Hydrodynamics of nonintegrable systems from a relaxation-time approximation

TL;DR

This paper introduces a kinetic theory framework using a relaxation-time approximation to accurately describe the hydrodynamics of weakly nonintegrable quantum systems, bridging generalized and conventional hydrodynamics.

Contribution

It presents a novel, simple approximation method for nonequilibrium transport in strongly interacting, weakly nonintegrable quantum systems, validated against various models.

Findings

Accurately reproduces crossover from generalized to conventional hydrodynamics.

Predicts hydrodynamics of chaotic quantum spin chains.

Agrees well with matrix product operator calculations.

Abstract

We develop a general kinetic theory framework to describe the hydrodynamics of strongly interacting, nonequilibrium quantum systems in which integrability is weakly broken, leaving a few residual conserved quantities. This framework is based on a generalized relaxation-time approximation; it gives a simple, but surprisingly accurate, prescription for computing nonequilibrium transport even in strongly interacting systems. This approximation reproduces the crossover from generalized to conventional hydrodynamics in interacting one-dimensional Bose gases with integrability-breaking perturbations, both with and without momentum conservation. It also predicts the hydrodynamics of chaotic quantum spin chains, in good agreement with matrix product operator calculations.