Dissipative Dynamics of Highly Anisotropic Systems

TL;DR

This paper introduces a novel method for modeling highly anisotropic dissipative systems in 0+1 dimensions, improving the description of their dynamics by reorganizing hydrodynamic expansion around an anisotropic ansatz.

Contribution

It develops a new framework that captures large momentum-space anisotropies and unifies ideal, free streaming, and viscous hydrodynamics limits in a single approach.

Findings

Reproduces ideal hydrodynamics and free streaming limits.

Reduces to Israel-Stewart viscous hydrodynamics when linearized.

Provides quantitative comparisons with existing hydrodynamic models.

Abstract

In this paper we present a method to improve the description of 0+1 dimensional boost invariant dissipative dynamics in the presence of large momentum-space anisotropies. We do this by reorganizing the canonical hydrodynamic expansion of the distribution function around a momentum-space anisotropic ansatz rather than an isotropic equilibrium one. At leading order the result obtained is two coupled ordinary differential equations for the momentum-space anisotropy and typical momentum of the degrees of freedom. We show that this framework can reproduce both the ideal hydrodynamic and free streaming limits. Additionally, we demonstrate that when linearized the differential equations reduce to 2nd order Israel-Stewart viscous hydrodynamics. Finally, we make quantitative comparisons of the evolution of the pressure anisotropy within our approach and 2nd order viscous hydrodynamics in both the strong and weak coupling limits.