Energy–Momentum Tensors for Dispersive Electromagnetic Waves

Abstract

Classical relativistic field theory is used as a basis for a general discussion of the problem of splitting up the total energy–momentum tensor of a system into contributions from its component subsystems. Both the Minkowski and Abraham forms (including electrostriction) arise naturally in alternative split-up procedures applied to a non dispersive dielectric fluid. The case of an electromagnetic wave in a (spatially and temporally) dispersive medium in arbitrary but slowly varying motion is then treated. In the dispersive case the results cannot be found by replacing the dielectric constant ε with ε(κ, ω) but include derivatives with respect to the wave vector κ and the frequency ω. Ponderomotive force expressions are obtained and the perturbation in the total energy–momentum tensor due to a one-dimensional wavepacket is found. A nonlinear Schrödinger equation is obtained for the evolution of a three-dimensional wavepacket. Both hot and cold plasmas are treated.