Quantum dynamics of Phi**4 field theory beyond leading order in 1+1 dimensions

Abstract

We consider the out-of-equilibrium evolution of a classical condensate field $\varphi =<\Phi >$ and its quantum fluctuations for a ${\Phi }^4$ model in 1+1 dimensions with a double well potential. We use the two-particle point-irreducible (2PPI) formalism in the two-loop approximation. We compare our results to those obtained in the Hartree approximation, in the bare vertex approximation (BVA) and in the two-particle irreducible next-to-leading order large-N (2PI-1/N) approach, with thermal initial conditions. In the 2PPI scheme we find that the system tends to the symmetric configuration at late times, as expected in the absence of spontaneous symmetry breaking.

Comments: 4 pages, 8 encapsulated postscript figures