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

TL;DR

This paper explores slow-roll inflation within a modified scalar-tensor gravity framework, demonstrating that specific potentials can produce observationally consistent inflationary predictions aligned with current cosmological data.

Contribution

It introduces a geometric scalar-tensor model with self-interacting potentials that can replicate Starobinsky-like and exponential tail inflationary potentials, aligning with observational constraints.

Findings

Models fit Planck and BICEP2/Keck data with n_s between 0.960 and 0.972

Predicted tensor-to-scalar ratio r is less than 0.02

Large Brans-Dicke parameter values suggest links to solar system tests

Abstract

We consider slow-roll inflation in the context of a modified Brans-Dicke dilaton gravity. From a two self-interacting potentials $V(\phi)$, we reproduce a Starobinsky-like potential and, commonly in syperstring models, an exponential tail potential $V(\phi)\sim(1-e^{\alpha_0\phi})$, with $\alpha_0$ being a constant coefficient related to the Brans-Dicke parameter $\omega$. 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 $\omega$ suggests a possible linkage of the inflationary regime and today's solar system bounds.