Quantum field thermalization in expanding backgrounds

TL;DR

This paper develops a formalism for studying quantum field thermalization in expanding backgrounds, solving evolution equations for a phi^4 model, and exploring phenomena like thermalization and reheating.

Contribution

It introduces a 2PI effective action approach for quantum fields in expanding spacetimes, including NLO calculations and discussions on renormalization and applicability.

Findings

Demonstrates thermalization in expanding backgrounds

Analyzes reheating processes in quantum fields

Addresses renormalization in curved spacetime

Abstract

The 2PI effective action formalism for quantum fields out of equilibrium is set up in an expanding (Friedmann-Robertson-Walker) background. We write down and solve the evolution equations for a phi^4 model at NLO in a coupling expansion. We comment on issues of renormalization, lattice discretization and the range of applicability of the approach. A number of example calculations are presented, including thermalization and (p)reheating. Generalizations to more complicated systems and applications are discussed.