In QED, Feynman talks about P(A to B), the probability that a photon starting at a particular point in space will travel to a different point in space (I've since learned that P(A to B) is actually the Feynman propagator, unless I was midled).(adsbygoogle = window.adsbygoogle || []).push({});

What I'm wondering is - what happens if there are multiple photons? Taking the simplest case with two photons interacting, do things like photons turning into particle-antiparticle pairs need to be taken into account?

Thanks!

-Vince

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# QED and Multiple Photons

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