Fluctuation-dissipation dynamics of cosmological scalar fields

TL;DR

This paper explores how dissipation affects cosmological scalar fields, impacting symmetry breaking, baryogenesis, and inflation, with detailed calculations and implications for observable signatures in the universe.

Contribution

It provides explicit calculations of dissipation coefficients for scalar fields in the Standard Model and extensions, and analyzes their effects on cosmological phenomena such as inflation and baryogenesis.

Findings

Dissipative friction can delay symmetry breaking and induce warm inflation.

Dissipation can produce the baryon asymmetry without symmetry restoration.

Characteristic baryon isocurvature perturbations can be tested with CMB observations.

Abstract

We show that dissipative effects have a significant impact on the evolution of cosmological scalar fields, leading to friction, entropy production and field fluctuations. We explicitly compute the dissipation coefficient for different scalar fields within the Standard Model and some of its most widely considered extensions, in different parametric regimes. We describe the generic consequences of fluctuation-dissipation dynamics in the post-inflationary universe, focusing in particular on friction and particle production, and analyze in detail two important effects. Firstly, we show that dissipative friction delays the process of spontaneous symmetry breaking and may even damp the the motion of a Higgs field sufficiently to induce a late period of warm inflation. Along with dissipative entropy production, this may parametrically dilute the abundance of dangerous thermal relics. Secondly, we show that dissipation can generate the observed baryon asymmetry without symmetry restoration, and we develop in detail a model of dissipative leptogenesis. We further show that this generically leads to characteristic baryon isocurvature perturbations that can be tested with CMB observations. This work provides a fundamental framework to go beyond the leading thermal equilibrium semi-classical approximation in addressing fundamental problems in modern cosmology.