O(N) Quantum fields in curved spacetime

TL;DR

This paper develops a framework for analyzing the nonperturbative, nonequilibrium dynamics of O(N) quantum fields with self-interaction in curved spacetime, relevant for early universe phase transitions.

Contribution

It constructs the 2PI-CTP effective action for O(N) fields in curved spacetime, enabling study of back reactions and fluctuations during cosmological phase transitions.

Findings

Framework for nonperturbative quantum field dynamics in curved spacetime

Coupled equations for mean field and variance derived

Applications to early universe phase transitions under investigation

Abstract

For the O(N) field theory with lambda Phi^4 self-coupling, we construct the two-particle-irreducible (2PI), closed-time-path (CTP) effective action in a general curved spacetime. From this we derive a set of coupled equations for the mean field and the variance. They are useful for studying the nonperturbative, nonequilibrium dynamics of a quantum field when full back reactions of the quantum field on the curved spacetime, as well as the fluctuations on the mean field, are required. Applications to phase transitions in the early Universe such as the Planck scale or in the reheating phase of chaotic inflation are under investigation.