Density perturbations in warm inflation and COBE normalization

TL;DR

This paper derives an analytical spectrum for density perturbations in warm inflation, explicitly shows adiabatic and entropy modes, and compares model predictions with COBE data to assess warm inflation's viability.

Contribution

It provides the first analytical expression for long wavelength density perturbations in warm inflation, including adiabatic and entropy modes, and applies it to observational constraints.

Findings

Analytical spectrum derived for warm inflation perturbations

Explicit representation of adiabatic and entropy modes

Constraints on dissipation term from COBE data

Abstract

Starting from a gauge invariant treatment of perturbations an analytical expression for the spectrum of long wavelength density perturbations in warm inflation is derived. The adiabatic and entropy modes are exhibited explicitly. As an application of the analytical results, we determined the observational constraint for the dissipation term compatible with COBE observation of the cosmic microwave radiation anisotropy for some specific models. In view of the results the feasibility of warm inflation is discussed.