Exploring the Parameter Space of Warm-Inflation Models

TL;DR

This paper investigates warm inflation models, extending previous work by including pole-dominated dissipation, which improves model performance and reduces required field content, aligning better with observational data.

Contribution

It introduces the impact of pole-dominated dissipation in warm inflation, showing improved model viability and reduced mediator field requirements compared to prior models.

Findings

Enhanced dissipation improves inflation duration and spectral index compatibility.

Quadratic hilltop potential performs better with pole-dominated dissipation.

Fewer mediator fields and smaller couplings are needed with the new dissipation term.

Abstract

Warm inflation includes inflaton interactions with other fields throughout the inflationary epoch instead of confining such interactions to a distinct reheating era. Previous investigations have shown that, when certain constraints on the dynamics of these interactions and the resultant radiation bath are satisfied, a low-momentum-dominated dissipation coefficient $\propto T^3/m_\chi^2$ can sustain an era of inflation compatible with CMB observations. In this work, we extend these analyses by including the pole-dominated dissipation term $\propto \sqrt{m_\chi T} \exp(-m_\chi/T)$. We find that, with this enhanced dissipation, certain models, notably the quadratic hilltop potential, perform significantly better. Specifically, we can achieve 50 e-folds of inflation and a spectral index compatible with Planck data while requiring fewer mediator field ($O(10^4)$ for the quadratic hilltop potential) and smaller coupling constants, opening up interesting model-building possibilities. We also highlight the significance of the specific parametric dependence of the dissipative coefficient which could prove useful in even greater reduction in field content.