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Feynman propagator and particle uniqueness

  1. Dec 26, 2013 #1
    In his layman's guide to QED Feynman defines a particle propagator as a function that gives you the amplitude that a particle, that was initially at spacetime event ##x##, will be found at spacetime event ##y##.

    But does this definition assume that the particle is unique so that if you find it at the spatial coordinates of ##y## then you are automatically guaranteed that it is no longer at the spatial coordinates of ##x##?

    As particles are indistinguishable maybe the propagator only specifies the amplitude that, given a particle is at event ##x##, then an *additional* particle of the same type will be found at ##y##.

    In that case maybe one also needs to apply a reverse propagator that gives the amplitude that an antiparticle will be found at ##x## given that a particle was found at ##y##?

    Perhaps this would destroy the original particle at ##x## and so ensure that we are only left with a particle at ##y##.

    Does this make sense?
     
  2. jcsd
  3. Dec 26, 2013 #2

    ShayanJ

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    Gold Member

    The introductory quantum mechanics is a single particle theory.I urge you to check that Feynman is talking about a single-particle problem or not.Things get different where the number of particles gets bigger than one.
     
  4. Dec 27, 2013 #3

    tom.stoer

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    Science Advisor

    The propagator does not act on a particle, but on a field. The amplitude you are talking about is related to this field. The particle interpretation is not based on propagators.
     
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