Keeping the relation between the Starobinsky model and no-scale supergravity ACTive

TL;DR

This paper introduces a modified Starobinsky inflation model with an added cubic Ricci scalar term, establishing a link to no-scale supergravity and showing compatibility with recent observational data.

Contribution

It extends the Starobinsky model by incorporating a cubic Ricci scalar term, connecting it to no-scale supergravity and analyzing its inflationary predictions.

Findings

Model remains consistent with observational data for specific alpha range.

Modified potential matches supergravity-based models.

Inflationary predictions align with recent CMB measurements.

Abstract

We introduce a modification of the Starobinsky model in the form of an additional cubic Ricci scalar curvature term $\sim \alpha R^3$, scaled by a dimensionless parameter $\alpha$, with the resulting inflaton potential being the standard Starobinsky potential modified to first parametric order by an additive term. The resulting potential is identical to the potential obtained by a modification of the superpotential employed in the construction of the Starobinsky model in the framework of no-scale supergravity, thus, extending the correspondence between a class of no-scale supergravity models and modifications of the Starobinsky model. We analyze the inflationary predictions of the model and find that for $-4.2 \times 10^{-5} \lesssim \alpha \lesssim -1.9 \times 10^{-5}$, the modified Starobinsky model is in full agreement with the recent observational data from the Atacama Cosmology Telescope, for a range of $e$-folds, $N_\star = 50-60$.