# Reheating constraints to WIMPflation

## TL;DR

This paper examines how reheating physics constraints influence WIMPflation models, updating previous analyses with Planck 2018 data and exploring the effects of entropy production on inflationary parameters.

## Contribution

It applies reheating constraints to WIMPflation models, updating prior work with recent data and analyzing the impact of entropy production on inflationary bounds.

## Key findings

- Certain inflaton potentials are ruled out or disfavored by the analysis.
- Viability of some models depends on specific reheating conditions.
- Entropy production reduces the effective number of e-folds, affecting model constraints.

## Abstract

Analyses of inflation models are usually conducted assuming a specific range---e.g., $N_k \simeq 50-60$--of the number $N_k$ of $e$-folds of inflation. However, the analysis can also be performed by taking into account constraints imposed by the physics of reheating. In this paper, we apply this analysis to a class of "WIMPflation" models in which the inflaton also plays the role of dark matter. Our analysis also updates prior WIMPflation work with more recent Planck 2018 data. With this new analysis, inflaton potentials $V(\phi)=\lambda\phi^4$ and $\lambda \phi_0^4[1-\cos(\phi/\phi_0)]^2$ are ruled out, while $V(\phi)=\lambda \phi_0^4\{1-\exp[-(\phi/\phi_0)^2]\}^2$ is slightly disfavored, and $V(\phi)=\lambda\phi_0^4\tanh^4(\phi/\phi_0)$ is only viable for certain reheating conditions. In addition, we also discuss for the first time the effect of post-reheating entropy production (from, e.g., cosmological phase transitions) in this reheating-physics analysis. When accounted for, it decreases the number of $e$-folds through $\Delta N_k=-(1/3)\ln(1+\gamma)$, where $\gamma\equiv\delta s/s$ is the fractional increase in entropy. We discuss briefly the possible impact of entropy production to inflation-model constraints in earlier work.