Relativistic Fluid Dynamics In and Out of Equilibrium -- Ten Years of Progress in Theory and Numerical Simulations of Nuclear Collisions

TL;DR

Over the past decade, significant theoretical and numerical advances have been made in relativistic fluid dynamics, enhancing understanding of non-equilibrium phenomena and improving simulations of nuclear collisions in high-energy physics.

Contribution

This paper reviews ten years of progress in relativistic fluid dynamics theory and numerical simulations, including new insights into non-equilibrium behavior and comparison with experimental data.

Findings

Understanding of divergence in gradient expansion

Development of non-equilibrium attractor solutions

Improved agreement between simulations and experimental results

Abstract

Ten years ago, relativistic viscous fluid dynamics was formulated from first principles in an effective field theory framework, based entirely on the knowledge of symmetries and long-lived degrees of freedom. In the same year, numerical simulations for the matter created in relativistic heavy-ion collision experiments became first available, providing constraints on the shear viscosity in QCD. The field has come a long way since then. We present the current status of the theory of non-equilibrium fluid dynamics in 2017, including the divergence of the fluid dynamic gradient expansion, resurgence, non-equilibrium attractor solutions, the inclusion of thermal fluctuations as well as their relation to microscopic theories. Furthermore, we review the theory basis for numerical fluid dynamics simulations of relativistic nuclear collisions, and comparison of modern simulations to experimental data for nucleus-nucleus, nucleus-proton and proton-proton collisions.