Wikipedia talk:WikiProject Mathematics/Archive/2016/May

RfC article title: "Area of a circle" or "Area of a disk"

There is an RfC at Talk:Area of a disk#RfC article title: "Area of a circle" or "Area of a disk" that would benefit from the insight of members of WPM. Please direct your comments there. Sławomir
Biały 17:04, 3 May 2016 (UTC)

Selection principle

The article titled Selection principle could probably use some work in the intro section. Michael Hardy (talk) 21:28, 4 May 2016 (UTC)

Article Importance Ratings

I've been looking at the "area of a disk"/"area of a circle" article...noticed it's rated "low importance"...was wondering why...it would seem it should be the exact opposite (that is, important for Wikipedia to have a good article on such a fundamental/elementary/and widely taught topic)...it seems the articles rated highly important are often of a very advanced nature (which may be fine, but less advanced though very important articles like this are also highly important)..I went to the pages on the ranking but it appears there has been no activity over there for many years...so posted here...are these ratings irrelevant at this point and of no consequence to anything? or should they be changed/done away with because they interfere with editorial activity?68.48.241.158 (talk) 14:11, 4 May 2016 (UTC)

It is not really a rating (like "C class" is), more of an assessment of importance. You can change the assessed importance yourself by editing the talk page. YohanN7 (talk) 14:39, 4 May 2016 (UTC)

okay, I suppose it was implemented to draw editorial attention toward certain articles? Does it actually do this in some manner or is it basically irrelevant (as I said the policy pages on it haven't been touched in some five years)?68.48.241.158 (talk) 14:54, 4 May 2016 (UTC)

I think this topic is so widely studied that its importance should be at least "mid". —David Eppstein (talk) 15:59, 4 May 2016 (UTC)

I have never liked the term "importance" because its meaning to editors is ambiguous. Is it a rating of how important a topic is in the field or is it an indication of the need for editors to work on the page? I think the latter may have been the intended meaning but the former is probably the interpretation of the casual editor. I prefer the use of the term "priority" (which we are allowed to use) as this more clearly indicates a directive to editors. With this terminology I interpret (and I am sure that not everyone will agree with this) a high priority rating as meaning an article that is important in the first sense that is in need of a lot of work by editors and a low priority rating as one that means not much attention needs to be paid to the article (could mean that the article is in good shape or that it is not a significant contribution). Mid priority would be the grab bag of whatever is left over. This aspect of the rating system has been discussed in the past and I am pretty sure that no general agreement was ever reached. Bill Cherowitzo (talk) 19:37, 4 May 2016 (UTC)

okay, seems like a mechanism that doesn't have a clear philosophy/utility behind it...so probably inconsistently used...it could be harmful to the project if fundamental articles aren't being looked at by serious editors because they've been labeled of low importance...but my feeling is the label is entirely ignored and irrelevant at this point...68.48.241.158 (talk) 21:29, 4 May 2016 (UTC)

I don't think it's entirely ignored; at least, I have occasionally used the chart of articles by quality+importance at Wikipedia:WikiProject Mathematics/Wikipedia 1.0 to help me see what needs more work. —David Eppstein (talk) 22:17, 4 May 2016 (UTC)

Need some free media

I'm looking for a "free" version of the image on the last page of this PDF: [1]. I would like to use it in the new section at pi, with a caption about Queen Dido and the isoperimetric problem. Does anyone know how we might find such a thing? (I was going to add: short of flying to Rome, but the irony is I actually will be in Rome. Still, let's not...) Sławomir
Biały 22:55, 4 May 2016 (UTC)

I reverted this, thinking that I had found a better image (http://math.arizona.edu/~dido/LordKelvin1894.pdf) but I don't think that PDF is free either. (I was thinking that it's published before 1900, but that would mean that I could probably go and make my own scan of the original, but that using someone else's scan without permission would be non-free.) So, if there's a "free" pdf out there, of either image, I'd appreciate to know where. Sławomir Biały (talk) 23:19, 4 May 2016 (UTC)

File:Dido purchases Land for the Foundation of Carthage.jpg maybe? It's not Rembrandt but it is Dido and the oxhide. —David Eppstein (talk) 23:58, 4 May 2016 (UTC)

Actually, I meant the image on the second page, showing a very circular Carthage, drafted by Lord Kelvin. Sławomir Biały (talk) 00:27, 5 May 2016 (UTC)

It's online at a bigger resolution at https://archive.org/stream/proceedings14roya/#page/112/mode/2up which (in the detail page for the proceedings) lists its copyright status as "not in copyright". So I think you could grab a copy from there to use. —David Eppstein (talk) 00:36, 5 May 2016 (UTC)

I grabbed a copy from Google Books. I'm hoping that public domain content hosted by Google is still suitable for derivative free works like the image I placed in the article. Sławomir Biały (talk) 01:03, 5 May 2016 (UTC)

Is this image label incorrect ?

Please see: [[2]]

73.4.14.51 (talk) 14:28, 6 May 2016 (UTC)

It is correct; explained there. Boris Tsirelson (talk) 15:55, 6 May 2016 (UTC)

Message for: RfC: Change Default Math Appearance Setting to MathML (Follow Up) Suggestion

Hi, so I don't know where the best place to post this is. I have this RFC that is highly applicable to this WikiProject that should be advertised here. — Preceding unsigned comment added by Hungryce (talk • contribs) 02:15, 23 April 2016 (UTC)

Looking at T131177 it looks like "Enable MathML by default" is going ahead. Probably your last chance to comment. --Salix alba (talk): 18:26, 6 May 2016 (UTC)

Some people have objected to firefox using MathML which is patchy. It looks like Firefox will get SVG as the default.--Salix alba (talk): 18:32, 6 May 2016 (UTC)

Takahiro4, Kawarabayashi, etc.

Could I get some more eyes on our WP:BLP article on Japanese graph theorist Ken-ichi Kawarabayashi, please? Takahiro4 has been making a mess of it. It's not the only recent problem involving this editor; see User talk:David Eppstein#kawarabayashi article (or Takahiro4's contributions) for context. —David Eppstein (talk) 18:11, 4 May 2016 (UTC)

I don't read Japanese, so it's hard to verify the added material at Ken-ichi Kawarabayashi. (User:TakuyaMurata perhaps could check it.) I've corrected some of the obvious grammatical problems there, and removed a sentence about what conferences he likes to attend as not especially noteworthy. Sławomir
Biały 19:10, 4 May 2016 (UTC)

I've checked some assertions that were backed by the Japanese source. Some minor points (e.g., the name of the supervisor) didn't appear in the source so, for those claims, I changed the ref to CV. The secondary source is better than the primary one (CV), but since the claim is not extraordinary, the CV is probably good enough. -- Taku (talk) 23:42, 4 May 2016 (UTC)

Thanks, both of you. —David Eppstein (talk) 23:55, 4 May 2016 (UTC)

The editor seems to be really keen on picking a fight with others. It isn't clear to me why, but I suspect he is not long for the English Wikipedia if his behavior continues in this vein. I was tempted to bring the matter to ANI, as the editor is technically over 3RR at π (against no less than four distinct editors), and has resorted to petty name-calling. I still hold out hope though that this will blow over. I do find it rather unpleasant that the discussion of my recent addition to π took this rather ugly turn, and although I certainly welcome discussion, I wish that the circumstances surrounding that discussion had been more amicable. Personally, I think Takahiro4 should be blocked, but discussion should be allowed to continue if there are any other editors wishing to take up the mantle. Sławomir
Biały 11:23, 5 May 2016 (UTC)

Disruption continues at pi. At some point, I think ANI is called for. I am convinced that the editor is just trolling. On the talk page, he requested a section on Fourier series, and now is intent on adding templates against policy. I think it's time this editor be blocked. He is wasting the time of productive editors. Sławomir
Biały 15:13, 8 May 2016 (UTC)

Arithmetic of quadratic forms – amusing typo

Just as one writes [[cat]]s so that the reader sees "cats" and clicks on it and sees the article titled "cat", someone typed [[arithmetic of quadratic form]]s in an article. That doesn't make sense and I changed it to [[arithmetic of quadratic forms]]. However, we currently have no article titled Arithmetic of quadratic forms. Should we? And can someone here start the article? Michael Hardy (talk) 17:14, 8 May 2016 (UTC)

Can someone create a very simple graph in Maple?

It was pointed out to me that the graph File:Champernowne_constant_logscale.svg used in Champernowne constant has a mistake: the dots corresponding to the 41-st digit is out of place (it should be at height 10^{2504}. Not sure how that happened! :/ Anyway, at the moment I don't have access to Maple, so it would be nice if someone could re-do the graph (the code should be just a couple of lines, one could also take the data from here). Notice that being the misplaced point much bigger than in the graph, this means that the graph is going to be really flat, I guess it's OK, but another option is to leave that point out of the graph (mentioning it in the caption), or to go for a double logarithmic scale.--Sandrobt (talk) 23:12, 10 May 2016 (UTC)

Chow group and Chow ring

We have a new article titled Chow group of a stack. In the first sentence, it links to Chow group, which redirects to Chow ring. Should it be left that way, or should Chow group perhaps be a disambiguation page, or should we leave Chow group intact as a redirect while also putting a hatnote atop Chow ring telling the reader that Chow group of a stack exists, or should something else be done? Michael Hardy (talk) 20:20, 14 May 2016 (UTC)

I've been thinking this awhile: I think we should rename Chow ring to Chow group. Given the materials there, the latter name looks more appropriate. -- Taku (talk) 21:45, 14 May 2016 (UTC)

Based on your comments I'd have gone ahead and clicked on the "move" button but for this: The first sentence and maybe somewhat more of the first paragraph should get somewhat rephrased if the name is to be changed. Michael Hardy (talk) 23:18, 14 May 2016 (UTC)

The move and the necessary rewriting of the intro have been done by User:Ozob. Thanks! -- Taku (talk) 02:13, 16 May 2016 (UTC)

(To give context for the new article, given an algebraic variety/scheme X, you can define its Chow group of X, which is like homology but uses rational equivalence. If X is smooth, you can define multiplication (intersection product), giving it a ring structure and the result is called the Chow ring of X. It is probably not too important whether th article is called Chow group or Chow ring, since they are the same in the smooth context. Now, you want to extend the definition to stacks, which is straightforward over Q at least for Deligne–Mumford stack but becomes more tricky in general; i.e., one should probably not define it as simply the group of the rational equivalence classes. It is known that a DM stack with the resolution property is an (essentially) global quotient stack and so one can (in fact should ?) use equivariant Chow group in such a case. Given this background, I thought it makes sense to have a separate article, since this type of technicalities would be distracting.) -- Taku (talk) 21:52, 14 May 2016 (UTC)

I agree that Chow group is a better name. One defines individual Chow groups first (the definition is quite elementary), and then, with effort, one shows that there is a ring structure (the intersection product; depending upon how generally one wants this to be defined, this is either fairly simple or quite involved).

Oddly enough, the article mostly omits the relation to motivic cohomology, and Bloch's higher Chow groups aren't mentioned at all. That's quite a gap. Ozob (talk) 01:28, 15 May 2016 (UTC)

I've moved the page to Chow group. Ozob (talk) 18:38, 15 May 2016 (UTC)

(See above). If I'm reading the same article, I think it mentions both motivic cohomology and higher Chow group; I think the POV adopted there is that higher Chow groups are special cases of motivic homology; I don't know "how valid" this idea is. Is really so in the non-smooth cases for instance? Maybe "philosophically true"? (smooth is needed to compare with motivic cohomology). What I want for my Chrismas is motivic homology of a stack, but maybe that's too much :) -- Taku (talk) 02:13, 16 May 2016 (UTC)

(Can't stop thinking) If I remember correctly, the main difference between Bloch's higher Chow group and motivic homology is that the former relies on Bloch's moving lemma (which was controversial initially) and the latter doesn't (it uses a sheaf with transfer.) Maybe this stuff is only of historical nature. -- Taku (talk) 06:03, 16 May 2016 (UTC)

The relevant question is not how the two constructions are performed, but what they're trying to accomplish. It is generally agreed that there is a universal cohomology theory, namely the category of mixed motives. Cohomology in this category, known as motivic cohomology, is a powerful invariant. While there are several definitions of categories of mixed motives in the literature, none of them have yet been proven to behave entirely as expected. Motivic cohomology, on the other hand, has had usable foundations since Bloch. It was well-known to experts that the weight-graded pieces of algebraic K-theory captured the rational part of the motivic cohomology groups, but that's not quite the same. Bloch's groups simply worked. Bloch's construction yielded, for varieties smooth and quasi-projective over a ground field, the true motivic cohomology groups.

But they were not a panacea. If pressed for specifics, however, experts will admit that just as in the topological case, in general one has to distinguish between homology and cohomology and between compact supports and not; and in order to study the relative situation (a family of varieties over P¹ or a variety over Spec Z) one actually wants a derived category and the usual six operations. Bloch's groups did not do any of this. Voevodsky's derived category of mixed motives comes much closer. Voevodsky constructed a triangulated category in which one can find homology and cohomology with and without compact supports. If I recall correctly, at least in some cases this triangulated category is known to admit the six operations. So it is an enormous technical improvement on what Bloch did, though it came at the cost of introducing additional technique from homotopy theory. Nevertheless, it is still trying to capture the same information; despite all the new ideas, it's still aimed at the same purpose. And Bloch's definitions are still useful (even if one is willing to simply treat Voevodsky's theory as a black box) because they can be used to make direct geometric computations in some situations, whereas in Voevodsky's setup everything is defined indirectly. Ozob (talk) 13:04, 16 May 2016 (UTC)

List of Laplace transforms

The article List of Laplace transforms was recently forked out of Laplace transform. Is this really necessary and helpful to likely readers of Laplace transform? Please comment at Talk:Laplace transform#List of Laplace transforms. Sławomir Biały (talk) 12:40, 17 May 2016 (UTC)

Function theory

The page titled function theory redirected to function (mathematics). I had followed a link to that name from a new biographical article on a mathematician, in which I suspected the term has the first sense listed below. So I changed it to a disambiguation page, as follows:

See:

• Complex analysis, the study of holomorphic functions of a complex variable. Especially in works written during the 19th century and the first half of the 20th century, the term function theory often has this sense.
• Function (mathematics)

This disambiguation page lists mathematics articles associated with the same title.

Quite possibly this could benefit from more eyeballs. Michael Hardy (talk) 17:44, 18 May 2016 (UTC)

Mathematicians biographies on the drafts name space

Is there any that should be moved to the main space? Grogamoco (talk) 12:31, 15 May 2016 (UTC)

I do not know about that, but I suggest that Draft:Niggonometry be deleted as a probable hoax and intended to be offensive. JRSpriggs (talk) 14:28, 15 May 2016 (UTC)

Speedied. Cheers! bd2412 T 14:59, 15 May 2016 (UTC)

"Niggonometry" referred to "the well known 20th century mathematician CJH". When you clicked on it, you saw the article on the 19th-century English novelist Charles Dickens. If everything else in the article were not enough to conclude it's a hoax, look at that. Michael Hardy (talk) 18:17, 18 May 2016 (UTC)

Related to the same editor, is the new Fluctuation spectra (a) comprehensibly about an actual topic, and (b) not a copyvio. Sławomir Biały (talk) 23:24, 15 May 2016 (UTC)

In there I did see a draft for Boris Levin. I recognized the name as that of a well-known Soviet functional analyst. I added some references to the draft, then it was re-reviewed and moved to main-space. Nsk92 (talk) 16:09, 15 May 2016 (UTC)

What about Draft:Spyros Alexakis? He has won a respectable prize (at least I think it is), but Google Scholar citations count is very low. 187.107.38.174 (talk) 18:06, 15 May 2016 (UTC)

Actually, citations count is not so low, it's just that Google Scholar did not find some of his papers the way I made the search the first time... But, still, by citation count alone it can't be accepted, but maybe because of the prize it can. I don't know. 187.107.38.174 (talk) 18:14, 15 May 2016 (UTC)

Classical decomposition at AFD

• Additive state decomposition (AfD discussion)

You might want to weigh in on what to do, here. Uncle G (talk) 21:09, 15 May 2016 (UTC)

This article is a complete orphan, i.e. no other pages link to it. Michael Hardy (talk) 18:23, 18 May 2016 (UTC)

Користувач:Перевод

Could someone who knows more about these things have a look at this? Obviously this title is incorrect... --Randykitty (talk) 10:49, 27 May 2016 (UTC)

"Differential geometry of curves" is meant. Boris Tsirelson (talk) 10:59, 27 May 2016 (UTC)

No, that is "Диференціальна геометрія кривих" that means "differential geometry of curves". By the way, looking on the history, it appears that the article is a (very bad) translation of the Russian WP article on the subject (probably an automatic translation). I have no idea of the meaning of the title. IMO this translation does not add anything useful to the content of Differential geometry of curves. Therefore, I suggest deletion. D.Lazard (talk) 11:12, 27 May 2016 (UTC)

(e/c) Differential geometry of curves already exists. There does not seem to be anything there that is not already covered in our existing article, apart from some material on curvature which is already covered in the curvature article. Moreover, the mistitled article looks like the result of a bad machine translation. I don't think anyone would lose sleep if this article were just deleted. I will add a prod tag, but feel free to remove it as per the usual WP:PROD rules. Sławomir Biały (talk) 11:14, 27 May 2016 (UTC)

Matrix decomposition into clans

Is there any content worth saving in Matrix decomposition into clans? —David Eppstein (talk) 05:28, 28 May 2016 (UTC)

On one hand, the author talks of solving linear systems over rings and monoids. We have an article Linear equation over a ring that covers some of the basics. But rather than a general monoid, what the author really seems to be discussing is a solution technique for solving a system of linear Diophantine equations over nonnegative integers, nonnegative integers being a simple type of monoid. For this, we already have Diophantine equation#System of linear Diophantine equations. The section doesn't discuss the nonnegative constraint, but there exists other papers out there, such as [3], which treat this common case in integer programming. The author's papers, while interesting, don't seem to have generated any secondary commentary or citations. Hence this work is non-notable and I don't think it would be of due weight to include it in Diophantine equation#System of linear Diophantine equations. In short, no content worth saving. --Mark viking (talk) 18:40, 29 May 2016 (UTC)

Ok, thanks; I've prodded it. Another of the same editor's contributions, about another piece of research by the same author (who is likely the same person as the editor) is also prodded: see Zaitsev neighborhood. —David Eppstein (talk) 19:21, 29 May 2016 (UTC)

John von Neumann GA review

John von Neumann is being reviewed as a potential Good Article. Please participate in the review at Talk:John von Neumann/GA1. —David Eppstein (talk) 16:52, 25 May 2016 (UTC)

I nominated the article under Military History because we're the ones who polished the article to bring it to GA, as part of a broader effort on Manhattan Project people, and our project is a multi-disciplinary one. Assistance is welcome. Hawkeye7 (talk) 22:03, 25 May 2016 (UTC)

The article has now passed its GA review. If WP-Mathematics has an A class Review process, it can nominated. Hawkeye7 (talk) 22:25, 28 May 2016 (UTC)

I think the WPM A-class process is defunct. —David Eppstein (talk) 22:52, 28 May 2016 (UTC)

Oh. It has nowhere to go then. I could nominate it for A class at MilHist, but there doesn't seem much point. Hawkeye7 (talk) 01:11, 29 May 2016 (UTC)

In my dream, all mathematicians from http://fabpedigree.com/james/gmat200.htm have featured articles here on Wikipedia. :D 189.6.194.219 (talk) 16:26, 30 May 2016 (UTC)

Advanced calculus

I occasionally see the phrase "advanced calculus". Sometimes it seems to mean introductory real analysis (e.g., sequences, continuity, what distinguishes the reals from the rationals) and sometimes it seems to mean topics in calculus that are usually introduced later rather than earlier in a sequence of calculus courses (e.g., trig substitution, multivariate calculus). Right now, Advanced calculus is a red link. What should we do with it? My first thought is to redirect it to Real analysis. —Kodiologist (t) 15:59, 30 May 2016 (UTC)

I think this terminology is more social than mathematical. I don't know in other countries, but here in Brazil, calculus courses are very different from analysis courses. In calculus one is more interested in the theorems and intuitions than in their rigorous algebraic, topological, number theoretic, etc... justifications. Maybe Advanced calculus could be a redirect to Calculus on manifolds? 189.6.194.219 (talk) 16:20, 30 May 2016 (UTC)

As said in the second paragraph of Calculus, calculus is essentially the elementary part of mathematical analysis. Therefore, this is the natural target for a redirect. I'll create the redirect. Calculus on manifolds is a dab page and is thus not a correct target for a redirect. D.Lazard (talk) 16:30, 30 May 2016 (UTC)

I once taught a course called "advanced calculus for engineers", consisting of topics needed as prerequistes to a fluid dynamics course, and about half of it was complex analysis, so "real analysis" might not be a perfect target for a redirect. Michael Hardy (talk) 18:00, 30 May 2016 (UTC)

In the spirit of Wikipedia:Verifiability, I took a peek at amazon.com's titles "Advanced Calculus". There is wide variety: everything from multivariable calculus and calculus on manifolds to Fourier series and topological vector spaces. Mgnbar (talk) 18:17, 30 May 2016 (UTC)