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

Abstract

We introduce a modification of the Starobinsky model in the form of an additional cubic Ricci scalar curvature term $\sim \hat{I}\pm R^3$, scaled by a dimensionless parameter $\hat{I}\pm$, 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 $-4.2\times 10^{-5}\lesssim \hat{I}\pm \lesssim -1.9\times 10^{-5}$, the modified Starobinsky model is in full agreement with the recent observational data from the Atacama Cosmology Telescope, for a range of $e$-folds, $N_{\star }=50-60$.

14 pages, 3 figures