Nonequilibrium 2PI evolution of the O(N) model with longitudinal expansion

TL;DR

This paper investigates the nonequilibrium dynamics of the O(N) model with longitudinal expansion, comparing 2PI formalism and classical statistical methods, and finds evidence of Bose-Einstein distribution emergence at strong coupling.

Contribution

It provides a numerical study of the O(N) model's evolution with expansion, highlighting differences between 2PI and classical approaches, and explores thermalization features.

Findings

Evidence of Bose-Einstein distribution at strong coupling

Differences observed between 2PI and classical statistical approaches

Insights into thermalization in expanding quantum fields

Abstract

Motivated by the problem of thermalization in heavy-ion collisions, we present numerical simulations of the nonequilibrium evolution of the O(N) model in 1+2 dimensions with longitudinal expansion and in the presence of a background field. We work in the NLO approximation of the 1/N expansion and consider both the strong and weak coupling cases. Special emphasis is put on the difference between the 2PI formalism and the classical statistical approach. In the 2PI case at strong coupling, we find some evidence of the Bose-Einstein (exponential) distribution in the expanding system.