Wikipedia talk:WikiProject Mathematics/Archive/2008/Feb

Calyx
The recently created stub, Calyx (mathematics), has been nominated for deletion. Is this surface notable? AfD discussion linked above. Geometry guy 19:02, 14 February 2008 (UTC)


 * Of the two sources, this one is a list of random shapes (some of which are inaccurate - see it's "cube"), but this one seems to mention it in a somewhat relevant mathematical context. However, I'm not sure if this is any sort of standard name, or if this surface has any meaningful notability beyond this single use. Note that the image in this PDF seems to be the same one as from the first source (not sure why/how that occurred or if it tells us anything). --Cheeser1 (talk) 19:37, 14 February 2008 (UTC)

Gauss-Markov-Aitken theorem?
Aitken's generalization of the Gauss-Markov theorem does not appear to get the recognition it deserves. Would it be in order to call the general theorem Gauss-Markov-Aitken? It it called this in any text book? Petergans (talk) 15:10, 15 February 2008 (UTC)


 * It is for instance here. --Lambiam 19:29, 15 February 2008 (UTC)

Coordinated math vandalism
I noticed some rather disturbing vandalism over at Runge-Kutta methods. Apparently this is part of a wider coordinated effort to vandalize the math articles. See. A bit of Googling shows that there are indeed attempts to organize an attack from outside Wikipedia. I don't know for how long this has been going on, although it seems relatively recent. So be on the lookout for dubious edits from anon IPs. Silly rabbit (talk) 21:58, 16 February 2008 (UTC)
 * It seems to stem from Encyclopedia_Dramatica:Today's_featured_article/February_16,_2008. Their todays featured article is on vandalising the Runge-Kutta article. Hence the damage is likely to go down tomorrow but it may get low level vandalism after that. --Salix alba (talk) 00:51, 17 February 2008 (UTC)
 * When people are doing the final cleanup, someone should check if this anon edit with no edit summary from 2008-01-21 is valid: 4101 -> 4104. I figure there is no point right now. JackSchmidt (talk) 18:03, 17 February 2008 (UTC)
 * I noticed some subtle vandalism too recently in ODE articles   . It would be a big problem if it were part from a trend. Such things are missed by people reverting vandalism and would be hard to catch later. Oleg Alexandrov (talk) 21:08, 17 February 2008 (UTC)

Invalid proofs
I think that here it is not clear why substitution is an invalid operation.--Pokipsy76 (talk) 20:53, 18 February 2008 (UTC)


 * The argument is correct. I will try to add a comment. Loisel (talk) 21:36, 18 February 2008 (UTC)


 * Substituting is correct, but taking the principle cube root is not. CRGreathouse (t | c) 21:37, 18 February 2008 (UTC)


 * Well, whatever. Substituting does add a root which is not part of the original system. Think of it this way. Let f(x,y)=x^2+y+1 and g(x)=-1-1/x. The first equation says that f(x,x)=0, its solutions are $$exp(\pm 2\pi i/3)$$. The third equation says that, for such an x, we have g(x)=x. However, this relation is not verified for all x. The substitution is f(x,g(x))=0. This new equation is solved whenever g(x)=y and f(x,y)=0. Apart from the solutions of the first equation, observe that also g(1)=-2 and f(1,-2)=0. Hence, substitution does introduce new solutions, and that is because x=g(x) is not verified for all x, but rather only for the solutions of f(x,x)=0. Loisel (talk) 21:41, 18 February 2008 (UTC)

Please. Write $$\exp(\pm 2\pi i/3)\,$$, not $$exp(\pm 2\pi i/3)\,$$. Michael Hardy (talk) 22:10, 18 February 2008 (UTC)


 * Oh bite me, on the talk page! Loisel (talk) 00:27, 19 February 2008 (UTC)

This has come up before, and I'd like to direct people's attention to this article's talk page. This article is seriously unencyclopedic, and it would require either alotof work, or deletion. I feel like maybe some opinions are needed there to hash out whether the article is worth fixing (instead of deleting the article after wasting time improving it). --Cheeser1 (talk) 22:15, 18 February 2008 (UTC)

Why this proof have ben removed? I found it interesting...--Pokipsy76 (talk) 08:12, 19 February 2008 (UTC)

Radius of curvature
I'm think that someone who understands this stuff should take a look at Radius of curvature. It starts with a strange and confusing definition, and it never really becomes clear what the article is supposed to be about. As far as I know, the "radius of curvature" (of a plane curve) is simply the reciprocal of the curvature, so there's no need to explain both things separately in separate articles. On the other hand, the Radius of curvature article seems to be preoccupied with the radii of curvature of ellipsoidal surfaces and suchlike. Is that a different meaning of the term, or is it just a specific application of the usual definition? I wonder if all the information about the generic meaning should be merged into the one article: curvature, and a separate article created to deal solely with the specifics of ellipsoids. Matt 19:46, 20 February 2008 (UTC).


 * Thanks for the note. I've converted that page into a disambiguation page, fixed the links to the best of my abilities, and moved the text to Radius of curvature (applications) (where it is crying for attention from someone understanding what all these incoming links want it to be). Arcfrk (talk) 00:09, 22 February 2008 (UTC)
 * Some of the link changes associated with that move and the new dab page are incorrect. Radius of curvature (optics), for example, is particular to the curvature of optical surfaces as used in optical design. You have changed "radius of curvature" in many optics articles to link there, when it should link to the standard definition of r.o.c. instead. In addition, this page move should have been discussed first. I have proposed reversing it at Talk:Radius of curvature (applications).--Srleffler (talk) 14:33, 22 February 2008 (UTC)


 * Well, they are optics articles, aren't they? Then it would stand to reason to discuss all possible uses of radius of curvature in optics in the article "Radius of curvature (optics)". Certainly, from the point of view of maintenance this would be preferable (why should anyone be left guessing that a use in optics is not the use in optics?). In the short run, feel free to change them to correct links — radius of curvature is presently explained best in the article "Curvature". Arcfrk (talk) 22:20, 22 February 2008 (UTC)


 * I think there are several definitions of "radius of curvature" in use. Since the concepts are similar/related, it makes sense to have one article that deals with all of them, explains them clearly, and explains the differences between them.--Srleffler (talk) 14:33, 22 February 2008 (UTC)


 * The disambiguation page seems more prudent. Arcfrk (talk) 22:20, 22 February 2008 (UTC)


 * But are they really different definitions, or is there really only one underlying mathematical definition which crops up in a number of different situations? Whatever the answer, I think that the old Radius of curvature article is/was a mess, so I don't think we should just put things back to how they were and leave it at that. Unless I am totally wrong, "Radius of curvature" (unqualified) needs to kick off with the standard, general mathematical meaning (i.e. the reciprocal of curvature). Then details of the applications (such as to lenses, to ellipsoids, or whatever) can follow, or links to separate articles where there is enough application-specific detail to warrant it. If there are any fundamentally different definitions of RoC then that needs to be made clear. Matt 18:51, 22 February 2008 (UTC).

Insulting mathematicians?
The new article Proof by intimidation appears to be an attempt to insult mathematicians. Instead of talking in a general way about the logical fallacy of that name, it ascribes it especially to lectures in mathematics. JRSpriggs (talk) 06:45, 22 February 2008 (UTC)
 * I don't think the article is meant to be insulting. It definitely needs some cleanup.  One of the lecturers accused of proof by intimidation is the physicist Richard Feynman, so I don't think the focus is entirely on mathematicians.  It is a little unclear to me how much humor should be in the article itself (the article is categorized as humor, joke, etc.).  I think it is intending to be funny by citing a source that is clearly not reliable, but it is unclear to me if that is a good idea. I stopped cleaning it up because the use of English was strange, and I was not positive if it was a dialect problem.  There were several near-homophones (I'm sure there is a word for that), being used instead of the "correct" word, but it happened too many times for me to be sure.  At any rate, the article definitely needs work, and probably needs several editors editing it to make sure the article itself does not become an In-joke. JackSchmidt (talk) 07:19, 22 February 2008 (UTC)
 * I like the article as it stands (currently), if the citation of Rota is accurate. I once spent an hour in Lazebnik's office arguing about whether something was obvious. Sometimes even math is funny in both senses of the term ("haha" and "peculiar"). Pete St.John (talk) 20:15, 22 February 2008 (UTC)

Probability semi-protected until 1 March
Thanks to Jmlk17, "probability" is semi-protected for one week to prevent vandalism by unregistered and newly registered users. I requested this as I was getting fed up with the level of vandalism and disruptive edits. As I said in my request, This is a vital article rated by WikiProject Maths as Top priority but only Start-class quality and the relatively small number of editors with the necessary expertise to improve it are likely either to be distracted or put off entirely by the level of vandalism.

So come on all you probabalists out there, you've now got a week free of distracting vandalism to improve the flagship article for your subject! (Nothing like a tight deadline to help concentrate the mind...) --Qwfp (talk) 12:29, 23 February 2008 (UTC)

Solution description of Monty Hall problem
Can some of you folks comment at Talk:Monty Hall problem? Thanks. -- Rick Block (talk) 16:40, 23 February 2008 (UTC)

The numbers template
numbers has again popped up over coutnless math articles, right on top, above any pictures, and rather wide. I suggested that we remove it. Should we perhaps even nominate it for deletion? Oleg Alexandrov (talk) 16:54, 23 February 2008 (UTC)


 * The reason I included it on the pages for basic number sets is because I couldn't get to any of the other sets from a given set's page. As I forgot the name for the set Z ("Integers"), it wasn't under "Z", and I couldn't navigate to it by looking up similar pages like "natural number" or "complex number". Since N, Z, Q, R, C etcetera are related, I think there should be a menu that connects them. Perhaps a smaller one than what we see now, but it's greatly appreciated if the pages are more linked. It now appears that these sets don't have any connection. A footer menu could also be helpful. SuperMidget (talk) 17:38, 23 February 2008 (UTC)


 * It might be better rewritten as a navbox and moved to the bottom of these articles, if mark-up will work within a navbox. Maybe you'd like to have a look at that SuperMidget? (in your userspace to start with i'd suggest) --Qwfp (talk) 17:50, 23 February 2008 (UTC)


 * I like the template, but maybe a navbox would be better. CRGreathouse (t | c) 18:34, 23 February 2008 (UTC)


 * What do you think of SuperMidget/navboxNumbers? It's quite difficult to make it look nice, since not all sets have symbols, and it seems impossible to use wikitables inside the navbox. Please don't edit it directly on my userpage, but copy it first. SuperMidget (talk) 18:57, 23 February 2008 (UTC)
 * Blimey, that was quick! Nice work. I think it's already a big improvement on numbers. Oleg? --Qwfp (talk) 19:42, 23 February 2008 (UTC)
 * Looks good. I think we should overwrite numbers with any of these (which are by the way horisontal, not vertical), and move them to the bottom of articles. We should not leave numbers the way it is since at some point it will again pop up tall and wide on top of all number articles. Oleg Alexandrov (talk) 22:13, 23 February 2008 (UTC)
 * The navboxes themselves are oriented horizontally, but the lists in them are either horizontal or vertical. If we would replace the Numbers by any of the navboxes, I think a lot of pages in the Maths portal will get distorted. The original template might be of use there. Probably if we replace the whole thing, it will be reverted instantly. It may be better to create a new template NumberSystems. This name would also be better so that it won't be used on every page about a number in general. SuperMidget (talk) 10:35, 24 February 2008 (UTC)
 * Looks better. The last section could be in three columns, too. If one of the items in the 2nd section could be suppressed, it would look even more smooth. Another suggestion is to make the subsections hideable. Jakob.scholbach (talk) 20:09, 23 February 2008 (UTC)
 * Another point is to decide which items should actually be included. I have personally never met Tessarines, which doesn't say anything about their notability, but as a general idea I'd suggest to include in the template only topics which have a non-stub-coverage in the corresponding article. One link I do miss in the template right now would be p-adic numbers. Jakob.scholbach (talk) 20:16, 23 February 2008 (UTC)
 * The template has the p-adics uner other. Personally, I find that having terms I don't know (likewise, tessarines for me) if the best part of such templates. CRGreathouse (t | c) 13:33, 24 February 2008 (UTC)


 * I don't think this is large enough to benefit from hideable subsections (unlike, say, ProbDistributions which certainly would). To make it a bit smaller, might I suggest suppressing the word "numbers" from the entries where it occurs in the same way that ProbDistributions suppresses "distribution" ? --Qwfp (talk) 20:33, 23 February 2008 (UTC)
 * I tried out some ideas, see SuperMidget/navboxNumbers. Personally I prefer the compact vertical table layout (first one). The vertical lists may be unconventional for a navbox, but it's much more readable than the horizontal navbox (see for yourself). I will not bother with questions of what should be in the box and what not.. I just want to put something on the pages for easy navigation. SuperMidget (talk) 21:41, 23 February 2008 (UTC)
 * I also like the compact vertical table. CRGreathouse (t | c) 21:44, 23 February 2008 (UTC)
 * Wouldn't Number systems be a better heading than Numbers? --Lambiam 22:57, 23 February 2008 (UTC)

I removed the template from the articles for now. I see there is good progress here towards an alternative version of this template to go to the bottom of articles. On top it was really staying in the way of the very nice illustrations many of the number articles have. 01:55, 24 February 2008 (UTC) —Preceding unsigned comment added by Oleg Alexandrov (talk • contribs)

Since there's no more response to this discussion, I created a new template Number Systems that can be used at the bottom of the relevant pages. Please continue any discussions about the template there. I put it on Natural number for a start, but I leave the rest up to you. SuperMidget (talk) 19:47, 26 February 2008 (UTC)

Mortgage-related entries
FYI: Entries related to mortgages, such as Mortgage Calculator, Mortgage, and Mortgage loan could use some attention from WikiProject Mathematics. --Pleasantville (talk) 23:24, 25 February 2008 (UTC)

Vector formatting
I don't want to cause more of a fuss than I have already, but I am concerned about some formatting changes to vector-related articles (so far only cross product and vector (spatial).) The question is whether a vector, when written inline in the text, should be typeset at $$\langle a,b,c\rangle$$ or as (a,b,c). I favor the latter since it doesn't force inline PNG rendering (which takes time, may cause the text to format badly, etc.) Furthermore the $$\langle\cdot,\cdot\rangle$$ is the preferred notation of most physicists and differential geometers for an inner product, such as a metric. Silly rabbit (talk) 21:52, 26 February 2008 (UTC)
 * Concur. &mdash; Arthur Rubin |  (talk) 22:00, 26 February 2008 (UTC)
 * I also concur. To be thorough, one might check if physicists would write |1,2,3> for a vector, but I would stick with (1,2,3), or [1,2,3] if one is not worried about the wiki-parser and wants the vector to be a "row vector".  If someone knows of a plain text alternative for \langle and \rangle, I would love to fix lots of other articles.  In most fonts, ⟨ and ⟩ are not much different than . JackSchmidt (talk) 23:08, 26 February 2008 (UTC)
 * Concur. In physics, |•> is Dirac's bra-ket notation for a quantum state. Although a quantum state can be represented as a vector in Hilbert space, it's not used as general notation for a vector in simpler contexts (see that article for full story). (I've seen <•> sometimes used to denote a mean in physics books, rather confusingly, and i'm sure but i've seen it somewhere on WP but I think WP is best avoiding that particular notation.) Qwfp (talk) 11:20, 27 February 2008 (UTC)


 * I don't recall seeing the notation $$\langle a,b,c\rangle$$ for a vector in any mathematics, physics, or engineering text. -- Fropuff (talk) 00:16, 27 February 2008 (UTC)
 * Yep, (1,2,3) is the standard notation. There may be a little of confusion with the notation for points, but after all, a point can be thought of as a vector starting at the origin. Oleg Alexandrov (talk) 04:43, 27 February 2008 (UTC)
 * I've seen those in texts or maybe at least in classes (they're "chevrons" as I recall), but parentheses are just as good. Parens are easier, although other html alternatives are available; these are the two that come to mind:
 * I assume these are helpful (?) --Cheeser1 (talk) 05:16, 27 February 2008 (UTC)
 * There has been quite a debate on Talk:Bracket about the proper symbols used to represent angle brackets.
 * There has been quite a debate on Talk:Bracket about the proper symbols used to represent angle brackets.

Some are vigorously against less than or greater than as semantically incorrect, however the strange unicode characters don't display unless people have fancy fonts installed, so other prefer to keep things simple. --Salix alba (talk) 07:50, 27 February 2008 (UTC)
 * I don't have fancy fonts (I don't think) and I see "single-left angle quotation" (which is what I called "chevrons" above). I don't see the others. --Cheeser1 (talk) 08:12, 27 February 2008 (UTC)
 * While I can see there's an argument that an article on Brackets should distinguish these and make clear the limitations of most current computer set-ups (including mine), I'd take the pragmatic line that other articles are ok using <> for angle brackets until such time as most computer set-ups can display the proper left angle bracket or mathematical left angle bracket or both. (single-left angle quotation should be used only for what its name suggests, i.e. languages such as French that often use this instead of quote marks. It's too small for an angle-bracket) Qwfp (talk) 11:35, 27 February 2008 (UTC)


 * I would like to "vote" on using the Standard keyboard symbols ("less than" & "greater than") (&lt; &gt;), since it seems like using the option is frowned upon.
 * The book that I have been using shows vectors as &lt; a, b, c &gt;, (as it uses ( x, y, z ) for points.) I also would like to argue that unless given a starting point, all vectors (technically) begin at the origin.
 * Ajl772 (talk) 21:06, 27 February 2008 (UTC)

Revision of navigational template for probability distributions
After some discussion at Template talk:ProbDistributions I've drafted a revised navigational template to replace ProbDistributions, which has grown too large. (This is the template at the bottom of some but not all of the probability distribution articles, not the infobox on the right.) For the moment the draft version is at User:Qwfp/tempprobdist. To keep all the conversation in one place, please post comments at Template talk:ProbDistributions not here. If I don't hear any views to the contrary, I'll go ahead and replace ProbDistributions at the weekend. Thanks, Qwfp (talk) 18:53, 27 February 2008 (UTC)

award-winner categories
Working with awards and award-winners and CFDs -- and now TFDs! -- all this time it occurred to me that perhaps the best solution is a single compressed template. So, I drafted Template:Awardwinners; other editors' thoughts would be appreciated. Maybe it'll work, maybe not, but I thought I'd at least ping some other folks involved in award-winner discussions for their opinions and thoughts. The math folks were particularly enamored of the math awards, so those of you with thoughts -- pro or con -- about award-winner categories being applied to articles, please stop by the template page and give your thoughts and reactions. --Lquilter (talk) 19:23, 27 February 2008 (UTC)

Trolling at Vector (spatial)
Any chance someone else is willing to handle the issue over at Talk:Vector (spatial)? I'm a bit stressed, and I don't feel like putting up with this trolling user. Silly rabbit (talk) 21:58, 21 February 2008 (UTC)


 * I spend all my time at the WQA, I might as well step in on this one. I've removed the entire new thread the user started to launch personal attacks at you. Hopefully that's a start. --Cheeser1 (talk) 22:13, 21 February 2008 (UTC)


 * I believe I'm the one labelled a trolling user. I would beg to differ.  I believe I have some significant contributions to make to Talk:Vector (spatial), given a fair opportunity.   --Firefly322 (talk) 03:41, 25 February 2008 (UTC)


 * One's editing experience is generally more pleasant if one manages to refrain from personal attacks, insulting qualifications, and snide remarks. Labelling editors you disagree with "Intellectually Unqualified" or their edits "Irrational Behavior" is not in accordance with proper Wikiquette, and may evoke a suspicion of trolling. Also, while the use of talk pages is generally recommended and commendable, flooding a talk page is not productive. --Lambiam 14:01, 25 February 2008 (UTC)


 * I took a look there, and thought that some of the difficulty was from defining vectors as "quantities". So as to distinguish vectors from scalars clearly, I said that (paraphrasing myself), "vectors are quantitative but not quantities. The are objects composed from numbers (e.g. ordered lists of numbers), but not numbers themselves". Imagine my surprise when they found numerous physisics textbooks referring to vectors as quanitities :-) I'd forgotten that nomenclature. They point out that quaternions are numbers, and quaternions are vectors, therefore vectors are numbers :-) Pete St.John (talk) 19:24, 25 February 2008 (UTC)
 * Physicists say "dimensioned quantity" when they mean a number with some unit of measurement attached, such as 1.8755459 × 10 &minus;18 C. Perhaps by "vector quantity" they similarly mean something like an "oriented quantity", a number with a direction attached. Something like this: "In some contexts, e.g. in the formula for kinetic energy, velocity can be handled as a scalar quantity, but in the law of conservation of linear momentum it is a vector quantity." --Lambiam 22:51, 25 February 2008 (UTC)
 * I think that's about right, except to get even more pedantic, i think velocity is always a vector; speed is the corresponding scalar... Qwfp (talk) 23:46, 25 February 2008 (UTC)
 * That's why I wrote "can be handled as" and not "is". In any case, dictionaries typically make no such distinction, and plenty of professional articles written by physicists (including Michelson) freely use "velocity of light" where clearly the scalar quantity is meant. --Lambiam 10:13, 26 February 2008 (UTC)
 * My apologies Lambiam, I regret writing that now. I clicked "edit" meaning to say i agree ((as does Google)) that "vector quantity" and "scalar quantity" are commonly used in physics. I see little wrong with these phrases myself. I'm sorry I went off into needless and distracting late-night pedantry instead. Qwfp (talk) 13:55, 26 February 2008 (UTC)

Can we have an extra pair of eyes at Vector? I fear that the quality of the article is rapidly deteriorating thanks largely to the efforts of one persistent new editor qwho behaves like a troll. In particular, I've rewritten the lead to take care of the basics of vectors (and remove the cruft) which quickly got reverted with no reason. Sockpuppetry is also a concern, since he alternately uses an anon account and a registered account. Arcfrk (talk) 02:09, 26 February 2008 (UTC)


 * Mr. Silly Rabbit and I have already apologized to each other for what happened a few days ago. Since then, the discussion seemed to be moving rapidly towards consensus. I believe Mr. Arcfrk's comments here and in the other discussion are rash and have slowed progress towards mutual agreement as to the type of vector described in vector (spatial).  In my mind, Mr. Arcfrk really seems out of touch with Mr. Johnson's and my consensus on some points.  And how critical such a consensus is and how it has not happened before now. --Firefly322 (talk) 03:39, 28 February 2008 (UTC)


 * I haven't figured out the (three?) senses of vector in discussion, yet, but I think patience will pay off. I suspect we would be better off with "Vector (abstract)" vs "Vector (introduction)" but we don't organize articles the way I would myself. The "spatial" vs "physical" distinction still confuses me. Pete St.John (talk) 20:15, 28 February 2008 (UTC)

There's now also a related deletion discussion: Articles for deletion/Vector (physical). —David Eppstein (talk) 22:02, 28 February 2008 (UTC)

Respect external references or internal consistency?
At Gauss-Newton algorithm, Petergans would like the step be given by
 * $$(\mathbf{J}^T\mathbf{J})\delta\boldsymbol\beta^k=\mathbf{J}^T \mathbf{r},$$

to be consistent with what is used at non-linear least squares, which he wrote.

I prefer the formula


 * $$(\mathbf{J}^T\mathbf{J})\delta\boldsymbol\beta^k=-\mathbf{J}^T \mathbf{r},$$

(note the minus), because that's all the references I've seen use. The discrepancy with the sign is because Petergans uses residuals of a special form, while the formula with the minus works for general residues.

So, what would readers prefer, to be consistent with other books and websites, or with another Wikipedia article (written by the same editor who wants the change at Gauss-Newton). We've been going back and forth for a few days on this, with no agreement. More comments are welcome at Talk:Gauss-Newton algorithm. Oleg Alexandrov (talk) 06:00, 27 February 2008 (UTC)


 * In general, I would prefer that articles be consistent, provided that someone uses the notation. Certainly, if two related Wikipedia articles use different notation, that should be noted.
 * See, for example, matrix calculus, where our references use different notations.
 * I haven't checked this particular article set, though. &mdash; Arthur Rubin |  (talk) 13:09, 27 February 2008 (UTC)


 * Two suggestions: 1) rewrite the other article to use "general residues" instead of the special form, or 2) Add some variant of the following sentence to the article: Many textbooks place a minus sign in the above formula; this is correct when general residues are used, but not the special residues used in this and other articles. linas (talk) 04:58, 29 February 2008 (UTC)

Super-recursive algorithm
A new editor has started working to improve this article, but as a new editor is unfamiliar with NPOV and NOR. It would be helpful to have a few other experienced editors look through the article to smooth out any biased claims, while still trying to keep the changes that improve the article or add detail in a neutral way. &mdash; Carl (CBM · talk) 23:25, 28 February 2008 (UTC)