Hydrodynamic fluctuations from a weakly coupled scalar field

TL;DR

This paper investigates how thermal fluctuations of a weakly coupled scalar field influence hydrodynamic properties like shear viscosity and gravitational wave production, with implications for cosmological phase transition simulations.

Contribution

It introduces the concept that scalar field thermal fluctuations induce measurable hydrodynamic effects, providing a new way to calibrate gravitational wave production in simulations.

Findings

Thermal fluctuations induce shear viscosity.

They contribute to gravitational wave production rate.

Potential to study bubble instability in cosmological contexts.

Abstract

Studies of non-equilibrium dynamics of cosmological phase transitions may involve a scalar field interacting weakly with the energy-momentum tensor of a thermal plasma. At late times, when the scalar field is approaching equilibrium, it experiences both damping and thermal fluctuations. We show that thermal fluctuations induce a shear viscosity and a gravitational wave production rate, and propose that including this tunable contribution may help in calibrating the measurement of the gravitational wave production rate in hydrodynamic simulations. Furthermore it may enrich their physical scope, permitting in particular for a study of the instability of growing bubbles.