Hydrodynamic Fluctuations in Relativistic Heavy-Ion Collisions

TL;DR

This paper introduces a new method to incorporate thermal fluctuations into 3+1D viscous hydrodynamic simulations of heavy-ion collisions, analyzing their effects on observables within a consistent, non-perturbative framework.

Contribution

It develops a novel scheme to treat hydrodynamic fluctuations as source terms in the evolution equations, improving the modeling of thermal noise in heavy-ion collision simulations.

Findings

Thermal fluctuations can influence final-state observables.

The new method captures non-perturbative effects of fluctuations.

Hydrodynamic response to fluctuations is systematically analyzed.

Abstract

We present a novel approach to the treatment of thermal fluctuations in the (3+1)-D viscous hydrodynamic simulation MUSIC. The phenomenological impact of thermal fluctuations on hadronic observables is investigated using the IP-Glasma + hydrodynamics + hadronic cascade hybrid approach. The anisotropic flow observed in heavy-ion collision experiments is mostly attributed to the hydrodynamic response to the event-by-event collision geometry and to the sub-nucleon quantum fluctuations. However, hydrodynamic fluctuations are present during the dynamical evolution of the Quark Gluon Plasma (QGP) and are quantified by the fluctuation-dissipation theorem. They can leave their imprint on final-state observables. By analyzing the thermal noise mode-by-mode, we provide a consistent scheme of treating these fluctuations as the source terms for hydrodynamic fields. These source terms are then evolved together with hydrodynamic equations of motion. Such a treatment captures the non-perturbative nature of the evolution for these thermal fluctuations.