Viscous hydrodynamics for strongly anisotropic expansion

TL;DR

This paper introduces a new second-order viscous hydrodynamics formulation based on anisotropic momentum distributions, improving accuracy in modeling strongly anisotropic expansions in relativistic systems.

Contribution

It extends anisotropic hydrodynamics to include all dissipative currents with derived equations of motion from the Boltzmann equation in the 14-moment approximation.

Findings

vaHydro outperforms other second-order viscous hydrodynamics models

It accurately describes (0+1)-dimensional expansion dynamics

The formalism improves modeling of strongly anisotropic systems

Abstract

A new formulation of second-order viscous hydrodynamics, based on an expansion around a locally anisotropic momentum distribution, is presented. It generalizes the previously developed formalism of anisotropic hydrodynamics (aHydro) to include a complete set of dissipative currents for which equations of motion are derived by solving the Boltzmann equation in the 14-moment approximation. By solving the vaHydro equations for a transversally homogeneous, longitudinally boost-invariant system ((0+1)-dimensional expansion) and comparing with the exact solution of the Boltzmann equation in relaxation-time approximation we show that vaHydro performs much better than all other known second-order viscous hydrodynamic approximations.