NATURE OF THE GAUSSIAN APPROXIMATIONS IN PHASE-ORDERING KINETICS

The structure of the Gaussian auxiliary field approximation in the theory of phase-ordering kinetics is analyzed with the aim of placing the method within the context of a systematic theory. While we are unable to do this for systems with a scalar order parameter, where the approximation remains uncontrolled, a systematic development about the Gaussian approximation can be outlined for systems with a vector order parameter in terms of a suitably defined 1/N expansion.