Highly-anisotropic and strongly-dissipative hydrodynamics for early stages of relativistic heavy-ion collisions

TL;DR

This paper presents a new anisotropic hydrodynamics framework with dissipation for modeling early-stage relativistic heavy-ion collisions, capturing the transition from anisotropic to isotropic fluid behavior.

Contribution

It introduces a novel hydrodynamics model incorporating dissipation via entropy source dependence on pressure anisotropy, applicable to early collision stages.

Findings

The model describes the evolution of pressure anisotropy over time.

Highly anisotropic matter naturally evolves towards isotropy.

The approach aligns with expected early-stage collision behavior.

Abstract

We introduce a new framework of highly-anisotropic hydrodynamics that includes dissipation effects. Dissipation is defined by the form of the entropy source that depends on the pressure anisotropy and vanishes for the isotropic fluid. With a simple ansatz for the entropy source obeying general physical requirements, we are led to a non-linear equation describing the time evolution of the anisotropy in purely-longitudinal boost-invariant systems. Matter that is initially highly anisotropic approaches naturally the regime of the perfect fluid. Thus, the resulting evolution agrees with the expectations about the behavior of matter produced at the early stages of relativistic heavy-ion collisions. The equilibration is identified with the processes of entropy production.