Long-time tails and cage effect in driven granular fluids

TL;DR

This paper investigates the velocity autocorrelation function in driven granular fluids, revealing cage effects and algebraic decay near the glass transition, with implications for understanding diffusion in non-equilibrium systems.

Contribution

It provides the first detailed analysis of VACF behavior and cage effects in driven granular fluids approaching the glass transition.

Findings

VACF exhibits cage effects near the glass transition

Diffusion constant decreases significantly at high densities

VACF decays algebraically as t^{-3/2} at moderate densities

Abstract

We study the velocity autocorrelation function (VACF) of a driven granular fluid in the stationary state in 3 dimensions. As the critical volume fraction of the glass transition in the corresponding elastic system is approached, we observe pronounced cage effects in the VACF as well as a strong decrease of the diffusion constant. At moderate densities the VACF is shown to decay algebraically in time (t^{-3/2}) like in a molecular fluid, as long as the driving conserves momentum locally.