On the consistency of warm inflation

TL;DR

This paper derives conditions under which warm inflation models exhibit attractor behavior, ensuring a slow-roll evolution with specific predictions for density perturbations and tensor-to-scalar ratios.

Contribution

It provides new criteria for the existence of warm inflation attractors, linking dissipative effects, thermal corrections, and potential gradients to observable predictions.

Findings

Conditions for warm inflation attractors are established.

Formulas for spectral indices and tensor/scalar ratios are derived.

Constraints on temperature dependence and thermal corrections are identified.

Abstract

Conditions are obtained for the existence of a warm inflationary attractor in the system of equations describing an inflaton coupled to radiation. These conditions restrict the temperature dependence of the dissipative terms and the size of thermal corrections to the inflaton potential, as well as the gradient of the inflaton potential. When these conditions are met, the evolution approaches a slow-roll limit and only curvature fluctuations survive on super-horizon scales. Formulae are given for the spectral indices of the density perturbations and the tensor/scalar density perturbation amplitude ratio in warm inflation.