Nonequilibrium dynamics of a stochastic model of anomalous heat transport: numerical analysis

TL;DR

This paper investigates the nonequilibrium heat transport in a stochastic harmonic oscillator chain, revealing boundary condition effects, boundary layer phenomena, and distinct relaxation time scales through numerical analysis.

Contribution

It provides a detailed numerical study of boundary condition impacts and boundary layer formation in a stochastic heat transport model, highlighting nonequilibrium effects.

Findings

Temperature profile depends on boundary conditions.

Boundary layers of size √N exhibit non-equilibrium behavior.

Two distinct relaxation time scales are identified.

Abstract

We study heat transport in a chain of harmonic oscillators with random elastic collisions between nearest-neighbours. The equations of motion of the covariance matrix are numerically solved for free and fixed boundary conditions. In the thermodynamic limit, the shape of the temperature profile and the value of the stationary heat flux depend on the choice of boundary conditions. For free boundary conditions, they also depend on the coupling strength with the heat baths. Moreover, we find a strong violation of local equilibrium at the chain edges that determine two boundary layers of size $\sqrt{N}$ (where $N$ is the chain length), that are characterized by a different scaling behaviour from the bulk. Finally, we investigate the relaxation towards the stationary state, finding two long time scales: the first corresponds to the relaxation of the hydrodynamic modes; the second is a manifestation of the finiteness of the system.