Wikipedia talk:WikiProject Mathematics/Archive/2019/Jul

Deletion

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

Footnotes request

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

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

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

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

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

Degrees of TeX literacy among Wikipedian mathematicians

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

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

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

Following Dieudonne, there is a unique

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

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

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

Is it possible that

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

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

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

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

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

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

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

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

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

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

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

All horses are the same color

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

Η-pseudolinearity

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

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

Unchecked erratas

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

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

Two grammatical numbers:

This erratum is....

These errata are....

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

False position method

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

Wikipedia:Meetup/Providence/NonlinearAlgebra 2018/ICERM

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

Template:Infobox mathematical constant

plz no mor infobox

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Style guide for parentheses for the argument of a function

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

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

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

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

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

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

@David Eppstein: I agree.

${\textstyle f(x)}$

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

New kind of references?

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

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

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

{{Citation|isbn=0521337798}}

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

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

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

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

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

Draft:Arnold Mathematical Journal

This journal is indexed in Scopus and zbMATH, which will be enough to pass WP:NJOURNALS usually. If someone would like to shepherd this to mainspace, see WP:JWG for how to expand the article up to our standards. The indexing information can be found at [1]. Headbomb {t · c · p · b} 19:52, 26 July 2019 (UTC)

Recently created article Codensity monad

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

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

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

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

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

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

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

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

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

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