Published online by Cambridge University Press: 09 March 2009
Possible modifications of some of the properties of an electromagnetic wave by a medium in which it propagates, are studied. The mechanism for mass generation is investigated. It is shown that, for some purposes, a medium may be replaced by a curved space. Furthermore, if the nonlinear interaction terms between the electromagnetic wave and the curvature of space-time are included, the resulting Maxwell equations are modified. These additional terms may be identified with the photon's mass, which is proportional to the curvature scalar. A laser intensity above 1020 W/cm2 produces a mass of the photons of about 10−5 times the mass of the electrons.