2
votes
1answer
105 views

How do photons decay in superconductors?

If $A$ is the vector potential, the London equations imply that: $$(\nabla^{2}-\mu^{2})A=0$$ if there is no external current. This can be interpreted as an effective photon mass and so, light ...
14
votes
1answer
462 views

Spontaneous breaking of Lorentz invariance in gauge theories

I was browsing through the hep-th arXiv and came across this article: Spontaneous Lorentz Violation in Gauge Theories. A. P. Balachandran, S. Vaidya. arXiv:1302.3406 [hep-th]. (Submitted on 14 ...
2
votes
1answer
982 views

Chiral anomaly and decay of the pion

I am told that if all classical symmetries were reflected as quantum symmetries, the decay of the neutral pion $$\pi^0 ~\longrightarrow~ \gamma\gamma$$ would not happen. Why would the conservation of ...