Numerical integration of thermal noise in relativistic hydrodynamics

TL;DR

This paper develops a numerical framework to incorporate thermal noise into relativistic hydrodynamics simulations, revealing its significant impact on observables in heavy-ion collisions and implications for QCD physics.

Contribution

It calculates noise correlation functions, implements stochastic integration in 3+1D viscous hydrodynamics, and analyzes noise effects on collision observables.

Findings

Thermal noise causes large variance in v2 distributions.

Including noise alters average flow values, affecting parameter fits.

Thermal fluctuations influence the interpretation of heavy-ion collision data.

Abstract

Thermal fluctuations affect the dynamics of systems near critical points, the evolution of the early universe, and two-particle correlations in heavy-ion collisions. For the latter, numerical simulations of nearly-ideal, relativistic fluids are necessary. The correlation functions of noise in relativistic fluids are calculated, stochastic integration of the noise in 3+1-dimensional viscous hydrodynamics is implemented, and the effect of noise on observables in heavy-ion collisions is discussed. Thermal fluctuations will cause significant variance in the event-by-event distributions of integrated v2 while changing average values even when using the same initial conditions, suggesting that including thermal noise will lead to refitting of the hydrodynamical parameters with implications for understanding the physics of hot QCD.