects, which seems wrong. I'd fix it myself if I knew what I was doing, but I haven't edited a Wiki article before. Iyyl (talk) 01:37, 25 September 2019 (UTC)

I've added the project page to the category. Certes (talk) 10:49, 25 September 2019 (UTC)

Need help with images in Geometry

I've been working on geometry, trying to add references for every controversial statement and expanding stubs. In describing the branches of geometry, I had added an image for each branch. Now, the images are too big and too many to be aligned correctly, even after I deleted my image for Convex Geometry and shrank the others. I could use some expert opinion on the image layout. I haven't finished my edits (I plan on going over the applications section, and adding congruence, similarity, area and volume to the 'main concepts' section), but they shouldn't involve as many images. Thanks! Brirush (talk) 16:17, 25 September 2019 (UTC)

If you're looking for more room, the "Geometry lessons in the 20th century" image looks superfluous. And in the computational geometry section, a problem we can't solve with an efficient algorithm seems an odd choice for the illustration. —David Eppstein (talk) 16:27, 25 September 2019 (UTC)

I tried removing those two and it fixed the issue. Thank you, it completely resolved my problem! Brirush (talk) 16:55, 25 September 2019 (UTC)

Also, I am now finished contributing to geometry. I'd love if people looked it over and made any changes they see fit, or fix anything they feel I did incorrectly.Brirush (talk) 20:10, 25 September 2019 (UTC)

Thanks for your edits! A minor thing I noticed: the Munkres book is listed in the references twice (currently numbers 52 and 109). XOR'easter (talk) 02:33, 26 September 2019 (UTC)

That seemed easy enough to fix, so I made a go at it. --JBL (talk) 11:00, 26 September 2019 (UTC)

I appreciate both of you checking this out. Thanks! Brirush (talk) 12:54, 26 September 2019 (UTC)

How do you create mathematical illustrations?

Can someone give advice what software is useful for creating mathematical illustrations? I am currently working on fundamental group and would like to create some pictures illustrating some computations of pi_1's. For example, I would like to quickly illustrate the usage of the Seifert-van Kampen theoren by (schematically) drawing a genus 2 surface, and some loops on it, together with labelling and coloring the objects (so, nothing fancy). And of course the software should be free to use. Thanks for any advice. Jakob.scholbach (talk) 17:36, 24 September 2019 (UTC)

An example for the kind of illustration I want to create. Jakob.scholbach (talk) 17:37, 24 September 2019 (UTC)

I don't think there is a definitive answer. For SVG illustrations, I tend to use inkscape (as was used in the illustration to the right) as a free alternative to illustrator. If you need the precision of a CAD program (e.g., dimensioning), I have used FreeCAD before and it was OK for my simple needs. Real programmers use tools like PostScript, PSTricks, MetaPost, or Asymptote (vector graphics language), but that can be a lot of work. --{{u|Mark viking}} {Talk} 18:04, 24 September 2019 (UTC)

I use Asymptote (unless the illustration is just a diagram); it takes time, but it gives nice results. Much better than PSTricks (that I used before; PostScript and MetaPost were beyond my patience). Especially on EoM; there a wikitext may contain <asy>some code for Asymptote</asy>; how nice: no separate file, no separate copyright, and anyone may look at the code, and change it "wiki-wiki"! (Well, anyone who knows Asy; but also our TeX code needs to be known...) My best example is here. Simpler examples: here, here,here. Still simpler:here,here,here,here. Though, really I prefer to write the asy code in separate files and transclude them, just for not intermixing wikitext and asycode (unless the asycode is quite short). Boris Tsirelson (talk) 20:11, 24 September 2019 (UTC)

Also, you may look at illustrations in "Space (mathematics)"; they are copied from "v:WikiJournal_of_Science/Spaces_in_mathematics"; there I was forced to create figures (unlike EoM), while the Asy code remains on my home computer (regretfully; ask me if you want to see it), and the corresponding SVG files are stored on Commons. Boris Tsirelson (talk) 20:27, 24 September 2019 (UTC)

I could help make the picture, if you'd be willing to delegate and had a sketch I could work from. I have some experience using Illustrator (and have a subscription for it) from my hobbies. Katja Berčič (talk) 15:09, 26 September 2019 (UTC)

Oct 2019

Morley-Wang-Xu element

I noticed Morley-Wang-Xu element in the new article report. It looks like it needs some care; for example, there's a reference to a figure that doesn't exist. XOR'easter (talk) 00:45, 1 October 2019 (UTC)

It doesn’t appear to be a particularly notable concept based on a preliminary search for sources and citations. Most articles describing it have very few citations and there’s no evidence that it is used in other major ideas.
Is this notable enough to merit a standalone article? — MarkH21 (talk) 01:30, 1 October 2019 (UTC)

Hmm, you raise a good point. What should be done with it if it doesn't stand on its own? XOR'easter (talk) 01:58, 1 October 2019 (UTC)

I've come to the same conclusion. The Morley finite element approximation is fairly well-known. The MWX element appears to be a derivative construction (no pun intended) without any uptake yet. As for actions, I have added a notability tag to scare up independent references, but AfD might be its final trajectory. --{{u|Mark viking}} {Talk} 02:27, 1 October 2019 (UTC)

Thanks! XOR'easter (talk) 02:29, 1 October 2019 (UTC)

MfD nomination of Draft:R. E. Moore Prize

Draft:R. E. Moore Prize, a page which you created or substantially contributed to, has been nominated for deletion. Your opinions on the matter are welcome; you may participate in the discussion by adding your comments at Wikipedia:Miscellany for deletion/Draft:R. E. Moore Prize and please be sure to sign your comments with four tildes (~~~~). You are free to edit the content of Draft:R. E. Moore Prize during the discussion but should not remove the miscellany for deletion template from the top of the page; such a removal will not end the deletion discussion. Thank you. Ivanvector (^Talk/_Edits) 12:41, 1 October 2019 (UTC)

Nomination of Portal:Statistics for deletion

A discussion is taking place as to whether Portal:Statistics is suitable for inclusion in Wikipedia according to Wikipedia's policies and guidelines or whether it should be deleted.

The page will be discussed at Wikipedia:Miscellany for deletion/Portal:Statistics until a consensus is reached, and anyone is welcome to contribute to the discussion. The nomination will explain the policies and guidelines which are of concern. The discussion focuses on high-quality evidence and our policies and guidelines.

Users may edit the page during the discussion, including to improve the page to address concerns raised in the discussion. However, do not remove the deletion notice from the top of the page. Certes (talk) 13:13, 1 October 2019 (UTC)

Hysteretic model

Someone created a new article titled Hysteretic model with no other articles linking to it. I added a link from Hysteresis to the new article. The new article begins with this sentence:

Hysteretic models may have a generalized displacement $u$ as input variable and a generalized force $f$ as output variable, or vice versa.

This is quite an extreme example of lack of context-setting at the outset, but I'm not sure how to phrase a better opening sentence. This is a very multidisciplinary subject. Michael Hardy (talk) 17:21, 1 October 2019 (UTC)

Draft:Direct discontinuous Galerkin method

Is this an original research or something in mainstream? I’m inclined to the former (and thus the deletion on the ground), but wondering what other editors think. —- Taku (talk) 23:18, 18 September 2019 (UTC)

The sources look legit and don't appear to be languishing in citation obscurity, and the SIAM one is ten years old. It looks like we could have an article, or at least a section of an article, on the topic, but the existing draft text would need serious editing before it could be called ready. Compare its prose with Discontinuous Galerkin method. XOR'easter (talk) 01:17, 21 September 2019 (UTC)

Sorry about the late response and thank you for the feedback. I will propose a merger and hopefully someone knowledgeable can deal with it. —- Taku (talk) 23:49, 2 October 2019 (UTC)

Improved {radic} rendering

I've proposed a change to improve rendering of {{radic}} (e.g. currently √3) to make the two lines meet. Input is requested at Template talk:Radic#Appearance again before I make such a widely-seen change. Thanks. —[AlanM1(talk)]— 23:00, 3 October 2019 (UTC)

Ivan Fesenko edit request

Hey,

Even though I actually do have a masters, I find myself a bit out of my depth looking at the edit request at Talk:Ivan Fesenko#Extended-confirmed-protected edit request on 12 September 2019. Can someone who knows more about number theory than I have a look over and assess it, so the XCP backlog can get cleared out? :) Sceptre (talk) 21:37, 2 October 2019 (UTC)

Done by Melmann. — MarkH21 (talk) 00:34, 4 October 2019 (UTC)

"Expected value": textbook or not textbook

The article "Expected value" was of length 37 Kb on Aug 7, 2017. Then User:StrokeOfMidnight made hundred of edits; on Dec 3, 2017 the length was 69 Kb, and the article became full of detailed rigorous proofs. Less intensively this was continued till Sep 23, 2018 (74 Kb), and slowly till Aug 2019. On Sep 26, 2019 User:Iyerkri started intensive work on that article, and now its length is 56 Kb. On Oct 3, 2019 StrokeOfMidnight initiated a discussion with Iyerkri on the talk page there: Talk:Expected value#"Cleaning up" Basic Properties. Much earlier I voiced there some doubts towards StrokeOfMidnight (see Section "Expected value#Proving that X=0 (a.s.) when E|X|=0" there); I wrote that your writings tend to smell advanced math, which irritates the majority; we are not on a professional math wiki like EoM, and the expectation is of interest for many non-mathematicians, and proofs are generally unwelcome here (and by the way, on EoM as well), but did not convince StrokeOfMidnight, and did not insist. So... now I am still not sure... the article tends to oscillate between encyclopedic and textbook-ish... is anyone willing to look? Boris Tsirelson (talk) 21:46, 3 October 2019 (UTC)

The article is in a pretty awful state, and that section really does need a massive clean-up. It definitely has too many properties and formulas, with too little prose that I wouldn't even call it textbook-like. To be fair, the pre-StrokeOfMidnight version wasn't great but the problems have only been exacerbated.
Perhaps spinning off the properties and mathematical details would be due? — MarkH21 (talk) 00:47, 4 October 2019 (UTC)

Spinning off to Proofwiki?   :-)   Boris Tsirelson (talk) 05:31, 4 October 2019 (UTC)

Edit war starting at Involute and Curvature

Recent edits to Involute and Curvature need attention of other eyes than mines. D.Lazard (talk) 14:33, 1 October 2019 (UTC)

Merely from a formatting perspective, this is not an improvement: encyclopedia text should be prose, not bullet points. And removing the short description is a bad move, though its effects are probably invisible to many. XOR'easter (talk) 17:19, 1 October 2019 (UTC)

Please, could some one stop user Lichinsol editing math articles. Since Sept. 29 I am fixing his mistakes on Involute. And Im not sure I found all. --Ag2gaeh (talk) 05:39, 4 October 2019 (UTC)

Extremely suspicious behavior on the talk page of Curvature, and continued edit-warring by Lichinsol. I tried discussing Lichinsol's behavior on their talk page but it doesn't appear to have done much. — MarkH21 (talk) 06:09, 4 October 2019 (UTC)

Anyone good at elegant/understandable descriptive text for tables?

So I've got a question about body text describing a table. [I may have another question later]. I am trying to write it, but what I've written sounds clunky (especially the second sentence) Can anyone improve it? If you want to explain the data in a completely different way, that's OK too. Tks!

The table below illustrates that land transfers increased significantly in each of four successive years. When compared to the base period of 190–41, the 1941–42 increase was 504%, 1942–43 was 665%, 1943–44 was 1,057% and the increase of 1944–45 compared to 1940–41 was 872% :

Land alienation in Bengal, 1940–41 to 1944–45: number of sales of occupancy holdings

1940–41	1941–42	1942–43	1943–44	1944–45
141,000	711,000	938,000	1,491,000	1,230,000

 ♦ Lingzhi2 (talk) 12:52, 4 October 2019 (UTC)

What about this?

Land alienation in Bengal, 1940–41 to 1944–45: number of sales of occupancy holdings

Time Period	1940–41	1941–42	1942–43	1943–44	1944–45
Sales of occupancy holdings	141,000	711,000	938,000	1,491,000	1,230,000
Percentage increase from 1940-1941		504%	665%	1057%	872%

If you're just summarizing information per year, I think it belongs in the table. Although I wonder what the benefit of this is. Wouldn't it be better to look at the percentage increase or decrease from the previous year, not just one base year?Brirush (talk) 13:10, 4 October 2019 (UTC)

Thanks for this. I'm not sure what the best way to express/explain the data would be. I want the reader who sees it to think, "Wow! Those numbers are exploding!" Because they were exploding. ♦ Lingzhi2 (talk) 13:22, 4 October 2019 (UTC)

Map projection

I’ve exhausted my patience for this dispute for the day and so I’m seeking a third opinion here. —Jasper Deng (talk) 09:37, 6 October 2019 (UTC)

Yikes. I have commented there. XOR'easter (talk) 21:30, 6 October 2019 (UTC)

@Jasper Deng: it would have been helpful to include a link to the discussion; for everyone else, it is here. I have also commented. --JBL (talk) 22:43, 6 October 2019 (UTC)

And in all that (still ongoing!) discussion, nobody has raised the vital question of what your favorite map projection says about you. XOR'easter (talk) 01:54, 7 October 2019 (UTC)

Three prodded calculus articles

Linearity of integration, Constant factor rule in integration, and Sum rule in integration have all been prodded. Someone who knows more than I about calculus pedagogy might want to evaluate whether they should be saved or let go. —David Eppstein (talk) 04:10, 7 October 2019 (UTC)

At first glance, these would belong on Wikiversity or Wikibooks. They read like course notes I might prepare for a first-year calculus course, not encyclopedia articles. Doubtless many texts cover these properties, but do they need separate articles from those on differentiation and integration? I don't think so.--Jasper Deng (talk) 05:40, 7 October 2019 (UTC)

• These are unsourced pedagogical essays and the content is covered already at Integral. These titles should redirect there. Reyk _YO! 09:01, 7 October 2019 (UTC)
• (edit conflict) Maybe not useful for me to add anything more, but I completely agree with the redirect. In particular, to the section Integral#Properties. — MarkH21 (talk) 09:07, 7 October 2019 (UTC)
  • Actually I’ll just convert them to redirects now. — MarkH21 (talk) 09:10, 7 October 2019 (UTC)
    • Redirecting is a good fix. Thanks. XOR'easter (talk) 17:44, 8 October 2019 (UTC)

Multiplicative digital root

This looks like OR, spread across 64 different anonymous edits. Opinions welcome. XOR'easter (talk) 17:38, 8 October 2019 (UTC)

Is "not everything in Mathworld is a real thing that should have a Wikipedia article, just delete it" the kind of opinion you are looking for?

More seriously (maybe): I would throw around a bunch of cn tags and start a discussion directly with the IP -- they've been editing from the same address in the same manner for several weeks on a bunch of probably-not-really-notable base-dependent number sequences, perhaps they are amenable to learning about our policies. (The editing reminds me of, but seems more competent than, that of User:Xayahrainie43‎.) --JBL (talk) 00:04, 9 October 2019 (UTC)

Pretty sure they're not the same person as X despite the overlapping interests. —David Eppstein (talk) 04:35, 9 October 2019 (UTC)

Notability of integer sequences

What makes an integer sequence notable? Is an entry in OEIS or MathWorld enough? Specifically this is a question for the following articles:

• Evil number
• Factorion
• Missing-digit sum
• Odious number
• Pernicious number (contains a dead link)
• Polydivisible number

but I suspect this to be the case for many other such articles on integer sequences on Wikipedia. They do not have references other than OEIS or MathWorld, if any at all, and are either stubs lacking content other than the information on OEIS or MathWorld, or articles filled with what seems to be original research not found in OEIS or MathWorld. Prova-nome (talk) 04:08, 9 October 2019 (UTC)

We have a guideline on this; see Wikipedia:Notability (numbers). I don't think OEIS or MathWorld by itself is enough, but they can contribute to notability together with academic journal articles and books that discuss these sequences. It's important to follow WP:BEFORE by looking for sources rather than assuming that a badly-written article is also non-notable. Sometimes it also works to search for the OEIS sequence numbers in other sources. The odious and evil numbers are clearly notable; e.g. "odious numbers" has 60 hits in Google scholar, many of which look sufficiently in-depth for both sequences. Factorions have fewer but see JSTOR 3620842 and JSTOR 3620841; that may be enough. I'm not sure about the rest, though. —David Eppstein (talk) 04:18, 9 October 2019 (UTC)

If the sequence has the keyword "dumb" in OEIS, it probably shouldn't be included. And appearing in MathWorld may mean that the idea or the name is solely that of Weisstein or some other MathWorld contributor. I'm not sure about pernicious or polydivisible, although I'm sure pernicious needs to have some trivia removed. — Arthur Rubin (talk) 09:51, 9 October 2019 (UTC)

Agree with David, and Arthur, neither OEIS, nor especially MathWorld, is enough. Paul August ☎ 17:09, 9 October 2019 (UTC)

I agree in particular that OEIS alone is not enough. That site has many thousands of integer sequences, and I don't think we should have articles on the majority of them. Many of the articles we do have, for instance polydivisible number may be notable but are also full of original research- much of it banal. Reyk _YO! 18:24, 9 October 2019 (UTC)

MacCullagh ellipsoid and Galois axis

The article MacCullagh ellipsoid survived a deletion debate last year (at the time, I said that where there might be an argument for a merge-and-redirect, that can be decided at a later date). It has since been moved to MacCullagh ellipsoid and Galois axis, which seems to give undue prominence to the "Galois axis" part, given that it appears to be the pet idea of Semjon Adlaj, himself of uncertain wiki-notability, and not an established term. I may take a crack at sorting all this out myself, but perhaps someone would like to beat me to it. XOR'easter (talk) 23:33, 6 October 2019 (UTC)

Moved back, seems silly when "Galois axis" is defined on "MacCullagh ellipsoids" and is of uncertain notability. — MarkH21 (talk) 21:35, 7 October 2019 (UTC)

The aformentioned article on Adlaj is now at AfD. — MarkH21 (talk) 21:47, 7 October 2019 (UTC)

And now there's an article Galois axis? XOR'easter (talk) 21:29, 10 October 2019 (UTC)

The IP/SPA edit-warring has continued on Galois axis and MacCullagh ellipsoid, so I have taken Galois axis to AfD to end the chance for future edit-warring. The activity has also spread to Tennis racket theorem, j-invariant, and WP:ANI#Please restore the stable version of MacCullagh ellipsoid and Galois axis. Attention appreciated. — MarkH21 (talk) 15:06, 11 October 2019 (UTC)

AfD closed due to some effective edit conflicts with sock disruption. Also forgot to mention the same disruption is also at Pendulum (mathematics).
— Preceding unsigned comment added by MarkH21 (talk • contribs) 15:34, 11 October 2019 (UTC)

The German Wikipedia has a better article on the topic de:Trägheitsellipsoid which seems to be related to inertial ellipsoid. It apparently the geometric location of all angular momenta corresponding to the same rotational energy. --Salix alba (talk): 19:46, 11 October 2019 (UTC)

@Salix alba: Yes, in fact that corresponds better to the article Poinsot's ellipsoid, which mentions the inertia ellipsoid and whose existence partially prompted the original AfD. — MarkH21 (talk) 19:55, 11 October 2019 (UTC)

Typo in an article (edit request?)

Very unfamiliar with how wikipedia works but this seems to be where to submit this. In this article, under the section "Extensions of the standard dictionary numbers", for the value of 10^51 sexdecillion, it instead says sedecillion. This also does not align with the "Standard dictionary numbers" section of the article with the proper spelling. Pnunya (talk) 16:21, 12 October 2019 (UTC)

Thank you for your comment. It looks like the "Extensions of the standard dictionary numbers" table is based on a different system, in which the prefix se- takes an x before octo but not before deci. XOR'easter (talk) 16:27, 12 October 2019 (UTC)

Article and talk page title mismatch for Dual-complex numbers

Currently, the page Dual-complex numbers redirects to Dual-complex number, but Talk:Dual-complex number redirects to Talk:Dual-complex numbers, not vice versa. Either the article and talk page should both be plural, or else, they should both be singular. JBW only moved the talk page back to the plural title, but not the article. GeoffreyT2000 (talk) 21:57, 4 October 2019 (UTC)

Done, moved the singular article title to the plural article title to match the talk page move by JBW. — MarkH21 (talk) 22:06, 4 October 2019 (UTC)

@MarkH21, JBW, and GeoffreyT2000:That seems backwards: compare complex numbers, real numbers, quaternions, etc. --JBL (talk) 22:45, 6 October 2019 (UTC)

@Joel B. Lewis: You’re completely right. I made the move just to match the talk page without actually looking at the discussion or reason for the talk page move itself. — MarkH21 (talk) 23:32, 6 October 2019 (UTC)

@GeoffreyT2000, Joel B. Lewis, and MarkH21: It seems to me more natural to have "complex numbers", "real numbers", etc, but since, as JBL has pointed out, we have the singular forms, I have moved Dual-complex numbers back to Dual-complex number for consistency. And of course moving just the talk page was a mistake; thank you GeoffreyT2000 for pointing it out. JBW (talk) Formerly known as JamesBWatson 12:41, 14 October 2019 (UTC)

De Bruijn index and De Bruijn notation

The current version of the former article links to the latter, with a note: "This notation has little to do with De Bruijn indices, but the name "De Bruijn notation" is often (erroneously) used to stand for it." I do not see how this can be correct - both are ways of representing lambda terms uniquely in terms of alpha-equality, and therefor identical. I'm considering removing this note. Airbornemihir (talk) 11:23, 14 October 2019 (UTC)

Done. Airbornemihir (talk) 11:30, 14 October 2019 (UTC)

Nevertheless, the article began with "Not to be confused with De Bruijn notation. In mathematical logic, the de Bruijn index is a notation..." This was highly confusing. Thus, I have modified the hatnote, and removed the use of "notaation" in the first sentence. In any case, it is wrong to say that De Bruijn index and De Bruijn notation are identical, as the bind variables are named in one case and not in the other. D.Lazard (talk) 13:15, 14 October 2019 (UTC)

Draft:Multiplicity (statistical mechanics)

Dear mathematicians: Here's a draft article that is within the interest of this WikiProject. Perhaps someone who with knowledge of this field can take a look at it.—Anne Delong (talk) 11:45, 15 October 2019 (UTC)

My first impression is that it is written like an essay and would need cleaning up before it could be suitable as an article. The content appears redundant with diversity index, surprisal, entropy and other existing articles. XOR'easter (talk) 17:25, 15 October 2019 (UTC)

Statement in the lead of the article on infinity

In the article Infinity, there's a statement in the lead: "For example, Wiles's proof of Fermat's Last Theorem uses the existence of very large infinite sets." I don't really know anything about this stuff, and this struck me as rather surprising, so I went to look for more. However, nothing in the article talks about this, and nothing at the article on the proof seems to say anything about this either. I also couldn't find anything after a cursory search. So I really have no idea if this is a valid statement or not; I've tagged it with a {{cn}} for now, but if anyone happens to know more about this, please feel free to either set me right, or even excise the statement with extreme prejudice. Thanks, –Deacon Vorbis (carbon • videos) 02:54, 8 October 2019 (UTC)

@Deacon Vorbis: It’s because Wiles’ proof (and much of the cohomology used in modern number theory) uses Grothendieck universes. Within ZFC, their existence is equivalent to the existence of certain large cardinals. Here is a suitable reference. You (or someone else) can judge whether this is appropriate in the lead there though - I don’t really know much about this kind of stuff. — MarkH21 (talk) 03:18, 8 October 2019 (UTC)

Just my impression but that sentence does look out of place, because in mathematics (or at least in algebraic geometry), one doesn’t worry too much about the set-theoretic issues. Some results might collapse without the existence of a strongly inaccessible cardinal. But they might not (with some care, it is sometimes possible to avoid the use of universe but I think people don’t bother). Determining that is an (interesting or uninteresting) original research and cannot be done in Wikipedia. — Taku (talk) 23:09, 8 October 2019 (UTC)

I added some words there ("in fact", maybe not "in principle"... according to that source); feel free to revert if you dislike it. Boris Tsirelson (talk) 20:30, 11 October 2019 (UTC)

Maybe I shouldn't argue again after writing "feel free to revert if you dislike it", but let me do. XOR'easter's text "For example, Wiles's proof of Fermat's Last Theorem uses the existence of very large infinite sets, though it may happen that another proof that avoids such sets will be found" is deleted by MarkH21 with edit summary "this whole bit feels unnecessary, the sentence is about Wiles’ proof - not all proofs - so there’s no implication about any other proof", logically flawless and nevertheless controversial. A reader (human, not robot) seeing that a famous proof uses (or "is written with the implicit reliance on" according to Takuya Murata) an exotic assumption, probably concludes that this assumption is, or at least is widely believed to be, necessary. Why? First, math textbooks often encourage a student to check that each assumption (of a theorem) is necessary; thus a student may believe that doing otherwise is unprofessional. Second, otherwise, why mention this fact in the lead to "infinity" article? Third, otherwise experts would find (or at least, actively seek; or, at the very least, debate possible existence) of a "better" proof. And really, it is debated (see the source [4]: used "in fact", not "in principle"), which is not even hinted at in our article. Thus is why I feel that our article is a bit misleading (or not neutral). Boris Tsirelson (talk) 17:43, 17 October 2019 (UTC)

I'm neutral on whether the whole sentence should be kept in the lead or not. (I can see Grothendieck universe might be an interesting thing to mention in the lead.) I changed "use" because the meaning of it is very unclear; one can argue that the use of "universe" is a stylistic choice but not a logical necessity (and I don't think we know the answer). I agree the wording I introduced was somehow strange but I couldn't figure out the better one (would be happy to see the others give a shot too). -- Taku (talk) 23:55, 17 October 2019 (UTC)

My feeling is that the mention of large cardinals in the use of a famous theorem is mildly interesting and engaging to any reader, but not essential to the lead. However, further elaboration on the possibility of resolving the reliance on Grothendieck universes (still unknown according to the cited source) seems unnecessary for a brief engaging digression. Since Wiles's proof relies on the existence of Grothendieck universes, and it's unknown whether that reliance may be removed by some other way, it seems completely honest to just say that Wiles's proof relies on it. So the current brief mention seems fine and mildly interesting to me, but I disagree with including a further digression on how it's unknown whether the reliance can be removed. — MarkH21 (talk) 08:43, 18 October 2019 (UTC)

I'd prefer nothing at all to something a bit misleading. Boris Tsirelson (talk) 10:12, 18 October 2019 (UTC)

I introduced this sentence by [this edit]. The purpose of it was to fix a common misconception that infinity would be a philosophical concept in mathematics. IMO, this is important to show that, in mathematics, infinity is no more a philosophical concept, but is, presently, a purely mathematical concept that is mathematically studied, and is widely used across. Looking at many Wikipedia article, such as this one, that are close to the interface between philosophy and mathematics, it appears that my above assertions, which are evidence for most mathematicians, are not widely known outside mathematics community. Thus my edit was a tentative for clarify this. The whole article would need to be clarified from this point of view, but, at least, the lead require to be clear, as many readers look only on it.

IMO, the example of Wiles's proof of Fermat's Last Theorem is essential in the lead, because it the only example that I know that can be used to show to non mathematicians that the manipulation of infinity as a mathematical concept is useful even for problems that seem unrelated. For making clear that this is the purpose of this example, I have completed the sentence by "for solving a long standing problem, which is stated in terms of elementary arithmetic". D.Lazard (talk) 11:28, 18 October 2019 (UTC)

Nice; but it is unfair to implicitly overstate it by exploiting the implicit assumption of some (or many?) readers that "uses" means here "uses in principle" rather than "uses in fact" (these phrases appear in the source [4] because McLarty recognizes this potential for confusion). Till now, no one addresses my "first", "second" and "third" arguments (above). Boris Tsirelson (talk) 11:45, 18 October 2019 (UTC)

“Quotient” of functional integrals

Normally, if we write one expression on top of a fraction line and another on the bottom, we evaluate both before dividing. This would yield an indeterminate form when both the numerator and denominator are functional integrals with infinite value. Yet the article on functional integrals states “Most functional integrals are actually infinite, but then the limit of the quotient of two related functional integrals can still be finite”. Huh?

The topic overall needs love. It’s way too hand-way right now.—Jasper Deng (talk) 04:31, 23 October 2019 (UTC)

Apparently, that phrase is like "$f'(x)={\tfrac {dy}{dx}}$" that hints at $\lim {\tfrac {\Delta y}{\Delta x}}$ rather than ${\tfrac {\lim \Delta y}{\lim \Delta x}}$. Boris Tsirelson (talk) 05:06, 23 October 2019 (UTC)

And by the way: I just added EoM article to "See also" there. But I was not able to use the Template:SpringerEOM, since its "http:" is obsolete and not working; now must be "https:". Oops, no; "id=" is needed, in addition to "title=". Boris Tsirelson (talk) 06:23, 23 October 2019 (UTC)

Glossary of Lie algebras → Glossary of Lie groups and Lie algebras

Maybe not controversial but I have made a proposal for the move in the title at Talk:Glossary of Lie algebras. —- Taku (talk) 04:04, 25 October 2019 (UTC)

Drafts to be watched

Hi all. There is a possibility that I will be banned in a next day or 2 for an indefinite or definite period of time (see the very last section of Wikipedia:Administrators' noticeboard#Topic Ban Request: TakuyaMurata).

So, it would be nice if some other editors can watch out for non-constructive edits (in good faith or not) to the draft pages listed in Wikipedia:WikiProject Mathematics/List of math draft pages. Also, in the thread, there is a proposal that drafts started by me over a year ago should be moved out of the draftspace. Since they are not my drafts, it would be natural to put them as subpages to the project page. If some other editors think this is a good idea, please go ahead and do. (I will not be able to do that myself because of the ban.) —- Taku (talk) 23:21, 24 October 2019 (UTC)

When/if banned, I will also try to publish some error fixes (e.g., typos) at my talkpage that should be made to articles in Wikipedia. -- Taku (talk) 10:54, 25 October 2019 (UTC)

Request for information on WP1.0 web tool

Hello and greetings from the maintainers of the WP 1.0 Bot! As you may or may not know, we are currently involved in an overhaul of the bot, in order to make it more modern and maintainable. As part of this process, we will be rewriting the web tool that is part of the project. You might have noticed this tool if you click through the links on the project assessment summary tables.

We'd like to collect information on how the current tool is used by....you! How do you yourself and the other maintainers of your project use the web tool? Which of its features do you need? How frequently do you use these features? And what features is the tool missing that would be useful to you? We have collected all of these questions at this Google form where you can leave your response. Walkerma (talk) 04:24, 27 October 2019 (UTC)

Nov 2019

Geometrization

The article titled Classification of manifolds says some manifolds are geometrizable and some are not, and the article titled Geometrization conjecture seems to suggest that that means a manifold admits a "geometric structure". The concept is not defined in either article, and Geometric structure redirects to an article in which that term appears once, without a definition, and the word geometrizable occurs twice, also without a definition. Can someone put a definition at some appropriate place in those articles? Michael Hardy (talk) 17:38, 29 October 2019 (UTC)

Isn't it (almost) defined in "Geometrization conjecture#The eight Thurston geometries" (plus the previous text)? Boris Tsirelson (talk) 22:50, 29 October 2019 (UTC)

Should the page Geometric structure be a disambiguation page? Th eredirect to differentiable manifold is certainly not acceptable, and I feel many mathematical concepts can qualify as describing some kind of geometric structure, and none of them is quite general enough to be a redirect. For example, a few that are relevant to the above discussion are :

* (G,X)-structure ;

* model geometries as described in Geometrization conjecture#The eight Thurston geometries ;

* Riemannian manifolds.

That might mean disambiguating a few links here and there but this seems much better than the current situation. jraimbau (talk) 09:14, 1 November 2019 (UTC)

Book "Differential Geometric Structures" by Walter A. Poor, 2007; annotation: Useful for independent study and as a reference work, this introduction to differential geometry features many examples and exercises. It defines geometric structure by specifying the parallel transport in an appropriate fiber bundle, focusing on the simplest cases of linear parallel transport in a vector bundle.

The treatment opens with an introductory chapter on fiber bundles that proceeds to examinations of connection theory for vector bundles and Riemannian vector bundles. Additional topics include the role of harmonic theory, geometric vector fields on Riemannian manifolds, Lie groups, symmetric spaces, and symplectic and Hermitian vector bundles. A consideration of other differential geometric structures concludes the text, including surveys of characteristic classes of principal bundles, Cartan connections, and spin structures.

Also Sect.2 in lectures Geometric structures by Werner Ballmann.

Also Terry Tao about Shing-Tung Yau, “What is a Geometric Structure”. Boris Tsirelson (talk) 10:26, 1 November 2019 (UTC)

Infinity article lead, technical correctness vs common language

Can someone else take a look at the lead of Infinity? It's gone through several changes recently and it's a balancing act between being technically correct and being common language. I suppose I lean farther towards being technically correct than towards using common language, since I think that the common language surrounding "infinity" is often be misleading (e.g. "it cannot be counted or measured even in principle").

More eyes are always welcome. — MarkH21 (talk) 23:28, 7 November 2019 (UTC)

I have edited the article before reading this thread. The begin of the disputed sentence is "In common language". Here is my edit summary which summarizes wle my opinion: This is about common language. It is therefore nonsensical to try introducing mathematical accuracy. "Number" without link would be fine except that it may be confusing for people knowing of infinite numbers. So I put "common number", but I will be fine if "common" is removed. On the other hand, I am strongly against linking. D.Lazard (talk) 23:40, 7 November 2019 (UTC)

An idea: for everyday usage, can we just follow dictionaries (if not urban dictionary)? Trying to come up with a *right* definition is a bit of original research after all. -- Taku (talk) 23:58, 7 November 2019 (UTC)

I agree with both D.Lazard and TakuyaMurata. Paul August ☎ 00:19, 8 November 2019 (UTC)

I guess my feeling is that we don't write encyclopedia articles to document "common language", and I have a general dislike of sourcing Wikipedia content from dictionaries, which I feel usually misses the point. Dictionaries, like encyclopedias, are tertiary sources, and we should be using primarily secondary sources.

The "larger than any common number" language is -- better than some other possibilities, but not ideal. What's a "common" number? Is that a precise notion? Isn't, say, Graham's number larger than any "common" number? The "larger than any natural number" language at least had the advantage of being meaningful and correct for just about any mathematical notion of infinity I can think of.

Which brings me to maybe the more difficult point, which is deciding what exactly the infinity article is supposed to be about. Right now there's a division between infinity and infinity (philosophy), which I suppose means that infinity itself is supposed to be about mathematics (and possibly natural science). To me this is a slightly artificial division; the proximate cause of the biggest philosophical disputes within mathematics has almost always been related to the treatment of infinity. I would support a merge of these articles, and that might change my view of the lead sentence, though I have no good candidate language for such a sentence. --Trovatore (talk) 02:57, 8 November 2019 (UTC)

I think it would be best if this discussion were to continue on Talk:Infinity, where there is a related discussion. Paul August ☎ 12:00, 8 November 2019 (UTC)

User:Math-drafts

This is an announcement that I have created an alternative account of mine: User:Math-drafts to move some of old drafts in the [[Draft:]] namespace to the subpages of that user page. While I am in control of the account, the draft pages in that user page are meant to belong to the community and all the editors should feel free to edit them as fit (including moving to mainspace or even deleting them). This alternative account itself will never make an edit.

Please let me know if there is any issue. —- Taku (talk) 09:14, 7 November 2019 (UTC)

By "issue", I mean this. WP:NOTWEBHOST is a policy and, because of the technical nature, I need the project's help to ensure that I am not using Wikipedia as my personal web host. -- Taku (talk) 22:54, 8 November 2019 (UTC)

Thanks for the clarification. NOTWEBHOST is mostly about disallowing significant non-encyclopedic uses of WP wiki pages. Because all the pages under User:Math-drafts are for the explicit purpose of community development of potentially long-term draft articles and the improvement of the encyclopedia, I don't see there being any problem with that policy. --{{u|Mark viking}} {Talk} 23:57, 8 November 2019 (UTC)

Unfortunately, NOTWEBHOST is not the concern we are allowed to summarily dismiss; see User_talk:TakuyaMurata#Suggestion. So, I really need to ask the project to ensure there is absolutely no violation of this policy (which has a very severe consequences). -- Taku (talk) 00:41, 9 November 2019 (UTC)

Any sufficiency advanced math draft pages are indistinguishable from spammy scientific personal notes. So, this project has to been in charge of that policy not being violated (as non-math editors cannot do the task); not only for drafts started by me. —- Taku (talk) 02:07, 9 November 2019 (UTC)

I concur with Mark viking here. Highly technical drafts can take a while to develop; they benefit from being available for multiple math-inclined people to work on. Keeping them somewhere that isn't attached to a specific person's name is good for that. XOR'easter (talk) 15:29, 9 November 2019 (UTC)

A math template at TfD

Folks here may be interested in the discussion at Wikipedia:Templates for discussion/Log/2019 November 10#Template:Mabs. –Deacon Vorbis (carbon • videos) 19:19, 10 November 2019 (UTC)

Notability/sourceability?

For your consideration: the new article Dubner's conjecture. The Dubner in question is Harvey Dubner, the subject of an old (2007) but weakly referenced biography. Do appropriate sources exist? --JBL (talk) 16:18, 17 November 2019 (UTC)

Hmm. I'm not finding anything that suggests people other than Dubner worked on this conjecture. XOR'easter (talk) 16:53, 17 November 2019 (UTC)

Still not turning up anything of substance; the closest is the Delahaye item already linked in the article, which is a pop-science story that has a sidebar on "la nouvelle conjecture de Dubner". Just for fun — I did find an old NYT piece that appears to mention Dubner himself. XOR'easter (talk) 20:44, 17 November 2019 (UTC)

Fun find. I think it's plausible that Dubner could be notable (though I was disappointed not to find a substantive obituary anywhere, so maybe not). The conjecture (in J. Recreational Math) seems much less likely. --JBL (talk) 13:37, 18 November 2019 (UTC)

MR numbers not rendering properly in citation templates

See discussion at Help talk:Citation Style 1#MR numbers not rendering properly. —David Eppstein (talk) 07:10, 21 November 2019 (UTC)

Please comment. This will also likely affect {{MR}}. Headbomb {t · c · p · b} 20:14, 21 November 2019 (UTC)

Structural Ramsey theory

Hi all, I have been writing the article Draft:Structural Ramsey theory, and have just submitted it for review. I have done my best to give a complete account, and provide adequate context and references. I would appreciate if anyone could give feedback and/or review.

--Jordan Mitchell Barrett (talk) 09:52, 30 November 2019 (UTC)

Welcome to Wikipedia, and nice work! The article is well structured and well-referenced. I have two minor suggestions. First, WP writing is a little different than the usual mathematical writing in that it is a bit more formal--use of "we", "us", "note that", etc. is discouraged, as discussed in MOS:MATH#TONE. Second, for non-experts in this topic, in the introduction section you may want to briefly explain or wiki link what an r-coloring is. --{{u|Mark viking}} {Talk} 11:37, 30 November 2019 (UTC)

Thanks Mark viking for your feedback - I fixed up the tone to be more in line with the style, and explained some of the conventions I use (including r-colouring). I expect this article will not be read much by those outside advanced mathematics, but still best to make it as accessible as possible. --Jordan Mitchell Barrett (talk) 21:26, 30 November 2019 (UTC)

Gave a quick spitshine to the refs, btw. Headbomb {t · c · p · b} 11:46, 30 November 2019 (UTC)

Thanks Headbomb. --Jordan Mitchell Barrett (talk) 21:26, 30 November 2019 (UTC)

Dec 2019

Wikipedia talk:WikiProject Mathematics/Archive/2019/Dec