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Polarization of a photon and Lorentz condition

  1. Feb 19, 2016 #1
    My Quantum Field Theory notes, after explaining the Lorentz condition, say this:
    I have some questions about this.
    1) What exactly does the polarization of a photon mean?
    2) Why do the degrees of freedom of the potentials determine the polarizations of the photon?
    3) If instead of the Lorentz condition we used another condition that didn't left any invariance, would it affect the polarizations the photon would have in our theory? Does such a condition even exists, or can it be proved that any condition would leave some residual invariance?

    Thank you for your time.
  2. jcsd
  3. Feb 24, 2016 #2
    Thanks for the post! This is an automated courtesy bump. Sorry you aren't generating responses at the moment. Do you have any further information, come to any new conclusions or is it possible to reword the post?
  4. Feb 24, 2016 #3


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    It's Lorenz, not Lorentz, suggest your professor that his notes need rewriting. The 2nd question is answered by Weinberg in his QFT book, 1st volume. The 3rd question has my answer only using BRST anti-bracket/anti-field formalism which allows for a full gauge-fixing. The 1st question is ill-posed, photons (photonic quantum states, to be precise) use helicity as a Casimir of the Poincare group. Polarization of light is a classical concept. The polarization of a photon is then a misnomer.
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