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

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, ξ, 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 ξ parameter is closely correlated with the primordial amplitude ; (ii) although improving the agreement with the CMB data in the r − ns plane, where r is the tensor-to-scalar ratio and ns the primordial spectral index, a non-null coupling is strongly disfavoured with respect to the minimally coupled standard ΛCDM model, since the upper bounds of the Bayes factor (odds) for ξ parameter are greater than 150:1.