Casimir-like force between intruders in granular gases

TL;DR

This study numerically investigates the fluctuation-induced Casimir-like force between intruder particles in a driven granular gas, revealing Gaussian force distributions and dependence on system parameters.

Contribution

It introduces a numerical analysis of Casimir-like forces in granular gases, highlighting the role of hydrodynamic fluctuations and system size effects.

Findings

Force distribution is Gaussian centered on a temperature-dependent mean.

Mean force grows logarithmically with system size.

Force magnitude is estimated via Fourier transform of hydrodynamic fluctuations.

Abstract

We numerically study a two-dimensional granular gas of rigid disks where an external driving force is applied to each particle in such a way that the system is driven into a steady state by balancing the energy input and the dissipation due to inelastic collisions. Two intruder particles embedded in this correlated medium experience a fluctuation-induced force -- that is itself a fluctuating quantity -- due to the confinement of the hydrodynamic fluctuations between them. We find that the probability distribution of this force is a Gaussian centered on a value that is proportional to the steady-state temperature and grows logarithmically with system size. We investigate the effect of the other relevant parameters and estimate the force using the Fourier transform of the fluctuating hydrodynamic fields.