Non-boost-invariant dissipative hydrodynamics

TL;DR

This paper investigates the non-boost-invariant evolution of quark-gluon plasma using viscous and anisotropic hydrodynamics, highlighting differences at the system edges and emphasizing the importance of comprehensive second-order terms.

Contribution

It compares various formulations of viscous hydrodynamics with anisotropic hydrodynamics in a non-boost-invariant setting, revealing the significance of including complete second-order terms.

Findings

Anisotropic hydrodynamics better controls viscous corrections at system edges.

Results depend on the specific second-order terms included in viscous hydrodynamics.

Both approaches agree in the central hot region of the system.

Abstract

The one-dimensional non-boost-invariant evolution of the quark-gluon plasma, presumably produced during the early stages of heavy-ion collisions, is analyzed within the frameworks of viscous and anisotropic hydrodynamics. We neglect transverse dynamics and assume homogeneous conditions in the transverse plane but, differently from Bjorken expansion, we relax longitudinal boost invariance in order to study the rapidity dependence of various hydrodynamical observables. We compare the results obtained using several formulations of second-order viscous hydrodynamics with a recent approach to anisotropic hydrodynamics, which treats the large initial pressure anisotropy in a non-perturbative fashion. The results obtained with second-order viscous hydrodynamics depend on the particular choice of the second-order terms included, which suggests that the latter should be included in the most complete way. The results of anisotropic hydrodynamics and viscous hydrodynamics agree for the central hot part of the system, however, they differ at the edges where the approach of anisotropic hydrodynamics helps to control the undesirable growth of viscous corrections observed in standard frameworks.