Ruling out an inflation driven by a power law potential: kinetic coupling does not help

TL;DR

This paper shows that current CMB data strongly constrain inflation models with power law potentials, ruling them out even when considering kinetic coupling to gravity, except possibly for negative coupling constants.

Contribution

It provides a comprehensive analysis demonstrating that positive kinetic coupling does not revive power law inflation models under current observational constraints.

Findings

Power law inflation models are ruled out by current CMB data.

Kinetic coupling with positive constants does not help in reconciling these models with observations.

Negative coupling constants require further investigation.

Abstract

We demonstrate that the latest constraints on inflationary observables, namely the tensor-to-scalar ratio $r$ and the scalar spectral index $n_{_S}$, from the Cosmic Background Radiation (CMB) observations are already strong enough to rule out the model of a scalar field with a power law potential even in the presence of kinetic coupling to gravity with a positive coupling constant. The case for a negative coupling constant needs special treatment.