Renormalised nonequilibrium quantum field theory: scalar fields

TL;DR

This paper develops a renormalisation approach for nonequilibrium quantum field theory with scalar fields using the 2PI formalism, emphasizing initial conditions and demonstrating a continuum limit through numerical analysis.

Contribution

It introduces a method to renormalise nonequilibrium dynamics in quantum field theory with self-consistent initial conditions using the 2PI formalism.

Findings

Renormalisation via equilibrium counterterms is effective for nonequilibrium dynamics.

Self-consistent initial conditions improve the physical realism of the model.

Numerical results support the existence of a continuum limit for these initial conditions.

Abstract

We discuss the renormalisation of the initial value problem in quantum field theory using the two-particle irreducible (2PI) effective action formalism. The nonequilibrium dynamics is renormalised by counterterms determined in equilibrium. We emphasize the importance of the appropriate choice of initial conditions and go beyond the Gaussian initial density operator by defining self-consistent initial conditions. We study the corresponding time evolution and present a numerical example which supports the existence of a continuum limit for this type of initial conditions.