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Revision as of 09:20, 11 April 2012 editF=q(E+v^B) (talk | contribs)4,289 edits →Index notation← Previous edit Revision as of 09:22, 11 April 2012 edit undoTimothyRias (talk | contribs)Extended confirmed users, Pending changes reviewers15,403 edits →Index notation: having a separate "Tensor index notation" article is probably the best optionNext edit →
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::There is '']'' that could be used as a central summary (currently a redirect to '']''). The name is probably too broad for the purpose, though. There is also '']'', which might be quite suitable (currently a redirect to '']'', which I feel should be renamed to '']''). How about using '']'' for your proposal? On a side note, until an article is found for this, I feel it should remain in '']''. — ]] 09:15, 11 April 2012 (UTC) ::There is '']'' that could be used as a central summary (currently a redirect to '']''). The name is probably too broad for the purpose, though. There is also '']'', which might be quite suitable (currently a redirect to '']'', which I feel should be renamed to '']''). How about using '']'' for your proposal? On a side note, until an article is found for this, I feel it should remain in '']''. — ]] 09:15, 11 April 2012 (UTC)
:::I think having a separate article on ] is probably a good idea. Having a place to link to for explaining notation is good, and having all the notation gathered in one place is good as well. I would not actually merge any of the notational content from the articles mentioned above though. Having the notation explained along side the concept it is supposed to express is very useful as well. There is no reason why we shouldn't have both.]] 09:22, 11 April 2012 (UTC)


:::As said this is only a potential alternative which may not happen, but thanks for pointing out the better link and title. For now ''(in principle)'' the summary above in the tensor article is plenty, but ] has reverted twice already... <span style="font-family:'TW Cen MT';">] ] ]</span> 09:20, 11 April 2012 (UTC) :::As said this is only a potential alternative which may not happen, but thanks for pointing out the better link and title. For now ''(in principle)'' the summary above in the tensor article is plenty, but ] has reverted twice already... <span style="font-family:'TW Cen MT';">] ] ]</span> 09:20, 11 April 2012 (UTC)

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restricted randomization

Restricted randomization has been nominated for deletion. Here's the discussion: Misplaced Pages:Articles_for_deletion/Restricted_randomization.

Apparently everyone has ALREADY forgotten that in 2002 probably 10% of Misplaced Pages articles were just copied from either the US Geographic Names Data Base or a federal agency web site on telecommunications. An article would say,

In telecommunications, the Atlantic Ocean is an ocean bounded on the east by Europe and Africa and on the west by the Americas, across which the transatlantic cable was laid.

It was crazy, but the policy was that we were to work on and improve them. Now this article is nominated for deletion only because its initial version is copied from a (non-copyrighted) federal government web site. The article needs work, but it's nowhere near as bad as lots of others that survive. Michael Hardy (talk) 17:50, 25 March 2012 (UTC)

This article is actually our only article on split-plot designs! Clearly it needs improvement. Michael Hardy (talk) 18:26, 26 March 2012 (UTC)

The question needs to be asked: why exactly is this article not considered a copyright violation? The original site doesn't have a clearly visible copyright notice, but I also can't see any explicit waiver of copyright or any statement giving permission for the content to be reproduced elsewhere. (I agree that we should have an article on this topic; I just want to understand this issues fully before I comment at the deletion discussion.) Jowa fan (talk) 06:57, 27 March 2012 (UTC)

Works created by U.S. Federal Government employees (as part of their employment) cannot be copyrighted, under U.S. copyright law. No copyright, no copyvio. —David Eppstein (talk) 07:07, 27 March 2012 (UTC)
There used to be a specific template for NIST:
Public Domain This article incorporates public domain material from the National Institute of Standards and Technology
(I had the same question, a couple years ago, regarding Optimal design, for which the NIST material too closely followed Montgomery's textbook, which too closely followed Box & Draper's textbook, which too closely followed Box's article on alphabetic optimality, which too closely followed Box....)  Kiefer.Wolfowitz 07:08, 27 March 2012 (UTC)
Haha, with the internet today you can easily find many examples of what people might call plagiarism today.--Milowent • 12:15, 27 March 2012 (UTC)
When you see an apparent case of plagiarism, please investigate it before deleting our text. Sometimes it is the other site plagiarizing us. For example, see Talk:Axiom of choice#Plagiarism?. JRSpriggs (talk) 13:04, 27 March 2012 (UTC)

class="texhtml" (used by template: math)

Should we make fonts in class="texhtml" look similar to ones used by user:Nageh/mathJax? Currently an article intermixing <math> and {{math}} formatting, e.g. Quaternions and spatial rotation, looks patchy. The letter x shows an especially ugly contrast between the (default browser) "italic" and cursive fonts used in both texvc PNGs and mathJax. Incnis Mrsi (talk) 07:55, 27 March 2012 (UTC)

No. In fact, the STIX fonts, used by the MathML renderer (and supported also by the HTML/CSS renderer once MathJax is available as an official Misplaced Pages/MediaWiki option), match quite well with the {{math}} template font. Since even the STIX and TeX fonts have different font faces hard-coding any font values is not a good idea. However, you can always specify a custom font family using CSS code in your common.css file. Btw, I noticed a discussion on the MathJax user mailing list, suggesting that a future release may support the selection between serif and sans-serif fonts, which may address objections previously raised regarding the clash between maths fonts and surrounding text fonts. Nageh (talk) 13:55, 27 March 2012 (UTC)
I think that we should wait to see what happens with a site-wide mathjax rollout before we worry about these things. The {{math}} template is not widely used, and is mentioned but not encouraged WP:MOSMATH. Once mathjax is enabled, I expect we will be able to merge {{math}} and <math>, eliminating the issue. — Carl (CBM · talk) 15:24, 27 March 2012 (UTC)
It would be very nice to have the option to specify the fonts to MathJax, I like a strong distinction between maths and text but others find the distinction very jarring and want to be able to join both into sentences. I don't think we need worry too much about the {{math}} template, I believe that soon and at long last we will have good rendering of inline <math> and be able to phase the math template out. Dmcq (talk) 16:45, 27 March 2012 (UTC)
These reasonings of Nageh and Dmcq sound good, but have actually nothing to do with the problem: which formatting guidelines ought en.WP to follow today. For example, see the recent clash in Robinson arithmetic. CBM, probably with some followers, tries to eradicate {{math}}, arguing that pre-existing raw wiki markup is better. When MathJax finally came, there will be no consensus again on how to implement it in such cases, and conflicts will erupt yet another time. CBM and Dmcq speak about merger of {{math}} and <math> like such a decision were already taken. But when en.WP will have a good <math>, numerous compatibility problems with HTML formatting will preclude the conversion to <math> in many cases, and such a move will be not so easy as one could imagine. Incnis Mrsi (talk) 10:32, 30 March 2012 (UTC)
Unlike with {{math}} and <math>, when we have MathJax available as the default for readers, I will support using MathJax alone for both inline and displayed formulas. I find the appearance of MathJax on other sites, such as mathoverflow.net, to be perfectly acceptable, and I'm willing to live with the change to the current HTML math to get its benefits. On the other hand I don't see any strong benefits to the {{math}} template as it is currently formatted, although some disagree. In my LaTeX documents the math is not typically in a larger, different font, so that seems quite strange to me on Misplaced Pages. But I am not trying to eradicate {{math}}; for example if someone starts a new article they are welcome to use any style they want. — Carl (CBM · talk) 10:50, 30 March 2012 (UTC)
What means "any strong benefits"? We may dispute the comparison of {{math}} to various <math> implementation (such as unclickable PNG/texvc and client-side resource consuming MathJax), but {{math}} has at least one advantage over a raw wiki code: it explicitly labels an expression as mathematical and hence protects it from various automated and semi-automated stupid changes. Incnis Mrsi (talk) 11:05, 30 March 2012 (UTC)
I'd be happy to search for {{math}} and replace it with <math> and redo the formulae in the articles I watch when MathJax comes along so I see the math template as being a good marker that way. Dmcq (talk) 12:01, 30 March 2012 (UTC)

Category:Featured articles on Mathematics Portal

As a result of this CfD discussion, 37 articles have Category:Featured articles on Mathematics Portal on their talk page. That's fine, but it is awkward how the category is stuck at the bottom of the page, where it will inevitably cause confusion to those adding comments in the last section. For example, click "edit" for the last section at Talk:Golden ratio and see that if you were adding a new comment, you should insert it above the "Category" line. Perhaps the category should be included as an option in {{Maths rating}}? Johnuniq (talk) 11:32, 27 March 2012 (UTC)

{{maths rating}} does not support portal pages; it's just for articles. But we could make a different template for these talk pages, like {{FA on Math Portal}}, that could be put at the top and which would categorize the articles. I'd be happy to do that if people want it, I think that the bare category at the bottom is indeed a problem. — Carl (CBM · talk) 15:26, 27 March 2012 (UTC)
But all the pages in Category:Featured articles on Mathematics Portal are standard articles which already have the template, an extra field would be easy enough to implement. Alternatively it is only a convention that categories need to be at the bottom of the page. It might be easier just to move these to the header.--Salix (talk): 16:35, 27 March 2012 (UTC)
I misunderstood, and thought these were portal pages. Since they're articles, I'm neutral between using the math rating template or a new one, or moving the category up (although I fear that some misguided bot will get confused in the third case and move it back to the bottom). — Carl (CBM · talk) 16:40, 27 March 2012 (UTC)
Yes bots might be a problem. I've now added a "portal" field to {{maths rating}}. Just add {{maths rating| ... | portal=true}} to place it in the category. I'm not entirely sure of the purpose of the category.--Salix (talk): 08:20, 28 March 2012 (UTC)

Original work

Dear mathematicians,

A contributor has put a theorem of his own in an article (Expander graph). He exhibits formulas that are not referenced in any academic source. Despite what he's saying, it requires much more than "routine calculations" to reach his result.

There was an interpretation mistake of one of the sources that led to a mistake in his formulas. This mistake stayed in the article during one year and a half. I did not succeed in convincing him that was the very illustration of the dangers of doing original work.

He "fixed" the formulas, but I'm still not perfectly convinced that the new version is correct. And no one can tell, since the result is not in the sources.

I also had him to remove a definition that was not in the sources (this time with success).

I would your need help to let him understand that, if something is not in the sources, it has nothing to do on wikipedia.

Discussion is here: Talk:Expander graph#"Original research" template.

Thanks in advance, --MathsPoetry (talk) 07:45, 28 March 2012 (UTC)

If the result is not published it should be swiftly removed regardless of correctness. Tkuvho (talk) 08:52, 28 March 2012 (UTC)
Ditto, and you can depend on support here if you remove questionable unsourced material and OR. Rschwieb (talk) 13:28, 28 March 2012 (UTC)
The question is whether it is indeed original research, as claimed above, or whether it is just a change of notation and routine calculations, which are allowed. I'm not sure myself, even after reading the source. -- Jitse Niesen (talk) 14:05, 28 March 2012 (UTC)
Tkuvho & Rschwieb, please have a look at the disputed paragraph; I am not sure you will retain your opinion after that. Sasha (talk) 14:28, 28 March 2012 (UTC)
I imagine what I wrote above was slightly misread, as I didn't make any comment on whether the material was OR or not. My opinion that OR should be deleted won't change. I am completely unaware if the content in dispute is OR or not, that is for someone familiar with the material to decide. Rschwieb (talk) 15:53, 28 March 2012 (UTC)
thanks for the clarification. Obviously, I agree with your opinion. Sasha (talk) 16:07, 28 March 2012 (UTC)
This seems to be a borderline case. On the face of it, it is a routine calculation, as long as you understand the different notations involved. However, the original editor did make an error that lost a factor of 2 {\displaystyle {\sqrt {2}}} (since corrected) so maybe its not quite as routine as it appears. Gandalf61 (talk) 14:38, 28 March 2012 (UTC)
There should be no question that this is not OR. MathsPoetry is obviously having a positive effect on the article, but I don't understand the particular focus on removing (rather than correcting) what is an immediate corollary of the cited work. The fact that a factor of 2 got lost in changing notations is not important at all, and putting the word "wrong" in boldface doesn't make it more so. --Joel B. Lewis (talk) 14:55, 28 March 2012 (UTC)
There are two points to it. First, I don't think it's an "immediate corrolary". I am not even sure his result is correct. Second, I don't think it's up to us to derive new corollaries from existing work.
Some background information: I'm no English speaker (sorry if my written English is suboptimal), and I am the guy who wrote the French article on expander graphs.
As a sidenote, I don't agree that losing a factor of 2 is not important: wrong math formulas have been online during one year and a half, due to that mistake.
Thanks to all for your kind advice on this. --MathsPoetry (talk) 16:25, 28 March 2012 (UTC)

I realize the subject is quite technical, so I have provided an outline of the proof of my contradictor on Talk:Expander graph#Ylloh's proof. This should enable you to judge whether it is an immediate corollary or not. I tried to make the presentation as neutral as possible, and I only did my remarks about possible problems after the demonstration. Best, --MathsPoetry (talk) 18:06, 28 March 2012 (UTC)

Persistent vandalism/self-promotion of Angle trisection

Some user is repeatedly vandalizing angle trisection in an attempt to insert links to his own webpage. (He has successfully managed to get such links included on a variety of other, non-math, pages; this appears to be the only purpose of the account.) If someone with appropriate powers could do something to prevent this, it would be wonderful. --Joel B. Lewis (talk) 18:04, 29 March 2012 (UTC)

Now accompanied with legal threats: http://en.wikipedia.org/search/?title=Angle_trisection&curid=91111&diff=484576133&oldid=484575649 (btw, the claim of copyright violation is obviously absurd.) --Joel B. Lewis (talk) 18:38, 29 March 2012 (UTC)
Now discussed at Misplaced Pages:Administrators' noticeboard/Incidents#Angle trisection, both editors blocked for a day. Could be a page to watch for further trouble,--Salix (talk): 23:02, 29 March 2012 (UTC)
Yes, please keep an eye on it -- I've agreed to leave it alone for a bit, but it seems extremely likely to me that the other user will continue to self-promote (as e.g. he continues to assert that he has a 1995 copyright on the idea of using repeated bisection to trisect an angle -- https://en.wikipedia.org/search/?title=User_talk:WIKI-1-PIDEA&diff=484617642&oldid=484606285 ). --Joel B. Lewis (talk) 01:51, 30 March 2012 (UTC)
There's always someone wrong on the internet ;-) I wouldn't worry, there's enough people watch that article. Dmcq (talk) 11:51, 30 March 2012 (UTC)

The concerned editor has been indefinitely blocked, see User talk:WIKI-1-PIDEA#March 2012. — D.Lazard (talk) 10:03, 1 April 2012 (UTC)

Robin Williams (in character): "I want to bisect her angle"

The project members may be interested in the article about Robin Williams and Steve Martin at the USA's Mathematical Sciences Research Institute (MSRI), which features e.g. William's ad-libbing about a math geek wishing "I want to bisect her angle". Or not.

 Kiefer.Wolfowitz 10:25, 1 April 2012 (UTC)

John Rainwater April Fools DYK: Peter Orno delayed

The pseudonymous mathematicians John Rainwater and Peter Orno were approved for the 2012 April Fools DYK in April 2011. John Rainwater's DYK should appear in a few hours. Peter Orno's DYK has been delayed.  Kiefer.Wolfowitz 10:30, 1 April 2012 (UTC)

New WPM guideline

Recent discussions at Talk:twice pi suggest that it may be helpful to have an explicit guideline to the effect that youtube videos and yellow media reports are not considered to be reliable sources for math-related articles. Tkuvho (talk) 14:52, 2 April 2012 (UTC)

Bogus mathematical theories that nevertheless receive significant popular attention should be considered notable. Yellow media should not be considered reliable in terms of their mathematical content but should certainly be considered sufficient to establish notability, and at least somewhat reliable when it comes to statements about cultural impact. 69.195.54.191 (talk) 18:58, 8 April 2012 (UTC)
This seems misguided since the article topic in question is more notable for its cultural impact than anything else. It's like Time Cube. Fringe/minority viewpoint, popular in spurts among the media, but not insane like Time, instead just frivolous. --Cybercobra (talk) 16:11, 2 April 2012 (UTC)
Cybercobra, you must be coherent with yourself: Half a month ago you have requested (and obtained) to revert the move of this article to "Tau against pi debate" with the reason "Significantly altering an article's topic". And now you say that the notable part of this article is the report by the news of this supposed debate. If the article topic is not about a mathematical constant but about its notability in popular culture, the article title and the two first sentences should be changed, for not mislead the reader: Presently, both asserts that the topic is a mathematical constant. D.Lazard (talk) 17:07, 2 April 2012 (UTC)

Obvious target candidate: 2π in popular culture. Sławomir Biały (talk) 21:34, 2 April 2012 (UTC)

Come on, guys, how many times are we going to keep spinning around the same issues? We need to stop conflating 2π and Tau for the sake of argument. The former is a well-sourced (mathematically speaking) concept regarding the usage of a different circle constant, and the latter is a recent proposal that received considerable adoption especially (but not exclusively) in non-mathematical circles. They are indeed inseparable as far as article content is concerned (both should be present in an article about this whole issue) but we can't discuss about the article by arguing for or against only one part of it. "2π in popular culture" would make sense if we decided to keep only the tau part (and then again wouldn't, for inexplicably keeping Tau out of the title), but again, omitting the background to the current surge of interest in 2π is just misleading and a disservice to readers. This would only make sense if the content grew so large that it would make reading the article cumbersome (case in point: Pi Day).
Regarding this proposal, I am entirely against more rule creep that attempts to define rigid boundaries and automatize the editorial process. We have enough policies and guidelines, we just need to use our common sense and be willing to consider compromise solutions. This is how Misplaced Pages works. Besides, Misplaced Pages is a general reference work, not a mathematical compendium. Nothing prevents a math-related article to include relevant non-mathematical content (see Pi#Outside the sciences for instance), which should naturally follow the appropriate proportion as agreed by editors. --Waldir 05:10, 3 April 2012 (UTC)
I agree that guidelines should not be created for the sake of having more guidelines. However, in this case we have encountered persistent misconceptions on the part of editors who think, for example, that youtube videos have weight in notability discussions. If not a guideline, perhaps we could have an extra question in the FAQ at the top of this page. Tkuvho (talk) 11:56, 3 April 2012 (UTC)
We already have the needed guidelines: WP:YOUTUBE and WP:ELNO. Nageh (talk) 12:29, 3 April 2012 (UTC)
Thanks, I did't see this. The clause about "case-by-case basis" could be clarified in the context of math pages. I think there is room for stronger opposition in the context of scientific pages. Again, having such a guideline may help us to orient well-meaning but misguided editors and save everybody time. Tkuvho (talk) 12:37, 3 April 2012 (UTC)
The other link you provided does not seem to say anything about media, tabloid or otherwise. Tkuvho (talk) 12:39, 3 April 2012 (UTC)
WP:ELPOV is also worth to be considered. D.Lazard (talk) 12:44, 3 April 2012 (UTC)

It would be nice if there were some concrete way to address the issue of "yellow media". This is not the first time this issue has arisen in science-related articles of the media running some story of dubious scientific merit, simply because some scientist somewhere had said something. My favorite example is Misplaced Pages:Articles for deletion/Jacob Barnett, which was picked up as a viral news story because upon posting his idiotic ramblings to YouTube, Jacob Barnett's mother contacted an MIT physicist who encouraged Barnett to continue studying math and physics. The media spun this as "Boy genius challenges all of modern physics" or other such ridiculousness. The point is, as a rule news media should not be allowed as a reliable source for this sort of thing. The news is a reliable source for news (e.g., what Russia is doing at the moment), less so for all the other stuff presented as a sideshow to the news. Sławomir Biały (talk) 12:47, 3 April 2012 (UTC)

I agree with the thrust of your comment but would like to limit it somewhat. Every now and then there are legimitate pieces on science that appear in the popular media. I would formulate an objection in terms of "tabloids" to avoid making them too sweeping. Sensationalism may be in the eye of the beholder, but when a number of WPM members behold an item of science "news that's fit to sell" and eye it with suspicion, this should be enough to block it systematically. Tkuvho (talk) 13:02, 3 April 2012 (UTC)
Note that twice pi currently has 13 (!) references to make the point that B. Palais proposed a new symbol for 2 pi, one of them a "Life of pi over" piece from the friendly Times of India. I have no previous experience with this best-selling journal but if anyone has additional evidence of it engaging in tabloid tactics to reach its best-selling status, they are invited to step forward with the information. Tkuvho (talk) 13:15, 3 April 2012 (UTC)
I propose the following addition to the FAQ at the top of this page: Question. Why don't math pages rely more on helpful YouTube videos and media coverage of mathematical issues? Answer. Mathematical content of YouTube videos is often unreliable, whereas media reports are typically sensationalistic. This is why they are generally avoided. Tkuvho (talk) 14:11, 4 April 2012 (UTC)
The change proposed above was performed without any consensus in this discussion. I reverted it for now. --Waldir 09:15, 10 April 2012 (UTC)

MathJax

Is anyone else having problems viewing maths text? All <math>...</math> strings are being displayed as $...$ with the LaTeX code being shown explicitly. — Fly by Night (talk) 20:11, 2 April 2012 (UTC)

Sorry, my bad. See User_talk:Nageh/mathJax#Troubleshooting. Nageh (talk) 20:44, 2 April 2012 (UTC)

On a related note, when is Misplaced Pages finally going to switch to MathJax? It has been working for me flawlessly for quite some time now (except all the text art in italic and bold with html super/subscripts instead of math looks bad in comparison - as it should), but when I arrive to a Misplaced Pages link without being logged in, I still see the legacy math rendering as images. Jmath666 (talk) 01:21, 7 April 2012 (UTC)

The last update I saw on this was on Wikipedia_talk:WikiProject_Mathematics/Archive/2012/Mar#MathJax_update. See also the list of dependencies of bug 31406. Helder 20:17, 9 April 2012 (UTC)

Merge help needed - Ordered ring

I need help with math merging. There is consensus at Talk:Partially ordered ring to merge in the page Ordered ring, but I don't know the math and have no idea how to do it. I was hoping that one of your math whizzes here could do that for Wiki. Thanks, D O N D E groovily Talk to me 02:26, 4 April 2012 (UTC)

Featured picture candidate

The ceiling of the 400 year old Sheikh-Lotf-Allah mosque in Isfahan, Iran

This picture has been nominated as a featured picture here it has been pointed out that the picture has little or no encyclopaedic value in describing symmetry to the reader. I am wondering is that correct ? Some editors in the discussion don't think so. Penyulap ☏ 04:52, 4 April 2012 (UTC)

Terminology of inflexion points

In the page inflexion point it is said (in other words) that it is a point where a curve has a contact of odd order with its tangent. The name of a contact of even order higher than two is not given. In French, it is "méplat", but the article Meplat does not give this meaning. What is the correct English word?.

By the way, "flex" is frequently used instead of "inflexion point" and this is not mentioned in the article.

D.Lazard (talk) 16:22, 7 April 2012 (UTC)

Coons surface

Coons surface is a really messy new article. Work on it. Michael Hardy (talk) 19:55, 7 April 2012 (UTC)

I'm not knowledgable on that specific topic to re-write, but still cleaned it up and removed the clean up banner. F = q(E+v×B) ⇄ ∑ici 09:23, 8 April 2012 (UTC)

Matrix multiplication

Given the importance of this article, and it hasn't really improved since last posted my own suggestions for improvement on the talk page (to which no one has responded to, or even at all since then, recently archived by myself), I intend to just re-write most of the first half of the article.

There is plenty of repetition and it just dribbles on and on. All that's really needed it the general definition and a couple of concrete examples, followed by the properties. By no means will remove anything referenced or the image already included, though the first half only has one reference, I (and surley many others) have access to loads (and if ordinary multiplication is such a trivial concept, why aren’t there more anyway??).

The "too technical" banner has been there a long time also... about time this was sorted out. F = q(E+v×B) ⇄ ∑ici 23:17, 7 April 2012 (UTC)

Combinatorial game theory

I don't want to edit the article as it is completely outside my area of expertise, but the recently added section on Fraser Stewart's PhD thesis reads to me like a shameless (self?-)promotion of a topic of marginal importance for this introductory article. Can someone knowledgeable have a look at it?—Emil J. 17:45, 8 April 2012 (UTC)

Judging from the way it is written, it is fully dependent on ideas from the dissertation. It might well be self-promotion, as there is a Fraser Stewart on google with email ending in computing.dundee.ac.uk, and geolocate puts the IP in the UK. I'll remove the section for now on the grounds that this dissertation is not notable. Rschwieb (talk) 19:55, 8 April 2012 (UTC)

Help needed with pi article

I'm planning on nominating the pi article soon for Featured Article status. I'm looking for math-knowledgable editors to review the article for accuracy & prose quality .... just post any comments or ideas for improvement on the article's Talk page. The criteria for FA are at Misplaced Pages:Featured_article_criteria. Thanks in advance for any help. --Noleander (talk) 14:04, 9 April 2012 (UTC)

Group theory templates

Hi, I noticed at least two group theory templates. There is the one at Abelian group and the one at group theory. They both have their strong points. The one without the picture is easier to navigate, and I like the last two items. On the other hand, the one with the picture is pretty neat, and pretty much subsumes the one without the picture. Should we think about merging or do we just use them haphazardly? Rschwieb (talk) 18:58, 9 April 2012 (UTC)

Probably should be merged. --Noleander (talk) 19:46, 9 April 2012 (UTC)
I merged them into the template with the picture: {{Groups}}. I put the misc groups at the bottom, into a new region called "Other" ... so an editor who is an expert in groups should probably review those articles and see if they are better off in another region in the template. --Noleander (talk) 20:11, 9 April 2012 (UTC)

saccheri quadrilateral: obtuse angle

Looking for help here about Saccheri quadrilateral. :)--Nickanc (talk) 22:12, 9 April 2012 (UTC)

Index notation

There are several articles which explain the meaning and use of this notation:

  1. Index notation
  2. Tensor
  3. Antisymmetric tensor
  4. Einstein notation
  5. Raising and lowering indices
  6. Abstract index notation
  7. Covariance and contravariance of vectors

yet the specialized notations of commas, semicolons, sqaure/round brackets (e.x. A α , β , A α ; β , A [ α β ] , A ( α β ) {\displaystyle A^{\alpha }{}_{,\beta },A_{\alpha ;\beta },\,A_{},\,A^{(\alpha \beta )}} ) seem to be dispersed, so readers will have to search them out (even if linked) which is not much help. It would be convenient to add a list of all the attributes just as a summary in one place (in an obviously titled article - like abstract index notation so people will look there and its easier for editors to remember that link), then linking to all of the main articles from there.

proposed summary:
  1. Covariant tensor Indices are lowered (subscript): A α β γ ⋯ {\displaystyle A_{\alpha \beta \gamma \cdots }}
  2. Contravariant tensor Indices are raised (superscript): A α β γ ⋯ {\displaystyle A^{\alpha \beta \gamma \cdots }}
  3. Mixed tensor Indices are raised and lowered: A α β γ δ ⋯ {\displaystyle A_{\alpha }{}^{\beta }{}_{\gamma }{}^{\delta \cdots }}
    4. Indices can be raised and lowered using the metric tensor.
  4. Partial derivative Comma before the index of spatial variable: A α β ⋯ , γ = ∂ γ A α β ⋯ = ∂ A α β ⋯ ∂ x γ {\displaystyle A_{\alpha \beta \cdots ,\gamma }=\partial _{\gamma }A_{\alpha \beta \cdots }={\dfrac {\partial A_{\alpha \beta \cdots }}{\partial x^{\gamma }}}}
  5. Covariant derivative Semicolon before the index of the tangent vector: A α β δ ⋯ ; γ {\displaystyle A_{\alpha \beta \delta \cdots ;\gamma }}
  6. Symmetric part of tensor
    Round ( ) brackets around the number of symmetrized indices, then permutations, divided by the factorial of the number of indices in round brackets:
    two symmetrized indices
    A ( α β ) γ ⋯ = 1 2 ! ( A α β γ ⋯ + A β α γ ⋯ ) {\displaystyle A_{(\alpha \beta )\gamma \cdots }={\dfrac {1}{2!}}\left(A_{\alpha \beta \gamma \cdots }+A_{\beta \alpha \gamma \cdots }\right)}
    example:
    A ( α B β ) γ = 1 2 ! ( A α B β γ + A β B α γ ) {\displaystyle A_{(\alpha }B_{\beta )\gamma }={\dfrac {1}{2!}}\left(A_{\alpha }B_{\beta \gamma }+A_{\beta }B_{\alpha \gamma }\right)}
    three symmetrized indices
    A ( α β γ ) δ ⋯ = 1 3 ! ( A α β γ δ ⋯ + A γ α β δ ⋯ + A β γ α δ ⋯ + A α γ β δ ⋯ + A γ β α δ ⋯ + A β α γ δ ⋯ ) {\displaystyle A_{(\alpha \beta \gamma )\delta \cdots }={\dfrac {1}{3!}}\left(A_{\alpha \beta \gamma \delta \cdots }+A_{\gamma \alpha \beta \delta \cdots }+A_{\beta \gamma \alpha \delta \cdots }+A_{\alpha \gamma \beta \delta \cdots }+A_{\gamma \beta \alpha \delta \cdots }+A_{\beta \alpha \gamma \delta \cdots }\right)}
    p symmetrized indices, sum over all permutations: A ( α 1 α 2 ⋯ α p ) α p + 1 ⋯ α q = 1 p ! ∑ α 1 α 2 ⋯ α p A α 1 α 2 α 3 ⋯ α p ⋯ α q {\displaystyle A_{(\alpha _{1}\alpha _{2}\cdots \alpha _{p})\alpha _{p+1}\cdots \alpha _{q}}={\dfrac {1}{p!}}\sum _{\alpha _{1}\alpha _{2}\cdots \alpha _{p}}A_{\alpha _{1}\alpha _{2}\alpha _{3}\cdots \alpha _{p}\cdots \alpha _{q}}}
  7. Antisymmetric part of tensor
    Square brackets around the number of antisymmetrized indices, simalarly
    two antisymmetrized indices
    A [ α β ] γ ⋯ = 1 2 ! ( A α β γ ⋯ − A β α γ ⋯ ) {\displaystyle A_{\gamma \cdots }={\dfrac {1}{2!}}\left(A_{\alpha \beta \gamma \cdots }-A_{\beta \alpha \gamma \cdots }\right)}
    three antisymmetrized indices
    A [ α β γ ] δ ⋯ = 1 3 ! ( A α β γ δ ⋯ + A γ α β δ ⋯ + A β γ α δ ⋯ − A α γ β δ ⋯ − A γ β α δ ⋯ − A β α γ δ ⋯ ) {\displaystyle A_{\delta \cdots }={\dfrac {1}{3!}}\left(A_{\alpha \beta \gamma \delta \cdots }+A_{\gamma \alpha \beta \delta \cdots }+A_{\beta \gamma \alpha \delta \cdots }-A_{\alpha \gamma \beta \delta \cdots }-A_{\gamma \beta \alpha \delta \cdots }-A_{\beta \alpha \gamma \delta \cdots }\right)}
    example:
    F [ α β , γ ] = 1 3 ! ( ∂ γ F α β + ∂ β F γ α + ∂ α F β γ − ∂ γ F β α − ∂ β F α γ − ∂ α F γ β ) {\displaystyle F_{}={\dfrac {1}{3!}}\left(\partial _{\gamma }F_{\alpha \beta }+\partial _{\beta }F_{\gamma \alpha }+\partial _{\alpha }F_{\beta \gamma }-\partial _{\gamma }F_{\beta \alpha }-\partial _{\beta }F_{\alpha \gamma }-\partial _{\alpha }F_{\gamma \beta }\right)}
    p antisymmetrized indices, sum over cyclic permutations: A [ α 1 α 2 ⋯ α p ] α p + 1 ⋯ α q = 1 p ! ϵ α 1 α 2 ⋯ α p A α 1 α 2 ⋯ α p ⋯ α q {\displaystyle A_{\alpha _{p+1}\cdots \alpha _{q}}={\dfrac {1}{p!}}\epsilon _{\alpha _{1}\alpha _{2}\cdots \alpha _{p}}A_{\alpha _{1}\alpha _{2}\cdots \alpha _{p}\cdots \alpha _{q}}}

Reference which includes all of these: Gravitation, MTW, 1972, p.85-86, §3.5 . If no-one objects I'll add it to the end of abstract index notation (an alternative place would be tensor but there is a section which links to abstract index notation anyway...). F = q(E+v×B) ⇄ ∑ici 09:28, 10 April 2012 (UTC)

The point that such a collected summary would be useful is well-made. I would however argue against such a central summary being placed under abstract index notation, since that is a side-branch and does not cover all uses of the notation). I would suggest that such a summary should rather be placed under tensor as the more central article. — Quondum 11:32, 10 April 2012 (UTC)
I had that in another mind, so you think in tensor under the subsection Abstract index notation? F = q(E+v×B) ⇄ ∑ici 11:45, 10 April 2012 (UTC)
The title of the article abstract index notation may be misleading. It is not about the index notation which uses numbers as indices. It is about a system which merely indicates which aspects of a tensor are equivalent or may be contracted with which other aspects. As such, I would avoid that article like the plague that it is. JRSpriggs (talk) 12:27, 10 April 2012 (UTC)
Well, in its own subsection titled as "summary of notation" under notation in the tensor article, or whatever. Thanks both of you for clarifying this in the right direction, I thought they were the same somehow... F = q(E+v×B) ⇄ ∑ici 12:40, 10 April 2012 (UTC)
(@JRSpriggs) I don't follow you. How exactly is abstract index notation a plague? This is standard terminology in physics and differential geometry, not a misleadingly titled article. Sławomir Biały (talk) 12:41, 10 April 2012 (UTC)
I think the point has been made and agreed that abstract index notation (or even such a section heading) is unsuitable for the purpose suggested by F = q(E+v×B) ⇄ ∑ici. Speaking of this, an alternative to tensor for such a summary may be the article Einstein notation. So my suggested candidates are these two articles, and I would welcome comments. — Quondum 14:18, 10 April 2012 (UTC)
The article Einstein notation is about the summation convention (as Einstein himself introduced) and pretty much every application of it in linear algebra. The link summation convention itself redirects to there. When people read tensor equations which happen to include commas/semicolons/brackets etc, the first place they will think of is tensor and hope to find the notation there. So I'd be inclined for the previous suggestion: in the article tensor, under the section notation, and start a new subsection called "summary of index notation for tensors" (or words to that effect) and simply paste the contents of that box under the heading. =) F = q(E+v×B) ⇄ ∑ici 15:43, 10 April 2012 (UTC)

Btw., the historical name is Ricci calculus , see Schouten (1924) Der Ricci-Kalkül.--LutzL (talk) 16:49, 10 April 2012 (UTC)

(ec) The article does create the impression that the phrase Einstein notation is synonymous with Einstein summation convention, but it also seems possible that it is a broader term to describe the use of superscripts, subscripts etc. to index coefficients, plus potentially all the twiddles in your proposed summary; if this is the case, the Einstein summation convention would be merely one facet thereof. I would not be surprised if this article focuses primarily on the summation convention as a result of a misconception amongst WP editors. I am having difficulty googling references that authoritatively support either view. I would appreciate input from people with experience on this point. — Quondum 16:54, 10 April 2012 (UTC)

I would like to ask a math historian about the origins of the summation convention and index convention. Tensor calculus was around before Einstein, and it wouldn't be surprising if these conventions were already in use before Einstein. Rschwieb (talk) 17:37, 10 April 2012 (UTC)
Fourier, I believe. --Matt Westwood 17:42, 10 April 2012 (UTC)
Its perfectly fine add a historical note about the notations when the time comes, but shall we add the box or not? If so where? Einstein notation would be unsuitable since that article does, and should, concentrate on the summation convention which is just one part of the index notation (and Einstien's contribution to the notation). It’s also trivial to get used to, and is without fail explicitly stated and linked "we are using the summation convention in this equation/what follows". What isn't trivial is knowing what the "punctuation" in the indices read. (Even a couple of tensor analysis books I have do not even include the index "punctuation": the theoretical physics book sourced above does, but do typical readers have access to degree-level books?).
By the way, there is another convention not included for spinors (since presumably not used for tensors): dotted indices for right-chiral spinors (no implication to include though)... F = q(E+v×B) ⇄ ∑ici 18:10, 10 April 2012 (UTC)
Let us assume that the article Einstein notation is about the summation convention, and that if there is conflict with actual usage, then it is a matter of renaming that article. Then IMO the answer is simple: the summary should be in Tensor, I propose under a subsection of its own in the section Notation. The ues of each notation can later be elaborated under the following section, Operations. — Quondum 18:46, 10 April 2012 (UTC)
I said identically above... F = q(E+v×B) ⇄ ∑ici 19:54, 10 April 2012 (UTC)
(Again you're repeating youself). Anyway the summary is really good, and by the look of it no one opposes the main article on tensors, so why don't you just add it? Maschen (talk) 20:05, 10 April 2012 (UTC)
The point of coming to this Wikiproject page is to discuss things for improving maths articles. Just as well I did, since everyone above has provided careful guidance (else would have just pasted it to abstract index notation by my own sore misunderstanding of that name, but waiting a little was worth it). You're right though - it'll be done now... and take discussion to the talk page there... F = q(E+v×B) ⇄ ∑ici 20:15, 10 April 2012 (UTC)
Done, see here. Thanks, F = q(E+v×B) ⇄ ∑ici 20:26, 10 April 2012 (UTC)
Nice work! Maschen (talk) 20:44, 10 April 2012 (UTC)
Actually, that is quite terrible (And I'm not just talking about the MOS rape going on there). It doesn't make much sense to talk about notation conventions for (covariant) derivatives in an article that is just about normal tensors, not tensor fields. (Not to mention that it suggests that this notation is universalm while it is my experience that the comma/semicolon notation is slowly going extinct, and rightly so I might add.) I will revert for now.TR 07:00, 11 April 2012 (UTC)
Thank you fantastically!! - do what the hell you like!!... For one thing: it wasn't just for covariant tensors either, and in the cited source it happens that those comma/semicolon derivatives are in those index positions, which is why it was written that way. Anyway its on you now... I tried... F = q(E+v×B) ⇄ ∑ici 07:45, 11 April 2012 (UTC)

To Sławomir Biały: So called 'abstract index notation' is for people who want to use index notation (because it is by far the most convenient way to express the ideas) while still pretending that they are not using index notation to manipulate arrays of numbers but instead some abstract notion of tensors which requires the use of " ⊗ {\displaystyle \otimes } " and such. So it allows people to do algebraic manipulations with indices, but if you dare to try to figure out what it means by substituting actual numbers, then you are violating the arbitrary rules of 'abstract index notation'. What a load of s--t. JRSpriggs (talk) 03:21, 11 April 2012 (UTC)

Potential alternative: Create an entire article dedicated to "index notation for tensors/tensor fields", and merge all notation content from
  1. Index notation (leave the computer science stuff and re-direct the maths section - for an introduction)
  2. Einstein notation (explain summation convention + applications)
  3. Raising and lowering indices (explain + applications)
  4. Symmetric tensor (explain the symmetrization notation)
  5. Antisymmetric tensor (explain the antisymmetrization notation)
  6. the summary above
into it (if articles become empty, they will clearly be redirects to the new main article). For articles 4 and 5, rather than "merge" I mean "copy and paste", but give a couple of examples in more detailed explanation.
That way, when it comes to explaining a tensor equation (in physics, maths or anything else) - we just link to that one article every time and everything will be in one place for convenient reference (the article which uses whatever metric and signature is a separate link with explanation):
"For details on the summation convention and how to raise and lower indices etc.. see the article tensor notation."
and of course it will not have to be re-explained in any other article because it can be linked?... The reason for kicking up such a fuss on this particular concept is becuase it's hoped to make life easier for the typical reader is all...
On the other hand... what are the chances of people agreeing with this thought? None. (Really - no offense taken, if you have a genuinely good reason to disagree please tell). F = q(E+v×B) ⇄ ∑ici 08:51, 11 April 2012 (UTC)
There is Tensor notation that could be used as a central summary (currently a redirect to Glossary of tensor theory). The name is probably too broad for the purpose, though. There is also Tensor index notation, which might be quite suitable (currently a redirect to Einstein notation, which I feel should be renamed to Einstein convention). How about using Tensor index notation for your proposal? On a side note, until an article is found for this, I feel it should remain in Tensor. — Quondum 09:15, 11 April 2012 (UTC)
I think having a separate article on tensor index notation is probably a good idea. Having a place to link to for explaining notation is good, and having all the notation gathered in one place is good as well. I would not actually merge any of the notational content from the articles mentioned above though. Having the notation explained along side the concept it is supposed to express is very useful as well. There is no reason why we shouldn't have both.TR 09:22, 11 April 2012 (UTC)
As said this is only a potential alternative which may not happen, but thanks for pointing out the better link and title. For now (in principle) the summary above in the tensor article is plenty, but user:TimothyRias has reverted twice already... F = q(E+v×B) ⇄ ∑ici 09:20, 11 April 2012 (UTC)

Stacks project dump

I don't have any particular plan, but what does anyone think of dumping materials from Stacks project ? (Apparently, there is no Misplaced Pages article on the project.) On the one hand, this is the quickest way to increase our coverage of scheme theory, and even more reliable (more reliable than some random graduate student.) On the other hand, ah..., there might be an issue like quality for instance. (The project is licensed under GFDL, which is compatible with Misplaced Pages. I know some people like/enjoy actual writing. But I'm more interested in the ends than the means. -- Taku (talk) 12:48, 10 April 2012 (UTC)

Oh, the materials I have in mind are statements of theorems and examples. -- Taku (talk) 12:51, 10 April 2012 (UTC)