Inflationary phenomenology of non-minimally coupled Einstein-Chern-Simons gravity

TL;DR

This paper explores inflation in a scalar-tensor theory with non-minimal coupling and Chern-Simons corrections, showing compatibility with observations and highlighting effects on gravitational wave chirality and spectral tilt.

Contribution

It introduces a comprehensive analysis of inflation with non-minimal coupling and Chern-Simons terms, including slow-roll and constant-roll scenarios, and examines their implications for gravitational waves and theoretical consistency.

Findings

Inflation models remain viable under observational constraints.

Chern-Simons term induces gravitational wave chirality.

Tensor spectral index can be blue-tilted due to Chern-Simons effects.

Abstract

In this work we investigate the inflationary era in the presence of a canonical scalar field and Chern-Simons parity violating corrections. It was also assumed that a non minimal coupling between curvature and the scalar field is present. For the shake of completeness, the slow-roll and the constant-roll scenarios were examined separately. In the context of this scalar-tensor theory, inflation can be viable for both scenarios since the observational indices take acceptable values according to the most recent Planck data. Furthermore, the involvement of the Chern-Simons term has no effect on the background equations, in contrast to the scalar function which couples with the Ricci scalar and participates in the equations of motion. However, the Chern-Simons term ensures the chirality of stochastic gravitational waves. A blue-tilted tensor spectral index of primordial curvature perturbations can be manifested since, tensor modes are strongly affected by the Chern-Simons term. Lastly, the Swampland criteria and the Lyth-bound were examined in order to distinguish the effective field theories towards the path of a consistent M-theory.