Observational tests of inflation with a field derivative coupling to gravity

TL;DR

This paper investigates how a derivative coupling to gravity affects inflationary models, showing that it can make steep potentials compatible with observations by reducing tensor-to-scalar ratios.

Contribution

It introduces a non-minimal derivative coupling to gravity that enhances friction during inflation, allowing steep potentials to fit observational data.

Findings

Most inflationary models become compatible with data due to suppressed tensor-to-scalar ratio.

The derivative coupling enables natural parameter values in steep potential models.

Observational constraints are placed on various inflationary potentials.

Abstract

A field kinetic coupling with the Einstein tensor leads to a gravitationally enhanced friction during inflation, by which even steep potentials with theoretically natural model parameters can drive cosmic acceleration. In the presence of this non-minimal derivative coupling we place observational constraints on a number of representative inflationary models such as chaotic inflation, inflation with exponential potentials, natural inflation, and hybrid inflation. We show that most of the models can be made compatible with the current observational data mainly due to the suppressed tensor-to-scalar ratio.