User talk:RobHar

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Hello, RobHar, and welcome to Wikipedia! Thank you for your contributions. I hope you like the place and decide to stay. Here are some pages that you might find helpful:

I hope you enjoy editing here and being a Wikipedian! Please sign your name on talk pages using four tildes (~~~~); this will automatically produce your name and the date. If you need help, check out Wikipedia:Questions, ask me on my talk page, or ask your question and then place {{helpme}} after the question on your talk page. Again, welcome!  VectorPosse 09:36, 24 March 2007 (UTC)

Also, thanks for checking in at Artin reciprocity. I look forward to any insight you might be able to add to that article if you ever have any free time. Good luck with your Ph.D. work. (I'm just trying to finish mine!) You also may want to check out Wikipedia:WikiProject Mathematics; it's where all the math people hang out. VectorPosse 09:36, 24 March 2007 (UTC)

Oh, wait. I just checked your contributions and I see you've actually been here at Wikipedia quite a while. Oh, well. Welcome and thanks anyway!  :)VectorPosse 09:40, 24 March 2007 (UTC)


Somehow, I missed the nice comment you made on my talk page. Sorry about that. Thank you very much for your support. Joeldl 07:11, 15 April 2007 (UTC)

David Mumford[edit]

Hi RobHar, you added David Mumford to the Mumford page, but he is already listed on the Mumford (surname) page. All the people called Mumford were moved to the surname page last month - not my idea, but apparently this is mandated by MOS:DP. --RichardVeryard 07:46, 27 August 2007 (UTC)

Strange. Ok, thanks. RobHar 16:40, 27 August 2007 (UTC)


WP:AWB is (correctly) trying to move interwiks to the end. It should perhaps, leave en: s alone. However they shouldn't really be there in the first place. Rich Farmbrough, 20:43 5 December 2007 (GMT).

Talk:Unitary group#Other fields[edit]

Howdy, I think you were correct to remove some of that, but I think even more might need to be removed. My viewpoint is from finite groups, so I wanted to use the talk page instead of deleting almost the entirety of the section. If we can agree on the definition for arbitrary fields, then I'll add some verbiage on the finite case. JackSchmidt (talk) 06:44, 14 December 2007 (UTC)

Hi Rob,
I've incorporated some of your and Jack's discussion in Unitary group#Generalizations; hope this helps!
Nbarth (talk) 00:10, 19 December 2007 (UTC)

Looking for photo of artifact at Princeton Art Museum[edit]

RobHar, I am looking for someone to drop by the Princeton Art Museum to take a photo of 1 or 2 particular Mesoamerican ballgame artifacts that should be on exhibit there. If this is possible for you, let me know. Thanks very much, Madman (talk) 12:29, 30 April 2008 (UTC)

Requested mathematician articles[edit]

You might be interested in WP:Requested articles/mathematics#Mathematicians. It already lists Mark Kisin, for instance. JackSchmidt (talk) 19:18, 25 June 2008 (UTC)

Thanks. Good point. RobHar (talk) 22:58, 25 June 2008 (UTC)

Discriminant of a number field[edit]

Thanks for those comments. I plan to expand root-discriminant soon, when I get some time. About references, by all mean add any reference you think useful, but why delete anything? As it happens I have Frohlich and Taylor right next to me but not Neukirch, so I wouldn't find it at all useful to delete that reference. Richard Pinch (talk) 16:38, 28 June 2008 (UTC)

John McCain article[edit]

The reason I removed the content is that it is incomplete and thus violates NPOV. The purpose of the article isn't to try to present McCain statements contradicting each other or to make votes seem bad. He opposes a cigarette tax. That's the relevant information for the article.Trilemma (talk) 00:47, 9 July 2008 (UTC)

Rob, I didn't intend to imply that you were not acting in good faith, only that the way the information was being presented was troublesome. I'll check into it some more and get back to you. Trilemma (talk) 03:25, 9 July 2008 (UTC)

Specific source templates[edit]

Howdy, I noticed you used a template to cite a source. This strikes me as a great idea. I noticed that actually tons of sources are done this way, but probably not very many in the math articles. Where did you hear about it? If you've been doing for a bit, how is it working out for you? JackSchmidt (talk) 17:13, 15 July 2008 (UTC)

I was over at french wiki and stumbled upon the fact that they have an entire "Reference space" [1] (like template space, and article space, etc) (the example I stumbled upon was, of course, [2]). So I brought up this idea at Wikipedia_talk:Citing_sources#Reference_Space and eventually someone mentioned that there were already specific source templates in use. I still think that the idea of a "Reference space" is a better one, but I figured I could at least, for now, start using the specific source templates, and maybe raise interest in a reference space (especially since I have no idea how to go about creating such a reference space). RobHar (talk) 17:19, 15 July 2008 (UTC)
The French wikipedia implementation looks very nice (I like how you can select bibtex output). I realized math articles do use a few of the specific source templates, {{springer}}, {{MR}}, {{JFM}}, {{PlanetMath}}, {{mathworld}}, etc. but they are all families of references, rather than truly a single source.
Let me know if you start making lots of these templates, and we can at least setup a category for mathematics source templates. JackSchmidt (talk) 17:32, 15 July 2008 (UTC)
For now, I'll keep a list on my user page of specific source templates I've created (or stumbled upon). But yeah, when there are more around a category for them would definitely be a good idea. RobHar (talk) 20:31, 15 July 2008 (UTC)


Hi, I just see that you are working on algebraic number theory. Great! I will join you as soon as I can (after some holidays and FAC for groups). I'm also working on field (mathematics), which is also Top importance (if ANT is Top, fields should actually be "XX-top"), and start class. Jakob.scholbach (talk) 16:13, 6 August 2008 (UTC)

Some help would indeed be much appreciated whenever available. Such articles are so vast it's pretty hard to just create them out of nothing. I'll take a look at field (mathematics) and see what I can do there as well. I'm rather busy as well, but I can probably find some time. Cheers. RobHar (talk) 17:33, 6 August 2008 (UTC)

Local Field[edit]

When you say in the header that "an absolute value may be defined on it," will the induced topology of the absolute value be the same as the original topology? Otherwise the definition is not equivalent. (talk) 15:06, 7 August 2008 (UTC)

I'm simply following Weil's Basic number theory. Corollary 1 on page 5 shows that the two topologies are equivalent. Sorry about removing much of your new content, it just didn't seem necessary once the absolute value was not integral to the definition. I'll add a section on defining this absolute value since it's kind of interesting. RobHar (talk) 16:39, 7 August 2008 (UTC)

Thank-you! No worries about the removal, I agree with it; that content is more appropriate for an article on valued fields. (talk) 17:13, 13 August 2008 (UTC)


Likes a MILF.

Well other than asexual nerds. —Preceding unsigned comment added by (talk) 16:36, 29 August 2008 (UTC)

hehe, burn! that was a zinger. Your friends must think you're sooo clever. Keep up the good work. RobHar (talk) 17:12, 29 August 2008 (UTC)

fields or vector spaces?[edit]

Hi Rob,

I'm hoping to finish the groups FAC adventure soon. Then, I will be free for another topic. I see you progressed somewhat at Algebraic number theory - I know the phenomenon that a topic like this is quite a burden (I thought I could do something for group theory but suddenly realized that I have no clue). Anyway, I think working on "easier" topics (both in terms of depth and concreteness) such as field (mathematics) or vector space is rewarding, too, for both editors and readers. (Vector space is among the 500 most viewed math articles, but in a crappy state). Do you want to join in to push one of the two to GA standard? I have done so with groups, and hopefully even FA there, so there is no miracle about this, just a fair amount of work (that I'd like to share :), together with any potential fame).

Btw. in your box on L-functions, p-adic L-function may deserve a link (even if red). Jakob.scholbach (talk) 10:35, 13 September 2008 (UTC)

Hey. I've actually been trying to cut down on my wikipedia editing lately since I'm otherwise pretty busy (trying to graduate and teaching, etc), so I wouldn't really want to commit to anything right now. Sorry. It would be cool to push something to GA, but I just don't think I have the time. You've done a great job with groups though, and hopefully sometime in the not-too-distant future I can participate more in something like that.
Yeah, I was thinking of adding a section to my L-functions box called "p-adic aspects", maybe include the main conjecture of iwasawa theory, too (also a redlink), but I've haven't really gotten around to any of that. Cheers. RobHar (talk) 23:36, 14 September 2008 (UTC)

Wikipedia's Expert Peer Review process (or lack of such) for Science related articles[edit]

Hi - I posted the section with the same name on my talk page. Could you take part in discussion ? Thanks ARP Apovolot (talk) 01:01, 27 October 2008 (UTC)

Picture work[edit]

GDBarnstar1.png The Graphic Designer's Barnstar
Great work in converting one two three four ALL FIVE of my sketches to computer graphics for the Mayer–Vietoris sequence article! Wikipedia teamwork, I love it! GeometryGirl (talk) 11:42, 18 December 2008 (UTC)
Thanks! RobHar (talk) 23:21, 18 December 2008 (UTC)

I responded to your comment at my talk page[edit]

Please no WP:OUTING (read the first paragraph carefully). And I am therefore moving your comment to this talk page. —Preceding unsigned comment added by Point-set topologist (talkcontribs) 18:13, 24 December 2008 (UTC)

Your comment:

With regards to your P.S., if you are not new to wikipedia, it is unacceptable for you to use the "new user" excuse. I am not saying that you are or aren't new, I'm just saying. RobHar (talk) 18:01, 24 December 2008 (UTC)
Please no WP:OUTING (please read the first paragraph very carefully). I am familiar to the Wikipedia policies because I have (in the past) read a lot of articles in Wikipedia (and edited with an IP now and then). If this implies that I am not new, then I am sorry. But technically, as this user, I am new to Wikipedia. --Point-set topologist (talk) 18:10, 24 December 2008 (UTC)
I don't care whether or not you are technically new. You were using "newness" as a defense for your actions, claiming that you just aren't used to wikipedia. If that's misleading, I find it unacceptable. That's all. RobHar (talk) 18:31, 24 December 2008 (UTC)
OK. But no matter what you think, what you wrote on my talk page was unacceptable if you read WP:OUTING. Not that I am angry with you, but in any case, what you posted was unecessary and irrelevant. Please don't do it again. I just don't want people to get the wrong idea about me.
--Point-set topologist (talk) 18:54, 24 December 2008 (UTC)
I completely disagree that RobHar's comments on your talk page constitute WP:OUTING. Outing is the dissemination of personal information that allows, or could allow, the identification of an editor with a specific "real world" person. The only person who has provided personal information about your real-life identity is you. This information is insufficient to identify you (it is not even self-consistent!). Rather the issue here is how to deal with multiple accounts by the same user. Your situation is covered under the "clean start" paragraph of WP:SOCK, which reads
"The most common two concerns and their usual answers are:
I'll be noticed: If you change your behavior, and also the articles you work on, there is no reason for a connection to be made. If you continue on the same articles or your writing style is so distinctive it will quickly be noticed, or you return to problematic editing, then it is likely a connection will be made whether or not you change account, and any perceived concealment will probably be seen more negatively when discovered.
I'll be identified by checkuser or accused of being a sock puppet later: Checkuser is used for suspected breaches of policy. If you don't use the old account or engage in problematic conduct, there is little reason a request would be made, and a request without good reason is likely to be declined for lack of cause.
If future usage does draw attention by concerned users or administrators, then it is likely the connection will be made. See alternative account notification for how to reduce the likelihood of problems."
This makes clear that there is no protection available to you if your behavior and editing patterns lead people to suspect that you are the same person who used a previous account. Saying that you are a new to wikipedia when you are not is not only dishonest but counterproductive: to ask experienced editors to pretend that there is no connection between User:Topology Expert and User:Point-set topologist insults our intelligence, and seriously jeopardizes your clean start. Dishonesty is a very serious issue both for academics and encyclopedists -- perhaps the most serious issue, in fact. Please reflect on this in the context of your continued participation in this project. Plclark (talk) 20:09, 24 December 2008 (UTC)

Could I request that this section be removed? As it is not relevant to the project (and is now resolved), I think we can get back to normal editing. PST —Preceding unsigned comment added by Point-set topologist (talkcontribs) 18:49, 9 January 2009 (UTC)

Rob, I request that you not remove it, for reasons which are probably clear to you. Plclark (talk) 06:36, 10 January 2009 (UTC)
Please at least remove User:Topology Expert from your post. I feel that this was totally unnecessary. If you don't, I will consider taking this issue to a higher level. PST


Original Barnstar.png The Original Barnstar
Thanks for the reply to my question over at the math project. I apreciate your assistance in resolving the matter. Keep up the good work! TomStar81 (Talk) 00:48, 11 January 2009 (UTC)
Thanks! RobHar (talk) 04:20, 11 January 2009 (UTC)

Your post[edit]

Hi RobHar,

I agree with some parts of your post but I still do not understand where I have behaved badly (could you please confirm this so I can improve?). That's all I want to know.


Picard–Lindelöf theorem[edit]

hello. names should be hyphenated, not dashed. --emerson7 18:00, 13 January 2009 (UTC)

That contradicts both the hyphen article and the guideline WP:ENDASH. Hyphenated names are only appropriate when both names refer to the same person. JackSchmidt (talk) 18:08, 13 January 2009 (UTC)
i'm not so sure it's all that cut-and-dried. the two sections seem, contradictory, showing McCain-Feingold with a dash and a hyphen as both correct. --emerson7 18:31, 13 January 2009 (UTC)
What do you mean? I find no mention of McCain Feingold in either hyphen nor WP:ENDASH. The wiki article Dash notes as a caveat that the "Chicago manual of style" would use a hyphen in McCain Feingold. However, wikipedia does not follow the chicago manual of style, it follows the wikipedia MOS at Wikipedia:Manual of Style, and on this page is the germane paragraph (linked to above as WP:ENDASH). This page also contains WP:HYPHEN that discusses the use of hyphens on wikipedia. RobHar (talk) 19:24, 13 January 2009 (UTC)

moving discussion → to: talk:Picard–Lindelöf theorem

Help please[edit]

Hi Rob. I heard that you were good with images and wondered whether you might be able to help me. A lot of WikiProject banners use a B-class checklist to help assess articles. At the moment the current icon is used:


But this is not ideal because the B is prominent and may confuse because if the criteria are not met then the article will not be B-class. I think what we need is a combination of a B and the magnifying glass. Perhaps in the style of Symbol merge review.svg. It seems that there is no such icon available yet and I would have no idea where to begin to create one. Perhaps you could (a) make one for me :) or (b) tell me where to start. Thanks! Martin 10:49, 17 January 2009 (UTC)

Well I've given it a try, tell me what you think:
which you can make smaller (or bigger), link and place on a background (notice that the background can be seen through the magnifying glass, too):
Wikipedia:Version 1.0 Editorial Team/Assessment/B-Class criteria
If you're interested in making files like this I suggest downloading Inkscape. It is a free vector graphics software for mac, windows, and linux alike. It isn't too hard to pick up on. RobHar (talk) 21:31, 17 January 2009 (UTC)
Thank you very much. I might take a look at that program and see what I can do! Martin 22:16, 17 January 2009 (UTC)
It is possible to make all of the background clear? Then the background could be changed without having an adverse effect on the image. Martin 23:42, 18 January 2009 (UTC)
I assume you mean to remove the green and make it see through. Yeah that won't be hard, but it'll have to wait until probably Thursday. Cheers. RobHar (talk) 04:55, 19 January 2009 (UTC)
Yes, that's what I meant! Thursday would be great. Cheers, Martin 19:40, 19 January 2009 (UTC)
Looks like someone beat you to it. (Off their own back, I didn't ask them to.) Anyway it will probably be implemented on a few thousand pages soon. Thanks again, Martin 15:59, 20 January 2009 (UTC)

general definition of "conductor"?[edit]


do you know a general definition of conductor that applies to abelian extensions of local/global fields as well as abelian varieties? I don't know how the conductor of an abelian variety is defined (I know it for abelian extensions of local/global fields---is there a generalisation for arbitrary extensions?), but I've got the impression that the discriminant is a more algebro-geometric term, while conductor has something to do with Galois representations. If you can give me some reference, I'll write probably an article on it.

Best regards, Ringspectrum (talk) 18:52, 19 January 2009 (UTC)

Yeah I think conductors are more arithmetic (as in related to Galois reps). The conductor of an abelian variety is indeed defined in terms of the associated compatible system of l-adic representations (Milne has a paper on arithmetic of abelian varieties that discusses conductors, see also section 2.1 of Serre's "Facteur locaux" article [3], which discuss the definition of conductor for compatible systems of l-adic representations). As for defining conductors for arbitrary extensions, there is no known general definition. I'm pretty sure that the conductor of an abelian extension is the gcd of the Artin conductors but I don't have a reference for that. This could give some sort of relation with the conductor of an abelian variety. I'd be very interested to know some more about this. I'll try to give it some thought. Cheers. RobHar (talk) 19:39, 19 January 2009 (UTC)

Charles Émile Picard[edit]

i invite your attention here regarding your comments to the Charles Émile Picard article. i trust you will take it to heart. cheers.--emerson7 18:30, 29 January 2009 (UTC)

I would direct you to your talk page where I politely asked you to revert your changes. I was seconded by someone there. Then go over to the discussion at Talk:Picard–Lindelöf_theorem that you participated in and see how several more people agreed that your "corrections" were in contradiction to WP:MOS. One of these people decided to go to the bother of fixing your edits themselves, but of course missed some since they were spread over several articles. You replaced several endashes with hyphens and when people told you that was incorrect you just left them there. In my opinion, the people that reverted them back to endashes were indeed cleaning up your mess. If you have a problem with this, or with our interpretation of the use of endashes, I invite you to take this up with an authority on these matters. Cheers. RobHar (talk) 18:48, 29 January 2009 (UTC)

Still looking for photo of artifact at Princeton Art Museum[edit]

RobHar, I am still looking for that certain someone to drop by the Princeton Art Museum to take a photo of some Mesoamerican artifacts there. If this is possible for you, let me know -- any of these would be great, but I really need a photo of ballplayer pair in third photo down.

Let me know. Thanks very much, Madman (talk) 03:55, 31 January 2009 (UTC)

Inkscape question[edit]

Do you know by chance how in Inkscape the arrowhead (which is part of the line) can be colored? Somehow, neither setting the brush nor the pen color work out, the arrowhead is always black. Up to now, I always worked around this, but it gets really cumbersome... Thanks Jakob.scholbach (talk) 22:45, 1 February 2009 (UTC)

Well I looked it up, and it's not something that is built-in (which is weird). So, you select your path, and go to "Effects->Modify Path->Color Markers to Match Stroke". This will colour the arrows the current stroke colour of the path. If you change the stroke colour and you want the arrows to change colour, too, you have to do the above again. Another option is to convert everything to a path, i.e. select your path and go to "Path->Stroke to Path". This will create a group containing the original path as an object and an object for each of the arrows. This of course will make the arrows lose their relationship to the path. Either way the arrows aren't tied to the path as they should be. Weird. RobHar (talk) 06:13, 2 February 2009 (UTC)
Thanks! At least I wasn't totally blind... Jakob.scholbach (talk) 08:44, 2 February 2009 (UTC)


That's exciting stuff - thanks for updating Sato-Tate conjecture. Charles Matthews (talk) 19:07, 9 July 2009 (UTC)

No problem. RobHar (talk) 22:25, 9 July 2009 (UTC)


Hi, I know it's not very important, but just wanted to let you know that em dashes are unspaced while en dashes are spaced per WP:MOSDASH. I know it's confusing. Cheers, Dabomb87 (talk) 20:26, 4 August 2009 (UTC)

oh yeah, oops. I forgot. Thanks. Also, I hadn't noticed that spaced endashes were sanctioned by MOS:DASH for the purpose of replacing unspaced emdashes. Sorry 'bout that. RobHar (talk) 20:32, 4 August 2009 (UTC)

Shur's lemma[edit]

I thought that I should clarify the change I made at field extension regarding the comment about Shur's lemma. Most forms of Shur's lemma are stated in the following form:

If M is an irreducible R-module then C(M) is a division ring. - I. N. Herstein, Theorem 1.1.1., p. 5

By C(M), it is meant "the commuting ring of R on M." If F is a field, then F is an irreducible right (or left, of course) R-module (since the submodules of F under this module action are precisely the right ideals of F, this follows from that which you asserted). Elements of C(F) are precisely those ring homomorphims of F and by Shur's lemma, we have that C(F) is a division ring. Therefore, any non-zero homomorphism of F is invertible (in C(F), in fact) so that any such element has trivial kernel. Note that this form of Shur's lemma can of course generalize to module homomorphisms between distinct fields (with the module structure described) so that it relates to the assertion within the article. Perhaps you are right that the assertion in the article is not exactly Shur's lemma, but it is nevertheless the "classical form" of Shur's lemma presented in some textbooks. In effect, that fields possess no non-trivial proper ideals does indeed imply the assertion in the article, but it is not wrong to say that Shur's lemma does too. --PST 11:11, 6 September 2009 (UTC)

I wasn't claiming that Schur's lemma doesn't imply the fact that homomorphisms between fields are injective, it's just overkill. Fields have no non-trivial ideals (since every non-zero element is a unit) and the kernel of a homomorphism is an ideal. It's that simple. Schur's lemma is something used in more complicated situations such as representation theory; not to prove one of the most basic facts in field theory. RobHar (talk) 20:23, 6 September 2009 (UTC)
I do not disagree that it is your opinion that my edit was "overkill". However, my opinion is that this illustrates the motivation for Shur's lemma - for regular right-R modules (R an arbitrary ring), irreducibility is equivalent to the division ring assumption (assuming the existence of a 1 in R, of course). Nevertheless, this dispute is more than just a disagreement regarding opinions. In my edit, I corrected a mistake (namely that the article initially appeared to assert that zero homomorphisms are injective) as well as explained an unreferenced/unsourced fact. Since the initial revision was technically incorrect, and I have corrected it and certainly not introduced any further errors, I do not see why it need be immediately reverted. Perhaps you are right that mentioning Shur's lemma is "overkill", but many textbooks and the literature do so in the same situation. The rule of thumb here is: when a constructive edit is made and reverted (both actions occuring with good reason), the benifit should be given to the person who first made the edit. Although I do not feel that this matter is of any worth, I wish to point out that you should have at least observed that I had corrected a mistake, when reverting. --PST 02:20, 7 September 2009 (UTC)
You did not correct any statement. My first edit summary included "also, ring homorphisms are unital (Category of rings)" to indicate that you should take a look at that article and see that on wikipedia ring homomorphisms are defined to be unital (and hence automatically non-zero). You could similarly check out the article Ring homomorphism. This is why I completely undid your edit. Furthermore, I have never seen any book that in discussing this basic feature of homomorphisms between fields mentions Schur's lemma. As you have reinserted your edit once again I'll simply post my concerns at Wikipedia talk:WikiProject Mathematics. I'll also post there your rating of Banach Manifold as top priority: groups are magmas, but magmas aren't as important as groups. Similarly for Banach manifolds; the level of generalization matters. RobHar (talk) 11:18, 7 September 2009 (UTC)
I did not know of this convention in Wikipedia so I apologize if this has created a misunderstanding. With respect to "priority ratings", your perspective is simply re-worded to achieve a purpose. Had you written "the class of groups is contained in the class of magmas so that magmas are less important than groups", it would have sounded rather odd although it is equivalent to what you have said. In effect, priority rating explanations depends on opinion and how one views it. I think that after reading Carl's explanation at WikiProject Mathematics, I appreciate the idea of priority ratings (Carl does not argue that priority ratings relate to how important a topic is but rather explains that they measure the need for an article on the topic depending on the audience who may read the encyclopedia). Nevertheless, I still firmly believe that all mathematical concepts are of equal importance and interest so that I disagree with your reasoning (more general ideas are in fact more interesting).
Lastly, I feel that I should point out the obvious that we have had some disagreements lately. I do not think that this dispute had any worth in that I do not believe that an immediate revert was crucial (which seems to be the case since it was followed by subsequent reverts). Although I do not have any particular belief that either my edit or your revert was justified and that it was appropriate to consult WikiProject Mathematics, I feel that your handling of the matter and the comments you made were not ideal. --PST 09:44, 8 September 2009 (UTC)
An immediate revert is completely in line with wiki's consensus-building process. My subsequent revert was because you didn't attempt to reach any sort of consensus before reinserting your edit. You made a comment on my talk page but didn't even bother to wait for me to reply.
Secondly, I believe you have mis-parsed the logic of my statement about magmas and groups, so I'll reword it. 1) Groups are a special case of magmas. 2) You say that if something is a special case of something more general, the more general thing is as important as the less general thing (as a side note, I use the term "important" because the parameter in the "maths rating" template is called importance, and I use it to refer to its importance in this encyclopedia, i.e. the priority with which resources "should" be dedicated to it; it is your misconception of my words that interpret "importance" as being "mathematical importance"). 3) But magmas do (and should) have a lower priority than groups. 4) Hence, I have given a counter-example to your argument stated in part (2). To contrast this, your reading of my statement is that: "every single thing that is a generalization of something is less important than the thing it generalizes". This is clearly wrong, but also clearly not what I said. Your parsing of universal quantifiers in my statement is off. I would appreciate it if you stopped making accusations so lightly. RobHar (talk) 15:18, 8 September 2009 (UTC)

Refs in templates[edit]

Hi, RobHar! I've noticed your comments at the TfD for {{EGA I}}, and the fact that the French Wikipedia has a dedicated space to hold the references really got me intrigued. Can you tell me if this approach is unique to the French Wikipedia, or are there other wikies that do it? I was once thinking about how it is too damn hard to work with the references in en_wiki, especially with those which are repeatedly re-used and occasionally need updating (like the laws), and concluded that for frequently re-used refs the template approach is ideal. In future, I think it'd be great to have something like the Commons or WikiSource, to hold all the references, enforce consistent formatting, and make them available for re-use across all language editions. It would be possible to immediately see which reference is used where (and to check whether it is used appropriately). In addition, people could kind of "sign" under the references they have access to, which would make it easy to find people with access to a certain book or a database or whatever. I don't suppose there are any plans to implement anything like that any time soon, but I was wondering if what the French Wikipedia is working on is at all similar (my French, unfortunately, is too lousy to understand well what's going on the discussion page you linked to). Cheers,—Ëzhiki (Igels Hérissonovich Ïzhakoff-Amursky) • (yo?); 15:56, January 18, 2010 (UTC)

Hi Ëzhiki. I haven't looked in to whether wikis of other languages do as the french do. I happen to speak French, so I was over on the french wiki one day and came across their references-as-templates approach and thought it was a great idea. As far as I know, all the french wiki is doing is collecting reference templates to specific books in a dedicated space. Each page in that space becomes a bibliographic entry for the corresponding book, and upon transclusion acts as a short reference with a link to the bibliographic entry (to me this makes perfect sense, but some here at english wiki seem to think it's absurd). I'm not aware of any other goals of their project akin to the ones you're thinking of. It would seem like a better organization of the reference material for wikipedia would be a good organizational goal that would make editing wikipedia much easier and investigating the sources of articles much simpler, alas there are many naysayers. RobHar (talk) 17:33, 19 January 2010 (UTC)


Thank you for your message. I know, there are few false positives. It is not easy to guess any kind of possible correct (and incorrect) section link. For example <ref name="#Hatcher|Hatcher, p. 149"> has got an odd syntax and had to be replaced. Instead "ref= kol1933" in Borel–Kolmogorov paradox was not recognized due the space after the = sign (now fixed). Thanks. -- Basilicofresco (msg) 16:19, 7 March 2010 (UTC)

maths rating[edit]

When you add the maths rating template to an article's talk page, please think about taking a second to fill in the priority= and field= parameters as well as the class= parameter. Otherwise, we end up with a backlog of articles that need to have their priority and field assessed. It doesn't take very long to fill in the other two parameters if you are already adding the template, and it saves time overall if nobody else has to come along and add them later. — Carl (CBM · talk) 02:21, 12 March 2010 (UTC)

I do take a second (and sometimes more) to figure out what I think those parameters should, but in some cases I simply can't decide (e.g. if I don't know that much about the field to know the priority I should assign; in the case of an empty field paramater, it's probably some topic in algebraic geometry that I can't pick either geometry or algebra). I feel like adding a maths rating template with at least one parameter filled is better than none so I go ahead anyway. Do you disagree? btw I have noticed the large amount of work you've been putting into this lately, and I'd like to thank you for it. RobHar (talk) 03:32, 12 March 2010 (UTC)
The algebraic geometry ones are particularly bad. I think that it might be better if we added a field for algebraic geometry. Articles on Riemannan geometry and other sorts of analytic geometry are also difficult for me to put into a field sometimes.
I have been meaning to start a discussion about this at the math project, so I'll go ahead and do that. — Carl (CBM · talk) 12:03, 12 March 2010 (UTC)

Mathematics of rigidity[edit]

I undid your recent edits to Laman graph and pseudotriangle. They really are about the mathematics of rigidity: that is, the theory of which structures made out of rigid pieces can still flex and which other structures have no degrees of freedom of motion left. Rigidity (mathematics) doesn't seem to cover that anywhere; the closest is the link to Cauchy's theorem but, while I think Cauchy's theorem falls into the mathematics of rigidity category it does not describe the theory that laman graph and pseudotriangle are related to. Most of the references in Structural rigidity are about the same thing: mathematical descriptions of the rigidity of bar-and-joint frameworks, so that seems like the best link to use. —David Eppstein (talk) 23:44, 19 March 2010 (UTC)

PS. Am undoing more of the same. Mostow rigidity is questionable and I'm not undoing your edits there, but most of the rest really are about rigidity of physical objects. E.g. Cauchy's theorem is about the fact that if you make a convex polyhedron by forming its faces out of some inflexible material and then linking those faces by flexible hinges, then the whole shape will not flex. —David Eppstein (talk) 23:47, 19 March 2010 (UTC)

I think it's pretty clear that there is some confusion here, but perhaps I picked the wrong option (I guess I should have seen what the references in the Structural rigidity referred to). The fact that the article refers to "an applied force", that it is labeled as part of the wikiproject "engineering" and not "math", and was only contained in the category "Mechanics" (before the creation 2 months ago of the category "Mathematics of rigidity") led me to believe this article was about actual physical objects. Perhaps the first sentence should start with something like "In graph theory" or "In geometry" or something. If this is indeed about a such objects, then I'm not sure the category "Mechanics" makes sense. Anyway, I'm sorry to have created that work for you, but there were some red flags for me (not least the facts that the new category "Mathematics of rigidity" was placed in the category "Subdivision of mathematics" as if it were a rather top-level category, and that I didn't manage to find many instances of the phrase "Mathematics of rigidity" upon a quick google). RobHar (talk) 00:42, 20 March 2010 (UTC)
I think the subdivisions of mathematics categorization was a mistake, because as you say it's not a top-level category. I put it under discrete geometry instead (e.g. one can find the subject surveyed in the Handbook of Discrete Geometry). —David Eppstein (talk) 01:10, 20 March 2010 (UTC)
Ok, that makes sense. Also, I'd like to comment on your comment on my proposal at the WPMath Talk page. I don't believe that I asserted/implied that a "major subarea of discrete geometry was not even mathematics at all". I made a mistake and misunderstood an ambiguous stub article as being more related to structural engineering than about math. I just found that new category that was a definite red flag and traced back to all related changes. All the changes I made were simply undoing the edits of a single user all originally made on one day two months ago. Perhaps I've misunderstood the tone of your comment on my proposal, but it certainly comes off as quite aggressive. RobHar (talk) 01:24, 20 March 2010 (UTC)
It was a response to the agressive tone I (perhaps mistakenly) perceived in your dismissal of discrete mathematics as a coherent subject. —David Eppstein (talk) 01:33, 20 March 2010 (UTC)
I'm sorry, I didn't mean to sound aggressive, I had simply never seen a discrete math course that was aimed at math students, nor had I encountered someone whose field of research was "discrete mathematics". I believe I was dismissing what I perceived to be a creeping in of the term "discrete math" from the misconception that the fact that there is a course called that means that it is a field of math. Apparently, I had the misconception. Perhaps it was my phrasing "word to throw around". I simply meant that I could understand that mathematicians might use it as a convenient way to sum up their interests without that meaning that it is a field of study (meaning that things in "discrete math" could all easily be classified in some other field, though they do share a certain kinship). I might very well be wrong about this as I'm an algebraic number theorist (though according to the current wikipedia category hierarchy number theory is a subfield of discrete mathematics). I certainly meant no affront. Sorry. RobHar (talk) 01:49, 20 March 2010 (UTC)

"Galois cohomology"?[edit]


"In algebra,", "In geometry,", "In number theory,", "In numerical analysis", etc., succeed in telling the lay reader that mathematics is what an article is about. But I think

In Galois cohomology

may leave the reader wondering if it's about sexual orientation or evolutionary biology or the geography of France. Michael Hardy (talk) 04:59, 28 March 2010 (UTC)

Morphism between two short exact sequences[edit]

Hi, I needed a depiction of a morphism between two short exact sequences and found your File:Morphism of short exact sequences.svg, however something seems to be wrong with the SVG code. Could you regenerate the file? Cheers, AxelBoldt (talk) 04:38, 3 April 2010 (UTC)

Hi, there's a png version of this file already uploaded at the commons. It appears the svg I uploaded simply contained a reference to a png file, so it wasn't worth being an svg anyway. If you know how to convert files from either pdf, or dvi, to svg, then I can post a real svg, but for now, I'd suggest using the png file I've linked to. Cheers. RobHar (talk) 16:18, 3 April 2010 (UTC)
Ok, thanks! I'll ask them to delete the old SVG. AxelBoldt (talk) 16:54, 4 April 2010 (UTC)

I have marked you as a reviewer[edit]

I have added the "reviewers" property to your user account. This property is related to the Pending changes system that is currently being tried. This system loosens page protection by allowing anonymous users to make "pending" changes which don't become "live" until they're "reviewed". However, logged-in users always see the very latest version of each page with no delay. A good explanation of the system is given in this image. The system is only being used for pages that would otherwise be protected from editing.

If there are "pending" (unreviewed) edits for a page, they will be apparent in a page's history screen; you do not have to go looking for them. There is, however, a list of all articles with changes awaiting review at Special:OldReviewedPages. Because there are so few pages in the trial so far, the latter list is almost always empty. The list of all pages in the pending review system is at Special:StablePages.

To use the system, you can simply edit the page as you normally would, but you should also mark the latest revision as "reviewed" if you have looked at it to ensure it isn't problematic. Edits should generally be accepted if you wouldn't undo them in normal editing: they don't have obvious vandalism, personal attacks, etc. If an edit is problematic, you can fix it by editing or undoing it, just like normal. You are permitted to mark your own changes as reviewed.

The "reviewers" property does not obligate you to do any additional work, and if you like you can simply ignore it. The expectation is that many users will have this property, so that they can review pending revisions in the course of normal editing. However, if you explicitly want to decline the "reviewer" property, you may ask any administrator to remove it for you at any time. — Carl (CBM · talk) 12:33, 18 June 2010 (UTC) — Carl (CBM · talk) 12:57, 18 June 2010 (UTC)

Galois module[edit]

I see that this diff from February cut out some classical material. Amongst other things, "normal integral basis" is referred to on four other pages, with a link that now goes to a page with no definition. While I understand why this has happened, it seems to me unfortunate that you omitted the material, given that there are whole books on Galois Module Structure of Algebraic Integers: basically NPOV says you preserve other meanings. Charles Matthews (talk) 07:34, 29 July 2010 (UTC)

Yes, I'm sorry I removed that. I'd like to begin by saying that I did not intend my edits to Galois module at that time to produce a strictly better article, but rather to provide basic material on Galois representations that was sorely missing from wikipedia. If you look at my edit history around that time, you'll see that I was in the process of writing a draft of an article on the Fontaine–Mazur conjecture (User:RobHar/Sandbox6) as well as the article on p-adic Hodge theory. It can be difficult to make an article strictly better and I count on the collaborative nature of wikipedia to accomplish this task. Mind you I realize that deleting a term that was in bold text without at least creating a stub is a pretty glaring mistake, but I hope you'll believe me when I say that it was an unintentional mistake on my part. In my edits, I tried to provide some structure to the article and, though the article was unreferenced at the time, I do remember checking on google books and attempting to grasp some of the subject (I fully admit I'm no expert on what one might call the "theory of Galois modules" as opposed to Galois representations), but it was hard for me to really see what of the material was meant to be important and what of it was off-hand comments. It was for this reason that I wrote "rewrite (some of the old material was not included)" in my edit summary, hoping that someone with more background on Galois module theory would see the edit and fit some of the material back in. As an immediate remedy, I will make a section titled "Galois module structure of algebraic integers" and put the old material in there. Going forward, I suspect it might be a good idea to split this article, perhaps even into a few pieces, such as "Galois module/Galois representation" vs "Galois modules in number theory" vs "Galois representations in number theory", since the first one could simply talk about Galois modules in general, and the latter two represent rather distinct branches of number theory, at least from my perspective. Cheers. RobHar (talk) 15:43, 29 July 2010 (UTC)
OK, I did assume your good faith. Charles Matthews (talk) 21:45, 29 July 2010 (UTC)
I see. Upon rethinking this, I guess I don't really understand what your initial comment was about. You say NPOV says I should preserve other meanings, but I did. I just replaced an article over half of which was about one example of a Galois module with an article that gave several examples in shorter form (including the algebraic integers example) and defined an important concept, that of ramification. I slipped up by not doing something about normal integral bases, but that definition is more appropriate in the Hilbert–Speiser theorem article than it is in the Galois module article. It seems to me like before my Feb 4th edit the article suffered from a bad case of non-NPOV, and that my edit made it be more in line with the NPOV guideline. For example, there are several books on the class groups of cyclotomic fields as Galois modules, or on the ℓ-adic cohomology of varieties as Galois modules, not to mention the idele class group and its relation to class field theory. Before my edit, the article made it seem like the Hilbert–Speiser theorem was the most important case of the study of Galois modules. RobHar (talk) 03:10, 30 July 2010 (UTC)

ANT, reciprocity[edit]

I've made two changes in accordance with what you suggested. It would be nice to get more feedback on other parts of the article! Garald (talk) 05:55, 26 August 2010 (UTC)


Thanks for all the disambiguations. For many articles I think I know what term is right, but I'm not sure enough to make the correction myself. Thanks for fixing these (and, so far, validating my guesses).

CRGreathouse (t | c) 04:24, 10 November 2010 (UTC)

No problem. And thanks for your work on dabbing all those articles. RobHar (talk) 05:15, 10 November 2010 (UTC)


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Hello, RobHar. You have new messages at C.Fred's talk page.
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SVG for Tableaux Diagrams[edit]

Hi RobHar -- How did you render the tableaux diagrams on

Pwagle (talk) 03:10, 6 February 2011 (UTC)

Well, I didn't make them, I just tweaked them so that they would render properly. For this, I used inkscape. This software (which is free) would also be able to make such diagrams very easily, of course. RobHar (talk) 04:19, 6 February 2011 (UTC)

Algebraic number[edit]

You reverted my edit to Algebraic number. What unclear phrase did I use?? Georgia guy (talk) 21:37, 19 March 2011 (UTC)

Well, "multiply all the numbers of the roots together" isn't really clear. But more importantly, what you are claiming is wrong; for example, \sqrt{2}+\sqrt[4]{2} has minimal polynomial of degree 4 (namely, x^4 - 4x^2 - 8x + 2), but, if I understand what you've written, you claim the degree should be 2×4 = 8. Am I misunderstanding your edit? RobHar (talk) 21:50, 19 March 2011 (UTC)
You've understood it correctly. But when is it wrong?? What is the correct way to decide the degree?? Georgia guy (talk) 22:33, 19 March 2011 (UTC)
I gave you an example of when it's wrong with \sqrt{2}+\sqrt[4]{2} above, didn't I? It's also unclear what you claim should be done with say \sqrt{2}/\sqrt[3]{3}. I'm not sure there is a quick, foolproof way to determine the degree. If I want to know the degree, I generally just try to find the minimal polynomial. You can try search google to see if you can find any books that discuss the subject. RobHar (talk) 00:26, 20 March 2011 (UTC)

Blackboard bold[edit]

Thanks for explaining the revert. I did not know that blackboard bold should not be used. That's the second time I made such a mistake. The first one was when I replaced 1/2 with 12 on Riemann hypothesis, while being unaware of MOS:MATH#Fractions. Actually I don't like these style guidelines, but I'll walk the line. ℚ does look better than Q, and so does 12 compared to 1/2. Anyway, thanks. --bender235 (talk) 23:00, 2 June 2011 (UTC)

proposal re academic journal abbreviations[edit]

Thanks for bringing up the subject of abbreviations on infoboxes on academic journal pages. There's a draft proposal. Would welcome your comments. -- Econterms (talk) 08:46, 5 August 2011 (UTC)

Number theory[edit]

The new page should go live soon. Since you are a past contributor to the talk page, I think your comments will be helpful. Garald (talk) 14:48, 7 October 2011 (UTC)

Thanks. I'll probably wait until Monday before putting it up anyhow - should I expect your comments by then?

I've removed the "we"'s in the history section. I would find it harder to remove it from the "diophantine geometry" section (for instance), since it is hard for me to give an overview of a subject to outsiders without lapsing into an ever so slightly conversational style. Of course, this may be exactly what I am being asked to avoid; I do not know. Some alternatives would be welcome. Garald (talk) 15:39, 7 October 2011 (UTC)

Thank you for the changes. As for the "starting point" - thanks for the quotations; I thought the current wording made clear that the starting point is fairly arbitrary, and that Dirichlet's theorem is one of the contenders. Note, however, that it does not use complex analysis, or even the zeta function as a function of a complex variable, if I remember correctly. The use of the zeta function as a function of a real variable in number theory goes further back (Euler). What Dirichlet did introduce was, um, Dirichlet L-functions.

I better get a "pro-Riemann" quote somewhere. Garald (talk) 12:54, 8 October 2011 (UTC)

Note that the text of the analytic number theory article gives Euler as "the beginning" (search for "beginning"). Garald (talk) 12:56, 8 October 2011 (UTC)

Strange grammatical construction[edit]

RobHar, you mentioned that

Bibliography of biology is a list of notable works on the subject of Biology organized by subdiscipline

has a strange grammatical construction. Although this sentence was clearly constructed by a committee, I'm not seeing any grammatical errors; but

Bibliography of biology is a list of notable works, organized by subdiscipline, on the subject of Biology

would read better. Does that sound o.k. to you? RockMagnetist (talk) 01:24, 8 November 2011 (UTC)

It's that the sentence as written is meant to be read as

"Bibliography of biology" is a list of ...

as in: This article, which we have called "bibliography of biology", is a list of ... So, I certainly think that without the quotation marks it's an incorrect sentence (perhaps strange grammatical construction is the wrong thing, do I mean strange semantic/syntactic construction?). Do you see what I'm saying? Like what you are trying to say is

This article is a list of ...

but because that would violate the wiki policy that says you need to mention the title of the article in the first sentence (or something to that effect), you have chosen to write what is currently there. You could circumvent this by writing

This bibliography of biology is a list of ...

but really I feel like this is just happening because you want the title to not be "List of notable works in biology" despite the fact that that's exactly what this is. So, what I actually want to see is a page move and then the first sentence can simply be

This is a list of notable works in biology.

Thanks for seeking my input despite the fact that it may not be in line with what you were looking for. RobHar (talk) 02:58, 8 November 2011 (UTC)
Thanks for pointing that out! Now I wonder why I didn't notice it before. I'll address the "notable" issue on my talk page. RockMagnetist (talk) 03:55, 8 November 2011 (UTC)

as a rule[edit]

Hi, Would you care to comment further at Talk:Function_(mathematics)#summary_of_rule_AND_correspondence? Tkuvho (talk) 08:44, 20 February 2012 (UTC)

Group of rational points on the unit circle[edit]

Hi, I put some more work into the above recently. I'd like someone else to read it and see if it still makes sense. If you have a chance and feel like it, I'd appreciate you doing that. Thanks, Richard Peterson198.189.194.129 (talk) 00:33, 22 February 2012 (UTC)

MSW3 templates[edit]

Yes, the publisher links are clutter. We don't link anything and everything that might conceivably be of interest: we use our intelligence, experience, and subject knowledge to make only smart links that are likely to be useful to the reader of the article. Here are a couple of extracts from the Manual of Style on linking and overlinking (emphasis mine):

  • In general, links should be created to relevant connections to the subject of another article that will help readers understand the article more fully.
  • An article is said to be overlinked if it contains an excessive number of links. Overlinking should be avoided, because it makes it difficult for the reader to identify and follow links that are likely to be of value.

Eliminating overlinking from a template is particularly valuable because it removes those excess links from hundreds or even thousands of articles. Colonies Chris (talk) 08:53, 8 May 2012 (UTC)

Why should the principles behind linking be any different just because it's a citation? Linking's purpose is to help a reader better understand the article. A link to a generalist publisher isn't going to do that. Colonies Chris (talk) 14:27, 8 May 2012 (UTC)
Wikilinks to isbn, oclc, mr are highly relevant to the citation - they can help the reader to track down the citation if they want to. However, a publisher link is exactly the kind of too broad wikilink that you agree should be avoided. The reader will gain no benefit from a link to a generalist publisher that produces a range of books on many subjects, almost all of which are unrelated to either the article or the citation. What benefit do you think a reader would get from such a broad and unfocused wikilink? Colonies Chris (talk) 15:58, 8 May 2012 (UTC)
The link to ISBN is automatically generated - it's outside the control of any editor or template writer - so it's not relevant to this discussion. Colonies Chris (talk) 16:39, 8 May 2012 (UTC)
isbn, mr, oclc, doi etc are abbreviations, so it's arguably useful to have them explained via a link (though I'd prefer some less obtrusive way). But the name of a publisher is clear, and nothing in the publisher's article is likely to be relevant to the citation or to the article. This is essentially the same argument that was resolved a few years ago about linking years - there may be something in a year article that's relevant to the article the link is in, but usually there isn't, so we don't routinely link years. That would be a scattergun approach to linking instead of a focussed approach. Colonies Chris (talk) 17:23, 8 May 2012 (UTC)
I notice you're conspicuously failing to answer my question about what use such a link would be to the reader. If you want to raise this on a wider forum, please go ahead. Colonies Chris (talk) 18:16, 8 May 2012 (UTC)


Hi RobHar, If you are in a drawing mood could you take a look at the figure at standard part? Tkuvho (talk) 19:18, 13 November 2012 (UTC)

Mirror symmetry article[edit]


I noticed that you're a member of WikiProject Mathematics and that you've expressed interest in mathematical physics. I wanted to let you know that the article on mirror symmetry is currently a featured article candidate.

If you're interested, we'd love to hear your thoughts on this page. Please note that you do not need to be an expert on the subject.

Thanks for your help!

Polytope24 (talk) 16:14, 23 March 2014 (UTC)