Far-from-equilibrium attractor in non-conformal plasmas

TL;DR

This paper investigates the far-from-equilibrium behavior of non-conformal plasmas, revealing the existence of a unique attractor for longitudinal pressure and evaluating the effectiveness of different hydrodynamic models in capturing this behavior.

Contribution

It demonstrates the presence of a far-from-equilibrium attractor in non-conformal systems and shows that modified anisotropic hydrodynamics accurately reproduces kinetic theory results.

Findings

An early-time attractor exists for scaled longitudinal pressure.

Second-order hydrodynamics fails to describe the attractor.

Modified anisotropic hydrodynamics matches kinetic theory closely.

Abstract

We study the far-off-equilibrium dynamics of a Bjorken expanding non-conformal system within kinetic theory and hydrodynamics. We show that, in contrast to the conformal case, neither shear nor bulk viscous pressure relax quickly to a non-equilibrium attractor. In kinetic theory an early-time, far-from-equilibrium attractor exists for the scaled longitudinal pressure, driven by the rapid longitudinal expansion of the medium. Second-order dissipative hydrodynamics fails to accurately describe this attractor, but a modified anisotropic hydrodynamic formulation reproduces it and provides excellent agreement with kinetic theory.