Thermalization in a one-dimensional integrable system

TL;DR

This paper demonstrates that single-particle observables in a one-dimensional integrable system can thermalize under certain initial conditions, explaining experimental observations in ultracold atomic gases.

Contribution

It shows that even integrable systems can exhibit thermalization of single-particle observables under specific initial conditions, supported by numerical simulations.

Findings

Single-particle observables relax to near thermal distribution

Thermalization occurs on a short (~1 ms) timescale

Numerical results explain experimental thermalization in ultracold gases

Abstract

We present numerical results demonstrating the possibility of thermalization of single-particle observables in a one-dimensional integrable system (a quasicondensate of ultra-cold, weakly-interacting bosonic atoms being studied as a definite example). These results may seem counterintuitive because the physical system is integrable in both the quantum and classical (mean-field) descriptions. However, we find a class of initial conditions that admits the relaxation of distributions of single-particle observables to the equilibrium state very close to the Bose-Einstein thermal distribution of Bogoliubov quasiparticles. Our numerical results allow us to explain experimentally observed thermalization in one-dimensional ultracold atomic gases on a short (~1 ms) time scale.