Supergravity, $\alpha$-attractors and primordial non-Gaussianity

TL;DR

This paper explores how deviations from Einstein gravity during inflation could produce detectable non-Gaussian features in the cosmic microwave background, using supergravity-based multi-field $oldsymbol{ extalpha}$-attractor models.

Contribution

It demonstrates that certain supergravity inflation models can generate observable non-Gaussianity, linking gravity modifications to potential cosmological signatures.

Findings

Non-Gaussianity of order unity can arise in these models.

The non-Gaussian features originate from kinetic terms, potential interactions, or the $oldsymbol{ extalpha}$-parameter.

Potential to constrain gravity laws at near-Planck energies.

Abstract

We compute in detail how deviations from Einstein gravity at the inflation energy scale could appear as non-Gaussian features in the sky. To illustrate this we use multi-field $\alpha-$attractor models in the framework of supergravity to realise inflation. We find no obvious obstacle for having choices of model's parameters that generate non-Gaussian features of the equilateral and local type at the $\cal O$(1) level in the $f_{\rm NL}$ non-Gaussianity parameter, thus being potentially detectable in future cosmological surveys. This non-Gaussianity has its origin in either the non-canonical kinetic term (which, in turn, is an immediate consequence of assuming an hyperbolic geometry of the moduli space), the interactions of the fields in the potential or the $\alpha-$parameter, or a combination of these three. This opens up the exciting possibility of constraining the law of gravity at energy scales close to the Planck one.