Relativistic Noise

TL;DR

This paper derives the relativistic hydrodynamic noise theory and explores its implications for high energy heavy ion collisions, highlighting how fluctuations influence correlations and depend on viscosities.

Contribution

It introduces a relativistic theory of hydrodynamic fluctuations and applies it to model correlations in heavy ion collisions.

Findings

Long-range rapidity correlations are induced by sound modes.

Correlation magnitude is proportional to viscosities.

Fluctuations are enhanced near phase transitions.

Abstract

The relativistic theory of hydrodynamic fluctuations, or noise, is derived and applied to high energy heavy ion collisions. These fluctuations are inherent in any space-time varying system and are in addition to initial state fluctuations. We illustrate the effects with the boost-invariant Bjorken solution to the hydrodynamic equations. Long range correlations in rapidity are induced by propagation of sound modes. The magnitude of these correlations are directly proportional to the viscosities. These fluctuations should be enhanced near a phase transition or rapid crossover.