Steady asymptotic equilibria in conformal relativistic fluids

CALZETTA, ESTEBAN

Physical Review D

APS

Año: 2022 vol. 105

2470-0010

When one considers a shock wave in the frame where the shock is at rest, on either side one has a steadyflow which converges to equilibrium away from the shock. However, hydrodynamics is unable to describethis flow if the asymptotic velocity is higher than the characteristic speed of the theory. We obtain an exactsolution for the decay rate to equilibrium for a conformal fluid in kinetic theory under the relaxation timeapproximation, and compare it to two hydrodynamic schemes, one accounting for the second moments ofthe distribution function and thus equivalent, in the small deviations from equilibrium limit, to an Israel-Stewart framework, and another accounting for both second and third moments. While still having a finitecharacteristic speed, the second model is a significant improvement on the first.