Chapman-Enskog expansion for chirally colliding disks

TL;DR

This paper develops a Chapman-Enskog expansion for a 2D fluid of chiral disks, deriving analytical transport coefficients and confirming them through molecular dynamics simulations, despite microscopic time-reversal symmetry breaking.

Contribution

It introduces a Chapman-Enskog framework for chiral disk fluids and provides analytical expressions for transport properties, validated by simulations.

Findings

Analytical expressions for shear and odd viscosity.

Confirmation of theoretical predictions via molecular dynamics.

Demonstration of the H-theorem in chiral disk systems.

Abstract

We study a two-dimensional fluid of hard disks undergoing chiral, energy- and momentum-conserving collisions. We show that despite the microscopic breaking of time-reversal symmetry, the H-theorem is obeyed, guaranteeing a relaxation towards equilibrium in the absence of external forces. In the dilute limit, a Chapman-Enskog expansion yields analytical expressions for the shear and odd viscosity and the thermal conductivity. Theoretical predictions are confirmed by nonequilibrium molecular dynamics simulations.