Thermal Properties of an Inflationary Universe

TL;DR

This paper explores the thermal properties of an inflationary universe, proposing a model where thermal fluctuations influence density perturbations, and introduces a Langevin-like equation to describe these effects within warm inflation scenarios.

Contribution

It provides a quantum field theory-based derivation of a Langevin-like equation for thermal fluctuations during inflation, extending warm inflation models with a particle physics interpretation.

Findings

Thermal fluctuations can dominate quantum fluctuations in seed formation.

Derived a Langevin-like rate equation from quantum field theory.

Connected the model to standard Langevin equations used in warm inflation.

Abstract

An energetic justification of a thermal component during inflation is given. The thermal component can act as a heat reservoir which induces thermal fluctuations on the inflaton field system. We showed previously that such thermal fluctuations could dominate quantum fluctuations in producing the initial seeds of density perturbations. A Langevin-like rate equation is derived from quantum field theory which describes the production of fluctuations in the inflaton field when acted upon by a simple modeled heat reservoir. In a certain limit this equation is shown to reduce to the standard Langevin equation, which we used to construct "Warm Inflation" scenarios in previous work. A particle physics interpretation of our system-reservoir model is offered.