Nonlinearity accelerates the thermalization of the quartic FPUT model with stochastic baths

TL;DR

This paper studies how nonlinearity in the quartic FPUT model with stochastic baths accelerates thermalization, showing that increased nonlinearity leads to faster energy distribution and system equilibration.

Contribution

It demonstrates that nonlinearity enhances energy redistribution, significantly speeding up the thermalization process in the FPUT model with stochastic baths.

Findings

Thermalization time scales linearly with system size.

Nonlinearity causes faster relaxation of high-frequency modes.

Energy distribution among modes is accelerated by nonlinear interactions.

Abstract

We investigate the equilibration process of the strongly coupled quartic Fermi-Pasta-Ulam-Tsingou (FPUT) model by adding Langevin baths to the ends of the chain. The time evolution of the system is investigated by means of extensive numerical simulations and shown to match the results expected from equilibrium statistical mechanics in the time-asymptotic limit. Upon increasing the nonlinear coupling, the thermalization of the energy spectrum displays an increasing asymmetry in favour of small-scale, high-frequency modes, which relax significantly faster than the large-scale, low-frequency ones. The global equilibration time is found to scale linearly with system size and shown to exhibit a power-law decay with the strength of the nonlinearity and temperature. Nonlinear interaction adds to energy distribution among modes, thus speeding up the thermalization process.