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

[kuon]

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 $$A_\mu$$ 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 $$A_\mu$$ 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 :)

 

[Bob_for_short]

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 $$A_\mu$$ 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 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.