Wikipedia talk:WikiProject Mathematics/Archive/2018/Jan

name of a polyhedron

Hi! I am revising the files uploaded for Wiki Science Competition 2017 and I have noticedthis one. Such picture of the interior of a small domen will never be a finalist of course, but I am trying to improve its categorization and description like I did with other ones. It has a shape of a some regular solid, it could be the sort of image it is used in a school text book to show how geometry appears in real life, for example.

So, if you had to put a specific category related to a polyhedric shape, which one would it be in your opinion? thank you in advance.--Alexmar983 (talk) 12:07, 3 January 2018 (UTC)

It is an example of a Geodesic dome. I've added the corresponding category. --Salix alba (talk): 12:33, 3 January 2018 (UTC)

RfC about the significance of properties of an integer

A Request-for-Comment has been opened at Talk:209 (number) which may be of interest to the community here. XOR'easter (talk) 20:52, 7 January 2018 (UTC)

Improving "Prime number" article towards Good Article criteria

Comments and concerns are welcome. Please join in the discussion here. Derek M (talk) 23:05, 8 January 2018 (UTC)

Stereotype space?

I just ran across this article. Is that a thing? I can't seem to find much in google or google scholar that isn't authored by the user, who apparently admits COI, or isn't simply copied wiki content or print-on-demand of wiki content. There was also a discussion in the nLab forum inquiring about the notability of the topic. Is this too OR for our taste? It doesn't seem like more than one or two people have written about it. Rschwieb (talk) 14:36, 10 January 2018 (UTC)

Spread in intuitionism (draft)

Could someone cast a glance over Draft:Spread(Intuitionism) and see at what level of readiness for mainspace it is. Many thanks! – Uanfala (talk) 00:36, 10 January 2018 (UTC)

The concept of a spread in the intuitionistic approach to mathematics is a real thing, see for instance the EOM entry Spread_(in_intuitionistic_logic). I am not an expert, but the prose seems reasonable. This is a somewhat esoteric concept in the foundations of mathematics and is a challenge to explain well in a lede to a lay audience. Except for some cleanup, like deleting Author's notes, etc., it looks like this could be an article upon which other editors could build. --Mark viking (talk) 01:31, 10 January 2018 (UTC)

I can't really say on its readiness directly (other than obvious things, like removing notes as mentioned), but if someone's going to try to clean it up, I think it should probably be renamed with (mathematics) as the disambiguator (lower case, and with a space). –Deacon Vorbis (carbon • videos) 02:36, 10 January 2018 (UTC)

That will be ambiguous: there's apparently another set-theoretic topic of the same name [1] (is it related?), and there's also Rational trigonometry#Spread and then all the uses in statistics.... – Uanfala (talk) 02:46, 10 January 2018 (UTC)

In discrete geometry a spread is a certain family of curves (an infinite system of pseudolines in the plane together with a continuous function from the unit disk to the pseudolines); see Grünbaum's book Arrangements and spreads. I agree that a more specific disambigator is needed. —David Eppstein (talk) 03:02, 10 January 2018 (UTC)

(edit conflict) This has got me thinking about disambig issues in general and I'm even asking about a similar one at WT:DAB. I think the rational trig article should be deleted, but that's a separate issue that I've just kinda made my peace with. In any case, this would probably take primary topic over that anyway, so a hatnote could be used. As far as stats, our regular Spread disambig page just points to Statistical dispersion where "spread" is listed as a synonym. This would be the primary topic itself, but that's just an alternate name, so again, maybe just a hatnote again is sufficient. We don't even have a Spread (statistics) redirect (should we? and if we do, would that necessitate using (intuitionism) here?). The more I think about the subtleties of disambiguation and article titling, the less clear it seems to be. –Deacon Vorbis (carbon • videos) 03:11, 10 January 2018 (UTC)

Never mind then, I guess I just don't really have a good enough handle on article naming. I guess I'm wondering if there should be a more specific disambiguator if the other article(s) don't actually exist, or if it should be changed if and when they do. –Deacon Vorbis (carbon • videos) 03:14, 10 January 2018 (UTC)

Provided there aren't reasons to see it as ambiguoius or misleading, Spread (statistics) should be a useful redirect (of the type: {{R from other disambiguation}}). It will likely appear in the search box drop-down suggestions when a user types "spread"; it will affect the ordering of search results, pushing its _target up in the list of results for vaguer queries like "spread statistics"; and it should help in linking (particularly when using the pipe trick). – Uanfala (talk) 23:21, 11 January 2018 (UTC)

Derivative of limit

Strangely, I did not find any result of the form "derivative of the limit is equal to the limit of derivatives whenever...". Neither in real analysis nor in complex analysis. Are they really not there on Wikipedia, or did I look for them in the wrong places? (I do not mean termwise differentiation of a power series, this is too special.) Boris Tsirelson (talk) 18:42, 13 January 2018 (UTC)

I find Interchange of limiting operations and Iterated limit, neither of which is in good shape. --JBL (talk) 20:10, 13 January 2018 (UTC)

(edit conflict) It's a case of the interchange of limit operations, with a specific result given under uniform convergence#To differentiability. Obviously we'd like a better result than that, but I've heard that differentiability is not as well-behaved as integration due to the lack of an analogue of $\int _{a}^{b}f(x)dx\leq (b-a)\sup _{x\in [a,b]}f(x)$.--Jasper Deng (talk) 20:11, 13 January 2018 (UTC)

The only articles that link to the two I mentioned are Symmetry of second derivatives and Leibniz integral rule. --JBL (talk) 20:14, 13 January 2018 (UTC)

Yes, uniform convergence#To differentiability is just the result I wanted to see in real analysis; thanks to J.D. Boris Tsirelson (talk) 20:18, 13 January 2018 (UTC)

In complex analysis I want to see this: proofwiki. Boris Tsirelson (talk) 20:20, 13 January 2018 (UTC)

Uniform convergence#To analyticity is the closest we have, and may be a good location to add that (I think that result is weaker than the one you want, since in the real case, harmonicness is preserved under taking a uniform limit but even if so, one can't necessarily use termwise diferentiation).--Jasper Deng (talk) 20:24, 13 January 2018 (UTC)

I see. But, as far as I understand, for a harmonic function, not only the value at the center of a ball (or another point inside), but also a derivative at the center is equal to some integral over the sphere, which does the job (similarly to the complex case), that is, one can use termwise differentiation. Thus, by the way, the complex result follows from the harmonic result (since every holomorphic function is harmonic). Boris Tsirelson (talk) 21:20, 13 January 2018 (UTC)

I was thinking of Harmonic function#Remarks (specifically the last paragraph), but now see that that actually considers the case when the sequence of derivatives is not uniformly convergent.--Jasper Deng (talk) 22:43, 13 January 2018 (UTC)

Ah, yes, a good example. And still, in the locally uniform convergence the differentiation operator is continuous (on harmonic functions, I mean), which probably is not claimed there. Boris Tsirelson (talk) 05:23, 14 January 2018 (UTC)

By the way, the same proof works for the pointwise (or even almost everywhere) locally bounded (or even dominated by a locally integrable function) convergence (of harmonic functions). But ultimately this convergence is equivalent to the locally uniform convergence (on harmonic functions, or even solutions of an elliptic PDE). Boris Tsirelson (talk) 06:09, 14 January 2018 (UTC)

Topological geometry

The new article titled Topological geometry, if indeed it ought to exist, could certainly use some work. Michael Hardy (talk) 04:55, 16 January 2018 (UTC)

Esotericism at Chaos theory

The IP 73.46.49.164 insists to link Interconnectedness, an article, certainly not covered by mathematical ideas, within the article Chaos theory, which has an explicit hat note, guiding to alternatives to mathematical treatment via a disambiguation page, and is of interest for WikiProject Mathematics. For to me not obvious reasons the article is also tagged with being of interest for WikiProject Religion, but I am unsure, if this should be discussed at all, and if yes, where.

I did discuss this linking already at the TP, but the IP started to insert this link again, without discussing, just claiming it were correct. Within this second effort I already reverted twice and asked for discussion again, but now I want to bring the situation there to the awareness of the project. Purgy (talk) 08:11, 16 January 2018 (UTC)

• Hmm. Looks like the IP has stopped edit warring. And the interconnectedness article is both extremely terrible and up for deletion at AfD. So I don't think this will be an ongoing problem beyond this week. Reyk _YO! 11:17, 16 January 2018 (UTC)

  The pages interconnectivity and interdependence look pretty bad too. XOR'easter (talk) 18:50, 16 January 2018 (UTC)

Request a Review of Draft:Multivariate quadratic random number generator

Will someone please review Draft:Multivariate quadratic random number generator and advise whether it should be accepted as an article? Please remember that the acceptance criterion is not whether the draft is a Good Article, but only whether it is mathematically sound, and whether it is worth keeping as an article. Robert McClenon (talk) 15:23, 17 January 2018 (UTC)

Wiki markup ce tag

In several articles, including Exact sequence, Cokernel, Snake lemma, and others, user Cedar101 has replaced, for exact sequences, the standard markup <math> by <ce> (or some variants of it), which is a markup with a uncommon syntax that he has implemented. The resulting rendering is correct, but the resulting source code in no more latex but a language that is unreadable for most of us. I have reverted him once, but, for avoiding edit warring, a consensus is needed about the use of this markup in mathematics. My opinion is that the use of <ce> is WP:disruptive editing, as it makes very time consuming to modify the involved exact sequences. But this is only my opinion, and a consensus is needed in favor or against the following assertion

The use in mathematics of <ce>, or of any of its variants is disruptive editing.

D.Lazard (talk) 10:54, 26 January 2018 (UTC)

I think using <ce> for things which are not chemical equations is semantically incorrect, and should be replaced by the proper <math> syntax. Helder 11:17, 26 January 2018 (UTC)

I agree that these changes make the code harder to read without making the result any nicer too look at. Reyk _YO! 12:38, 26 January 2018 (UTC)

Yeah, this is a bad idea. I'm reverting the changes and asking him to look for consensus here before continuing. –Deacon Vorbis (carbon • videos) 13:21, 26 January 2018 (UTC)

And I might add that this is exactly how the WP:BRD process among good-faith and well meaning editors is supposed to go. Gold stars for everyone! Reyk _YO! 15:21, 26 January 2018 (UTC)

Article talk page participation sought

I invite any interested editors to join this discussion about the page Linear differential equation. Loraof (talk) 17:13, 27 January 2018 (UTC)

Good article nomination: Prime number

David Eppstein has recently nominated Prime number for a Good Article. I will begin reviewing the article in the next few days, but more reviewers are more than welcome! Leave your review at Talk:Prime_number/GA1. Jakob.scholbach (talk) 14:47, 28 January 2018 (UTC)

Multivariable/Vector Calculus expert needed

I have for a long time thought that wikipedia's article on stokes' theorem was inadequate. The first equation of the article is completely incomprehensible to me in terms of applying it to an example. If you know anything about multivariable calculus or vector calculus please help! Brian Everlasting (talk) 20:56, 28 January 2018 (UTC)

Is your complaint that the article is too far away from elementary calculus or too far away from applications? What about the hat note telling you to look at the Kelvin-Stokes theorem? What about the second equation in the introduction, which is the Kelvin-Stokes theorem? What about the "Special cases" section, which includes applications to electromagnetism? And how do you feel about the applicability of the article Kelvin-Stokes theorem? Mgnbar (talk) 01:45, 29 January 2018 (UTC)

To be fair, the latter article is unreadable to the average calculus student, who will not know the bra-ket notation used in the proof section.--Jasper Deng (talk) 01:49, 29 January 2018 (UTC)

Also to be fair, the hatnote is useless to someone trying to learn this material, because the Kelvin-Stokes' theorem is simply called Stokes' theorem in many elementary vector calculus and physics books. The lede should mention this practice and talk about the more common Kelvin-Stokes theorem first and leave more advanced, generalized theorem for later in the lede. The rest of the article should probably follow suit. --Mark viking (talk) 04:50, 29 January 2018 (UTC)

Here on Wikipedia we'd better outline shortly several proofs and arguments. It is rather typical that intuitively convincing arguments are hard to convert into rigorous proofs, and rigorous proofs fail to be intuitively convincing. Boris Tsirelson (talk) 06:00, 29 January 2018 (UTC)

Geometry specialist needed

Please help to review Draft:Binary Tiling a very brief draft at AFC. Roger (Dodger67) (talk) 16:57, 28 January 2018 (UTC)

@Dodger67: I'm not a geometer, so maybe someone else can say more, and I'm also not sure how the review process works, but in my opinion, this doesn't seem to meet notability requirements to have its own article. It's sourced to a single paper and to the article creator's own an answer on MO (Edit: I'm not sure why I thought the article creator here was the same as the author of the MO answer; I probably just mis-saw something) (I couldn't find much else, but maybe there is). I wonder if this information could be added to an existing article instead, like Uniform tilings in hyperbolic plane and/or Pentagonal tiling#Regular pentagonal tilings in non-Euclidean geometry. –Deacon Vorbis (carbon • videos) 18:07, 28 January 2018 (UTC)

I don't think it is a tiling in the sense of those articles. Three of the five boundaries are horocycles rather than lines. Also it is not regular. So a merge/redirect to an existing article would not be appropriate in my opinion. Perhaps there is a more general sense of "tiling" to which this example belongs? Sławomir Biały (talk) 18:15, 28 January 2018 (UTC)

There must be more sources than the ones shown, which are not enough by themselves for notability. I know I've seen this before and may have even used it myself sometime, I don't remember. But it's in a weird limbo between periodic and aperiodic (tiles can be labeled by infinite binary sequences describing which way the tiles above them are placed and you can only map a tile to another with the same sequence), which may account for its obscurity. Also like the Penrose tiling it's not a single tiling but a class of tilings (there are uncountable binary sequences only countably many of which can label the tiles in a single tiling). If nothing else, it could be mentioned at quadtree. —David Eppstein (talk) 18:16, 28 January 2018 (UTC)

It seems like a pretty harmless stub, at least until someone find a place for it. Then again, WP:ILIKEIT. Sławomir Biały (talk) 20:45, 28 January 2018 (UTC)

I expanded it from sources given by the sources already listed. After expansion, it looks sufficiently notable for a standalong article, so I moved it to mainspace as binary tiling. —David Eppstein (talk) 21:10, 28 January 2018 (UTC)

I've added the maths project tag on the talk page (usually done semi-automagically by the AFC process) but an article class assessment and various other parameters need to be added too. It may also be possible to improve the categorisation. Roger (Dodger67) (talk) 21:25, 28 January 2018 (UTC)

We might need to be careful about the name there are other things called binary tilings. For example the Tiling Encyclopedia binary tiling which is connected to Penrose tilings.--Salix alba (talk): 00:09, 29 January 2018 (UTC)

Salix alba I came across this issue last night while trying to de-orphan the article, perhaps it should be moved to hyperbolic binary tiling to disambiguate it from other binary tilings. Roger (Dodger67) (talk) 13:53, 29 January 2018 (UTC)

Focus on women mathematicians in February

		Welcome to Women in Red's February 2018 worldwide online editathons. New: "Black women" New: "Mathematicians and statisticians" New: "Geofocus: Island women" Continuing: #1day1woman Global Initiative
		(To subscribe: Women in Red/English language mailing list. Unsubscribe: Women in Red/Opt-out list)

--Ipigott (talk) 14:28, 30 January 2018 (UTC)