Tagged Questions
4
votes
1answer
102 views
Mass gap for photons
I am puzzled by the answers to the question:
What is a mass gap?
There, Ron Maimon's answer gives a clear-cut definition, which I suppose applies to any quantum field theory with Hamiltonian $H$, ...
2
votes
2answers
158 views
Where does the mass term come from in the Proca Lagrangian?
There are many good books describing how to construct the Lagrangian for an electromagnetic field in a medium.
$$
\mathcal{L}~=~-\frac{1}{16\pi}F^{\mu\nu}F_{\mu\nu}-\frac{1}{c}j^{\nu}A_{\nu}
$$
...
6
votes
3answers
261 views
What is the massless limit of massive electromagnetism?
Consider electromagnetism, an abelian gauge theory, with a massive photon. Is the massless limit equal to electromagnetism? What does it happen at the quantum level with the extra degree of freedom? ...
3
votes
1answer
265 views
Effects of parallel superconducting plates
Assuming the existence of virtual particle field ( zero point energy field) Casimir force is produced by 2 parallel conducting plates excluding some of the frequencies between the plates, if these 2 ...
2
votes
5answers
2k views
Why can't photons have a mass
Why can't photons have a mass? Could you explain this to me in a short and mathematical way?
