Wikipedia talk:WikiProject Mathematics/Archive/2021/Apr

Cleanup of articles on algebras

It seems to me that the articles on algebra over a field, associative algebra and non-associative algebra could use a thorough workover and possibly a merge.

The article on non-associative algebras says that '"non-associative" means "not necessarily associative"' (rather than "not associative") – but then it's not clear why this article is distinct from algebra over a field, which is also about algebras that "may or may not be associative". The sentence "The multiplication operation in an algebra may or may not be associative, leading to the notions of associative algebras and nonassociative algebras." in algebra over a field seems to imply that "non-associative" does mean "not associative".

Constructions such as quotients and products are briefly listed in associative algebra, but no reason is mentioned why these should require associativity; they're not mentioned in the more general articles. The most detailed discussion of direct sums and products of algebras in fact appears to be in yet another article on the direct sum of modules. This warns of a terminological pitfall that the articles on algebras don't mention.

In algebra over a field, the field is in the title and there's a section near the end on the generalization to algebras over a ring. In associative algebra, the introduction starts out saying that an algebra is over a field but the definition section uses a ring instead. In non-associative algebra, a field seems to be assumed, but there's no definition section and the introduction is very similar in this respect to the one in associative algebra.

Quite generally, it feels as if a lot of the content is spread somewhat randomly among these three articles. There should either be a single article about algebras, or, if associative algebras deserve an article of their own, that article should concentrate on the features that depend on associativity, and presumably general things like products and quotients should be in the general article.

(I don't want to do this myself since my understanding of algebras is somewhat superficial.)

Joriki (talk) 19:29, 28 March 2021 (UTC)

One more thing: There's also an article algebra homomorphism, to which both algebra over a field and associative algebra refer as a "main article", even though it assumes associative algebras. The article on non-associative algebras doesn't mention homomorphisms.

Joriki (talk) 19:36, 28 March 2021 (UTC)

Further information about products of algebras is spread over tensor product of algebras and free product of associative algebras.

Joriki (talk) 20:44, 28 March 2021 (UTC)

I agree that the contents of non-associative algebra should be merged into algebra over a field (and reworked, in some cases also trimmed). The article about associative algebras does have a bit of an overlap, but also a lot of content that is special, so these I wouldn't merge. I suggest merging algebra homomorphisms into ring homomorphisms. Tensor product of algebras deserve their own home. The free product of associative algebras is a bit of a stub right now, but I think it makes sense to keep it separately. Jakob.scholbach (talk) 11:28, 1 April 2021 (UTC)

Weird recommendations in MATLAB article

Some Mathworks employees have been making suggestions about the MATLAB page recently, but not directly making edits, in order to maintain neutrality.

One pointed on that page's talk page that the 'list of alternatives' on the MATLAB page is kind of weird. It's unsourced and is basically just a list of recommendations, which I'm pretty sure should be covered under one of the list of things Wikipedia is not.

On the one hand, I can see how this directly benefits the corporation, which is suspicious. On the other hand, I really don't think that kind of list is appropriate in an article. We don't have a list of alternatives for Adobe Photoshop, despite its awful business practices, or McAfee VirusScan, despite its shady nature.

I'd suggest removing that section or replacing it with something sourced (perhaps a review article describing commonly used mathematical languages). As it is, I don't think it should remain in its current form. I wanted to check in here before doing anything, but if people don't seem interested in discussion, I'll just remove it after a day or two. Brirush (talk) 04:25, 1 April 2021 (UTC)

Yes, definitely trim it to something sourced. There are plenty of sources discussing alternatives. Dicklyon (talk) 04:59, 1 April 2021 (UTC)

Okay, I removed the big recommendations section and replaced it with a sourced paragraph listing some popular tools. As always, anyone's free to edit and improve. Brirush (talk) 22:05, 1 April 2021 (UTC)

How to add external interactive animations about some Math subject

I see that some mathematical subjects benefit immensely of animations and in particular interactive ones. How can we make possible to link those animations to an specific article? Would it be via external links? — Preceding unsigned comment added by Ninguem wiki (talk • contribs)

For background on this question, see Talk:Taylor_series#New_external_link and User_talk:DVdm#Reversion_on_the_Taylor_Series_page. --JBL (talk) 16:30, 2 April 2021 (UTC)

Looking at Commons:Project scope/Allowable file types the best you could do is a some kind of animation. There is mw:Extension:Graph which allows quite complex graphs which can be interactive. There are some Demos which are could be adapted to fit. Examples of using this extension can be found at Category:Pages using the Graph extension. --Salix alba (talk): 17:38, 2 April 2021 (UTC)

Thank you for the reply. Based on Talk:Taylor_series#New_external_link and User_talk:DVdm#Reversion_on_the_Taylor_Series_page seems that a common user can't contribute with an interactive animation. As pointed in the discussion I had with the other users, any contribution is to be considered non-reliable if it comes from a common user. I'd interested in knowing what is the difference between a written contribution in an article (writing, editing, etc) and an external contribution (in a form of a link to a page with no advertisement and following all the rules). I have a contribution which I would like to share in Wikipedia because I thick its valuable for understanding of the topic (see discussion mentioned above). How can I reach a consensus on it? Is THIS the right forum? In my understanding the page itself was the right forum so I insisted on keeping the link until someone accesses it and started a discussion wether it is valuable or not. Please notice that the contribution does not have any affiliation, propaganda, logo, advertisement of any kind. Its a simple plain interactive animation. Since you are an organised group and decided to support each others view, how can I reach a consensus? If its a consensus that the page is not the right place to discuss, I stoped posting there and Im bringing the discussion here. It would be very good if User:DVdm and the others could participate.Allan Martins (talk) 20:05, 2 April 2021 (UTC)

Answering to talk:Salix alba, thank you for the answer. I have already a complex Javascript interactive animation, the question was more on the sense of wikipedia rules. See first reply above.Allan Martins (talk) 20:06, 2 April 2021 (UTC)

Wikipedia cannot allow any user to add random JavaScript to articles, that would be a security nightmare. You can modify your personal JavaScript, at Special:MyPage/vector.js but that will not be seen by other users. The graphs package is the only way you can get interactivity. --Salix alba (talk): 20:50, 2 April 2021 (UTC)

I agree with you and understand that Javascript on Wiki pages is far too potentially harmful. That is exactly why I want to contribute by placing all in an external link and adding it as an external link. You suggestion on the graph package is very interesting though, I'll take a look to try other contributions. Allan Martins (talk) 22:51, 2 April 2021 (UTC)

What I don't understand is how can we incentive people to contribute if they additions of a simple external link is not cordially analysed and simply reverted by the interpretation of the rules. The link Im providing is absolutely in accordance will all WP:External_links except that we didn't reach a consensus on the WP:Reliable_sources. But I'm willing to discuss it and try to show, in a consensus, that the link I'm providing is no different than an edit that people like me (a professor) would do in an article to contribute. I'm not sure if people even bother to take a look at the link and see that its in accordance with WP:External_links policies. There is no advertisement, not even the name of the author is promoted there. I'm don't know why people think I gain in insisting on doing this contribution. I'm a professor and credentials are not relevant here, but my job is to educate people and Wikipedia is a very powerful tool for it. I would understand the argument that "if everyone start putting links, it would be a mess". But so is "if everyone start editing pages would be a mess". Thats the whole point of Wikipedia. it works! So, I'm pretty sure if I was just practicing vandalism in trying to place one harmless (on the contrary, useful) link to an article I would not wasting my time here explaining everything. So I ask people that read this discussion (not specifically you talk:Salix alba since your answer was very productive for me showing me the graph functionality) to take a moment to reflect on their actions. Impose wikipedia rules just the bold "letter" of it is not ok. That is to ignore the true principle behind Wikipedia. Wikipedia is NOT a place where you have fun catching "bad edits". It has a serious goal of promoting knowledge and disseminate information. And mainly, to stimulate and encourage contributions. Im just starting to contribute and, honestly that was not a nice welcome. You can't use people's serious contribution to collect patrol points or satisfy some personal vanity. Let's discuss. Present arguments that sustain your interpretation of the rules.Allan Martins (talk) 22:51, 2 April 2021 (UTC)

I'm sorry for the heavy text above, but I like Wikipedia a lot. I feel its worth fight for its correct use.Allan Martins (talk) 22:51, 2 April 2021 (UTC)

Blackboard bold (again)

Our discussion from November 2020 has been reopened at Wikipedia talk:Manual of Style/Mathematics#Blackboard bold. D.Lazard (talk) 11:19, 24 March 2021 (UTC)

Indeed, on a white background, blackboard bold seem difficult to read. If we would like to deprecate blackboard bold, I think it would be useful to change the extension math so that we can type \Complex and display $\mathbf {C}$. For example, in Complex analysis and Several complex variables, even if I stopped using blackboard bold, the meaning seemed clear. White letters on a black background are personally easy to read, but the blackboard bold is a bit hard to read because I can't change the background color.--SilverMatsu (talk) 15:33, 24 March 2021 (UTC)

What does mean difficult to read? Do you mean read or distinguish from anything else? If you have difficulties to read $\mathbb {C}$, you must also have difficulties to read most characters, including $\mathrm {C} .$ If, by "read", you mean "distinguish", it seems that $\mathbf {C}$ has much more problems, at least outside complex analysis. For example, many authors use boldface for denoting vectors and matrices. In this case, one has to look to the context for distinguishing, in a formula, a matrix from the complex numbers. The great advantage of blackboard is to be definitely not ambiguous. Another example: If you read $\mathbf {R} [x],$ you have to look at the context to know whether this is the polynomial ring over the reals or over an arbitrary ring, while $\mathbb {R} [x]$ is definitevely not ambiguous in any context, and more specially in a context that is not specially about the reals (for example in mechanics). So I strongly oppose to deprecate blackboard bold. I oppose also to change the rendering of \complex, as this would automatically change many articles without any consensus of their editors. D.Lazard (talk) 09:13, 25 March 2021 (UTC)

Thank you for the reply. I agree that blackboard bold is clearer, and my comment is based on the assumption that blackboard bold would be abolished, so thank you for your advice. The meaning of difficult to read is a little dazzling on the display, but I was taught at the tea house that the colors can be reversed.--SilverMatsu (talk) 13:29, 26 March 2021 (UTC)

---

My eyes are bad, but i can read black blackboard bold on white background without any difficulty.

I totally agree with D.Lazard's whole reply.

Sorry, SilverMatsu! :-)

RavBol (talk) 00:04, 4 April 2021 (UTC)

In fact, I don't think anyone at Wikipedia talk:Manual of Style/Mathematics#Blackboard bold was recommending deprecating blackboard bold! Maybe this was a misunderstanding. Anyway, it seems to be straightened out now. Ebony Jackson (talk) 03:16, 4 April 2021 (UTC)

Currently, I can invert colors using gadgets. Thank you for your concern:) It seems that I overlooked that the style manual had changed (I thought blackboard bold was not recommended on wikipedia.). But the extension:math outputs as an image, so I'm not sure how it affects the reading software. Also, since Unicode characters cannot be used for blackboard bold, I am wondering what to do when using it for the section title. The link I showed used two different notations. If possible, I'm thinking of using one notation. The main reason I decided to comment here was to get advice on the pages shown in the links.--SilverMatsu (talk) 15:44, 4 April 2021 (UTC)

Induced metric

Does anyone know offhand of a good reference to add to Induced metric? The reason for the "expert needed" tag is technically untrue (one reference exists rather than zero), but an additional pointer couldn't hurt. XOR'easter (talk) 15:50, 4 April 2021 (UTC)

This is a fairly basic concept that is discussed in textbooks on manifolds. For instance, see pages 25-27 of Lee, John M., Riemannian Manifolds: An Introduction To Curvature, (GTM no. 176, Springer,1997)(ISBN 038798271X). --{{u|Mark viking}} {Talk} 17:42, 4 April 2021 (UTC)

about Plurisubharmonic function

Regarding section Oka's theorem, the content of the theorem seems correct (since the article name is a plurisubharmonic function, there is no need to use the term pseudoconvex domain.), but I have doubts about calling the content of this section Oka's theorem. (also, I think the prove to $\mathbb {C} ^{n}$ space was the IX'th Oka's paper in 1953.) There is no doubt that it was Kiyoshi Oka who solved Levi's problem for $\mathbb {C} ^{n}$ space (Riemannian domain), but it was Cartan who extended Levi's problem for Stein manifolds, which is written on this article and it seems like Grauert prove that. I'm wondering if Levi's problem with Stein manifolds should be included in Oka's theorem. I'm not sure about this because I just called it Levi's problem. thanks!--SilverMatsu (talk) 15:00, 5 April 2021 (UTC)

Good edit?

Did this edit fix an error, or introduce one? Maths articles can be quiet, and problems might linger unnoticed; this seemed like the best place to ask. Cheers, BlackcurrantTea (talk) 10:21, 10 April 2021 (UTC)

Looks good to me: a function of s is integrated over the range s=0 to s=t. However, you're right in principle that lots of superficially similar edits are mistakes or subtle vandalism, both of which need to be reverted. Certes (talk) 11:06, 10 April 2021 (UTC)

It's those mistakes or subtle vandalism I fear I'd miss in this area. Thanks for taking a look at it. BlackcurrantTea (talk) 14:34, 10 April 2021 (UTC)

Typesetting \mathbb{1} within Wikipedia articles

How can I use 𝟙 in a math equation? It seems from various sources that I need to use the bbm package. Is it possible to use LaTeX in Wikipedia articles that use packages? --Yoderj (talk) 13:37, 9 April 2021 (UTC)

I have used some funny business in the Heaviside step function article:

<big>𝟙</big><math>\,\!_{x > 0}</math>

but there must be a better way --Yoderj (talk) 13:45, 9 April 2021 (UTC)

I asked this question over at the help desk and Mike Turnbull guided me here:

Hi Yoderj. You should be able to get some guidance at WP:LATEX. Alternatively, seek out the Talk Pages for the maths projects and an expert in this stuff will likely help. Mike Turnbull (talk) 15:16, 9 April 2021 (UTC)

Thanks! --Yoderj (talk) 18:38, 9 April 2021 (UTC)

I've created a phabricator task. T279805. --Salix alba (talk): 19:31, 9 April 2021 (UTC)

Looks like its upstream, and the syntax does not work in standard mathjax. It might be possible to add one of the packages mentioned in the stack exchange thread. --Salix alba (talk): 19:44, 9 April 2021 (UTC)

For an indicator function, I'm sure this isn't the answer you wanted, but I would suggest using a plain $1$ or bold $\mathbf {1}$ which are more common notations than blackboard bold in this context. (I don't mean to detract from your technical typesetting question which is interesting in its own right and I hope will be resolved.) Adumbrativus (talk) 19:48, 9 April 2021 (UTC)

I agree with Adumbrativus. --JBL (talk) 19:55, 9 April 2021 (UTC)

A bold one it will be. Thank you. --Yoderj (talk) 22:05, 9 April 2021 (UTC)

So are there any cases where we would want this notation? Getting something through code review is a lot of work for something which might not be used. --Salix alba (talk): 15:36, 10 April 2021 (UTC)

Script to show short descriptions in Wikipedia categories

I'd like to call attention to a user script that has been developed to show WP:Short descriptions in category listings: User:SD0001/shortdescs-in-category

This might be of particular interest to mathematics users as categories of mathematical theorems typically show titles of the form "So-and-so and Other-person theorem," i.e. just the names of discoverers, which conveys little or no information about the result proved (or conjectured). When this script is installed and the Show SD button that appears is clicked, any short description associated with an article title is displayed beneath it. To the extent that these SDs are available and informative, it becomes much easier to understand the content of a theorem category.--agr (talk) 17:54, 14 April 2021 (UTC)

@ArnoldReinhold: Neat! — MarkH₂₁^talk 18:00, 14 April 2021 (UTC)

New promotional math articles

Editors may want to monitor the flurry of new math articles by Remitbuber, including Math crisis, Adrián Macías, Blas Méndez, Virus Matemático, General Assembly of the International Mathematical Union, ICM 1966, ICM 2014, ICM 2026. Many do not seem notable and may involve a fair amount of COI. — MarkH₂₁^talk 20:35, 14 April 2021 (UTC)

Nicolás Atanes was also very promotional when first created; it's now been stubbed down (and is still not a good article but at least is not overwhelmed with promotionalism). [Of course you MarkH21 know this, since you did much of the cleanup.] Most of these topics are closely related to Atanes, suggesting paid editing or at a minimum a serious COI. Probably worth a trip to WP:COIN. --JBL (talk) 22:01, 14 April 2021 (UTC)

@JayBeeEll: In fact, someone has since taken this to ANI: Wikipedia:Administrators' noticeboard/Incidents#User:Remitbuber! — MarkH₂₁^talk 22:05, 14 April 2021 (UTC)

Math crisis has been BOLDly redirect to Math anxiety. One of the remaining articles is now at AfD: Wikipedia:Articles for deletion/Adrián Macías. — MarkH₂₁^talk 13:29, 15 April 2021 (UTC)

@MarkH21: If Math crisis isn't noticeable, I'd suggest AfD instead of redirects. See the Foundations of mathematics lead statement.--SilverMatsu (talk) 15:01, 15 April 2021 (UTC)

by the way, the story changes but, I happened to see Math anxiety with redirects. I thought Hereditary Genius and American math education were over-summarized. Hereditary Genius was later added and summarized. Therefore, although it has references, it does not seem to have much to do with the referenced books and treatises. --SilverMatsu (talk) 23:35, 18 April 2021 (UTC)

Is it better to avoid just writing domain in articles?

Complex analysis articles sometimes say open connected set, is this better than writing domain alone?--SilverMatsu (talk) 08:57, 17 April 2021 (UTC)

Using domain seems correct, and may lead to a simpler (and thus clearer) formulation. However, we have several articles on related sorts domains (some of them being not listed in Domain (disambiguation)): Domain of a function, Domain of definition, Domain of holomorphy, Natural domain, and maybe others that I have not identified, and some that are lacking (Domain of continuity, Domain of differentiability, Domain of smoothness, ...). My suggestion is to merge all these articles into Domain of a function or Domain (mathematical analysis). I have not a clear opinion whether these two articles should be merged. A possibility would be to redirect Domain of a function to function (mathematics), with a clear link in the lead of the new Domain (mathematical analysis). D.Lazard (talk) 09:56, 17 April 2021 (UTC)

There is value in cleaning up the terminology, to make it less confusing. There is also value in using the same terminology as other sources (even before we bring Wikipedia policy into it). How about explicitly stating which meaning of "domain" is meant, at the first use in the article? And the correct wikilink might suffice for that. Mgnbar (talk) 14:03, 17 April 2021 (UTC)

Thank you for your reply. D.Lazard's advice will take some time, but I think we can clearly formulate the domain. but, I don't think we have to merge. Even if the content is duplicated, I think it is okay to write what is written on the branch again on the trunk. In other words, improve Domain (mathematical analysis) based on your ideas and and think about merge as another discussion. As another topic, I think that complex analysis can be improved based on such an idea. Of course, I will try to be as concise as possible ... On the other hand, Mgnbar's idea is that it can be implemented immediately. Already, domain has been used for various articles, and the articles need to be improved immediately. On wikipedia, we can't expect to read all the articles from top to bottom, so we probably need to include that in article lead. Conversely, if we can't include it in we lead statement, you probably need to improve that lead statement. thanks!--SilverMatsu (talk) 00:02, 19 April 2021 (UTC)

Minimal polynomial of 2 cos(2π/n)

The formatting of the title of Minimal polynomial of 2cos(2pi/n) is abominable, and the DISPLAYTITLE template didn't help. How to proceed? Michael Hardy (talk) 00:11, 11 April 2021 (UTC)

The present title is not only not convenient for a good display, it is also not convenient from an encyclopedic point of view: Viewing this title, a reader should naturally ask the question "Why considering specifically these numbers". So, I suggest to rename the article Real parts of roots of unity. One may object that this article is not about the the real parts, but about twice the real parts, but the difference is small enough for not being confusing.

Another question is whether this article should be merged into Cyclotomic polynomial. D.Lazard (talk) 09:48, 11 April 2021 (UTC)

Merging it into Cyclotomic polynomial, perhaps into a section entitled "Related polynomials", sounds like a good idea to me. Ebony Jackson (talk) 02:45, 13 April 2021 (UTC)

That seems plausible to me also, although I also like D.Lazard's suggestion for a better title. Something I wonder in thinking about this possible merge: the article states that these polynomials can be expressed either in terms of the cyclotomic polynomials or the Chebyshev polynomials, so I would think this also means that the cyclotomic and Chebyshev polynomials can be related by transitivity. But currently neither the cyclotomic polynomial nor the Chebyshev polynomials article mentions the other. Should they? —David Eppstein (talk) 06:46, 13 April 2021 (UTC)

Requested move opened. The current title should not be kept as a redirect, regardless of whether this article should be merged into another. –LaundryPizza03 (dc̄) 13:16, 25 April 2021 (UTC)

A cube, but with rhombuses for faces

On first glance the articles Rhombohedron and Trigonal trapezohedron are about the exact same object (the equilateral parallelepipeds). Before I start a merge discussion, I was hoping someone else would check that I'm not missing some meaningful subtlety. --JBL (talk) 15:18, 24 April 2021 (UTC)

@JayBeeEll: By the descriptions in Rhombohedron#Special cases by symmetry, it looks like a trigonal trapezohedron is a type of rhombohedron where all of its faces are necessarily congruent. — MarkH₂₁^talk 16:26, 24 April 2021 (UTC)

[ec] The difference appears to be that in rhombohedron the rhombi can be of three types, in three opposite pairs, but in trigonal trapezohedron they're all the same as each other. But as usual the "related polyhedra" section of the trigonal trapezohedron article looks mostly off-topic and removable. —David Eppstein (talk) 16:28, 24 April 2021 (UTC)

Great, thanks both -- I knew I must be missing something. David, indeed. --JBL (talk) 14:04, 26 April 2021 (UTC)

Group (mathematics) Featured article review

User:Graham Beards has nominated Group (mathematics) for a featured article review here. Please join the discussion on whether this article meets featured article criteria. Articles are typically reviewed for two weeks. If substantial concerns are not addressed during the review period, the article will be moved to the Featured Article Removal Candidates list for a further period, where editors may declare "Keep" or "Delist" the article's featured status. The instructions for the review process are here. SandyGeorgia (Talk) 16:01, 26 April 2021 (UTC)