If the momenta on the three external legs p(incoming fermion), p'(outgoing fermion) and(adsbygoogle = window.adsbygoogle || []).push({});

p-p' (photon) of a vertex diagram are replaced by -p, -p' and p'-p respectively (i.e., all the external momenta are multiplied by -1) does the amplitude remain unchanged?

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# QED vertex

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