Energy and Heat Fluctuations in a Temperature Quench

TL;DR

This paper investigates energy and heat fluctuations during relaxation after a temperature quench, revealing a condensation phenomenon driven by out-of-equilibrium dynamics similar to Bose-Einstein condensation.

Contribution

It analytically demonstrates a condensation of fluctuations in Gaussian and large N models following a temperature quench, highlighting a novel out-of-equilibrium phase transition.

Findings

Fluctuations exceeding a critical threshold condense.

The phenomenon is driven by breaking of energy equipartition.

The transition is out-of-equilibrium and dynamically characterized.

Abstract

Fluctuations of energy and heat are investigated during the relaxation following the instantaneous temperature quench of an extended system. Results are obtained analytically for the Gaussian model and for the large $N$ model quenched below the critical temperature $T_C$. The main finding is that fluctuations exceeding a critical threshold do condense. Though driven by a mechanism similar to that of Bose-Einstein condensation, this phenomenon is an out-of-equilibrium feature produced by the breaking of energy equipartition occurring in the transient regime. The dynamical nature of the transition is illustrated by phase diagrams extending in the time direction.