Salvaging Power-Law Inflation through Warming

TL;DR

This paper explores how power-law inflation models can be reconciled with observational data by incorporating warm inflation dynamics and small modifications to enable a graceful exit, showing compatibility with Planck and BICEP/Keck results.

Contribution

It introduces a perturbed modification to power-law inflation that allows for a graceful exit and demonstrates its consistency with observational constraints in both warm and cold inflation scenarios.

Findings

Power-law inflation models can match observational data with appropriate dissipation parameters.

A small perturbation to the power-law form enables a viable exit from inflation.

The modified models are consistent with Planck and BICEP/Keck constraints.

Abstract

Power-Law inflation with scale factor $a \propto t^m$ is investigated in the context of warm inflation. The treatment is performed in the weak and strong dissipation limits. In addition, we discuss the three common cases for the thermal dissipation coefficient $\Gamma(T)$. We compare the theoretical results of the Power-Law model within warm inflation with the observational constraints from Planck $2018$ and BICEP/Keck 2018, as presented by the tensor-to-scalar ratio $r$ and spectral index $n_s$. The model results agree largely with the observations for most of the $\Gamma(T)$ cases. Furthermore, in order to address the problem of exiting the inflationary epoch, we suggest a perturbed modification to the power-law definition so that it becomes affine, and find that this small change indicates a way for having an exit scenario with a suitable e-foldings number. Finally, we examine this perturbation ansatz within the context of cold inflation with exponential potential, and we find that it can accommodate the observational data with sufficient e-foldings. Our study suggests that the power-law inflation and the exponential potential, in both warm and cold inflation contexts, can in principle be made consistent with the observations and with a possible graceful exit.