User talk:Zaslav

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Hello, Zaslav, 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!  Oleg Alexandrov (talk) 03:02, 22 March 2007 (UTC)

Arrangement of hyperplanes[edit]

Hello and welcome to Wikipedia.

  • Your editing of arrangement of hyperplanes prompts these suggestions: There is no need to write [[subspace | subspaces]], since writing [[subspace]]s has the same effect. Similarly, [[apocrypha]]l and [[Austria]]n, etc.
  • A stubby little hyphen used as a minus sign is sometimes nearly illegible on some browsers. Contrast (-1) with (−1).
  • Italics are easier to write like this A then like this A. In expressions like L(A) I wouldn't include the brackets () among the parts that get italicized.

I'm glad to see someone working on the topics you've been working on.

Michael Hardy 23:43, 22 Aug 2004 (UTC)

Thanks for the comments. I've realized all those things by now. No doubt there are others to learn. Thanks for the appreciation. You'll notice I've also logged in as "Ttzz" due to forgetfulness. If I ever find out how to merge user names, I'll simplify that. Zaslav 23:14, 27 September 2005 (UTC)

Belarusian language[edit]

Hi, I've seen your comments on the talk page (I don't know why those were deleted). Generally, yes, the article is overweight and too in-context and too technical in parts. Also, both language and its extensive history are there, actually.

The reason for this was that before my active work on the subject it was an arena of "struggle" of the neighbouring nations' and local political opportunists' stereotypes. Even partial clearing of all this, and introducing some rationality and sense in the issue took time and effort. So, the text grew. I've tried not to remove anything just for the sake of brevity, yet.

And the work isn't finished, by a long way. There still remain lots of irrelevancies by which arguing sides tried to push their point, circumspectly. Look at the "comparative list of the words" -- why it's there at all?? Because some people wanted language represented with more "Western smell", and some wanted "Eastern".

Anyway, I'm going to renew my active reworking of the article, and I'd be grateful for your comments from the perspective of the "common" Anglophone reader. Feel free to leave those on my talk page. The issue is too mis- and under- represented in online encyclopedias. Yury Tarasievich 08:19, 19 January 2007 (UTC)

Citizen of the Galaxy[edit]

I wasn't responsible for the Kim reference. Though I can see a few connections:

  • Baslim and Mahbub Ali/Teshoo Lama
  • the British secret service and X Corps

I'm not convinced they're strong enough to support a direct link.

I also changed the section titles for The Stars are Ours! and removed the first sentence, which IMO isn't really necessary. Clarityfiend 06:36, 24 February 2007 (UTC)

Cryptomorphisms etc.[edit]

Hi, Zaslav. No complaints about your cryptomorphism sentence at all! Also, I really like the way matroid is turning out. Let me know if you ever start work on anything related. Changbao 08:47, 26 February 2007 (UTC)

The Star Beast[edit]

You assert that all editions except the Scribners omit two pages. What is the basis for this assertion, and can you elaborate as to the content of those pages? I have done a quick comparison of the hardcover with the various editions I have and can find nothing omitted. I'd be delighted to learn of this difference! Signinstranger 22:50, 19 March 2007 (UTC)

Missing page found and info added to The Star Beast page. Signinstranger 16:35, 5 April 2007 (UTC)

I found the missing page by borrowing a hardcover of The Star Beast from my local library, and following your lead as to where the omission occurred. Any US Scribner edition uses the original plates. As for the magazine version, I own a near-complete run of The Magazine of Fantasy & Science Fiction. Signinstranger 15:20, 9 April 2007 (UTC)

Style notes[edit]

Hi Zaslav. Just a note. The comma is better off in the math tags I believe, so this:


rather than this:


because if you put the comma outside sometimes the browser moves to a new line, and then it looks odd, like this:


Wonder what you think. You can reply here. Thanks. Oleg Alexandrov (talk) 05:26, 9 June 2007 (UTC)

Thanks! If you saw this happen even once, that's the proof. I just never noticed this, and since in ordinary Tex it makes no difference, I never thought about it. I will keep your advice in mind. Zaslav 17:15, 21 June 2007 (UTC)
It does happen, not that seldom. :) Thanks. Oleg Alexandrov (talk) 01:58, 22 June 2007 (UTC)

Seismic shadowing[edit]


Since you made a wiki-link in the epicenter article, I have created a new article Seismic shadowing. Thank you... my first new article. Feel free to come by and add more to it. Astronaut 20:07, 17 August 2007 (UTC)

Thank you for your additions to this article. Yes, it is better from the layman's point of view to say in the first sentence that the phenomenon is caused by earthquakes. However, I have corrected a few small errors in the English grammar and I have changed some of the phrasing so it reads even better. Astronaut 11:28, 24 August 2007 (UTC)

Pregeometries in physics?[edit]

Hi Zaslav, I just became aware of you because of your orthographic clean-up in lattice (order). It looks like you are a matroid theorist. A while ago I edited the pregeometry article, which claimed at the time that the term is obsolete. I think that's only true for finite matroids / pregeometries, but I am not sure about the terminological conventions for infinite ones in general. The article also claims that "pregeometry" plays a role in physics. The uncountable use of the word is a bit suspicious, and I have no idea whether this word actually refers to a version (finite or infinite) of matroids, or to something completely different. It would be nice if you could have a quick look at the article. --Hans Adler (talk) 01:08, 4 February 2008 (UTC)

Without seeing the original Wheeler article, I would say there is no connection with physics. Furthermore, if Wheeler did think there was such a connection, it hasn't turned out to have any merit at all, as far as I know. If it did, I want to know about it! But unless it has been pursued in physics, it's a red herring and is only clutter in a serious article about matroids. Maybe it should be in the "Historical trivia" section along with "Combinatorial pregeometry" (see my edit to Talk:Pregeometry. Zaslav (talk) 01:31, 4 February 2008 (UTC)
I think Wheeler's "pregeometry" has nothing to do with matroids. See the paper "Multiboundary Algebra as Pregeometry" from the Electronic Journal of Theoretical Physics. Zaslav (talk) 06:52, 4 February 2008 (UTC)
I've edited "Matroid" on infinite matroids to add "finitary matroid" as well as "finite-rank matroid" as relatively simple infinite versions. I edited "Pregeometry" to add the name "finitary matroid". The "Pregeometry" article should, in the view of this matroid theorist, be moved to "infinite matroids" and substantially rewritten, to remove duplication with "Matroid" and also maybe take advantage of some things that are well stated and could be used to improve "Matroid". Please let me know your feelings about these ideas, and also about my rewrites. Thanks.
A question to which I'd really like the answer: Do real model theorists use the term "pregeometry"? It's a horrible mistake of Rota's and very inappropriate in my opinion, for reasons which I can explain if you wish. The term "finitary matroid" is much more suitable, because it sounds like what it means--the term "finitary" is well established and exactly describes these infinite (or finite) matroids. Zaslav (talk) 02:13, 4 February 2008 (UTC)
Thanks, I am very happy with your changes. The reason why I haven't done something like this myself is ignorance of matroid theory. I know the basics from browsing some books, but often you can't learn certain cultural aspects of a subject in this way. It wasn't clear to me that the closed sets definition (or those definitions that are equivalent to it) is a sufficiently accepted standard definition for the infinite case. Our current matroid article is no great help in this respect, because it never gives a clear definition of an infinite matroid, and I had the same problem with the matroid theory literature.
Yes, real model theorists use the word "combinatorial geometry" exclusively: Compare [1] and [2]. The standard reference for the basics of our subject is "Model theory" (or "A shorter model theory") by Wilfrid Hodges. Here are the relevant lines of his section "Geometries":
A combinatorial geometry, or for short a geometry, consists of … [closure axioms for a simple not necessarily finitary matroid]
This definition (Crapo & Rota [1970]) was intended for dealing mainly with finite sets, and indeed I have left out a clause which says that every closed set is the closure of a finite set. Instead we add another condition: [finite character]
A pregeometry (some say matroid) is defined the same way as a geometry, but without clause [simplicity].
I think this has happened because apart from having acquired this term in the early seventies we have no real connection to matroid theory. The alias "matroid" seems to be less common than references to "van der Waerden's axioms". Our matroids are all infinite and embedded in a lot of extra structure. We usually work in a "monster model", i.e. a generalisation of a vector space or algebraically closed field of dimension κ, where κ is a cardinal number larger than any cardinal that arises in our arguments. This is really just a trick to avoid category theory when working with the category of vector spaces or of algebraically closed fields. The automorphism group of the monster model is fundamental for us, and you can think of our monster model as a large finitary matroid equipped with a subgroup of its automorphism group that needs to satisfy certain conditions.
I wonder how it is the other way round: Did you know that model theory uses infinite matroids? Have you heard of Zilber's conjecture?
Here is why I think the "pregeometry" / "geometry" nomenclature is non-optimal: The word "pregeometry" is alread too long, and you can't expect people to add "combinatorial". Matroids are the real objects of study, the simple matroids are just an abstraction, so they should get an adjective. The word "geometry" is too common. Neither "geometry" nor "geometry theory" is a good name for matroid theory. Have I found everything? --Hans Adler (talk) 09:47, 4 February 2008 (UTC)
I'm delighted with your explanations. Must rush out now but more later. I agree with your objections to "geometry". It's a huge area; you can't take that word for the little corner called matroid theory, finite or infinite. Zaslav (talk) 13:46, 4 February 2008 (UTC)

Enumeration of Pseudoforests[edit]


With the current definition of pseudotree, I will edit the text:

"-The number of maximal pseudotrees with n nodes, and cycles of length at most one is equal to the number of rooted trees with n nodes. OEIS sequence number OEISA000081." To:

-The number of unlabeled pseudotrees with n nodes, and cycles of length one is equal to the number of unlabeled rooted trees with n nodes. OEIS sequence number OEISA000081.

I will also edit the text:

"-The number of maximal pseudotrees on [n] with cycles of length at most one is nn-1. OEIS sequence number OEISA000169." To:

-The number of pseudotrees on [n] with cycles of length one is nn-1. OEIS sequence number OEISA000169. There are also results about both labeled and unlabeled maximal pseudoforests with loops, not only about labeled pseudotrees. The given bijection is between rooted forests and maximal pseudoforests with cycles of length at most one.

Perhaps those pseudoforests are a very specialized subtopic, so I do not now add this information to the article.

--Webonfim (talk) 07:15, 18 February 2008 (UTC)

Thank you for thinking about this question. I feel that pseudotrees/forests with at most one cycle, whose length is one, are best treated as rooted trees/forests. Enumeration should be in an article on trees and forests, if it is in Wikipedia. The pseudoforest article could have information on counting general pseudoforests and simple pseudoforests, labelled or unlabelled, if such results are known. I know of one paper on exactly this:
  • Nancy Ann Neudauer, Andrew M. Meyers, and Brett Stevens, Enumeration of the bases of the bicircular matroid on a complete graph. Congressus Numerantium 149, 109-127 (2001). Zbl. 1003.05031.
This counts labelled maximal simple pseudoforests. There are also related articles by some or all of these authors. Zaslav (talk) 08:12, 18 February 2008 (UTC)

Speedy deletion of Al Khamsa (organization)[edit]

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A tag has been placed on Al Khamsa (organization) requesting that it be speedily deleted from Wikipedia. This has been done under section A7 of the criteria for speedy deletion, because the article appears to be about a person or group of people, but it does not indicate how or why the subject is notable: that is, why an article about that subject should be included in an encyclopedia. Under the criteria for speedy deletion, articles that do not indicate the subject's importance or significance may be deleted at any time. Please see the guidelines for what is generally accepted as notable, as well as our subject-specific notability guideline for biographies.

If you think that this notice was placed here in error, you may contest the deletion by adding {{hangon}} to the top of the page (just below the existing speedy deletion or "db" tag), coupled with adding a note on the talk page explaining your position, but be aware that once tagged for speedy deletion, if the article meets the criterion it may be deleted without delay. Please do not remove the speedy deletion tag yourself, but don't hesitate to add information to the article that would would render it more in conformance with Wikipedia's policies and guidelines. Hennessey, Patrick (talk) 00:32, 4 March 2008 (UTC)

Zaslav's comments on Intersection graphs[edit]

I do not agree with you. You do it if you understand what it is or ask the one who wrote the "Intersection graph". or you may delete it with my permission. Thanks.

--Tangi-tamma (talk) 10:43, 3 April 2008 (UTC)

Please relax and let us have a polite discussion. There is much to discuss, and I am not planning to do editing in the near future. Here are some reasons that I propose merging this article, but not Line graph, into "Intersection graph". 1. Line graphs have an extensive theory and literature with special properties, not shared by all intersection graphs, that are important in graph theory. Thus, line graphs are a topic of separate interest in their own right. A person interested in graph theory is very likely to want to know about line graphs, separately from intersection graphs. (I say this as a graph theorist who knows something of the interests of graph theorists.) 2. Article size: line graphs form a large article on their own, which would greatly lengthen "Intersection graph" if included. (This is one of the criteria for splitting up topics.) 3. Hypergraphs are the same as set systems. Thus, the general theory of intersection graphs is really the same as the theory of intersection graphs of hypergraphs. As far as I know, there is not such a large or distinctive theory of line graphs of hypergraphs as to belong outside a general article on intersection graphs. If I'm wrong, then an article on hypergraph line graphs is justified, but I don't see that the current article justifies being separate. 4. The material in this article would be beneficial to "Intersection graph". It would provide the concrete examples and liveliness that you find missing in "Intersection graph" (and I agree with you there). 5. The simplest title is "Intersection graph". 6. I am sorry to say this, especially since I think you must have written most of the article "Intersection (Line) Graphs of hypergraphs", but it really is poorly written in several ways. The English is poor. The organization is bad. The content is interesting, so major rewriting is needed and worth doing. The article "Intersection graph" will provide much of the introductory background needed, so it makes sense to use it. Here is a reason to oppose merging the articles. 1. Possibly, the techniques and theorems of hypergraph intersection graphs are significantly different from those of general intersection graphs. I don't see that they are, but those who know more about it may have arguments (that I would like to see). Finally, please keep in mind that Wikipedia articles do not belong to any one person. I look forward to continuing this discussion and arriving at concensus. Zaslav (talk) 19:34, 3 April 2008 (UTC) Retrieved from ""

I repeat - you please start editing it if you want to see it on Wikipedia. (I assume you have some knowledge of Graph Theory. I have listed there all the references you may need to read). This addresses item 6.

Item 2: Huge articles are not meant for pleasure reading. The existing article needs further editing to make it fit into the regular size. It also needs editing.

Item 3: I have problem in understanding what you wrote. “Intersections graphs of hypergraphs..” by itself is very infinite.

Item 4: I do not know what you are trying to say.

Item 5: That is your perspective. It would vary if you ask someone. This is my observation on Wikipedia.

Item 6: Read below.

Also it is difficult to write high-level math on Wikipedia for a common man’s understanding. High-level math should remain in journals to preserve its beauty rather than transferring them to somewhere for the sake of doing some business. I do not have expertise to translate them to wikipedia’s standards. I have read several math articles on Wikipedia including yours – all have some or the other kind of problems.

The other article “Intersection graph” does not serve any purpose at all. It has nothing but the definitions. It is isolated. No comments about how it is written.

Since I started to write it, I authorize you to edit rather than spending your time on criticizing.

I’m removing your stuff from there and transferring it here- – let it be yours. --Tangi-tamma (talk) 21:49, 3 April 2008 (UTC)

Cographs and P_4[edit]

I don't know why you deleted the explicit reference to P4 in the first alternate definition of cograph, but I've reinstated it. If you're interested to know why, see my year-old entry in the discussion page.—PaulTanenbaum (talk) 00:59, 3 September 2009 (UTC)

Reason for deleting the notation: Usage is highly inconsistent in graph theory. Sometimes the subscript refers to vertices and sometimes to edges. Reason for not deleting the notation: You had it in the introduction with a clear definition. That's a good reason. I apologize; I done wrong. Zaslav (talk) 05:11, 3 September 2009 (UTC)

"Inline" TeX[edit]

I find some aspects of this edit unfortunate. TeX doesn't behave the same way within Wikipedia that it does when used in the normal way. If you write the x appears lower than the letters in the surrounding text, and all sorts of things fit badly, including the fact that the letters are three or four times as big as the surrounding letters on many browers. ("Displayed" TeX, however, works well.) Michael Hardy (talk) 19:38, 5 November 2009 (UTC)

Well, thanks for taking a look at it. I agree that text Tex has problems. The WP italics also give problems, especially with the space or punctuation after the italicized symbols and with the smallness of the sub- and superscripts. It was hard to decide what was best. I followed what appeared to be the general style of that article. But please feel free to adjust it (of course). Zaslav (talk) 03:45, 6 November 2009 (UTC)

Welcome to Oriented matroid article, if you have time and interest[edit]

Hello Zaslav! You were very helpful (and gentle!) with my edits on matroids, so I welcome you to examine the expanded stub on oriented matroids. I am trying to recruit volunteers to help with the expansion more than I am asking for comments on a serious article (because tonight's writing has been nasty, brutish, and short). Best regards, Kiefer.Wolfowitz (talk) 02:45, 18 January 2010 (UTC)

Infinite matroids[edit]

Based on this, I assume you will be interested in the following paper, and especially in Footnote 2: Bruhn, Henning; Diestel, Reinhard; Kriesell, Matthias (2010), Axioms for infinite matroids, arXiv:1003.3919v1 . Hans Adler 11:36, 24 March 2010 (UTC)

Thank you. I've heard about this article three times already! I haven't had time to look at it yet. Maybe it's the big advance we've been waiting for. Zaslav (talk) 07:35, 25 March 2010 (UTC)

GAC comments on Saadanius[edit]

I have addressed the specific concerns you listed on the GAC for Saadanius. Please revisit the review at your earliest convenience and let me know if you are happy with the changes. Thank you for your time and comments. – VisionHolder « talk » 14:59, 17 July 2010 (UTC)

Merge discussion for completeness axiom[edit]

Information.svg An article that you have been involved in editing, completeness axiom, has been proposed for a merge with another article. If you are interested in the merge discussion, please participate by going here, and adding your comments on the discussion page. Thank you. Jim (talk) 18:45, 23 October 2010 (UTC)

Proposed deletion of Susanne (1950 film)[edit]

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Skew-symmetric vs bidirected graphs[edit]

I see you've been adding material to the articles on skew-symmetric and bidirected graphs stating that skew-symmetric graphs are the double covers of bidirected graphs. But I'm a bit confused about how the double cover works. If you do it the way you describe (using the edge orientations to partition the edges incident to each vertex into two subsets, giving a polar graph, and then using the equivalence between polar graphs and skew-symmetric graphs) you lose information about the bidirections — you can't recover the original bidirected graph from its double cover. On the other hand there's a different way of orienting the double cover directly from the bidirected graph, by letting one of the two copies of each vertex control the orientation of its copy of each edge. As long as you remember which copy was the controlling one, this keeps all of the bidirection information, but it isn't skew-symmetric because some edges have the same orientation as their copy instead of always having the opposite orientation. So while what you describe makes sense, I guess I'm curious: why do it in the information-losing way? —David Eppstein (talk) 00:03, 10 January 2013 (UTC)

Thank you for pointing that out. I didn't add the description of the construction of the skew-symmetric graph from the switch graph. I did add the double cover and polar graphs. I may have made a mistake by assuming too much or (inclusive or) leaving out detail. A quick look at Cook's paper suggests that it was perhaps not accurately described in the article. I'll deal with this as soon as I can. Zaslav (talk) 01:03, 10 January 2013 (UTC)
Still needs to be looked at; sorry for delay. Zaslav (talk) 08:33, 23 November 2016 (UTC)

Double factorial vs semifactorial[edit]

There are too many conversations about this. You seem to say that you want to revert your changes. I'm willing to try, if you can point out which of your edits are about this concept, or even when you started. — Arthur Rubin (talk) 06:16, 17 July 2014 (UTC)


Congratulations to all the contributors to today's featured article. You deserve a lot of applause, recognition and appreciation. What a interesting and wonderful article.

  Bfpage |leave a message  11:45, 13 April 2015 (UTC)

Speed of light[edit]

You undid my edit, claiming that the speed of light wasn't "exact". I'm not sure what you mean by this; 299792458 m/s is the speed of light. Can you clarify why you changed it? KSFTC 13:20, 26 June 2016 (UTC)

I was too old-fashioned. You are correct, I was ignorant, and I'm reverting it. My apology to you! Note that the meter was not defined in terms of the speed of light until relatively recently (and I mean relatively). Zaslav (talk) 20:29, 26 June 2016 (UTC)
P.S. I think the approximate value 300,000 is more suitable to the purpose on this page, but it's not worth arguing over. Zaslav (talk) 20:31, 26 June 2016 (UTC)

Thomas Zaslavsky?[edit]

So, are you perhaps Thomas Zaslavsky? (talk) 20:16, 27 August 2016 (UTC)

Yes, as it happens. Who are you? Zaslav (talk) 00:00, 28 August 2016 (UTC)
I am, uhh (my apologies in advance) an "anonymous coward", with apparently too much free time on their hands. (talk) 21:19, 29 August 2016 (UTC)
Do you answer to "67" or is it best to address you as "Hem 16"? (It took me this long to formulate an answer. "Hem": Gender-neutral, rank-neutral honorific, used in intragalactic all-species polyglot.) Zaslav (talk) 08:38, 23 November 2016 (UTC)