# Slow-Roll Inflation in Scalar-Tensor Models

## TL;DR

This paper develops the perturbation theory for a scalar-tensor inflation model with multiple non-minimal couplings, deriving power spectra and a consistency relation, showing that additional interactions can align predictions with observational data.

## Contribution

It introduces a comprehensive perturbation framework for scalar-tensor inflation models with non-minimal couplings, providing new ways to match observations.

## Key findings

- Non-minimal, kinetic, and Gauss-Bonnet couplings can reduce the tensor-to-scalar ratio.
- The model's consistency relation helps distinguish it from standard inflation.
- Certain potentials avoid large field issues in chaotic inflation.

## Abstract

The linear and quadratic perturbations for a scalar-tensor model with non-minimal coupling to curvature, coupling to the Gauss-Bonnet invariant and non-minimal kinetic coupling to the Einstein tensor are developed. The quadratic action for the scalar and tensor perturbations is constructed and the power spectra for the primordial scalar and tensor fluctuations are given. A consistency relation that is useful to discriminate the model from the standard inflation with canonical scalar field was found. For some power-law potentials it is shown that the Introduction of additional interactions, given by non-minimal, kinetic and Gauss-Bonnet couplings, can lower the tensor-to-scalar ratio to values that are consistent with latest observational constraints, and the problem of large fields in chaotic inflation can be avoided.