# Photon mass and life time

In this article, the author tried to explain that, Einstein's theory may not valid because he says "photon can decay because it may have minute amount of mass". I'm totally in a conundrum state that how to take this article? Anyone can explain a bit please.

• The current text of this questions is deeply misleading. The article assumes the correctness of relativity which investigating a theory in which the photon has mass. – dmckee --- ex-moderator kitten Aug 4 '13 at 18:58
• Dear Raisa - just scanning the text, I can't find mention of relativity. I presume then you mean that a photon mass would imply variable lightspeed, thus overturning SR and GR. Not so. $c$ is simply the speed of a massless particle - whether or not light has mass has no impact on relativity - there are still very basic symmetry reasons for SR that have nothing to do with light - see a description of relativity without consideration of light of mine. – WetSavannaAnimal Aug 4 '13 at 22:29

## 1 Answer

You can postulate the existence of a photon mass and then use experiments to put an upper bound on it. The mass-modified Lagrangian is called the Proca Lagrangian (see Jackson's Classical Electrodynamics, second edition page 597). In the static case you get a Yukawa type potential. If the photon has nonzero mass, then it should decay. Of course, this would change a lot of what we think we know, but the limits on the mass are very small. Here is a nice overview of mass limits on the photon and graviton. http://arxiv.org/abs/0809.1003

Incidentally, some people like a symmetric form of Maxwell that includes a magnetic "charge density" (monopole). Similar efforts can put bounds on the existance of monopoles.