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Gauge fixing in 5D vs 4D, and photon polarization

  1. Aug 11, 2009 #1
    I'm sorry if what I say is not right, or I haven't understood it right,

    - In 3+1 D we have the photon with spin 1 => it has two polarizations.

    Our Gauge field [tex]A_\mu[/tex] has 4 components => We have two extra degrees of freedom. => We need to get rid of the extra 2 fixing the gauge.


    1. The Lorentz gauge is not enough to fix them. What else can we do?


    - In 4+1 D we have the photon with spin 1=> it has two polarizations.

    Our Gauge field [tex]A_\mu[/tex] has 5 components => We have THREE extra degrees of freedom. => We need to get rid of the extra 3 fixing the gauge.

    2. The Lorentz gauge is not enough to fix them. What else can we do?

    Thank you very much for your attention :)
     
  2. jcsd
  3. Aug 11, 2009 #2
    In the Lorentz gauge there are two extra degrees of freedom which do not contribute even without getting rid of them. They cannot exchange the energy-momentum with physical degrees of freedom.
     
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