On the thermodynamic origin of the initial radiation energy density in warm inflation

TL;DR

This paper investigates the thermodynamic origins of the initial radiation energy density in warm inflation, deriving an effective Stefan-Boltzmann law that explains its finite value at inflation onset and explores implications for GUT baryogenesis.

Contribution

It introduces a thermodynamic analysis leading to an effective Stefan-Boltzmann law consistent with temperature-dependent potentials in warm inflation.

Findings

Radiation energy density increases from zero at GUT epoch to finite at inflation start.

Derived an effective Stefan-Boltzmann law accounting for non-zero trace of energy-momentum tensor.

Established conditions for sufficient radiation density for GUT baryogenesis.

Abstract

In warm inflation scenarios, radiation always exists, so that the radiation energy density is also assumed to be finite when inflation starts. To find out the origin of the non-vanishing initial radiation energy density, we revisit thermodynamic analysis for a warm inflation model and then derive an effective Stefan-Boltzmann law which is commensurate with the temperature-dependent effective potential by taking into account the non-vanishing trace of the total energy-momentum tensors. The effective Stefan-Boltzmann law shows that the zero energy density for radiation at the Grand Unification epoch increases until the inflation starts and it becomes eventually finite at the initial stage of warm inflation. By using the above effective Stefan-Boltzmann law, we also study the cosmological scalar perturbation, and obtain the sufficient radiation energy density in order for GUT baryogenesis at the end of inflation.