# Wikipedia talk:WikiProject Mathematics Information

https://en.wikipedia.org/wiki/Wikipedia_talk:WikiProject_Mathematics
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WikiProject Mathematics (Rated Project-class)
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## Pétur Blöndal

He is listed in Category:Icelandic mathematicians, but I was wondering whether he satisifes WP:PROF.-- SilverMatsu ( talk) 15:55, 2 May 2022 (UTC)

He may not pass WP:NPROF, but as a member of the Icelandic Parliament should be notable by WP:NPOLITICIAN. Felix QW ( talk) 17:10, 2 May 2022 (UTC)
Thank you for your comment. I agree that this article meets WP: NPOLITICIAN, but I wondering whether it is possible to add Category: Icelandic mathematicians to this article.-- SilverMatsu ( talk) 16:52, 3 May 2022 (UTC)
@ SilverMatsu Having a doctorate in mathematics does not make one a mathematician. Voting to not add to your proposed category unless you can document that he has produced substantial mathematical research output. PatrickR2 ( talk) 08:28, 5 May 2022 (UTC)
Thank you for your comment. Removed Category:Icelandic mathematicians from article.-- SilverMatsu ( talk) 15:21, 5 May 2022 (UTC)
Getting a PhD requires writing a PhD thesis, which requires producing substantial mathematical research output. Separately, I doubt you will find consensus for the idea that "producing substantial mathematical research output" is a necessary criterion to be classified as a mathematician. -- JBL ( talk) 17:10, 5 May 2022 (UTC)
True about the need to write a PhD thesis, although I have personally witnessed a few cases where the corresponding research was not "substantial" (without mentioning any names, e.g., a case where the advisor moved to another school, the student was passed to another professor not really familiar with the area, and the student ended up putting in his thesis results that were not even original research but things that the first professor had mentioned and explained in one of his classes. The advising committee said it was pretty weak, but let him pass anyway, knowing he was going to go to a teaching school.) [Note I am not claiming this is the case here for Blondal, just mentioning in support of the point that a PhD does not a mathematician make.]. More of a case in point, looking at Math Genealogy project for example, you can see lots of new PhD's being granted every year. Quite a few of these don't stay in academics, move to industry, become programmers, work in finance, etc, either right after the PhD or after just a few years, realizing academics is not for them. I don't think anyone can say these people are mathematicians (not to diminish anything to what they might have done for their thesis). PatrickR2 ( talk) 04:44, 6 May 2022 (UTC)
@ JayBeeEll and PatrickR2: Thank you for your(s) comments. Both agree to comments. I'd like WP: PROF will give an explicit explanation for this case, but as already pointed out, there seems to be no consensus, so I think it is better to decide each case individually.-- SilverMatsu ( talk) 03:25, 7 May 2022 (UTC)
I think the relevant policy here is WP:Categorization of people, which states:
"For example, a film actor who holds a law degree should be categorized as a film actor, but not as a lawyer unless their legal career was notable in its own right or relevant to their acting career. Many people had assorted jobs before taking the one that made them notable; those other jobs should not be categorized."
So the question is whether our mathematician-turned-politician was notable as a mathematician. And this notability may come from WP:NPROF, but in our case the subject is almost certainly not notable by WP:NPROF standards. So on that basis I would remove him from the category. Felix QW ( talk) 15:19, 7 May 2022 (UTC)
WP:COP is just what I was looking for. Thank you so much !-- SilverMatsu ( talk) 01:09, 8 May 2022 (UTC)

## Hole

The article Hole (topology) seems to revolve around an idiosyncratic definition which is better subsumed in the homology (mathematics) and homotopy groups articles, the term hole is often used in a colloquial sense to give an idea of what these notions mean but presenting it as a formal notion as in done in the article seems to be counterproductive to me (and it is not supported by the given reference). I think the article should be deleted or made a redirect (probably to the article on homotopy groups or homotopical connectivity ; it may also make sense as a disambiguation page). jraimbau ( talk) 07:40, 3 May 2022 (UTC)

Just to clarify: Did you check the offline reference (If not, I could do so at some point this week in our library)? Felix QW ( talk) 07:57, 3 May 2022 (UTC)
Never mind, I managed to check it and you are right. It doesn't support the formal definition. Felix QW ( talk) 08:15, 3 May 2022 (UTC)
I blanked and redirected. I'll notify the page creator, if they disagree i'll make an afd. jraimbau ( talk) 12:02, 8 May 2022 (UTC)
I feel like the original redirect target was better. — JBL ( talk) 20:32, 8 May 2022 (UTC)
The reference [1] defines "a hole in dimension ${\displaystyle \ell }$ is something that prevents some suitably placed ${\displaystyle S^{\ell }}$ from shrinking to a point". While the definition is not written in mathematical notation, it is clear and accurate. The way to write it in mathematical notation is indicated at the bottom of the same page (specified in the opposite sense): it is "a continuous map ${\displaystyle f:S^{\ell }\to X}$ that cannot be extended to a continuous map ${\displaystyle {\bar {f}}:B^{\ell }\to X}$", or equivalently "a continuous map ${\displaystyle f:S^{\ell }\to X}$ that is not nullhomotopic". It is not colloquial - it is completely formal. The advantage of this definition over the one using homotopy groups is that it requires less previous knowledge - it does not require any background in group theory. In contrast, while the page on homotopy groups mentions that they are somehow related to holes, it is not clear from this page what a hole is.
If you still think that the concept of a "hole" does not deserve a page on its own, then I think it is better to merge it into homotopical connectivity. -- Erel Segal ( talk) 04:48, 9 May 2022 (UTC)

References

1. ^ Matoušek, Jiří (2007). Using the Borsuk-Ulam Theorem: Lectures on Topological Methods in Combinatorics and Geometry (2nd ed.). Berlin-Heidelberg: Springer-Verlag. ISBN  978-3-540-00362-5. Written in cooperation with Anders Björner and Günter M. Ziegler , Section 4.3
Since there was no objection, I changed the redirect to homotopical connectivity. -- Erel Segal ( talk) 11:24, 15 May 2022 (UTC)
I do strongly object to the mention of "hole" as a formal object in mathematics, be it on its own page or on the page about homotopical connectivity.
Here is the relevant excerpt from Matoušek's book :

Informally, a topological space X is k-connected if it has no “holes” up to dimension k. A hole in dimension k is something that prevents some suitably placed Sk from continuously shrinking to a point (...) Of course, things can be more complicated: A torus certainly has a hole in dimension 1 in this sense, but what about dimension 2? Fortunately, we need not contemplate such ﬁne points here, since the formal deﬁnition is simple

and a proper definition of a k-connected space follows. It is clear from this excerpt that there is no formal definition of "hole", as opposed to one of k-connectivity, in this reference and that it actually provides a rationale against such a formal definition: "things can be more complicated", meaning that there is no reason that a "hole" in a topological space should be a missing ball rather than something else; the word is employed here as an intuitive explanation bulding on the (deceptively) simple 2-dimensional case (what is the "number of holes" in a 3--manifold?).
I do support the suggestion of putting the original redirect, to Hole#In_mathematics, back (i chose "homotopy groups" as a target because i was not aware of this original redirect). jraimbau ( talk) 16:03, 15 May 2022 (UTC)
I agree wholeheartedly with Jean Raimbault and Felix QW -- the presentation of this as a formal definition of "hole" is deeply misleading at best, close to source falsification (even if not intentionally so). JBL ( talk) 17:16, 15 May 2022 (UTC)
I have gone ahead and restored the earlier redirect. -- JBL ( talk) 17:17, 15 May 2022 (UTC)
Question: the "main article" link is to Homotopy group, but the text at Hole#In_mathematics is about homology. (The latter usage is what I have always heard!) Should there be multiple main article links, and/or should the text under Hole in mathematics be adjusted? Russ Woodroofe ( talk) 17:38, 15 May 2022 (UTC)
I added some stuff about homotopy in the hole article (i think the Matoušek quote given by Erel Segal actually fits perfectly there). jraimbau ( talk) 18:13, 15 May 2022 (UTC)

## Vertical alignment of \overrightarrow

The latex command \overrightarrow is used many times in Euclidean space, affine space, and other articles of geometry. It is awfully aligned when used with two letters, as in ${\displaystyle {\overrightarrow {PQ}}}$ (to compare with ${\displaystyle {\overrightarrow {P}},}$ which is correct). This misalignment is less visible in displayed formulas. However, if the vector in enclosed with brackets, the brackets are much too long below the line, as in

${\displaystyle \left\|{\overrightarrow {PQ}}\right\|.}$
Also, in some cases, the upper part of the arrow is not displayed, as in
${\displaystyle {\overrightarrow {PQ}}.}$

Does anybody know some work-around, and/or asking for fixing the bug? D.Lazard ( talk) 16:51, 4 May 2022 (UTC)

It may be too short … :
${\displaystyle {\vec {PQ}}.}$
${\displaystyle \left\|{\vec {PQ}}\right\|.}$
-- SilverMatsu ( talk) 15:11, 5 May 2022 (UTC)

The image below is what I see when I look at the posting by D.Lazard above. I suspect others looking at that, including D.Lazaard, see something different because of different settings. @ D.Lazard: Is something "awfully aligned" about the arrows as they appear in this screenshot, or do you see something different when you look at the articles and at your own posting above? Michael Hardy ( talk) 17:44, 5 May 2022 (UTC)

The screenshot is correctly formatted, except maybe that the vertical lines are too long toward bottom. On my screen, in the inline formula ${\displaystyle {\overrightarrow {PQ}}}$, the bottom of P is aligned with the middle of text characters such as "n". For the displayed formula with brackets the bottom of PQ and the period are aligned with the middle of the brackets, when the formula should be centered with respect to the brackets. In both displayed formulas the upper part of the arrowhead is lacking. I ignore which sort of setting can produce this sort of display errors. D.Lazard ( talk) 20:01, 5 May 2022 (UTC)
Apparently, this is a bug in "MathML with SVG or PNG fallback (recommended for modern browsers and accessibility tools)", as, when I change my math preferences to "PNG images", I get the same rendering as you. D.Lazard ( talk) 20:11, 5 May 2022 (UTC)
I think the svg fallback is likely to look more or less the same as Michael Hardy's screenshot, so my guess is that Wikimedia thinks your browser can properly render mathml and is not using the fallback, but your browser's rendering of mathml is bad (as is most browsers' renderings of mathml). — David Eppstein ( talk) 21:40, 5 May 2022 (UTC)

@ D.Lazard: Why don't you post a screenshot, as I did, so that we can tell what you're trying to say? In your comment saying "the upper part of the arrow is not displayed, as in", I see something displaying the entire arrow normally. You require us to take on faith that you see something of which you offer this verbal description but no image matching the discription, while at the same time you appear to intend to show us an image. It's not working at all. Michael Hardy ( talk) 18:09, 11 May 2022 (UTC)

I see the same problem as D.Lazard. Here is my screenshot:
. Note that the connection between arrow and extension line is also misaligned. It looks bad. --{{u| Mark viking}} { Talk} 19:22, 11 May 2022 (UTC)

This is a problem with the SVG rendering, you can tell this by looking at the code in the developer console. It seems like somewhere in the process, the vertical-align style attribute is incorrect. I've added a Phabricator bug T308188. -- Salix alba ( talk): 21:19, 11 May 2022 (UTC)

## Labeling "press recognition" and "a proof" based on Quanta & press releases

See Talk:Jinyoung Park (mathematician)#"Widespread recognition" for a content dispute about a recent arXiv preprint that has been discussed in a Quanta article ( link) and two department/institute press releases ( link 1, link 2).

The dispute is on whether:

1. The Quanta article and press releases can be summarized in WP:WIKIVOICE as Park having received recognition for her preprint
2. The preprint contents can be described as a 6-page proof or a 6-page proposed proof

Any input is much appreciated. Thanks! — 05:50, 9 May 2022 (UTC)

Agree with MarkH21's comments at the link, particularly that the IAS and Stanford press releases are not good sources. The Quanta article is solid verification that the paper is of interest. But it is probably too early to say unambiguously that the result is proved, although (just making educated guess as non-expert in combinatorics) it seems very likely. Gumshoe2 ( talk) 06:39, 9 May 2022 (UTC)
Thank you for the input here! Resolved. — Preceding unsigned comment added by Caleb Stanford ( talkcontribs)

## Chinese Postman Problem and other arc routing Variants

I am reading a lot about the Chinese Postman problem, which is NP hard for mixed graphs that contain undirected edges and directed arcs. These arcs and edges can be weighted, and solving the mixed Chinese Postman is something I've been working on a lot recently its possible to fit everything about the Chinese Postman Problem in to the article Route Inspection. I would like to suggest a series or template on operations research and arc routing problems. I would like to make the documentation of the Chinese postman problem more comprehensive. ScientistBuilder ( talk) 23:24, 9 May 2022 (UTC)

## Need to rephrase Commutative property

I think this article needs to rephrase, for example, the section in Commutative property#Example made the reader, probably, confused to read what it means. It's not also be made confused to read, but it also didn't well written. I'm afraid that this GA will be delisted due to didn't meet one of the criteria of GA. Dedhert.Jr ( talk) 13:15, 11 May 2022 (UTC)

Your concern is not written in coherent English, but it lacks references and does seem to contain original research.LaundryPizza03 ( d ) 20:52, 19 May 2022 (UTC)
EDIT: Partially redacted per WP:BITE rule. – LaundryPizza03 ( d ) 01:26, 21 May 2022 (UTC) 03:37, 21 May 2022 (UTC)

## Deletion of "Greatest integer" proposed

Greatest integer redirects to Floor and ceiling functions. Deletion of the redirect is proposed. Post opinions at Wikipedia:Redirects_for_discussion/Log/2022_May_19#Greatest_integer. Michael Hardy ( talk) 23:47, 20 May 2022 (UTC)