# Talk:Sign convention

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Perhaps some new theorems will be found someday which 'might' bring some order to different usages of the sign conversion. Or a term is really not so important in discerning of one theory's correctness?.. --XJamRastafire 02:05, 26 Aug 2003 (UTC)

## Self-reference

I (rephrased and) removed the following self-referential text from the article:

Since the physics-related content in this encyclopedia is written by many different mathematicians and physicists, there is no guarantee of consistency in sign conventions here.

I suppose sign conventions ought to be established here, then. —Kdau 19:24, 2005 Jan 3 (UTC)

I've replaced the reference to the Faraday two-form by 'field strenght tensor', since I've never before heard the other term used. In addition, the problem with sign conventions in the exponential factor arises not only with electrodynamic waves but in all cases where one deals with Fourier transforms of real-valued waves, and the choice is that of whether positive-energy (=positive-frequency) waves turn clockwise or counterclockwise, I'm happy if someone puts this into a few more words.

Finally, the choice of the sign of work in the first law of thermodynamics is really different from the other sign choices because this happens to change the physical meaning. One way, work is defined as the work done on the system, the other way it's the work done by the system. So it's not really a sign convention, but rather a convention as to what the symbols mean.

TobiS 15:55, 2005 Jun 17 (UTC)

## Anecdote

Don't even think about using +--- in a WP article! :-/ ---CH 02:09, 25 May 2006 (UTC)

Simple example: charge of electron

## Story

I'm not convinced that it's necessary to include the (fairly long) story about Einstein, Veblen and the sign convention. Surely the story could be summarised in a few sentences while giving a weblink or some other ref. to the actual story. MP (talk) 06:52, 27 June 2007 (UTC)

Agreed. I've deleted it.--Fashionslide (talk) 01:29, 10 November 2012 (UTC)

Although we appear to have a consensus expressed on the talk page, somebody undid my delete without participating in discussion here. I've redone the deletion.--Fashionslide (talk) 14:21, 3 May 2013 (UTC)

## Curvature

The contraction of the Riemann Tensor is wrong for $R_{ab} \, = R^c{}_{cab}$, since this yields zero due to the anti-symmetry of the Riemann tensor. I'm changing it to $R_{ab} \, = R^c{}_{abc}$ to be correct. Koroll (talk) 15:51, 10 June 2008 (UTC)

## s.c. in statics and mechanics of materials

Does a defining of the "positive" directions of forces and moments, in a section of a beam (like the convention mentioned in the Shear and moment diagrams article), relates to this article? 21:01, 16 December 2008 (UTC) —Preceding unsigned comment added by 62.219.54.250 (talk)

Yes, it does. Feel free to add this to the article. MP (talkcontribs) 21:11, 16 December 2008 (UTC)

## Dubious edit

This edit seems to be wrong; at least it makes no sense to me. However, as a layman, I hesitate to undo it. --Florian Blaschke (talk) 23:52, 29 June 2011 (UTC)

It is in fact accurate, allthough this is the same as -+++. Check Gravitation and cosmology, Weinberg 1972, p 26. It is also correct that it really doesn't make sense to put the 0th index after 1, 2, 3, but that is how he does it: "In our notation, $\alpha, \beta, \gamma$ will always run over the four values 1, 2, 3, 0 [...]". 83.254.85.135 (talk) 16:23, 23 January 2012 (UTC)

The way it is written now is not in accordance with the sign convention Weinberg uses in his "The Quantum Theory of Fields" books. I have the Volume I printed in 1995 which states at page xxv: "The spacetime metric eta_munu is diagonal, with elements eta_11 = eta _22 = eta_33 = 1, eta_00 = -1." So at least in the QFT books, Weinberg uses -+++. Shouldn't this be changed? (In addition, the standard QFT book by Peskin and Schroder uses +---, if one needs a reference to a book which uses that metric. — Preceding unsigned comment added by 87.212.23.26 (talk) 14:36, 23 April 2012 (UTC)

There is also +++- ranged over 1 to 4 so that the usual lambda 00 is lambda 44 instead....Selfstudier (talk) 11:29, 12 July 2012 (UTC)

There's a lot of confusion here. The paragraph starts with a discussion of the selection of the signature (+,-,-,-) versus the signature (-,+,+,+). Then the text selects two textbooks, Misner, Thorne & Wheeler and Weinberg (Grav & Cosmology) that use the same signature (-,+,+,+). The text gets itself tongue-tied by then further complicating the issue by mentioning in an unclear way that Weinberg lists coordinates in the order (x1,x2,x3,x0). I will correct the text in a little while unless someone objects to what I've written here.MarkWayne (talk) 17:32, 7 July 2014 (UTC)

## Classification of Clifford algebras / matrix forms

As an amateur, I don't want to add this without getting some other opinions, but it seems to me that there is a straightforward link to classification of Clifford algebras: (-+++) corresponds to a 4x4 matrix of real numbers, while (+---) corresponds to a 2x2 matrix of quaternions, as can be seen by checking row 4, columns 2 and -2 of the table on that page. (Interestingly the direct product of two copies of either form results in an algebra corresponding to an 8x8 matrix of quaternions, rather than the other form of 8-D algebra which is a 16x16 matrix of reals. If one is going to end up working with quaternions anyway in multi-particle systems, then perhaps the (+---) form is preferable.)Enon (talk) 20:50, 1 July 2012 (UTC)

There is some related discussion here although I would say that there is no consensus on which is better (or even if one is better, most treat as the same)Selfstudier (talk) 11:25, 12 July 2012 (UTC)