Isotropization by shock waves generation in anisotropic hydrodynamics

TL;DR

This paper explores shock wave formation in anisotropic hydrodynamics, introducing new analytical solutions and numerical methods to understand isotropization in quark-gluon plasma with rapid expansion.

Contribution

It presents a novel analysis of shock waves in anisotropic hydrodynamics, accounting for variable anisotropy and providing insights into isotropization processes.

Findings

Analytical solutions for shock waves without flow refraction.

Numerical simulations demonstrating isotropization mechanisms.

Identification of two compression parameters for pressures.

Abstract

Anisotropic hydrodynamics (aHydro) has proven successful in modeling the evolution of quark-gluon matter created in heavy-ion collisions. The hydrodynamic description of quark-gluon plasma has also been widely used to study sound phenomena, such as shock waves. It has recently been shown that initial fluctuations in energy density and supersonic partons can generate fairly strong shock waves. However, significant anisotropic properties of the system due to the rapid longitudinal expansion of matter have not been taken into account in such studies. Moreover, the process of isotropization and its characteristic time-scales were not considered along with the question of the shock waves formation. Previous studies on shock discontinuous solutions in anisotropic hydrodynamics assumed constant anisotropy, leading to flow refraction towards the anisotropy axis and flow acceleration, characteristics of rarefaction waves, indicating limitations in this approach. This paper investigates discontinuous solutions for normal shock waves without flow refraction, introducing two compression parameters for longitudinal and transverse pressures. The resulting analytical solutions, as well as numerical computations, provide an isotropization mechanism of the system.