Wikipedia talk:WikiProject Mathematics/Archive/2015/Feb

Irreducibility (mathematics) needs help in a bad way

Irreducibility (mathematics) is awful as a disambiguation page, and really should either be moved to Irreducibility (disambiguation) and simplified to conform with MOS:DAB, or turned back into an article describing the primary usage of this term with respect to mathematics. Cheers! bd2412 T 18:59, 1 February 2015 (UTC)

I confess that I'm responsible for turning the page into a disambig page. I do believe there is no uniform definition of "irreducibility" in mathematics, aside from the usual English sense of "not reducible". For example, "irreducible" as in irreducible representation, one as in irreducible polynomial and one as in irreducible component (of a topological space) have nothing in common. -- Taku (talk) 00:53, 2 February 2015 (UTC)

It's not a disambiguation page. It's possibly been mislabelled as such, but it's really a collection of distinct but related uses of a term in mathematical discourse. It would certainly be ideal for someone to link to a more specific meaning of the term in mathematics, but (as often is the case) the usage of a term in mathematics often has more to do with analogies than "this usage or that one". Such pages are useful and important, but should not be treated like "disambiguation pages". If their designation as such confuses various editors, then re-designate them to a more appropriate category. Such pages are very useful and should be allowed and encouraged to stay. Taku has my full support here. Sławomir Biały (talk) 01:06, 2 February 2015 (UTC)

Ok. How do you call that page then? I have just fixed some incoming links (most of times to irreducible representation). The fix was no-brainer. It's very unhelpful for us to direct the readers to Irreducibility (mathematics) instead of "irreducible representaion", when the latter is meant in linking the term. I can ask: on what occasions do we want to have a link to Irreducibility (mathematics)? "A page that must not be linked" is more or less a disambig page. -- Taku (talk) 01:22, 2 February 2015 (UTC)

The title "Irreducibility (mathematics)" seems perfectly reasonable as a title for such a page. Why should there even be a question? I think the issue is that there is some template on that page that tells all the dab-droids that it's a disambiguation page. Remove that template, and the problem is solved, as far as I can tell. Of course, we should link as many things to a specific page as possible, using discretion. But it's wrong to say that each and every time for which the concept of irreducibility appears in a mathematics article that it needs to be completely nailed down to one of the articles. That's what a "disambiguation" page entails, and that's clearly not what we have here. Sławomir Biały (talk) 01:45, 2 February 2015 (UTC)

User:R.e.b. has fixed the problem by replacing the dab template by {{sia}}. It's not really a dab, because the thing that is ambiguous is not the word "irreducibility" but the concept: what kind of decompositions are we talking about? Set index articles are the right way to handle conceptual rather than verbal ambiguities, and don't have such severe formatting and linking constraints as dabs. —David Eppstein (talk) 02:25, 2 February 2015 (UTC)

Yes, SIA was the answer to my question (though why we need to have a distinction is beyond me, reminding me of tax code). To Sławomir, no, I think it is "wrong" to have a link to irreducibility (mathematics), because readers have to look at the list and choose the correct destination. Doesn't that make the page precise a disambig page? (or SIA as some would prefer). Anyway, the problem has been solved so it's ok now. -- Taku (talk) 12:28, 2 February 2015 (UTC)

Lewis Carroll

The page currently contains the following material:

Speculation on Dodgson's sexuality[edit] Dodgson's nephew and biographer Stuart Dodgson Collingwood wrote: And now as to the secondary causes which attracted him to children. First, I think children appealed to him because he was pre-eminently a teacher, and he saw in their unspoiled minds the best material for him to work upon. In later years one of his favourite recreations was to lecture at schools on logic; he used to give personal attention to each of his pupils, and one can well imagine with what eager anticipation the children would have looked forward to the visits of a schoolmaster who knew how to make even the dullest subjects interesting and amusing.[73] Despite comments like this, and the fact that his pictures of children were taken with a parent in attendance (many in the Liddell garden),[39] modern psychological interpretations of Dodgson's friendships with young girls and of his related work—especially his photographs of nude or semi-nude girls—have led some late twentieth century biographers to speculate that he was a paedophile, including Morton N. Cohen in his Lewis Carroll: A Biography (1995),[74] Donald Thomas in his Lewis Carroll: A Portrait with Background (1995), and Michael Bakewell in his Lewis Carroll: A Biography (1996). All of these works more or less assume that Dodgson was a paedophile, albeit a repressed and celibate one.[page needed] Cohen, in particular, claims Dodgson's "sexual energies sought unconventional outlets", and further writes: We cannot know to what extent sexual urges lay behind Charles's preference for drawing and photographing children in the nude. He contended the preference was entirely aesthetic. But given his emotional attachment to children as well as his aesthetic appreciation of their forms, his assertion that his interest was strictly artistic is naïve. He probably felt more than he dared acknowledge, even to himself.[page needed] Cohen goes on to note that Dodgson "apparently convinced many of his friends that his attachment to the nude female child form was free of any eroticism", but adds that "later generations look beneath the surface" (p. 229). He and other biographers[who?] argue that Dodgson may have wanted to marry the 11-year-old Alice Liddell, and that this was the cause of the unexplained "break" with the family in June 1863,[26] an event for which other explanations are offered. Biographers Derek Hudson and Roger Lancelyn Green (Green also having edited Dodgson's diaries and papers) stop short of identifying Dodgson as a paedophile, but concur that he had a passion for small female children and next to no interest in the adult world; in the last ten years[dated info] several other writers and scholars have challenged the evidentiary basis for Cohen's and others' speculations regarding this interest of Dodgson. In addition to the biographical works that have drawn the foregoing conclusion, there are modern artistic interpretations of his life and work that do so as well, in particular, Dennis Potter in his play Alice and his screenplay for the motion picture Dreamchild, and Robert Wilson in his film Alice. In a 2015 BBC programme The Secret World of Lewis Carroll experts indicated their belief that a photograph of a naked teenage girl, was the oldest Liddell girl Lorina, and was the work of Dodgson. The programme speculated that this was the possible cause of the break in the relationship between him and the Liddell family. Will Self in the same programme called Dodgson 'a heavily repressed paedophile. Without a doubt.' [75][76]

Note the abundance of footnotes. How much of this should be retained? Tkuvho (talk) 16:52, 2 February 2015 (UTC)

What does this have to do with the Mathematics project or mathematics? Dodgson may have been a mathematician among other things, but his biography does not have our rating template. JRSpriggs (talk) 04:45, 3 February 2015 (UTC)

Well I think it should. He did important work both in mathematics and logic. Tkuvho (talk) 14:18, 3 February 2015 (UTC)

I think this discussion is better kept at Talk:Lewis Carroll. Ozob (talk) 14:26, 3 February 2015 (UTC)

M-theory

Hello mathematicians,

I just wanted to let you all know that M-theory is currently a featured article candidate. While this is not exactly a math topic, it's related to some very exciting areas of modern mathematics such as geometric representation theory, categorification, and noncommutative geometry.

It would be great if someone here could review the article. Even if you're not an expert on math or physics, I would love to hear your views and whether you find the writing accessible.

Thanks. Polytope24 (talk) 05:01, 4 February 2015 (UTC)

Help with Covering in topology/graph theory

Hi all, I've got a handful of links that go to the disambiguation page Covering in a mathematical sense but I can't figure out which article they need to point to. Could I interest a local math maven in taking a look?

List of articles with ambiguous links to "covering"

Thanks, --JaGa^talk 21:39, 6 February 2015 (UTC)

 Done D.Lazard (talk) 10:56, 7 February 2015 (UTC)

Lie algebra extension

Do we have an article on Lie algebra extensions (under some unexpected name) or perhaps a section on it? In case we don't, and if nobody is in the process of writing one, I might write one. It would parallel group extension. YohanN7 (talk) 16:07, 5 February 2015 (UTC)

There is a section Affine Lie algebra#Classifying the central extensions, but I do not know of any standalone articles. --Mark viking (talk) 19:59, 5 February 2015 (UTC)

Thanks. For a start, I have rewritten Wigner's theorem from scratch. There are clearly connections between the subjects due to the projective representations popping up as a result of Wigner's theorem. YohanN7 (talk) 12:14, 7 February 2015 (UTC)

Navbox for "classes" of matrices?

Given that we have this neat navbox for prime number classes, I wonder if we should create a similar one for different types of matrizes. However, I'm not a mathematician (just an economist ;-) ), so apart from the ones commonly seen in economics, I don't know which of these matrices are important, let alone how to categorize a navbox. Is it a good idea though? --bender235 (talk) 15:02, 26 January 2015 (UTC)

I made Template:Prime number classes but don't think I know enough to make a proper version for matrices. I like the idea though. List of matrices may help with the grouping if somebody wants to give it a go. PrimeHunter (talk) 15:17, 26 January 2015 (UTC)

On second thought, I will make a crude version based on just copying most of List of matrices. I will post later when a draft is ready. PrimeHunter (talk) 15:24, 26 January 2015 (UTC)

I have created {{Matrix classes}} based entirely on copying every link (including red links and links with the same target) in List of matrices. Others are very welcome to make improvements. PrimeHunter (talk) 16:22, 26 January 2015 (UTC)

I think the template needs a little more focus. Right now it has too many different kinds of matrices; most of the entries have no relationship to each other besides the fact that they're matrices. A comprehensive navbox would be too big, and a suitably sized navbox is necessarily more focused. I think it would useful to have a template that discussed types of matrices that are generally of interest within linear algebra proper (sparse, banded, Hermitian, idempotent, etc.) and left out matrices which are of interest because they arise in applications (DFT, Bezout, adjacency, etc.). Ozob (talk) 04:00, 27 January 2015 (UTC)

And it looks like this:

YohanN7 (talk) 07:07, 27 January 2015 (UTC)

To give a perspective, the box looks too large, to me. I suppose it is probably hard to decide on what to include and what to exclude. (The choice would likely reflect editor's background.) -- Taku (talk) 04:30, 29 January 2015 (UTC)

Please be bold and make any improvements. I haven't added it to any articles but just wanted to quickly make a framework for others by indiscriminately copying the whole list without evaluating anything or looking for other groupings or potential additions in Category:Matrices. PrimeHunter (talk) 00:51, 8 February 2015 (UTC)

That is like asking someone to do the work for you. Will not happen. I like the thing. But it is too large, so I ask you to rinse out some. (Like stuff you've never heard of.) It can always be put back later. YohanN7 (talk) 01:02, 8 February 2015 (UTC)

Imaginary point

The article titled imaginary point has sat around for years with almost no attention. It lacks references. If the article should indeed exist, could someone cite some geometry textbook there? Michael Hardy (talk) 01:05, 5 February 2015 (UTC)

How about merging it to rational point? I have put tags proposing the merger. -- Taku (talk) 01:24, 5 February 2015 (UTC)

Call me arrogant if you like, but I can't shake the feeling that there is good reason that there are no solid references: the concept as defined in the stub appears (to me, at least) to be mathematical nonsense in the purely geometric context. I've expounded at Talk:Imaginary point. —Quondum 02:18, 8 February 2015 (UTC)

Is this award for real or is it a hoax?

Please see Stampacchia Medal. The external links do not seem to go anywhere. Is this a hoax? Having an award for such a narrow field as Calculus of variations seems unlikely to me. JRSpriggs (talk) 02:57, 8 February 2015 (UTC)

Check all the links. One of the references is [1] and one of the the external links (only linked on the pdf icon due to a syntax error) is page 17 of [2]. Clearly not a hoax. PrimeHunter (talk) 03:21, 8 February 2015 (UTC)

Here is the announcement of this year's prize by VARANA. It is real. Calculus of variations is a huge field, as it is basically calculus in infinite dimensions. It forms the foundation for both classical and quantum field theories in physics. --Mark viking (talk) 03:34, 8 February 2015 (UTC)

Thanks. Someone who knows Italian should fix the majority of the links which do not go anywhere. JRSpriggs (talk) 03:51, 8 February 2015 (UTC)

Draft help needed

Hermann Mayer is writing a draft about Rouben V. Ambartzumian and asked for help via IRC. The subject seems notable with sources such as this, but the draft is a CV that's largely based on Ambartzumian's own publications, not on what third-party coverage we have. Getting full access to the references would be a significant effort for me; thus I'd prefer if someone else could give Hermann Mayer a helping hand and improve the draft so that it can be accepted. Huon (talk) 23:55, 8 February 2015 (UTC)

Where should "Hindu numerals" redirect?

Where should "Hindu numerals" redirect, to Hindu–Arabic numeral system, or to Arabic numerals? Paul August ☎ 13:59, 10 February 2015 (UTC)

Links in Math tags

Hi,

I had a look at https://en.wikipedia.org/wiki/Wikipedia:Rendering_math with the intention to figure out what else is needed after MathML got the default rendering mode for math-tags.

I think it will take a while to get rid or the requirement that people have to learn tex. The visual math input plugin I have investigated see http://math-min.wmflabs.org/w/extensions/MathSearch/modules/min/index.xhtml produces some reasonable results, but is not production ready yet.

However, I get the feeling that the other main disadvantage Unable to place wikilinks on parts of formulae. is easy to fix.

The only question that is open to me is how to call a tex macro for that. Maybe \wref or just \w could be an option so that

<math>\wref{d:Q11379}{E}=\wref{d:Q11423}{m}\wref{d:Q2111}{c}^2</math>

Could replace https://en.wikipedia.org/w/index.php?title=Mass%E2%80%93energy_equivalence#MassEnergyEquivalence

What do you think?

PS: Even though, there are some characters that do not exists in TeX's math mode, the third disadvantage Lacks some characters (such as Cyrillic script) is already solved from my point of view. --Physikerwelt (talk) 15:19, 7 February 2015 (UTC)

My general feeling is that placing links inside math formulas is a bad idea. It interacts badly with some features of rendered math (such as the one where you can click on a formula to embiggen it), the link coloring distracts from the meaning of the formula, and often the pieces of the formula are small making the links non-obvious. It's almost always better to put links on nearby text. So I don't see this as a high priority. —David Eppstein (talk) 18:46, 9 February 2015 (UTC)

The problems mentioned in mw:Extension:Math/Roadmap#Next steps appear to be more crucial. Any progress there? --Quartl (talk) 18:58, 9 February 2015 (UTC)

Ah you are referring to the double subscript ... use braces to clarify problem. I'll double check if that's fixed in upstream and ask the ops team to deploy the fix in production. I do not want to be the judge in spacing questions. The W3C defines the sizes and spacing rules, or is there a problem with the generated MathML? --Physikerwelt (talk) 21:30, 9 February 2015 (UTC)

I wasn't referring to a specific problem mentioned on the page. Many of them result in ugly or even unreadable output and it seems the majority of them have not been resolved yet. --Quartl (talk) 21:45, 9 February 2015 (UTC)

I have created a task for double subscript bug... https://phabricator.wikimedia.org/T89044 to ensure that this will be fixed and no red error messages will appear. Unreadable and ugly are two different things to my mind. If something is unreadable, it needs to be fixed before moving ahead; Currently, I do not see anything that I could not read in my browser on that page. Ugly seems to refer to refer to personal preferences. --Physikerwelt (talk) 22:05, 9 February 2015 (UTC)

Formulas where symbols overlap or are too close together are unreadable. Ugliness is not that subjective as you think since our reference is the output produced by LaTeX. Remember that we look at these formulas every day (I have MathML enabled). For example, the extra space after inline formulas is a major headache and should definitely be removed. Could you please organize the reported bugs into subsections such as open, fixed, reported, wontfix? For some problems that cannot easily be fixed we can think of workarounds such as inserting extra brackets or spaces, but we need to know which ones. Btw. to ask all readers to install some add-on is not a solution. --Quartl (talk) 05:13, 10 February 2015 (UTC)

PS: Lately I have encountered formulas that don't display at all in MathML, currently almost all the formulas in de:Drehmatrix. Purging the page doesn't help. Seems to be a caching problem. --Quartl (talk) 06:12, 10 February 2015 (UTC)

I do not want to argue against you, but we need to differntiate between differend kinds of problems. Howerver, MathML is different from TeX and some rendering is supposed to look different by definition. This does not relate to horizontal distance bug https://github.com/mathjax/MathJax/issues/948 that has not been fixed. I'll implement your suggestion to organzie the potential problems as soon as I can. --Physikerwelt (talk) 09:39, 10 February 2015 (UTC)

"Ugliness is not that subjective ... the extra space after inline formulas is a major headache" I think the juxtaposisitioning of these two sentences maximally undermines your point. It is not possible that some minor aesthetic thing like this is a top priority. --JBL (talk) 13:35, 10 February 2015 (UTC)

No it doesn't since all I'm concerned about is readability. I encourage you to continuously enable MathML and use Firefox or another Gecko-based browser as your working environment (apologies if you are doing this already). --Quartl (talk) 14:14, 10 February 2015 (UTC)

I'm with David that the priority seems wrong; for example, it's not that too important to implement a feature so that people don't have to learn tex. Many math editors, both existing and potential, already know tex. On the other hand, some very basic features are currently lacking. Maybe it's just me but I really want a "commutative diagram" support. This is very important; in some areas of math (e.g., category theory and homological algeba), commutative diagrams are like integral signs in calculus; without them is inconceivable. Mathematics is a little more than computing integrals after all....

Finally, i don't want to just complain but would like to acknowledge how much I (and presumably we) appreciate your work on the math support. My big thanks to you for the work. -- Taku (talk) 02:30, 10 February 2015 (UTC)

I totally agree. Commutative diagrams are something that would be really nice. Howerver, I think those have to be represented as image. http://www.w3.org/TR/MathML3/chapter6.html#interf.graphics

Currently, we would need to support that for all rendering modes. If we had only one rendering mode, this is something that should be fixable much easier, e.g. by just enabeling the appropirate mathjax extension. However, to switch to only one rendering mode, we need to implement PNG to SVG conversion. See https://phabricator.wikimedia.org/T78046 for the details --Physikerwelt (talk) 09:39, 10 February 2015 (UTC)

There is a linux utility pdf2svg that's available in the Ubuntu repository, for what it's worth. In the past, I've used a hack involving an appropriate combination of pdfchop and pdf2svg. See File:Commutative diagram SO(3, 1) latex.svg for an example. (Apologies if you already know about this.) Sławomir Biały (talk) 14:11, 10 February 2015 (UTC)

Do you see align environments?

Hi!

I cannot see anything sensible in the "m=2" section of the article Abel's binomial theorem. (There seems to be some attempt to load an image of some kind; but the result just is a warbled space.) I looked at the source text, and noted that it contains a latex align environment (within wp math-mode).

Now, I could easily rewrite this; but if this is only some problem with my browser, I shouldn't. Therefore, I'd like to know whether the m=2 example is legible for the rest of you. JoergenB (talk) 18:27, 8 February 2015 (UTC)

I just took a look and everything seems fine to me. (Windows 7 - Chrome - MathJax enabled) Bill Cherowitzo (talk) 18:36, 8 February 2015 (UTC)

It looks fine to me on the iPad, iOS8, PNG rendered LaTeX. --Mark viking (talk) 18:58, 8 February 2015 (UTC)

Firefox + XP + PNG = Firefox + XP + MathML = fine. It is nice that we have so many options for math display (none of which work in full). YohanN7 (talk) 17:10, 9 February 2015 (UTC)

@JoergenB: What environment are you using? RockMagnetist(talk) 17:32, 9 February 2015 (UTC)

Firefox, possibly a too old version; under Linux, employing Fluxbox.

Thanks for your answers! Clearly, I should not try to fix this by changing the article; but instead should consult our IT experts. JoergenB (talk) 17:32, 10 February 2015 (UTC)

Could anyone please proofread my new section?

See Cauchy_product#Products_of_finitely_many_infinite_series. Thanks. --Mathmensch (talk) 16:34, 9 February 2015 (UTC)

You have left out something from most of the sums. Each of them should have a variable of summation and its lower and upper bounds. But only two of those are shown in most of the sums. So your meaning is far from clear. JRSpriggs (talk) 17:46, 9 February 2015 (UTC)

Thanks. I fixed this. --Mathmensch (talk) 09:13, 10 February 2015 (UTC)

I want to point out that a less notationally demanding approach is to use convolution: think of a series as a function on the integers with support contained in the nonnegative integers. In this viewpoint, Cauchy product is a convolution. -- Taku (talk) 20:40, 9 February 2015 (UTC)

I guess to mention convolutions in this context is advantageous, but I would still use the sum notation, because otherwise, if you want to calculate the product of the series and want a series (as needed for example in finding a non-recursive expression of a sequence using generating functions) or a number (as needed if the series are not easily calculated), you would have to insert the convolution definition, and this would be even more fiddly, so let the article do it for you. --Mathmensch (talk) 09:13, 10 February 2015 (UTC)

Thanks for fixing the lower limits of summation. However, I now notice that the conclusion which you reach for n+1 is not in the same form as the inductive hypothesis for n, even if you move the first coefficient through the sums. JRSpriggs (talk) 08:14, 11 February 2015 (UTC)

Thanks, it should be fixed now. --Mathmensch (talk) 09:23, 11 February 2015 (UTC)

Mathematics of finance

Wikipedia has many pages in the field of mathematics of finance, for example Category:Mathematical finance, and more. None of those articles belong to this project and many are project-orphaned. Just wondering why they can't call this project home? Thanks in advance, Ottawahitech (talk) 14:42, 11 February 2015 (UTC)

There is nothing wrong in principle with a mathematics of finance article being part of WP:MATH, but I think it needs to be decided on a case by case basis. Some articles, like Malliavin calculus are firmly in the math camp. Others, like Cash on cash return is about a financial ratio--the financial aspect of quantity is the important thing, not the simple division used. --Mark viking (talk) 23:04, 11 February 2015 (UTC)

Agree. (As I understand it, whether an article has been tagged for WP:MATH is merely a consequence of whether someone has bothered to so tag it.) --JBL (talk) 23:54, 11 February 2015 (UTC)