An improved anisotropic hydrodynamics ansatz

TL;DR

This paper presents an improved anisotropic hydrodynamics model that better captures the evolution of distribution function moments, especially for moments without longitudinal momentum, aligning more closely with kinetic theory results.

Contribution

The authors introduce a new anisotropic hydrodynamics ansatz that separately accounts for free-streaming and equilibration, enhancing accuracy in modeling distribution function moments.

Findings

Improved reproduction of exact moment evolution results.

Enhanced agreement with kinetic theory attractors.

Better modeling of early-time dynamics for specific moments.

Abstract

We introduce an improved form for the anisotropic hydrodynamics distribution function which explicitly takes into account the free-streaming and equilibrating contributions separately. We demonstrate that with this improvement one can better reproduce exact results available in the literature for the evolution of moments of the distribution function, in particular, for moments which contain no powers of the longitudinal momentum in their definition (m=0 moments). Using the resulting dynamical equations, we extract the non-equilibrium attractor associated with our improved aHydro ansatz and demonstrate that the improvement also allows one to better reproduce the exact dynamical attractor obtained using kinetic theory in the relaxation time approximation, particularly at early rescaled times and for m=0 moments.