Brans-Dicke inflation in light of the Planck 2015 data

TL;DR

This paper investigates inflation within Brans-Dicke gravity, deriving observable predictions for various potentials and comparing them with Planck 2015 data, identifying which models are compatible or ruled out.

Contribution

It provides a comprehensive analysis of inflationary potentials in Brans-Dicke gravity and assesses their viability against the latest observational data.

Findings

Power-law, inverse power-law, and exponential potentials are ruled out by Planck 2015 data.

Hilltop, Higgs, Coleman-Weinberg, and natural potentials are compatible at 95% CL.

D-brane, SB SUSY, and displaced quadratic potentials fit within 68% CL of Planck data.

Abstract

We study inflation in the Brans-Dicke gravity as a special model of the scalar-tensor gravity. We obtain the inflationary observables containing the scalar spectral index, the tensor-to-scalar ratio, the running of the scalar spectral index and the equilateral non-Gaussianity parameter in terms of the general form of the potential in the Jordan frame. Then, we compare the results for various inflationary potentials in light of the Planck 2015 data. Our study shows that in the Brans-Dicke gravity, the power-law, inverse power-law and exponential potentials are ruled out by the Planck 2015 data. But, the hilltop, Higgs, Coleman-Weinberg and natural potentials can be compatible with Planck 2015 TT,TE,EE+lowP data at 95\% CL. Moreover, the D-brane, SB SUSY and displaced quadratic potentials can be in well agreement with the observational data since their results can lie inside the 68\% CL region of Planck 2015 TT,TE,EE+lowP data.