Anisotropic fluid dynamical simulations of heavy-ion collisions

TL;DR

This paper introduces VAH, a (3+1)-D anisotropic fluid dynamics simulation for quark-gluon plasma in heavy-ion collisions, featuring an adaptive numerical scheme that efficiently models early-stage collision dynamics.

Contribution

The paper presents a new (3+1)-D anisotropic hydrodynamics simulation with an adaptive Runge-Kutta method, enabling early-time modeling without separate pre-equilibrium modules.

Findings

VAH accurately reproduces known flow solutions like Bjorken and Gubser flows.

Non-conformal anisotropic hydrodynamics better captures longitudinal flow gradients.

Simulation results show improved modeling of early-stage quark-gluon plasma dynamics.

Abstract

We present VAH, a (3+1)-dimensional simulation that evolves the far-from-equilibrium quark-gluon plasma produced in ultrarelativistic heavy-ion collisions with anisotropic fluid dynamics. We solve the hydrodynamic equations on an Eulerian grid using the Kurganov-Tadmor algorithm in combination with a new adaptive Runge-Kutta method. Our numerical scheme allows us to start the simulation soon after the nuclear collision, largely avoiding the need to integrate it with a separate pre-equilibrium dynamics module. We test the code's performance by simulating on the Eulerian grid conformal and non-conformal Bjorken flow as well as conformal Gubser flow, whose (0+1)-dimensional solutions are precisely known. Finally, we compare non-conformal anisotropic hydrodynamics to second-order viscous hydrodynamics in central Pb+Pb collisions and find that the former's longitudinal flow profile responds more consistently to the fluid's gradients along the spacetime rapidity direction.