Cosmic inflation in metric-affine gravity

TL;DR

This paper investigates inflationary models within metric-affine gravity, analyzing how quadratic curvature terms coupled to a scalar field influence inflationary predictions and their consistency with observations.

Contribution

It introduces a novel inflationary framework in metric-affine gravity with quadratic curvature terms and a pseudoscalar degree of freedom, expanding the understanding of inflation in alternative gravity theories.

Findings

Models are consistent with recent observational data.

Higher tensor-to-scalar ratios are possible.

Spectral index behavior varies with parameters.

Abstract

In the context of metric-affine gravity theories, where the metric and connection are independent, we examine actions involving quadratic terms in the Ricci scalar curvature and the Holst invariant. These actions are non-minimally coupled to a scalar field. We explore the behavior of the corresponding effective metric theory, which includes an extra dynamic pseudoscalar degree of freedom. Detailed analysis of inflationary predictions reveals compliance with recent observations across various parameters, potentially allowing a higher tensor-to-scalar ratio. The spectral index's direction of change varies based on parameter positioning.