Critical behavior of two freely evolving granular gases separated by an adiabatic piston

TL;DR

This paper investigates a phase transition in a system of two granular gases separated by an adiabatic piston, revealing spontaneous symmetry breaking and unique temperature and cooling rate behaviors.

Contribution

It introduces a simple kinetic model that accurately describes the phase transition and the piston’s behavior in granular gases separated by an adiabatic piston.

Findings

A phase transition with symmetry breaking occurs when piston mass exceeds a critical value.

The piston stabilizes away from the system's center, breaking symmetry.

Final state characterized by equal cooling rates, not equal temperatures.

Abstract

Two granular gases separated by an adiabatic piston and initially in the same macroscopic state are considered. It is found that a phase transition with an spontaneous symmetry breaking occurs. When the mass of the piston is increased beyond a critical value, the piston moves to a stationary position different from the middle of the system. The transition is accurately described by a simple kinetic model that takes into account the velocity fluctuations of the piston. Interestingly, the final state is not characterized by the equality of the temperatures of the subsystems but by the cooling rates being the same. Some relevant consequences of this feature are discussed.