Real-time dynamics of the O(N) model in 1+1 dimensions

Abstract

We study the non-equilibrium dynamics of the O(N) model in classical and quantum field theory in 1+1 dimensions, for N > 1. We compare numerical results obtained using the Hartree approximation and two next to leading order approximations, the bare vertex approximation and the 2PI-1/N expansion. The later approximations differ through terms of order g^2, where g is the scaled coupling constant, g=\lambda/N. In this paper we investigate the statement regarding the convergence with respect to g. We find that the differences between these twoapproximation schemes diminish for larger values of N, when \lambda is fixed.