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Could positrons be electrons from the future traveling back in time?

  1. Nov 30, 2008 #1
    Could positrons be electrons from the future traveling back in time? The Feynman diagrams suggest mirror time symmetry.
  2. jcsd
  3. Nov 30, 2008 #2


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    Actually I think that is one possible interpretation. The interpretation is supported by the fact, that if you add "classical propagators" for particles going forward in time (retarded Green's functions for positive frequency modes) and anti-particles going backward in time (advanced Green's functions for negative frequency modes) you recover precisely the Feynman propagator [IIRC].

    This may sound weird, and one should convince oneself that no causality is violated (e.g. by creating a positron now, we cannot affect an electron in the past; or something like that).
  4. Nov 30, 2008 #3


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    FDs are 4D Fourier transforms of space and time, so there is no time variable in a FD.
    Nothing is going "backward in time".
  5. Nov 30, 2008 #4
    This may be too limited a perspective to really answer the question, but in quantum field theory a particle and it's antiparticle (electron and positron,say) can momentarily emerge from the vacuum as a quantum fluctuation; conversely if a pair aninihilate one another the resulting photon can subsequently give rise to another particle antiparticle pair....

    These are observed experimentally, I think, so I don't see anything from this that is as mysterious as traveling back in time. Furthermore, these antiparticles can be sucked into a black hole (from just outside the event horizon) where upon the mass of the black hole theoretically decreases....Haven't read anything here either about time reversal.

    Would ALL antiparticles be "expected" to travel back in time if any did?? Does big bang theory have any explanations about why matter predominated over anitmatter...I don't recall how much is theorized about that...
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