Power spectra from an inflaton coupled to the Gauss-Bonnet term

TL;DR

This paper investigates how a Gauss-Bonnet correction influences power-law inflation, analyzing stability, perturbations, and observational constraints, revealing potential instabilities and effects on the tensor-to-scalar ratio.

Contribution

It provides a detailed analysis of the stability and observational implications of Gauss-Bonnet corrections in inflationary models inspired by string theory.

Findings

Ultra-violet instabilities appear on small scales in GB-dominated inflation.

Gauss-Bonnet correction can reduce or enhance the tensor-to-scalar ratio.

Model parameters are tightly constrained by WMAP 5-year data.

Abstract

We consider power-law inflation with a Gauss-Bonnet correction inspired by string theory. We analyze the stability of cosmological perturbations and obtain the allowed parameter space. We find that for GB-dominated inflation ultra-violet instabilities of either scalar or tensor perturbations show up on small scales. The Gauss-Bonnet correction with a positive (or negative) coupling may lead to a reduction (or enhancement) of the tensor-to-scalar ratio in the potential-dominated case. We place tight constraints on the model parameters by making use of the WMAP 5-year data.