Higher Curvature Corrections to Primordial Fluctuations in Slow-roll Inflation

TL;DR

This paper investigates how higher curvature corrections, especially the Gauss-Bonnet term, influence primordial fluctuations and gravitational wave polarization during slow-roll inflation, potentially leading to observable signatures.

Contribution

It demonstrates that higher curvature terms can significantly affect inflationary observables and introduces the possibility of detecting gravitational wave polarization effects.

Findings

Higher curvature corrections can enhance the tensor-to-scalar ratio.

The tensor spectral index can become blue due to Gauss-Bonnet effects.

Circular polarization of gravitational waves may be observable.

Abstract

We study higher curvature corrections to the scalar spectral index, the tensor spectral index, the tensor-to-scalar ratio, and the polarization of gravitational waves. We find that the higher curvature corrections can not be negligible in the dynamics of the scalar field, although they are energetically negligible. Indeed, it turns out that the tensor-to-scalar ratio could be enhanced and the tensor spectral index could be blue due to the Gauss-Bonnet term. We estimate the degree of circular polarization of gravitational waves generated during the slow-roll inflation. We argue that the circular polarization can be observable with the help both of the Gauss-Bonnet and parity violating terms. We also present several examples to reveal observational implications of higher curvature corrections for chaotic inflationary models.