Observational Constraints on Monomial Warm Inflation

TL;DR

This paper investigates observational constraints on monomial warm inflation models, analyzing parameter space using PLANCK data, and finds that the tensor-to-scalar ratio is much smaller than current observational bounds, challenging the Lyth bound.

Contribution

It provides the first detailed analysis of warm inflation with monomial potentials in light of PLANCK constraints, highlighting the small tensor-to-scalar ratio and its implications.

Findings

Tensor-to-scalar ratio r is about 10^{-8} in these models

Warm inflation can evade the Lyth bound despite large field excursions

Current observational bounds do not exclude monomial warm inflation models

Abstract

Warm inflation is, as of today, one of the best motivated mechanisms for explaining an early inflationary period. In this paper, we derive and analyze the current bounds on warm inflation with a monomial potential $U\propto \phi^p$, using the constraints from the PLANCK mission. In particular, we discuss the parameter space of the tensor-to-scalar ratio $r$ and the potential coupling $\lambda$ of the monomial warm inflation in terms of the number of e-folds. We obtain that the theoretical tensor-to-scalar ratio $r\sim 10^{-8}$ is much smaller than the current observational constrain $r \lesssim 0.12$, despite a relatively large value of the field excursion $\Delta \phi \sim 0.1\MP$. Warm inflation thus eludes the Lyth bound set on the tensor-to-scalar ratio by the field excursion.