On the consistency of warm inflation in the presence of viscosity

TL;DR

This paper investigates how viscous pressure affects the stability and spectral predictions of warm inflation models, showing viscosity broadens stability ranges with minimal impact on spectral ratios, and uses observational data for parameter constraints.

Contribution

It introduces viscous pressure into warm inflation analysis, demonstrating its stabilizing effect and deriving spectral parameters aligned with observational data.

Findings

Viscous pressure widens the stability range of warm inflation.

Viscosity has little impact on the spectral index ratio.

Model parameters are constrained using WMAP7 data.

Abstract

This paper studies the stability of warm inflationary solutions when the viscous pressure is taken into account. The latter is a very natural and physically motivated ingredient of warm inflation and is seen to widen the stability range of warm inflation. The spectral index parameters, $n_{s}$, $n_{T}$, and their ratio are derived. The corresponding WMAP7 data are used to fix some parameters of the model. Two specific examples are discussed in detail: (i) a potential given by $V(\phi, T) = v_{1}(\phi)\, + \, v_{2}(T)$, and (ii) a potential of the form $V(\phi, T) = \alpha \, v_{1}(\phi) \, v_{2}(T)$. In both cases, the viscosity has little impact on the said ratio.