Observing the Inflationary Reheating

TL;DR

This paper demonstrates that Planck satellite measurements significantly constrain the reheating epoch after inflation by analyzing a wide range of inflationary models, highlighting the importance of reheating in cosmological data interpretation.

Contribution

It provides the first comprehensive Bayesian analysis of reheating constraints across approximately 200 inflationary models using Planck data, emphasizing the impact on model evidence.

Findings

Planck data constrains reheating parameters in most inflation models.

Reheating properties can alter the Bayesian evidence of inflationary models.

Current CMB data's precision necessitates including reheating details in model evaluations.

Abstract

Reheating is the the epoch which connects inflation to the subsequent hot Big-Bang phase. Conceptually very important, this era is however observationally poorly known. We show that the current Planck satellite measurements of the Cosmic Microwave Background (CMB) anisotropies constrain the kinematic properties of the reheating era for most of the inflationary models. This result is obtained by deriving the marginalized posterior distributions of the reheating parameter for about 200 models taken in Encyclopaedia Inflationaris. Weighted by the statistical evidence of each model to explain the data, we show that the Planck 2013 measurements induce an average reduction of the posterior-to-prior volume by 40%. Making some additional assumptions on reheating, such as specifying a mean equation of state parameter, or focusing the analysis on peculiar scenarios, can enhance or reduce this constraint. Our study also indicates that the Bayesian evidence of a model can substantially be affected by the reheating properties. The precision of the current CMB data is therefore such that estimating the observational performance of a model now requires to incorporate information about its reheating history.