Slow-roll inflation from a geometric scalar-tensor model with self-interacting potentials

Abstract

We consider slow-roll inflation in the context of a modified Brans-Dicke dilaton gravity. From a two self-interacting potentials $V(\ddot{I}•)$, we reproduce a Starobinsky-like potential and, commonly in syperstring models, an exponential tail potential $V(\ddot{I}•)\sim (1-e^{\hat{I}{\pm }_0\ddot{I}•})$, with $\hat{I}{\pm }_0$ being a constant coefficient related to the Brans-Dicke parameter $\ddot{I}‰$. Using the observational bounds on the spectral index $n_s$ and tensor-to-scalar ratio $r$ imposed by Planck-CMB baseline data and the BICEP2/Keck collaboration with combination with Planck 2018 and the Baryonic Acoustic Oscillations(BAO), we obtain for both models a good agreement with current observations with $n_s=0.960-0.972$ and $r<0.02$. In addition, the resulting large values of $\ddot{I}‰$ suggests a possible linkage of the inflationary regime and today's solar system bounds.

revised version, updated references