Chern-Simons gravitational term coupled to a spectator field
Abstract
The Chern-Simons gravitational term is typically coupled to the inflaton field during inflation. In this work, we explore an alternative scenario where the Chern-Simons term is minimally coupled to a massive spectator field, , within a multi-field inflationary framework where the spectator field is linearly coupled to the inflaton. We derive the corresponding parity-violating cubic interaction Lagrangian involving the curvature, spectator and tensor perturbations and compute how it affects primordial scalar-tensor bispectra. We find that these correlators yield distinctive parity-odd shapes. Perturbativity and consistency bounds are derived, constraining the couplings and the amplitude of the associated non-Gaussianities.
Keywords
Cite
@article{arxiv.2501.09630,
title = {Chern-Simons gravitational term coupled to a spectator field},
author = {Giorgio Orlando},
journal= {arXiv preprint arXiv:2501.09630},
year = {2026}
}
Comments
38 pages, 9 figures, v4: final changes: 1) The effect of the $\sigma-\phi$ coupling on $\sigma_0$ was considered. The new $\dot \sigma_0$ now introduces a tighter constraint on the strength of primordial non-Gaussianity. 2) Instead of "isocurvature field", the terminology "spectator field" was implemented. Matched published version in JCAP