Wikipedia talk:WikiProject Physics/Archive March 2013

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Over my head

Someone at commons has uploaded this file as a replacement for this file. If it is more accurate would it be easiest to overwrite the older file instead of replacing the file name in all the multi-language articles that it is used in?--Canoe1967 (talk) 13:55, 1 March 2013 (UTC)

The new one looks better to me, but it is outside of my field of expertise. JRSpriggs (talk) 14:24, 1 March 2013 (UTC)

If it is really better (actually it contains less information but looks slightly cleaner) there's universal replace to replace a file across all Wikimedia projects. -- Patrick87 (talk) 14:50, 1 March 2013 (UTC)

I am afraid to push that button though. If someone else wants to then I can link the two files in 'other versions' sections at commons. Then when other editors go to one image page they can see the other as well. I will do that now.--Canoe1967 (talk) 14:58, 1 March 2013 (UTC)

Possible merger

Why are Principle of least action and Hamilton's principle two separate articles? Should we merge them? I noticed that one can get from the first to the second via interwiki links (foreign languages). JRSpriggs (talk) 18:32, 25 February 2013 (UTC)

There certainly are different principles, at least on the face of it. There can be different conditions on variations at endpoints/boundaries, and different dependent (of time) variables. Unfortunately, I can't be more specific because I don't remember the details, but I think Goldstein (2nd ed.) elucidates a bit on various principles. If anybody has that book at hand, it could provide input to a merge/no merge discussion.

Perhaps having one small principles of least (or stationary) action article mostly emphasizing differences and main articles for the specific principles is a good option. YohanN7 (talk) 13:03, 7 March 2013 (UTC)

If so, then all of Hamilton's principle#Comparison with Maupertuis' principle, Hamilton's principle#Action principle for fields and Hamilton's principle#Quantum mechanics and quantum field theory could be moved to Principle of least action making space for elaboration on the special case at hand (Hamilton's principle proper) in Hamilton's principle. What I suggest then is a reorganization, but not a complete merger. (An aside: I find the section Principle of least action#Apparent teleology a bit murky. Particles just aren't very clever even if some philosophers have historically thought that the action principles implied so. I think I can find a source for that.) YohanN7 (talk) 15:09, 7 March 2013 (UTC)

IEEE Trans Antenn & Prop coverimage.gif

file:IEEE Trans Antenn & Prop coverimage.gif has been nominated for speedy deletion -- 65.92.180.137 (talk) 05:15, 4 March 2013 (UTC)

Declined, tidied a bit. Materialscientist (talk) 05:21, 4 March 2013 (UTC)

Matrix representation of Maxwell's equations

Raised at talk:Maxwell's equations.

You may know already, anyway and this edit has introduced a link to a recent article Matrix representation of Maxwell's equations, with an excessive number of 6 refs. Similarly in other articles linked to there, mainly this edit (and those following it) in Foldy–Wouthuysen transformation and this edit (and those following it) in Riemann–Silberstein vector.

What should we do about the new article? It passed creation, but it looks like promotion of work and conflict of interest?... Thanks, M∧Ŝc²ħε И_τlk 08:33, 5 March 2013 (UTC)

Template:Equation box 1

It has been requested that this be deleted, by user:JordiGH. The main use of the box is in physics articles. Do people agree to delete? I have a feeling some of you may (which is perfectly fine). M∧Ŝc²ħε И_τlk 22:18, 6 March 2013 (UTC)

Seems a rather odd way to ask for deletion. He should use WP:TFD if he feels that strongly about it. -- 65.92.180.137 (talk) 03:15, 7 March 2013 (UTC)

Right. You're the creator, Maschen, so unless you request speedy deletion it would could only be removed via WP:TFD. Since it is used in over 50 articles, the deletion probably should be discussed properly. RockMagnetist (talk) 14:13, 14 March 2013 (UTC)

Portraits at APS March meeting

Hi, I'll be at the APS March Meeting this next week, and when I'm not in talks I was planing on taking pictures of physicists who have bios on WP but no pictures. I have a few on my list so far, but does anyone else have suggestions for people I should try to look for? Thanks, a13ean (talk) 21:27, 11 March 2013 (UTC)

Be sure to get their permission before taking their photo. Some people value their privacy. Xxanthippe (talk) 22:16, 11 March 2013 (UTC).

Of course, sorry, I thought that part went without saying. I'm still working on my "Hi my name is ... I contribute to ... would you mind if I took your picture" spiel, so if you have any suggestions on that end I would appreciate it. a13ean (talk) 22:36, 11 March 2013 (UTC)

Fine, providing that you tell them the purpose of the photo and make it clear that you don't have any official connection with Wikipedia. Xxanthippe (talk) 22:42, 11 March 2013 (UTC).

Right; I'm also planning on making it clear that this is unrelated to my work as a graduate student. a13ean (talk) 22:58, 11 March 2013 (UTC)

Grey hole

We have an article on Grey hole that is unreferenced, and a different article on Gray hole and a different redirect at Gray hole... -- 65.92.180.137 (talk) 05:42, 14 March 2013 (UTC)

Both articles we have are different from the definition I've previously encountered Bibcode:1993AAS...182.5507B -- 65.92.180.137 (talk) 05:48, 14 March 2013 (UTC)

Grey hole seems like an obvious hoax. JRSpriggs (talk) 07:38, 14 March 2013 (UTC)

That was my thinking as well, as I couldn't find the credited PhD; but the edit history since it was turned into an article, from being a redirect shows, aside from myself, only highly established editors editing it. Do we return it to the target it used to have (exotic star, where the information was removed in 2011), the article with more information (compact star, which contains a summary of what used to be at exotic star), point it at the separate article Q star that says it is about gray holes, or create a new article about it? -- 65.92.180.137 (talk) 09:26, 14 March 2013 (UTC)

For crying out loud, they're making fun of us for this. I've nominated it for PROD. — A. di M. 11:25, 14 March 2013 (UTC)

Why didn't you just revert it to the redirect it was before it was converted into an article last year? (I didn't do that since I'd probably get an automated vandalism warning from a bot, or a busybody vandalism warning from an editpatroller, especially, as noted, several well established wikipedians didn't have a problem with the article) -- 65.92.180.137 (talk) 05:00, 15 March 2013 (UTC)

BTW, what I propose to do is to make grey hole a disambiguation and gray hole a redirect to it (or vice versa). I'd also include packet drop attack in the dab, as most Google results for "gray hole" appear to be about that. — A. di M. 14:06, 14 March 2013 (UTC)

I've WP:BOLDly disambiguated Gray hole, since that's the spelling used. If someone is up to it, they can redirect the prodded variant spelling grey hole (I'm not doing it, since I don't want someone giving me a vandalism warning because they think you're not allowed to delete a PROD tag until it's expired (yes people do do that)) -- 65.92.180.137 (talk) 05:05, 15 March 2013 (UTC)

Let's wait for the PROD to expire, on the off chance than meanwhile someone comes up with something we haven't thought about, and then redirect grey hole to Gray hole. — A. di M. 09:34, 16 March 2013 (UTC)

PROD expiry means that it will be deleted, not redirected. The recommended actions in the PROD instructions says if you can do something, then do it, not wait until PROD expires. The reason I didn't do it, is because editpatrollers give out vandalism warnings for everything, even though supposedly, anyone can delete the PROD tag, but several editpatrollers think otherwise, when an IP editor does it. -- 65.92.180.137 (talk) 20:41, 16 March 2013 (UTC)

User:StringTheory11 has already done that. (I think that cases when removing a PROD is considered vandalism are those when the article is kept as-is without providing any argument against the PROD reason, so that wouldn't apply here.) — A. di M. 09:50, 19 March 2013 (UTC)

I've had an edit patroller tell me that removing a PROD for any reason is vandalism, even with content changes and expansion. Expanding an article under prod itself was vandalism, because it was prodded so should not be changed by an IP editor, since people cannot evaluate the article since it was changed from the date of prod application. (proper editing, not vandal editing). -- 65.92.180.137 (talk) 05:21, 20 March 2013 (UTC)

Huh... Who was that? Doesn't that defeat the whole point of the PROD system? :-/ — A. di M. 13:37, 20 March 2013 (UTC)

Indeed. WP:PROD says that if you remove a PROD tag you are "encouraged, but not required" to explain why you disagree with deletion, improve the article etc. etc. So that edit patroller was definitely wrong - removing a PROD tag is not vandalism. Maybe they were somewhat confused about the differences between the PROD and AFD processes. Gandalf61 (talk) 14:16, 20 March 2013 (UTC)

Is "Golden age of general relativity" well defined?

See the discussion on this talk page. RockMagnetist (talk) 21:21, 20 March 2013 (UTC)

Actually the question may be moot since the article was all but merged into History of general relativity. I have proposed to complete the merger here. RockMagnetist (talk) 22:04, 20 March 2013 (UTC)

General article on Transformation may be needed

I suggest that an article on transformations may be needed, covering co-ordinate transformations such as rotations, translations or Lorentz transformations and the corresponding transformation laws for physical quantities. We seem to have many specific articles but no general article.

Coordinate system#Transformations is too general as this would cover things like converting to spherical coordinates.

How is that too general? Certainly spherical coördinates are used in physics.

IMHO the thrust of such an article should be the coördinate transformations of geometric objects on a manifold associated with coördinate transformations on the manifold, to include transformations weighted by powers of the Jacobian. Shmuel (Seymour J.) Metz Username:Chatul (talk) 16:11, 20 March 2013 (UTC)

Covariant transformation and Tensor cover some types of transformation but not all.

Symmetry (physics) would appear to be the most relevant article at the moment, although its scope is slightly too narrow. It covers the importance of considering some types of transformations (e.g. Noether's theorem (I'd add creation of quantum field theories as well)), but this only deals with transformations of physical coordinates, which transform the same way as vectors. This doesn't cover the idea of a "transformation law" though. If it were just tensors which were different, the article on tensor would be good enough. However, there are spinors as well, so I think it would be worth summarizing and comparing the transformation laws of vectors, tensors and spinors together in a single article along with the meaning and significance of a transformation. Many people have commented on the talk page for the spinor article that they find it hard to understand, and I think if they could read about the background of transformation laws (without cluttering up the spinor article with this) then they would find it significantly easier. Count Truthstein (talk) 16:38, 16 March 2013 (UTC)

Sounds like a good idea, in particular the part on Lorentz transformations (rotations/accelerations in spinor language are not covered in that article, only in terms of gyrovectors). Although a lot of good effort has been put into the spinor article, it drags on and on... (P.S. You may want to edit/extend the Van der Waerden notation article on spinor indices also if time/inclination allows, because the similarities/differences between tensor/spinor indices is confusing...). Thanks, M∧Ŝc²ħε И_τlk 16:52, 16 March 2013 (UTC)

You miss one thing about philosophy, Count Truthstein. A symmetry is something about the world or a particular class of physical systems, something falsifiable. But a transformation is a formal thing. Symmetries are not a partial case of transformations. Quite contrary, a transformation is one of possible ways to express the idea of symmetry, although, obviously, not all transformations express something about physical symmetry. These concept are intertwined, but neither is a partial case of another. Incnis Mrsi (talk) 17:05, 16 March 2013 (UTC)

It's hard to tell the difference because you would not normally talk about transformations which are not symmetries. However, parity transformations would seem to meet this criteria: certain nuclear interactions are not parity-invariant. So there are interesting transformations which are not symmetries. I agree that symmetries are falsifiable. So I agree with you; transformations are important to symmetries but there is extra meaning to symmetries that wouldn't be covered by transformations. Count Truthstein (talk) 17:17, 16 March 2013 (UTC)

Would I not normally talk about transformations which are not symmetries? There are many things in both mathematics and physics which are transformations, but do not pretend to describe a symmetry. Various non-invertible maps and operators in mathematics, which never form a group. In physics, there are both transformations which conserve simplistic theories but break realistic systems (such as conformal transformations), and transformations which actually are translations from one notation to another (such as Bogoliubov transformation). Incnis Mrsi (talk) 17:48, 16 March 2013 (UTC)

So given an arbitrary transformation of the coordinates, is there always a derived to way to transform tensors, etc. as well? Or do you have to come up with transformation rules on a case-by-case basis? Count Truthstein (talk) 17:54, 16 March 2013 (UTC)

Why are you so preoccupied with tensor fields? Were all physical quantities expressed with differential geometry and nothing else, we would not have to write a new article. A new article can be justified only by the general case, and spinors are not the only thing beyond tensors. Incnis Mrsi (talk) 18:07, 16 March 2013 (UTC)

Tensor/spinor fields are what I am most aware of but other transformed quantities could be discussed as well. Count Truthstein (talk) 21:18, 16 March 2013 (UTC)

Although coming back to parity transformations, I'm not sure how you would express a transformation law for them, because when you are applying a transformation law (to tensors, etc.) I would expect to end up with a different description of the same physical state. Count Truthstein (talk) 17:20, 16 March 2013 (UTC)

Thinking about it, I think that a parity transformation would be defined by what is mathematically elegant (e.g. x to -x) and not motivated by physical observation. Count Truthstein (talk) 17:24, 16 March 2013 (UTC)

I agree with Incnis Mrsi; symmetry and transformations are different concepts. Symmetry is about the underlying group structure of the physical system. A transform describes how a quantity changes under a group action. It seems you are interested in the Lorentz group in particular. Perhaps the Lorentz transformation article would be the best place for this. In addition to scalars, vectors, pseudo vectors, tensors, and spinors, you may also want to consider differential forms, as these are also prominent in physics. Note that parity is just a reflection symmetry and is also part of the larger symmetry group used in modeling nuclear and high energy particle systems. --Mark viking (talk) 17:35, 16 March 2013 (UTC)

The covariance group of general relativity is also applicable, and transformations under rotations, translations and reflections are also interesting (if the reader isn't interested in relativity), so it isn't just the Lorentz group. Count Truthstein (talk) 21:18, 16 March 2013 (UTC)

The homogeneous Lorentz group contains rotations and the inhomogeneous Lorentz group (Poincare group) contains translations. --Mark viking (talk) 02:48, 17 March 2013 (UTC)

I know, but the article could be accessible to someone who knows what a rotation is but doesn't know what the Poincaré group is, without making the article too unwieldy/boring. Count Truthstein (talk) 09:28, 17 March 2013 (UTC)

I've started a draft at User:Count_Truthstein/Transformation_(physics). Count Truthstein (talk) 21:27, 16 March 2013 (UTC)

The first things that need to get pinned down are the definitions of a transformation, a symmetry, and a symmetry transformation. I haven't seen any rigorous definition of these concepts in the literature. (Citations are needed.) I mean, a Laplace transform is as much a transformation as a Lorentz transformation.

Then there are articles that (are supposed to) cover much of what is mentioned here. Much can go into Representation theory of the Lorentz group. (Lorentz transformation is the wrong place to discuss various representations.) Then there are articles on Lorentz scalars, 4-vectors, bispinors and tensors. For other types (other groups) of transformations (like SU(2), SU(3), ...), the pattern ought to be the same. Besides, i want to beef up articles like Representation theory to make linking of basic concepts easier. (See talk page there.) YohanN7 (talk) 19:28, 20 March 2013 (UTC)

To Truthstein: Perhaps you are failing to distinguish between general coordinate transformations and those which are isometries? JRSpriggs (talk) 11:31, 21 March 2013 (UTC)

Perhaps it is actually "transformation rules" rather than "transformations" where I think there is a gap. That is, transformations of quantities which derive from co-ordinate transformations. I don't see that there will necessarily be a transformation rule for tensors or spinors for arbitary co-ordinate transformations. Transformations (i.e. Lorentz transformations) where we can do this are indeed usually isometries; however, even a simple scaling of Euclidean co-ordinates yields an obvious transformation of vectors, and that is not an isometry. Count Truthstein (talk) 12:08, 21 March 2013 (UTC)

Variational method

The usage of "Variational method" is up for discussion, see talk:Variational method -- 65.92.180.137 (talk) 01:06, 25 March 2013 (UTC)

Copernican principle

Could someone please review recent changes to Copernican principle by Wyattmj (talk · contribs) (see its history and last thread on the talk page). Poor grammar and formatting aside, I see it as WP:OR, where an editor draws conclusions from primary sources. Thanks. Materialscientist (talk) 05:27, 29 March 2013 (UTC)

Perhaps this should be merged with the Cosmological principle? JRSpriggs (talk) 09:28, 29 March 2013 (UTC)

Biocentrism

There is a proposed move of Biocentrism_(theory_of_everything) to Biocentrism_(metaphysics). more input welcome: Talk:Biocentrism_(theory_of_everything)#Requested_move IRWolfie- (talk) 19:03, 29 March 2013 (UTC)