Gravitational field of the quantised electromagnetic plane wave

Abstract

The quantum and classical descriptions of an electro-magnetic field are connected by the correspondence principle. We consider the electromagnetic field as a source of gravity and compare the metrics due to a classical and quantized electromagnetic field. The quantization of the source demands the quantization of gravity. We also show that (i) the conformal degree of the freedom is not an unphysical mode, and (ii) quantum gravitational effects can exist even when the light cones do not fluctuate.