# Testing non-minimally coupled inflation with CMB data: a Bayesian analysis

## TL;DR

This paper evaluates the observational viability of non-minimally coupled inflationary models using recent CMB data, finding that such models are strongly disfavored compared to minimal coupling models despite some improved fit in certain parameters.

## Contribution

It provides a Bayesian analysis of non-minimal coupling inflation models with CMB data, focusing on small and large field potentials, and quantifies their statistical support.

## Key findings

- Non-minimal coupling parameter $\xi$ is correlated with primordial amplitude.
- Non-minimal coupling models are strongly disfavored compared to minimal models.
- Bayes factor for $\xi$ parameter exceeds 150:1 against non-minimal models.

## Abstract

We use the most recent cosmic microwave background (CMB) data to perform a Bayesian statistical analysis and discuss the observational viability of inflationary models with a non-minimal coupling,~$\xi$, between the inflaton field and the Ricci scalar. We particularize our analysis to two examples of small and large field inflationary models, namely, the Coleman-Weinberg and the chaotic quartic potentials. We find that (i) the $\xi$ parameter is closely correlated with the primordial amplitude; (ii) although improving the agreement with the CMB data in the $r - n_s$ plane, where $r$ is the tensor-to-scalar ratio and $n_s$ the primordial spectral index, a non-null coupling is strongly disfavoured with respect to the minimally coupled standard $\Lambda$CDM model, since the upper bounds of the Bayes factor (odds) for $\xi$ parameter are greater than $150:1$.