Talk:Cartan formalism (physics)

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Misnamed[edit]

I fail to see how this article pertains to cartan connections. It might be better off in moving frame, or other such place. It is nearly the standard connection form formalism (not Cartan), presenting the exterior covariant derivative as the centerpiece, but with a lot of fanfare and excessive bold type. I'll see what I can do with it later, but I have my hands full now. Silly rabbit 20:15, 30 June 2006 (UTC)[reply]

I agree, this article has very little to do with Cartan connections and should be renamed. There is a link, but it is somewhat indirect. This article is connected with the Einstein-Cartan theory of gravity, which is an extension of Einstein's theory of general relativity in which the Levi-Civita connection of the metric is replaced by a metric connection with torsion. This torsion is supposed to describe the coupling of spin to gravity. Underlying Cartan's idea, however, is the philosophy that one should not be working with an O(3,1) connection on the orthonormal frame bundle (equivalently, a metric linear connection), but a Cartan connection for the Poincare group. The torsion then appears as the translational component of the curvature of this connection. Unfortunately, the Einstein-Cartan article doesn't bring this out (indeed it seems to be mostly written by someone wishing to promote the theory to experts in general relativity rather than describe and explain it to a wider audience). Geometry guy 17:31, 14 February 2007 (UTC)[reply]

I found it useful under the current title - I think it's a physicist's angle on the subject rather than a mathematician's, and as such probably either belongs here or indeed in the cartan connections article itself. --Strange but untrue 21:46, 4 October 2007 (UTC)[reply]

It would be nice to be told why we want to use this formalism, since tensors seem to be equivalent and are more familiar. Give the uninitiated guy a break, eh? Brews ohare (talk) 00:17, 3 August 2008 (UTC)[reply]

Agreed. This article has nothing to do with Cartan connections. The last three sentences in the section on relativity are total gibberish. And the same crap is here: http://www.statemaster.com/encyclopedia/Vierbein, and here: http://www.bambooweb.com/articles/V/i/Vierbein.html

Enough! Please consider deleting rather than moving. Mjmarkowitz (talk) 00:21, 1 May 2009 (UTC)[reply]

Planck's constant[edit]

I'm baffled as where the hbar in the Planck mass comes from (al least I suppose that $M_{pl}$ stands for Planck mass). Please add an explanation to that, define M_pl, or remove it. Thank you. — Preceding unsigned comment added by 193.206.68.165 (talk) 09:05, 17 January 2017 (UTC)[reply]

I removed it. It comes from Hawking radiation; it was someone's attempt to maintain physical units in the expression. (In physics, the action has units of angular momentum, and so one must always divide by hbar to get a dimensionless action). Discussion of units is inappropriate for this particular article, so I removed it. 67.198.37.16 (talk) 20:55, 2 May 2019 (UTC)[reply]

Delete this article?[edit]

I kind of want to prod this article for deletion. It never actually describes what the Cartan formalism is; it rehashes some worn-out territory on veilbeins already covered in the Frame fields in general relativity and Tetrad formalism, both of which are themselves also rather inadequate and unsatisfying. So we have three articles on the same topic, all of which are in sad shape; this being the saddest of all. In addition, some of what one might have wanted to say here is already hammered to a fine pulp in connection form and Cartan connection and spin connection and many other surrounding articles. I just don't see much of a redeeming value in this one. Nor do I see any way of fixing it. So if someone wants to prod this for deletion, this is my pre-vote: delete. 67.198.37.16 (talk) 05:53, 3 May 2019 (UTC)[reply]

Oh, and to avoid a dangling link, REDIRECT to Tetrad formalism. 67.198.37.16 (talk) 05:54, 3 May 2019 (UTC)[reply]

Oh, and looking at the article history, there are exactly zero substantial changes since June 2006, when the first complaints up top were made. Almost all of the changes are cosmetic, vague attempts to clean this thing up. So, up above, I already see two or three delete votes, besides my own. So... 67.198.37.16 (talk) 06:00, 3 May 2019 (UTC)[reply]