Is warm inflation quasi-stable?

TL;DR

This paper examines the thermodynamics of warm inflation, revealing that exact adiabatic radiation production is unrealistic and proposing a variable cosmological constant to support quasi-stability.

Contribution

It demonstrates the inconsistency of exact adiabatic radiation production in warm inflation and introduces a variable cosmological constant to achieve quasi-stability.

Findings

Exact adiabatic radiation production is unrealistic in warm inflation.

Radiation particle number, temperature, and energy density are conserved only at zeroth order.

A variable cosmological constant can support quasi-stable warm inflation.

Abstract

The present work deals with a non-equilibrium thermodynamics that is associated with the scenario of warm inflation. The premise is that an adiabatic radiation production process holds exactly i.e. the radiation dilution is exactly counterbalanced by a dissipation term. Under this hypothesis, it is found that radiation particle number, temperature, radiation energy density and pressure are all conserved -- a contradiction to the very nature of the warm inflation dynamics. However, such exact adiabatic radiation production process never happens in any realistic analysis of warm inflation. In the slow roll approximation this holds at best at the zeroth order. Finally it is shown that a variable cosmological constant may accommodate the quasi-stable process in warm inflation with non-equilibrium thermodynamic description.