The irreversible relaxation of inflation

TL;DR

This paper proposes a mechanism for the irreversible relaxation of the cosmological constant during inflation, driven by a thermal bath, eliminating the need for an inflaton potential and naturally producing cosmological perturbations.

Contribution

It introduces a novel thermodynamic approach to inflation by incorporating a thermal bath into Friedmann equations, explaining graceful exit without reheating or inflaton potential.

Findings

Provides a mechanism for the relaxation of the cosmological constant.

Produces scale-invariant, Gaussian cosmological perturbations.

Eliminates the need for an inflaton potential in inflation models.

Abstract

Based on the results of a previous analysis of the Markovian master equation for the irreversible evolution of an open system embedded in de Sitter space, we include in the cosmological Friedmann equations a contribution from the presence of a physical bath at temperature $T_{\rm dS} = h / 2 \pi$, where $h$ is the Hubble parameter. We show that this provides a mechanism for the irreversible relaxation of the cosmological constant and a graceful exit to inflation, without need for subsequent reheating. Thermal particle production during inflation gives adiabatic, Gaussian, and approximately scale-invariant cosmological perturbations. We thus obtain the main features of inflation without any inflaton potential. To clarify the thermodynamic interpretation of these results, we consider the analogy of this irreversible relaxation to superfluorescence in quantum optics.