Wikipedia talk:WikiProject Mathematics/Archive/2016/Nov

Scale of chords
The article titled Scale of chords is incomprehensible without the link to the Google Books item on engineering drawing. Maybe I'll do something with it, unless someone else gets there first. Michael Hardy (talk) 04:09, 1 November 2016 (UTC)

Semi-inner product
I once introduced the terminology semi-inner product in inner product to mean a product satisfying all axioms of inner product except
 * $$\langle x,x\rangle = 0 \Rightarrow x = \mathbf{0}.$$

This definition is used in John B. Conway, A course in functional analysis. It turned out to clash with the official Wiki-definition given in semi-inner-product. I want to reintroduce it, under a different name, because I need to reference it elsewhere. For one thing, in semi-inner product spaces the Cauchy–Schwarz inequality holds.

What would be a good common name for it? YohanN7 (talk) 13:38, 1 November 2016 (UTC)


 * But I see there: "The definition presented here is different from that of the "semi-inner product" in standard functional analysis textbooks". If so, it should not be treated as "the official Wiki-definition". Boris Tsirelson (talk) 16:45, 1 November 2016 (UTC)


 * Okay..., but that might add up to hard work to change. YohanN7 (talk) 11:00, 2 November 2016 (UTC)

Perhaps renaming Semi-inner-product to Semi-inner-product space is the best option. It would even match Lumer's original publication on the subject. Fortunately, there aren't many incoming links to the article. YohanN7 (talk) 09:54, 3 November 2016 (UTC)

Secant plane
The article titled Secant plane is perhaps imperfect in its present state. Michael Hardy (talk) 17:43, 6 November 2016 (UTC)

Light bulb model
Does anyone know what the alleged "counterintuitive" result is in the article titled Light bulb model? Michael Hardy (talk) 18:17, 6 November 2016 (UTC)


 * It seems to be a parody of a Wikipedia article. For example, the image captioned "Many Light Bulbs operated simultaneously" has many lightbulbs, only one of which is being operated. Mgnbar (talk) 23:40, 6 November 2016 (UTC)

Proposed move from ±1-sequence to sign sequence
There's an ongoing discussion at Talk:±1-sequence about a proposed move from ±1-sequence to sign sequence. Please participate. —David Eppstein (talk) 06:43, 11 November 2016 (UTC)

"degree" or "order"
Should one refer to the "degree" of a pole of a meromorphic function, or to the "order" of the pole? The former seems analogous to the degree of a polynomial, so that seems to count in its favor. Michael Hardy (talk) 18:42, 11 November 2016 (UTC)


 * Searching in GBooks and GScholar, order of a pole seems much more common. I have seen degree of a pole in the signal processing literature, however. --Mark viking (talk) 20:17, 11 November 2016 (UTC)
 * IMO, a century ago, "order" and "degree" were almost synonymous. We still have a dab page Order of a polynomial. Nevertheless, the modern trend seems to use "degree" for global properties and "order" for local properties. For example, the degree of an affine variety is the sum of the orders (of multiplicity) of its intersection with a linear variety of the right dimension. An important class of meromorphic functions consists of the rational functions, which have the property that the signed sum of the orders of its poles and zeros is equal to zero. How would you say that if you use degree for the poles. Moreover, the degree of a rational function is the difference of the degrees of its numerator and its denominator (or, in some contexts, the maximum of these degree); this has nothing to do with the orders of zeros and poles.
 * In summary, I agree with Mark. However, we must mention that old texts use "degree of a pole". D.Lazard (talk) 21:05, 11 November 2016 (UTC)

Lie derivative
Lie derivative has been nominated as a good article and needs a reviewer. It would probably be more important for such a reviewer to be somewhat familiar with Lie derivatives and with how we write about mathematics within Wikipedia than it would to have much experience with good article reviewing. If you're interested, see WP:GAN for the nomination (scroll down to "Mathematics") and reviewing instructions. —David Eppstein (talk) 00:41, 12 November 2016 (UTC)

Two mathematical AfDs
Additional opinions at Articles for deletion/Jacobi point and Articles for deletion/Visible factor number would be welcome. —David Eppstein (talk) 19:59, 12 November 2016 (UTC)

Interview invitation from a Wikipedia researcher in University of Minnesota
Hello all,

I am Bowen Yu, a Ph.D. student from GroupLens Research at the University of Minnesota - Twin Cities. Currently, we are undertaking a study about turnover (editors leaving and joining) in WikiProjects within Wikipedia. We are trying to understand the effects of member turnovers in the WikiProject group, in terms of the group performance and member interaction, with a purpose of learning how to build successful online communities in future. More details about our project can be found on this meta-wiki page.

If you are interested in our study and willing to share your experience with us, please reach me at bowen@cs.umn.edu. The interview will be about 30 - 45 minutes via phone, Skype or Google Hangout. You will receive a $10 gift card as compensation afterwards.

Thank you, Bowen Bobo.03 (talk) 23:06, 13 November 2016 (UTC)

Jacob Barnett
Back at AfD: Articles for deletion/Jacob Barnett (3rd nomination). Sławomir Biały (talk) 01:00, 14 November 2016 (UTC)

Latest at User:Mathbot/Changes to mathlists
At User:Mathbot/Changes to mathlists, this is the latest list of articles that are either newly categorized or new:
 * Added  0-1 quadratic knapsack problem
 * Added  Asymptotic dimension
 * Added  Bernoulli's triangle
 * Added  Frobenius inner product
 * Added  Fully irreducible automorphism
 * Added  Gradient discretisation method
 * Added  Graph entropy
 * Added  Individual pieces set
 * Added  Multidimensional Empirical Mode Decomposition
 * Added  Normal contact stiffness
 * Added  Permutational analysis of variance
 * Added  Topological recursion
 * Added  Universal chord theorem
 * Added  Universal chord theorem

Michael Hardy (talk) 21:24, 15 November 2016 (UTC)

Enneahedra vs nonahedra
An anonymous editor has been pushing to rename enneahedron to nonahedron (in a clumsy way, but I hope to redirect that to a more constructive discussion). Please participate at Talk:Enneahedron if you have an opinion. —David Eppstein (talk) 07:31, 17 November 2016 (UTC)

New or newly categorized articles at User:Mathbot/Changes to mathlists
Here are the latest new or newly categorized articles at User:Mathbot/Changes to mathlists:

November 22, 2016

 * Removed Canonical basis (disambiguation) (article deleted/does not exist)
 * Removed Canonical line bundle (disambiguation) (article deleted/does not exist)
 * Removed Glossary of graph theory (is a redirect to Glossary of graph theory terms)
 * Removed Natural neighbor (is a redirect to Natural neighbor interpolation)
 * Removed Weighted planar stochastic lattice (WPSL) (is a redirect to Weighted planar stochastic lattice)
 * Added  Calculus I
 * Added  Glossary of graph theory terms
 * Added  Natural neighbor interpolation
 * Added  Nonagonal prism
 * Added  Tattvacintāmaṇi
 * Added  Weighted planar stochastic lattice


 * Mathematicians:added  Janusz Grabowski
 * Mathematicians:added  Vladimir Burkov

— Preceding unsigned comment added by Michael Hardy (talk • contribs)
 * Note also the deletion discussion at Articles for deletion/Calculus I. —David Eppstein (talk) 21:17, 22 November 2016 (UTC)

Birch : Stan Laurel :: Swinnerton-Dyer : Oliver Hardy
More comments are welcome at Talk:Birch and Swinnerton-Dyer conjecture. Solomon7968 07:54, 25 November 2016 (UTC)

New or newly categorized articles at User:Mathbot/Changes to mathlists
Here are the latest new or newly categorized articles at User:Mathbot/Changes to mathlists:

November 25, 2016

 * Removed Malcev operation (is a redirect to Heap (mathematics))
 * Removed Purplemath (article deleted/does not exist)
 * Removed Risk limiting post-election audit (is a redirect to Risk-limiting audit)
 * Removed Santangelo Field (S-Field) mathematics (is a redirect to Santangelo field)
 * Added  Annales de Gergonne
 * Added  Notakto
 * Added  Risk-limiting audit
 * Added  Santangelo field


 * Mathematicians:added  Kim Thomas

November 24, 2016

 * Removed Complex vector space (disambiguation) (article deleted/does not exist)
 * Added  Carry-less product
 * Added  Fibonacci nim
 * Added  Santangelo Field (S-Field) mathematics


 * Mathematicians:added  Alfred Inselberg

November 23, 2016

 * Removed Cobordism theorem (disambiguation) (article deleted/does not exist)
 * Removed Nonagonal prism (is a redirect to Enneagonal prism)
 * Added  California Mathematics Project


 * Mathematicians:added  James Morton Hyslop

Michael Hardy (talk) 16:25, 25 November 2016 (UTC)

Italicizing lower-case Greek letters
TeX and LaTeX, and Wikipedia's notation that is consistent with those, sets lower-case (but not capital) Greek letters in italics, thus:
 * $$ \Gamma(\sin\theta) = x \, $$

WP:MOSMATH accordingly prescribes that style for non-TeX notation, thus:
 * Γ(sin θ) = x

However, it seems almost universal not to italicize lower-case Greek letters in Wikipedia articles. One sees things like this:
 * exp(−βx)

when they ought to look like this:
 * exp(−βx)

Why is this almost universally done? Is there something we can do about it? Michael Hardy (talk) 03:09, 24 November 2016 (UTC)


 * I'm not sure that this is the reason, but I think that the MOSMATH entry may be partially at fault. It says to italicize lower-case Greek letters when they are variables, but remains silent about what to do when they are constants. The example given then muddies the water by italicizing the constant $\pi$. An explicit statement there might help, but I am not sure what that should say. I think a case can be made for lower-case Greek letters representing constants or parameters not being italicized.--Bill Cherowitzo (talk) 04:00, 24 November 2016 (UTC)
 * That is not consistent with TeX style, and moreover, "variables" is meant in a typographical rather than mathematical sense. Michael Hardy (talk) 04:49, 24 November 2016 (UTC)
 * I think it's just that editors have often been sloppy about such details. Except in cases where there's a good reason, we should follow TeX's defaults. —David Eppstein (talk) 06:46, 24 November 2016 (UTC)
 * If it's just sloppiness, how do we explain the seeming consistency? Go through an article in which "βx" and things like it appear a hundred times, and it happens in every case without exception. Then go to the next such article and the same thing happens. Michael Hardy (talk) 17:22, 24 November 2016 (UTC)
 * Until reading the above I for one would have sworn that MOS:MATH actually recommends not to italicize lower-case Greek letters. (No idea why I never questioned this since every other style guide I have ever seen recommends to use italics for greek letters if they denote variables. For what it's worth, even the International Union of Pure and Applied Chemistry mentions that "authors often appear to resist putting Greek letters into italic." ) Anyway, MOS:MATH used to say this:
 * Some editors italicize lower-case Greek letters when they are variables (in line with the general advice to italicize variables): the example expression λ + y = πr2 would then be typeset as . However the examples in the other sections of this guide do not specify italic formatting of Greek letters.
 * This was changed in July 2014 to say this:
 * Italicize lower-case Greek letters when they are variables (in line with the general advice to italicize variables): the example expression λ + y = πr2 would then be typeset as . However consistency with TeX or LaTeX style would not italicize capital Greek letters.
 * See . That's much clearer now. Tea2min (talk) 09:42, 25 November 2016 (UTC)
 * Ah, I knew it. In 2011, MOS:MATH used to say this:
 * Greek letters are not commonly italicized, so that one writes, for example,, for the expression λ + y = π r2. However, the TeX font for Greek letters is an italic style, and some editors italicize Greek letters when they are variables (in line with the general advice to italicize variables): the example expression would then be typeset as λ + y = π r2 (by using  ).
 * See . Tea2min (talk) 17:03, 25 November 2016 (UTC)

Can we create an effective orphanage?
Perhaps the most frequent flaw in new mathematics articles is that no other articles link to the new article. (I just found Borell–TIS inequality and Three spheres inequality and added them to the List of inequalities, and so far that's the only link to either of those two.)

Is there something that can be done to remedy the frequent occurrence of that particular fault among new math articles? Michael Hardy (talk) 21:06, 26 November 2016 (UTC)


 * Orphan has a link to Orphaned articles by WikiProject, from which "Orphaned articles in Mathematics" is missing but to which it possibly can be added.
 * —Wavelength (talk) 21:37, 26 November 2016 (UTC)


 * Editors who have User:AlexNewArtBot/MathSearchResult watchlisted can check its entries for orphaned articles.
 * —Wavelength (talk) 21:48, 26 November 2016 (UTC)
 * Or just use Google . —David Eppstein (talk) 23:01, 26 November 2016 (UTC)
 * We have Pages_needing_attention/Mathematics. In terms of remedy, is encouraging wiki links something to explicitly put into MOS:MATH? --Mark viking (talk) 23:47, 26 November 2016 (UTC)
 * PNA/M stopped being automatically updated in June 2015. —David Eppstein (talk) 00:23, 27 November 2016 (UTC)