Higher-Curvature Corrections and Tensor Modes

TL;DR

This paper explores how higher-curvature corrections in inflationary models can affect tensor perturbations, potentially leading to observable signatures in gravitational wave spectra, and constrains these effects using current data.

Contribution

It investigates the impact of inflaton coupling to higher-curvature tensors on tensor spectra and provides observational constraints on such models.

Findings

Violation of tensor consistency relation implies large running of tensor tilt.

Higher-curvature effects can produce a blue tilted tensor spectrum detectable by future experiments.

Current data disfavors large higher-curvature corrections.

Abstract

Higher-curvature corrections to the effective gravitational action may leave signatures in the spectrum of primordial tensor perturbations if the inflationary energy scale is sufficiently high. In this paper we further investigate the effects of a coupling of the Inflaton field to higher-curvature tensors in models with a minimal breaking of conformal symmetry. We show that an observable violation of the tensor consistency relation from higher-curvature tensors implies also a relatively large running of the tensor tilt, enhanced even by some order of magnitude with respect to the standard slow roll case. This may leave signatures in the tensor two-point function that we could test to recognize higher-curvature effects, above all if they are translated into a blue tilted spectrum visible by future Gravitational Wave experiments. Exploiting current cosmic microwave background and gravitational wave data we also derive constraints on the inflationary parameters, inferring that large higher-curvature corrections seem to be disfavored.