Hunting Down the Best Model of Inflation with Bayesian Evidence

TL;DR

This paper uses Bayesian evidence to compare different single field inflation models, finding small field models currently favored over large field ones, and introduces a numerical pipeline for constraining early Universe physics.

Contribution

It presents the first Bayesian evidence calculations for various inflation models, integrating inflationary code with MultiNest for model comparison.

Findings

Small field models are preferred with a 3:1 posterior odds.

Large field models with power p>4 are strongly disfavoured.

Methodology paves the way for constraining early Universe models with future data.

Abstract

We present the first calculation of the Bayesian evidence for different prototypical single field inflationary scenarios, including representative classes of small field and large field models. This approach allows us to compare inflationary models in a well-defined statistical way and to determine the current "best model of inflation". The calculation is performed numerically by interfacing the inflationary code FieldInf with MultiNest. We find that small field models are currently preferred, while large field models having a self-interacting potential of power p>4 are strongly disfavoured. The class of small field models as a whole has posterior odds of approximately 3:1 when compared with the large field class. The methodology and results presented in this article are an additional step toward the construction of a full numerical pipeline to constrain the physics of the early Universe with astrophysical observations. More accurate data (such as the Planck data) and the techniques introduced here should allow us to identify conclusively the best inflationary model.