Does reversing time give parity reversed antimatter or just antimatter?

Question

Feynman's idea states that matter going backwards in time seems like antimatter.

But, since nature is $CPT$ symmetric, reversing time ($T$) is equivalent to $CP$ operation. So, reversing time gives parity reversed antimatter, not just antimatter.

What is happening here? Why does nobody mention this parity thing when talking about reversing time? What am I missing?

You're right, never mind. – probably_someone Mar 20 '18 at 00:45 — probably_someone, Mar 20 '18 at 00:45

score 1 · Answer 1 · answered May 24 '18 at 23:07

1

Positrons have equal and opposite charge and parity to electrons. Hence when combined, they can produce a neutral gamma ray with no parity.

https://en.m.wikipedia.org/wiki/T-symmetry

answered May 24 '18 at 23:07

CriglCragl

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Oh, I get the problem now, after reading the first answer of https://physics.stackexchange.com/questions/391/is-anti-matter-matter-going-backwards-in-time Which also gives the explanation. Truly reversed, it is the same particle..! – CriglCragl May 25 '18 at 14:15

score 1 · Accepted Answer · answered Jun 19 '19 at 04:39

The statement that antimatter is matter going back in time is usually associated with Feynman diagrams in QED, so we're talking about electrons, and electrons have parity +1, so:

$$ CPT = C1T = CT = 1 $$

So the parity part doesn't come into play, but it is required in general.

Does reversing time give parity reversed antimatter or just antimatter?

2 Answers2