Wikipedia talk:WikiProject Mathematics

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Multidimensional integrals before one-dimensional integrals?[edit]

There is a discussion at Talk:Integral#Adding sections on the multivariate integral before the standard integral in one dimension? of relevance to this project, concerning this edit. Sławomir
21:02, 12 November 2015 (UTC)

The discussion at Talk:Integral has evolved into a suggested major restructuring. Given my history with the editor making the proposal, we could use some third input. Also, I would very much prefer it if this proposed restructuring were brokered by a more competent mathematics editor. (The errors this editor made here do not fill one with confidence.) Sławomir
14:45, 13 November 2015 (UTC)

Coordinate system, frame or basis[edit]

I am writing the section affine space § coordinates, and I have encountered a terminology problem that involves a lot of articles, in fact, most articles that deal with coordinates.

The first part of the problem is '"what is the name of a coordinate system defined by an origin and a basis of the associated vector space?" This is sometimes called [an [affine coordinate system]], but this term is ambiguous as barycentric coordinates are also an affine coordinate system. Thus, I would prefer to call it a Cartesian coordinate system, as, as far as I know, Cartesian coordinates need not be defined by an orthonormal frame. Thus my first question is "do reliable sources require that Cartesian coordinates are based on an orthonormal frame".

While looking for an answer to this question in WP, it appeared that the article Frame (geometry) does not exist, and that most Wikipedia article use "coordinate system" or "basis" when "frame" should be used. The fact that "coordinate system" is not a synonymous of "frame" is exemplified by the fact that Cartesian and polar coordinates of the Euclidean plane are based on the same orthonormal frame. Another example is the awful first sentence of Translation of axes. "Basis" is also used instead of "frame", for example in Basis (linear algebra) § Geometry. Although confusing, this may be acceptable when all components of the frame are of the same nature. It is not for a frame consisting of an origin and a basis of the associated vector space.

IMO, we need a coherent terminology. When we will get a consensus, a lot of articles will need to be edited accordingly. D.Lazard (talk) 10:15, 16 November 2015 (UTC)

For the first question, I would say "linear coordinate system". I don't think it is desirable to achieve uniform terminology in all of our articles, because different fields of mathematics use terminology in slightly different ways. For example, in linear algebra, we would often just say "coordinates", where it is understood that we mean linear coordinates. Cartesian coordinates are also called rectangular coordinates. I think it would be very confusing to refer to general linear coordinates as Cartesian coordinates, where there are no "rectangles" to speak of, just parallelograms. I don't doubt that you can find this use somewhere in the literature, but I don't think we should push that usage. On the issue of frame versus basis, here it obviously does depend on the area of mathematics. In linear algebra, "frame" is sometimes used as a synonym for "basis" (and sometimes it means just a spanning set). In affine geometry, an "affine frame" is something else: a basis and choice of origin. More generally, in geometry a frame is whatever gives a reduction of a structure group to the identity. Thus, the moving frame (repère mobile). Sławomir
12:05, 16 November 2015 (UTC)
A coordinate system is a continuous (usually C) injective map from an open set in an n-dimensional manifold to Rn. JRSpriggs (talk) 04:02, 17 November 2015 (UTC)
Unfortunately this is only the definition of local coordinate systems on manifold. It is much too technical to be used for Cartesian coordinate system, as everybody, who knows about manifolds, certainly knows already Cartesian coordinates. Also this definition is a non-sense for affine coordinate systems, as affine spaces exist over any field. It is a part of above mess that many articles of WP refer to JRSpriggs's definition, without any link to the primary definition in elementary geometry. For example, Cartesian coordinate system does not says that Cartesian coordinates are related to an orthonormal frame, and none of Orthogonality, Orthonormal basis, Orthonormal frame mentions Cartesian coordinates. D.Lazard (talk) 10:33, 17 November 2015 (UTC)

Jacobian Conjecture: Suggested text removal[edit]

I would like to draw attention to the section "Suggested Removal" that I posted to the JC article.

L.Andrew Campbell (talk) 03:55, 18 November 2015 (UTC)

Suggested removal done. D.Lazard (talk) 10:41, 18 November 2015 (UTC)

AfC submission[edit]

See Draft:Symmetrization Methods. Thank you, FoCuS contribs; talk to me! 18:20, 19 November 2015 (UTC)

As for me, this is good enough. Maybe the context could be richer, but the same can be said about quite many "old" math articles on WP. Let it exist and grow on the wiki. Boris Tsirelson (talk) 19:05, 19 November 2015 (UTC)
Thanks for the input, Tsirel - I've moved the article to mainspace. Perhaps you could drop by and make sure it is in the correct categories? Thanks. Take it easy. Onel5969 TT me 14:24, 21 November 2015 (UTC)
Nice; I did. Boris Tsirelson (talk) 15:13, 21 November 2015 (UTC)

RefDesk question: Continuous mathematics?[edit]

There is a question at the ref desk that confused me, as it made me find out that Continuous mathematics redirects to Numerical analysis. Is there an obvious reason why this is a good idea? I am going to change the redirect to mathematical analysis, but I would hope that somebody reverts me if I am wrong. —Kusma (t·c) 15:28, 24 November 2015 (UTC)

Another AfC draft![edit]

Hi all, Draft:Banach Game is in the AfC queue and I would be happy to accept it if the math checks out. I noticed in the second reference that the formulation of the problem is given as x_{n+1}<x_{n} for every n<\omega, but I did not know if \omega is an ordinal or merely a variable. /wia /tlk 04:54, 25 November 2015 (UTC)

In this case, I would interpret \omega as an ordinal. So n<\omega is just another way of saying that n is a natural number.
If 0 < x_{\omega} < x_{n} for any n < \omega, then sum of the series would always be infinite. That is, it could never converge to an element of X. JRSpriggs (talk) 21:26, 25 November 2015 (UTC)

Axonometric projection[edit]

Could use some help here. Talk:Axonometric projection#Types of axonometric projections. There is a disagreement over the taxonomy of parallel projection. We need some input. Thanks! SharkD  Talk  05:22, 25 November 2015 (UTC)

Implicit curve[edit]

What software did you use to create File:Fl-sin-cos-nivk-s.svg? I am looking for 3D software that can output SVG. SharkD  Talk  05:26, 25 November 2015 (UTC)

I created an EPS-file of the object, transformed it with pstoedit into a FIG-file (xfig) and exported the result into a SVG-file. Another way is: use ps2pdf and pdf2svg.--Ag2gaeh (talk) 10:48, 25 November 2015 (UTC)

AfC submission[edit]

See Draft:Enoch Lewis, a biography this time. Best, FoCuS contribs; talk to me! 12:20, 25 November 2015 (UTC)

PlanetMath Exchange dead or alive?[edit]

I'm trying to engage researchers in Sweden to be active contributors to Wikipedia. I will today talk to the department of Mathematics at Uppsala University. Some researchers from their department have earlier said that PlanetMath has the same function as Wikipedia has for other areas and that it might be more wise to be active on PlanetMath instead. It seems that a long time ago, people tried to do both, but what has happened since with the Exchange project? Olle Terenius (SLU) (talk) 10:48, 27 November 2015 (UTC)

Planetmath itself was dead for a long time. Now I see that the site seems to be back online. Sławomir
13:01, 27 November 2015 (UTC)
It seems to be far less active than Wikipedia, though. Try a search like Cauchy sequence and you will find the WP article at the top while PlanetMath is - hard to find. Also compare the PlanetMath article with Cauchy sequence. PlanetMath seems to be more oriented towards mathematicians than the general public, so the choice of platform may depend on who you wish to write for. RockMagnetist(talk) 13:52, 27 November 2015 (UTC)