Wikipedia talk:WikiProject Mathematics/Archive/2016/Feb

Asking for suggestions
Sorry for asking something that's not really related to Wikipedia, but here goes. I recently put on line a paper I wrote commenting on the attempt of Louis de Branges de Bourcia to prove the Riemann Hypothesis. How can I bring it to the attention of those who would be interested? Eric Kvaalen (talk) 09:08, 2 February 2016 (UTC)


 * Why not put it on the arXiv? I did once something similar . Boris Tsirelson (talk) 09:38, 2 February 2016 (UTC)

RfC of interest
Please offer comments at Wikipedia talk:Special:Preferences. --Sammy1339 (talk) 19:54, 2 February 2016 (UTC)

AfC help again
Hi everyone. Can we get some eyes to take a look at Draft:Extended mathematical Programming (EMP)? Comments and thoughts will be greatly appreciated. Thanks in advance for your help.  Onel 5969  TT me 12:55, 4 February 2016 (UTC)

Draft:Robust fuzzy programming
This draft is stalled at AFC because regular reviewers are unable to evaluate the validity of the subject as an acceptable article topic, please help. Roger (Dodger67) (talk) 10:19, 5 February 2016 (UTC)
 * It looks like all the sources are primary research papers by a single author/research group. This is not enough to show WP:N. I've tried to declined it, but may have messed up as its hard to do without the helper script. --Salix alba (talk): 19:06, 5 February 2016 (UTC)

Global Digital Mathematics Library
I'm currently attending this workshop which is charged with producing a white paper on how to make (or the prospects for making) progress towards a library of mathematics suited to today's digital world. As there are already a number of candidate languages in current use there are questions of who such a GDML is for, how compatible or intertranslatable the extent candidates are, whether the initial focus should be at the level of vocabulary, syntax, ambiguity (in either vocabulary or syntax), functions, concepts, or semantics, and like questions.

Are there members of WikiProject Mathematics who feel they could usefully represent the wikiproject's (or more generally Wikipedia's) attitudes towards, and opinions about, GDML's goals, prospects, methodology, etc.? Vaughan Pratt (talk) 20:36, 5 February 2016 (UTC)


 * When discussing semantics and ontologies, especially upper ontologies, it is very easy to fall into the trap of endlessly discussing abstract systems of classification, and formal languages for talking about mathematics. For all the tremendous amount of work that has gone into the semantic web, for instance, there is no one ontology that is universally accepted.
 * In this context, I think the most useful thing a Wikipedia approach can bring to this project is to urge the group to be relentlessly practical. There already exist practical ontologies on which to hang mathematical knowledge: for example, the Mathematics Subject Classification scheme and Wikipedia's own set of categorical classifications for mathematical topics. These should be built on, rather than a new ontology created ab initio. The other fundamental practicality is that any knowledge incorporated into the GDML must be easily verifiable. This is especially true if some sort of machine learning automatic summarization is going to be attempted. Neutrality would be good, too, but is perhaps too ambitious at the outset. My two cents, --Mark viking (talk) 19:58, 6 February 2016 (UTC)

Matrix_calculus
Hello there. Recently I am reading matrix calculus and there is one scalar-by-matrix identity that I could not understand.

According to my understanding and nominator layout, it should be $${\partial\text{tr}\big(\mathbf{X}^{-1}\mathbf{A}\big)\over\partial\mathbf{X}} = -\mathbf{X}^{-1}\mathbf{AX}^{-1}$$ while the wiki page suggests that it should be $$-\big(\mathbf{X}^{-1}\big)^\mathrm{T}\mathbf{A}\big(\mathbf{X}^{-1}\big)^\mathrm{T}$$ instead. There is no such identity in the matrix cookbook (perhaps we can replace the matrix A with I in derivative #124?), so I seek your advice.Estorva (talk) 14:04, 5 February 2016 (UTC)


 * I am not acquainted with "nominator layout", but according to my understanding, the differential of $$\text{tr}\big(\mathbf{X}^{-1}\mathbf{A}\big)$$ is $$-\text{tr}\big(\mathbf{X}^{-1}\mathbf{A}\mathbf{X}^{-1}d\mathbf{X}\big)$$. Boris Tsirelson (talk) 19:29, 5 February 2016 (UTC)
 * Well, after reading that article about "nominator layout" for scalar-by-matrix derivatives I believe that it means $$dy = \text{tr}\Big({\partial y \over \partial \mathbf{X}} d\mathbf X \Big)$$; and if so, then $$-\mathbf{X}^{-1}\mathbf{AX}^{-1}$$, indeed. Boris Tsirelson (talk) 19:48, 5 February 2016 (UTC)

@Estirva and @Tsirel: You deficiency of TeX skills is showing. Here's a comment I just left on the talk page of the article discussed here: When one writes {\rm tr} in TeX one does not get proper spacing before and after "tr". Thus
 * $$ a {\rm tr} B \, $$ is coded as a {\rm tr} B, and
 * $$ a \operatorname{tr} B \, $$ is coded as a \operatorname{tr} B, and
 * $$ a \operatorname{tr} (B) \, $$ is coded as a \operatorname{tr} (B).

Writing \operatorname{tr} results in a certain amount of space before and after tr, and there is less space when (round brackets) follow tr than when they don't. The form {\rm tr}, on the other hand, involves no spacing conventions. The form \operatorname{tr} is standard usage and I edited accordingly. The same thing applies to \text{tr}, which both of you used here. Michael Hardy (talk) 21:31, 7 February 2016 (UTC)


 * Surely I use "operatorname" (if not "DeclareMathOperator") when TeXing my articles, lecture notes etc. But this is not article, just discussion, and I did copy-paste from Estorva (who in turn did copy-paste from the article, as you alreardy know). Boris Tsirelson (talk) 06:18, 8 February 2016 (UTC)
 * But some people get their ideas of how to code these things by looking at stuff like this. Michael Hardy (talk) 19:56, 8 February 2016 (UTC)


 * That's true, but I support a relaxed attitude to talk pages. Let's not make editing Wikipedia a job. Let's not let perfect become the enemy of good. Cheers. Mgnbar (talk) 21:37, 8 February 2016 (UTC)


 * And let us avoid biting the newcomers (by such words as "your deficiency of TeX skills"); save this for us seniors. Estorva is here from Feb 5, 2016. Boris Tsirelson (talk) 21:45, 8 February 2016 (UTC)

Feynman dagger in PigTeX
Both variants,


 * $$(i\nabla\!\!\!\!/' - m)S_F(x', x) = I_4\delta^4(x'-x),$$


 * $$(i\not\nabla' - m)S_F(x', x) = I_4\delta^4(x'-x),$$

(from propagator and history) are bad. In the first, the prime is misplaced. In the second, the dagger fails to penetrate its victim and there is an ugly gap between the $i$ and the del operator. Does anyone know of a workaround (or even a supported feature)? YohanN7 (talk) 10:05, 4 February 2016 (UTC)


 * For Feynman slash notation, I would put the prime after the nabla, before the shifted slash, as in
 * $$(i\nabla'\!\!\!\!\!/ - m)S_F(x', x) = I_4\delta^4(x'-x),$$
 * --Mark viking (talk) 10:55, 4 February 2016 (UTC)


 * Thank you. I though I tried that, but must have messed up. YohanN7 (talk) 11:20, 4 February 2016 (UTC)
 * That looks OK for me in PNG, but terrible in MathML (the slash is almost invisible there). —Kusma (t·c) 12:52, 4 February 2016 (UTC)
 * Wow, in MathML all are unacceptable. YohanN7 (talk) 13:01, 4 February 2016 (UTC)
 * For me the first one has the best slash. How about using that but spacing the prime a little farther,
 * $$(i\nabla\!\!\!\!/\,' - m)S_F(x', x) = I_4\delta^4(x'-x),$$
 * —David Eppstein (talk) 21:48, 8 February 2016 (UTC)

Mathematician needed
Here: Talk:Wave function YohanN7 (talk) 13:44, 8 February 2016 (UTC)
 * I, for one, am already there.  :-)   Boris Tsirelson (talk) 15:33, 8 February 2016 (UTC)
 * No, I am not. There, editors ask simple but somewhat special mathematical questions (about vectors and operators in a Hilbert space) and accepts answers only in the form of a reliable source that treats literally the given question; any combination of two (or more) sources is rejected as OriginalResearchBySynthesis. Is there a mathematician able to satisfy them? If you are, please help them. Boris Tsirelson (talk) 11:03, 10 February 2016 (UTC)


 * I think that that is a bit unfair. I am personally perfectly happy with your replies. No complaints on my part. YohanN7 (talk) 12:08, 10 February 2016 (UTC)

Spacetime triangle diagram technique
I'm wondering if Spacetime triangle diagram technique should be moved either to Spacetime triangle diagram or to Spacetime triangle? (I found the article full of crude solecisms, some of which I cleaned up, and bizarrely over-complicated TeX code written by a psychotic (which probably means it was written by some software package of the kind used by people who don't know TeX code) and I cleaned up some of that too.) Ceteris paribus, I think shorter titles are better, partly because they're more likely to be found by using the search box. Michael Hardy (talk) 19:58, 16 February 2016 (UTC)

Special purpose account
The user, Ryanexler is planting a reference in various articles. He/she (most likely to be Jakob Schwichtenberg ) has done this once before (last year) and was then reverted by me. I don't feel like being this mans nemesis around here. Someone else should have a look. YohanN7 (talk) 12:30, 12 February 2016 (UTC)

Others did revert, but he is at it again. YohanN7 (talk) 10:29, 16 February 2016 (UTC)
 * I've warned the user about WP:REFSPAM. -- Kinu  t/c 20:13, 16 February 2016 (UTC)

This proposed change in the title of an article might perhaps benefit from more eyeballs.
This proposed change in the title of an article might perhaps benefit from insights of participants in this page. Michael Hardy (talk) 20:21, 16 February 2016 (UTC)

Georg Cantor's first set theory article
We have a new article titled Georg Cantor's first set theory article, written largely by an expert on the history of the matter, R. J. Gray, who has published refereed papers on the topic.

I have added a "mergefrom" tag to it, which may be controversial. There is a large overlap between the two articles. The rationale for creating a separate article with a separate title is explained by R. J. Gray in this section of my user talk page.

Currently no other articles link to this new article. So that's something to work on. Michael Hardy (talk) 03:27, 13 February 2016 (UTC)


 * It strikes me that the article might better be titled "On a Property of the Collection of All Real Algebraic Numbers" after the title of Cantor's article. Or perhaps it should be named "Ueber eine Eigenschaft des Inbegriffes aller reellen algebraischen Zahlen" after the original title. It's a very nice article.  Ozob (talk) 04:03, 13 February 2016 (UTC)
 * I already made that comment at the article's talk page. --Trovatore (talk) 04:06, 13 February 2016 (UTC)
 * Update: I made it a formal requested move.  --Trovatore (talk) 20:26, 13 February 2016 (UTC)
 * I would say this article is a good candidate for Good article/Featured Article status, if anyone want to guide it through the process.--Salix alba (talk): 00:18, 17 February 2016 (UTC)
 * See Talk:Cantor's first uncountability proof/GA1 for a previous review (that led to the restructuring that created the present article). If someone does want to take it to GA, it would be a good idea to make sure the issues found there have all been taken care of. —David Eppstein (talk) 01:19, 17 February 2016 (UTC)

Copyvio
The article Effect algebra was copied from http://arxiv.org/pdf/1602.00567v1.pdf, making it a copyright violation. GeoffreyT2000 (talk) 01:49, 17 February 2016 (UTC)


 * Good catch. I think the copy was done in good faith; the whole text was put in a blockquote. It may be too extensive for fair use. I put up a copypaste notice on the article to encourage a rewrite. --Mark viking (talk) 04:20, 17 February 2016 (UTC)


 * Thanks to both of you for bringing this to my attention! Yes, I had indeed thought blockquoting the text, which is only a small section of the paper I copied it from, would constitute 'fair use'. Further, I couldn't think of how to rephrase it in my own words, given it's mostly technical definitions that I felt I could only make small changes to the wording of - which would then constitute plagiarism. This then brought me back to simply blockquoting. But having now read Copying text from other sources, and that I don't know how to rewrite the text in a non-plagiarising way, I will accept the article in its current form simply being deleted. Sorry for my mistake! --Thoughtactivist (talk) 05:50, 17 February 2016 (UTC)


 * It would be easy enough to rewrite the definitions so they are not copyvios; I can try later this afternoon, perhaps. More important (from the editorial point of view) would be to add a few sentences saying why anyone would care about these things. , can you do that?  --JBL (talk) 14:40, 17 February 2016 (UTC)

I've done some editing on this article. If it was a copyright violation earlier, it probably is not now. It didn't have a proper introductory sentence; I've added that. Michael Hardy (talk) 18:48, 17 February 2016 (UTC)


 * Well, but is it notable? Boris Tsirelson (talk) 19:46, 17 February 2016 (UTC)


 * Its a good question. There is an nLab page on them with a number of references. Probably mostly of interest to quantum mechanics or C*-algebra folk. --Mark viking (talk) 21:43, 17 February 2016 (UTC)

Editing help needed
Recap: I am blind and a newbie, but an expert on the Jacobian Conjecture(JC). Around January 20, I proposed a change to the JC article on the talk JC page, under the title Symmetric Case. I pointed to it here, but the pointer was archived with no action. Needs a reference to two papers by the same two authors in the same year. Please help.

L.Andrew Campbell (talk) 01:38, 18 February 2016 (UTC)


 * Probably you mean these:
 * de Bondt, Michiel; van den Essen, Arno. The Jacobian conjecture for symmetric Druzkowski mappings. Ann. Polon. Math. 86 (2005), no. 1, 43--46. MR2183036 (2006i:14069)
 * P.K. Adjamagbo and A. van den Essen (2007) and Alexei Belov-Kanel and Maxim Kontsevich (2007) showed that the Jacobian conjecture is equivalent to the Dixmier conjecture.
 * Boris Tsirelson (talk) 12:25, 18 February 2016 (UTC)

New article
I have created the System U article and would appreciate if somebody checked its wikiness. Also, looking at related articles, I noticed they have this WikiProject's rating template on their talk pages. I don't know what the process around these is, but this article should probably have one as well. —Matěj Grabovský (talk) 12:37, 19 February 2016 (UTC)


 * Thanks for your contribution! This looks like a well-formatted start-class article to me and I've added the wikiproject template. As a layman in this field, I don't understand the notation in your formal definition section. You might add a few words of explanation. --Mark viking (talk) 13:51, 19 February 2016 (UTC)


 * Thanks. I'll try to add an intuitive interpretation of the symbols. —Matěj Grabovský (talk) 15:02, 19 February 2016 (UTC)


 * Thanks for adding the explanatory prose. That makes it much clearer. --Mark viking (talk) 01:17, 21 February 2016 (UTC)

P-value fallacy for DYK
I'd like to get P-value fallacy in WP:DYK. (User:Sunrise gets all the credit, not me.) It'd be nice to have a decent mathematics article on the Main Page. I'd appreciate it if a few stats people looked it over and/or suggested a good "hook" for it. Realistically speaking, we probably can't expect to find very many stats people among the DYK reviewers, so I'm asking here. If anyone has comments, please be bold, or leave notes on the article's talk page. WhatamIdoing (talk) 01:56, 22 February 2016 (UTC)

List of sieve methods
In this section I found only two sieve methods listed, not including the sieve of Eratosthenes about which everyone learns in elementary school, and which is in fact the only one that I know anything about. I added several more. Quite possibly the section needs more work. Maybe even subsections on different kinds of sieves? Or maybe not? Michael Hardy (talk) 18:43, 25 February 2016 (UTC)

Tech Talk on Zotero and citations
Some of you may be interested in this:

There is a Tech Talk next Monday, 29 February at 20:00 UTC (12 Noon Pacific Time) about Zotero and the citoid service.

The main subject is how to extract accurate, automated bibliographic citations from websites. This talk is mostly about Zotero, which is a free and open-source citation management tool. Zotero is used on the Wikipedias through the automagic citoid service. Citoid is currently an option in the visual editor and will (eventually) be used for automated citations in the wikitext editor at some Wikipedias. Zotero is also used by many academics and researchers, and most of the information presented will be useful to people outside of Wikipedia as well.

Please share this invitation with anyone that you believe will be interested. If you have questions, then please leave a note on my talk page. Whatamidoing (WMF) (talk) 03:43, 24 February 2016 (UTC)


 * Would this be a related question?: Do page numbers in references cited in Wikipedia obey Benford's law? Gathering data to examine this would be quite onerous without software designed for the purpose. Michael Hardy (talk) 18:52, 25 February 2016 (UTC)

Gimel function
Could someone please take a look at this article. The "Gimel" hebrew letter in the images looks like a Nun rather than a Gimel. A Gimel has a foot in the lower right.Naraht (talk) 22:00, 26 February 2016 (UTC)
 * Hmm, the article uses inline LaTeX, which we tend to discourage, but in any case it's producing $$\gimel$$ from the code, so if it's wrong, then it's actually wrong in our TeX rendering engine, not just the article. --Trovatore (talk) 00:38, 27 February 2016 (UTC)
 * The unicode for HEBREW LETTER GIMEL is &#x5d2;, which looks more like what you describe, but less like what I've seen used to notate the gimel function. Maybe this is an issue of calligraphic style or something?  Anyway, the version in the article looks like what I've seen in Jech, for example. --Trovatore (talk) 00:49, 27 February 2016 (UTC)
 * It looks like this is pretty much the way the character works in the font used by LaTeX, using the amssymb package. I did it on my local machine with \Huge and a fontsize of 20, and took a screenshot GimelLaTeX.png.  You can see that ther is a "foot", but it's very small, and when it's cut down to the size in the article, it's not surprising you can't see it. --Trovatore (talk) 21:34, 27 February 2016 (UTC)
 * In Jech's writings (http://matwbn.icm.edu.pl/ksiazki/fm/fm81/fm8116.pdf), you can clearly see the foot. What are the choices other than inline latex?Naraht (talk) 03:07, 28 February 2016 (UTC)
 * Why would you want to write mathematical notation to look different from the way professional mathematicians would write it? —David Eppstein (talk) 03:42, 28 February 2016 (UTC)
 * Exactly, the entry in Jeck's writing clearly shows the foot, the Wiki engine output of the LaTeX looks like a completely different Hebrew letter. The best comparison that I could give outside Hebrew would be if the LaTeX Capital Omega was shown without the two tails and as such it looked like an Omicron or a Latin Alphabet O. What can be we do make it look like what is in Jeck's article?Naraht (talk) 05:17, 28 February 2016 (UTC)
 * The letter should look like File:GimelLaTeX.png which clearly has the foot, the question is why the use of that letter in the article doesn't have the foot. Are the bottom lines of pixels being cut off? (Note, in this font, the letters are as different looking as ג and נ — Preceding unsigned comment added by Naraht (talk • contribs)
 * It probably depends on (1) your browser, OS, and what fonts you have loaded, and (2) the setting in your Wikipedia preferences for how you want math to be rendered. For me (using Chrome on OS X with the "MathML/SVG fallback" option turned on, which with that browser uses the SVG fallback rendering) the png file and the formula look basically the same. But this confusion of rendering combinations also means that trying to do something complicated to make it look better for you may be a waste of time if it ends up making things look worse for people with other settings and browsers. —David Eppstein (talk) 05:54, 28 February 2016 (UTC)
 * It turns out that there's a unicode GIMEL SYMBOL which is distinct from HEBREW LETTER GIMEL and looks like the one we want. We should probably change to use that, so that we don't have the sizing problems of inline PNG files. --Trovatore (talk) 06:06, 28 February 2016 (UTC)
 * Here's how it looks in inline text: ℷ. And inside math: $ℷ$. Presumably one advantage of using this unicode would be that it works in left-to-right text unlike the usual right-to-left ordering that you get when you use Hebrew text unicodes. The page I got the character from says: "You need a font that supports this character to even have a hope of seeing it correctly in the browser." I'm not convinced that I have a good enough font because for me it just looks like some kind of sans-serif lambda instead of like the big image above. —David Eppstein (talk) 06:31, 28 February 2016 (UTC)
 * That's a pity. For me it looks almost exactly like the picture, but with sharper edges.  Post a screenshot? --Trovatore (talk) 06:37, 28 February 2016 (UTC)
 * Ok, see —David Eppstein (talk) 06:44, 28 February 2016 (UTC)
 * Hmm, yeah, on yours it looks the same as HEBREW LETTER GIMEL as far as I can tell. Well, not an ideal solution then.  Still might be better than the PNGs? --Trovatore (talk) 06:47, 28 February 2016 (UTC)
 * My mobile modern browser is not able to display either Unicode character, for what it's worth. --JBL (talk) 15:53, 28 February 2016 (UTC)
 * Oh well. Nothing to be done, I guess.  Someone should set a reminder to look at this again in a few years, see if browsers have caught up. --Trovatore (talk) 21:40, 28 February 2016 (UTC)

Modified KdV–Burgers equation and the List of dynamical systems and differential equations topics
Our list of new articles at User:Mathbot/Changes_to_mathlists includes a new article titled Modified KdV–Burgers equation. It was a total orphan, so I created one link to it in the "See also" section of the article titled Korteweg–de Vries equation. Then I decided to add it to the List of dynamical systems and differential equations topics, and I found that even "Korteweg–de Vries equation" is not listed there, and it's not immediately clear where within that list it would belong. Should the list itself get reorganized? Michael Hardy (talk) 00:51, 29 February 2016 (UTC)