Equilibration and symmetry breaking in vibrated granular systems

TL;DR

This paper investigates non-equilibrium phase transitions and spontaneous symmetry breaking in vibrated granular gases separated by an adiabatic piston, combining kinetic theory and molecular dynamics simulations.

Contribution

It introduces a simple kinetic theory model that explains symmetry breaking in vibrated granular systems and validates it with simulation results.

Findings

Observation of symmetry breaking despite identical conditions on both sides.

Good agreement between kinetic theory predictions and molecular dynamics simulations.

Identification of a non-equilibrium phase transition in vibrated granular gases.

Abstract

The steady states of two vibrated granular gases separated by an adiabatic piston are investigated. The system exhibits a non-equilibrium phase transition with an spontaneous symmetry breaking. Even if the gases at both sides of the piston have the same number of particles and are mechanically identical, their steady volumes and temperatures can be rather different. The transition can be explained by a simple kinetic theory model expressing mechanical equilibrium and the energy balance occurring in the system. The model predictions are in good agreement with molecular dynamics simulation results. The macroscopic description of the steady states is discussed, as well as some physical implications of the symmetry breaking.