Talk:C-symmetry

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Spinors?

Would it make sense to add spinors, where conjugation rules are for Weyl spinors are:

$\psi _{L}^{c}=i\sigma ^{2}{\overline {\psi }}_{L}$

$\psi _{R}^{c}=-i\sigma ^{2}{\overline {\psi }}_{R}$

And for Dirac spinor:

$\Psi ^{c}={\begin{pmatrix}-i\sigma ^{2}{\overline {\psi }}_{R}\\i\sigma ^{2}{\overline {\psi }}_{L}\end{pmatrix}}=-i{\begin{pmatrix}0&\sigma ^{2}\\-\sigma ^{2}&0\end{pmatrix}}{\overline {\Psi }}$

$\left(\Psi ^{c}\right)^{c}=\Psi$

--Plaes (talk) 07:46, 8 November 2010 (UTC)[reply]

Yes. See Weyl–Brauer matrices for the general n-dimensional case. 67.198.37.16 (talk) 20:31, 17 November 2020 (UTC)[reply]

Done. Although it was more painful than anticipated. Minus signs are like vermin, every time you lift up some equation, a bunch of them come scurrying out like cockroaches, and you're dancing "La Cucaracha" before you know it. I swear, life would be so much easier if the American Mathematical Society got off their butts and simply outlawed the minus sign. Everything would then be positive, and a lot of mathematical flim-flam would evaporate. 67.198.37.16 (talk) 21:36, 25 November 2020 (UTC)[reply]

charge definition

I don't see the point of this last chapter... Could it be better explained? Thanks

Rasco 12:10, 20 June 2007 (UTC)[reply]

"I think this theory needs to be disproven, for isn't it clear that the 'forms' are different, not the same. Invariance is something different than this."- ParkerE

Merge

The following discussion is closed. Please do not modify it. Subsequent comments should be made in a new section. A summary of the conclusions reached follows.

The result of this discussion was no consensus D O N D E groovily Talk to me 16:57, 9 December 2011 (UTC)[reply]

Merge with C parity or vice-versa? Headbomb {ταλκ – WP Physics: PotW} 05:29, 20 June 2008 (UTC)[reply]

Yes, please. Besselfunctions (talk) 16:27, 30 September 2008 (UTC)[reply]

No, definity not. C Parity is not the same thing as C-symmetry. There is an issue of whether or not light and gravity are c-symmetric that needs to be resolved first, which I address below130.207.180.80 (talk) 13:13, 25 November 2008 (UTC)[reply]

I would also agree that this page should be merged with C parity. I propose to make a more generic page on "charge conjugation", with C parity (of systems of particles / fields) and C symmetry (of theories) as subtopics. Jasondet (talk) 21:56, 19 July 2010 (UTC)[reply]

The discussion above is closed. Please do not modify it. Subsequent comments should be made on the appropriate discussion page. No further edits should be made to this discussion.

gravity is not C symmetry i think it should be merged with C parity as well it makes more sense we need to have a new generic page on charge conjugation — Preceding unsigned comment added by 173.184.253.182 (talk) 14:49, 27 April 2015 (UTC)[reply]

Gravity is not C-Symmetric

I put up a dubious text because I honestly belief that gravity is not C-symmetric. As a physicist I have generally learned that anti-gravity is not possible because gravity has no charge conjugate since its charge is zero. If there is a source of information that shows gravity to be C-symmetric you need to cite an example.

Furthermore there need to be clarification on the word electromagnetism vs. the phrase "electricity and magnetism". Do you mean the quantum mechanics of electricity and magnetism or the quantum mechanics of optics? While Electricity and magnetism both have charge and produce something called Electromagnetism, Electromagnetism in itself lacks charge because the photon and the electromagnetic wave lacks charge even though the electromagnetic waves components have charge. In fact to my knowledge if electromagnetism is C-symmetric then wouldn't that mean anti-photons exist? 130.207.180.80 (talk) 13:13, 25 November 2008 (UTC)[reply]

I corrected the spelling errors and grammatical errors, I made before. (talk) 09:51, 8 December 2008 (UTC)[reply]

When we say 'gravity is C-symmetric' we mean that gravitational interactions conserve C-symmetry, and the same goes for electromagnetism etc. I have no idea what you mean by 'the wave components have charge', if that makes sense - perhaps you could clarify that. Electromagnetism is C-symmetric, and anti-photons do exist: they are called 'photons'. —Preceding unsigned comment added by 41.145.122.175 (talk) 21:48, 3 September 2009 (UTC)[reply]

FYI, re: gravity, there is a more general setting in terms of Riemannian manifolds (gravity in n-dimensions) and one can use spin representations (see spin structure) to provide a local frame (see vielbein, the dirac gamma matrices provide a local "flat" vielbein) So, generically, in n-dimensions, Weyl spinors have a C-symmetry (see Weyl–Brauer matrices) so, to the best of my understanding, you can talk about the C-symmetry in a general setting. Presumably its some kind of topological invariant, the details of which I'm not aware of. 67.198.37.16 (talk) 20:50, 17 November 2020 (UTC)[reply]

Also, the discovery of ELKO leaves the whole thing frustratingly opaque. One has to go back to first principles to figure out which symmetry is acting on what, where and how. Until now, charge conjugation was treated a bit glibly, it would seem. I'm trying to untangle the pieces-parts now. 67.198.37.16 (talk) 17:53, 25 November 2020 (UTC)[reply]

Error?

This article states: "Notice that these transformations do not alter the chirality of particles." However, the transformations on spinors *do* seem to transform LH into RH and vice versa under the action of gamma_2.

Furthermore, in Zee's textbook p. 101 it states that "the charge conjugate of a LH field is a RH field". Am I missing something?

131.111.5.181 (talk) 01:01, 8 November 2017 (UTC)[reply]

New comments go to the end. You might read the first comment (now) on this page. The article is right: C does not change the spin or chirality of a particle. Some authors like the one you mention abuse language a little, but make sure they are talking about the same object. Note

\gamma _{5}

commutes with

\gamma _{0}\gamma _{2}

. Zee should (or probably does?) contrast fields to particles. The charge conjugate field has chirality reversed, but it describes the absence of a particle of a given energy, momentum and spin direction, so the presence of an antiparticle with those reversed; so the entire operation leaves energy, momentum, and spin/chirality untouched for a particle-to-antiparticle transition. A somewhat brutal orientation mnemonic is that in the "older" hypothetical V-A world lacking a right-handed neutrino and so a left-handed antineutrino, a C operation of the standard left-handed kinetic term would annihilate it, and only a CP operation would preserve it. Cuzkatzimhut (talk) 01:22, 8 November 2017 (UTC)[reply]

Thank you very much for taking the time to clarify. I have been asking around, and this seems to be a confusing topic for many a physicist. I am sorry to belabour the point, but could I trouble you to be explicit mathematically about what you mean? That is, could you rephrase what you wrote in the form of (Operator)(Eigenstate) = Eigenvalue (Eigenstate)? I mean, for both spin and chirality operators, and for both particle and field eigenstates, before and after they've been charge conjugated? 131.111.5.181 (talk) 20:54, 8 November 2017 (UTC)[reply]

Sorry, your Bjorken & Drell v 1 (Relativistic Quantum Mechanics 1964--i'm sure available in your library) do just that, with similar verbiage. Itzykson and Zuber appendices are almost, but not quite as good. Try your field theory text, not Zee, or, better yet, work it out in your conventions. For fields, it is trivial,

(\psi _{L})^{c}=(\psi )_{R}^{c}

, but, as I indicated, this is not the antiparticle--it is the absence of a particle with negative energy and momentum direction. The antiparticle has positive energy and opposite momentum, so same as the particle, and same chirality. A pure kinetic term for a left-handed neutrino and nothing else , so, then CP invariant but not C invariant, should settle all questions. Cuzkatzimhut (talk) 22:36, 8 November 2017 (UTC)[reply]

Thank you, a published reference is better. FYI, I have been through these textbooks: Schwartz, Burgess and Moore, Peskin & Schroder, Tong's QFT lecture notes, Zee, and there is not a lot of information on the topic. B&M seem to have the most detail, although with the number of typos in the text, I have a hard time trusting the reference.131.111.5.181 (talk) 23:27, 8 November 2017 (UTC)[reply]

I added the bibliographical info. But frankly, this page is not a forum. Cuzkatzimhut (talk) 23:43, 8 November 2017 (UTC)[reply]

Thank you - how very kind of you. 131.111.5.181 (talk) 01:00, 9 November 2017 (UTC)[reply]