A simple supergravity model of inflation constrained with Planck 2018 data

TL;DR

This paper demonstrates that a simple supergravity inflation model, initially thought to be incompatible with observations, can be made consistent with Planck 2018 data through a field transformation, resulting in a viable single-field inflation scenario.

Contribution

It shows the equivalence of two supergravity inflation models via a field transformation and confirms the viability of the model with recent CMB data.

Findings

Model compatible with Planck 2018 data

Tensor-to-scalar ratio constrained to r<0.065

Observables invariant under field transformation

Abstract

We study a model of inflation based on $\mathcal{N}=1$ supergravity essentially depending on one effective parameter. Under a field transformation we show that this model turns out to be equivalent to a previously studied supergravity model known to be ruled out with the original choice of the parameter. Such parameter measures the slope of the potential at observable scales. Through a Bayesian parameter estimation, it is shown how this model is compatible with recent CMB temperature measurements by {\it Planck 2018} giving rise to a simple, viable, single field model of inflation. The tensor to scalar ratio constraint is found to be $r_{0.002}<0.065$ with negative running. We discuss how observables are invariant under the field transformation which leaves unaltered the slow-roll parameters. As a consequence the use of one presentation of the model or its field-transformed version is purely a matter of convenience.