Non-thermal fixed points: effective weak-coupling for strongly correlated systems far from equilibrium

TL;DR

This paper demonstrates that strongly correlated systems far from equilibrium can develop scaling solutions with an effective weak coupling, influencing thermalization processes in cosmology and heavy-ion physics.

Contribution

It introduces the concept of non-thermal fixed points in relativistic quantum field theories, showing how they lead to effective weak coupling in nonequilibrium conditions.

Findings

Non-thermal fixed points prevent rapid thermalization.

Classical fluctuations dominate quantum fluctuations near fixed points.

Implications for early universe heating and heavy-ion collisions.

Abstract

Strongly correlated systems far from equilibrium can exhibit scaling solutions with a dynamically generated weak coupling. We show this by investigating isolated systems described by relativistic quantum field theories for initial conditions leading to nonequilibrium instabilities, such as parametric resonance or spinodal decomposition. The non-thermal fixed points prevent fast thermalization if classical-statistical fluctuations dominate over quantum fluctuations. We comment on the possible significance of these results for the heating of the early universe after inflation and the question of fast thermalization in heavy-ion collision experiments.