Inflationary flavor oscillations and the cosmic spectroscopy

TL;DR

This paper explores how mixing between different inflationary states affects the three-point function of curvature perturbations, revealing new oscillatory and spectral features that enable detailed cosmic spectroscopy of inflation's particle content.

Contribution

It introduces the concept of inflationary flavor oscillations and demonstrates their impact on the primordial bispectrum, providing a novel approach to probe inflationary particle spectra.

Findings

New oscillatory behaviors in the squeezed limit of the bispectrum.

The primordial signal can be dominated by states other than the lightest degree of freedom.

Potential to perform detailed cosmic spectroscopy of inflationary particles.

Abstract

Inflationary scenarios motivated by high-energy physics generically contain a plethora of degrees of freedom beyond the primordial curvature perturbation. The latter interacts in a simple way with what we name "inflationary flavor eigenstates", which differ, in general, from freely propagating "mass eigenstates". We show that the mixing between these misaligned states results in new striking behaviors in the squeezed limit of the curvature perturbation three-point function, depending not only on the mass spectrum but also on the "mixing angles" of the theory. These results bring about a new perspective on the cosmological collider program: contrary to a widespread belief, the primordial signal needs not be dominated by the lightest extra degree of freedom. Instead, we show that it may display either modulated oscillations, a broken power law, or a transition from oscillations to a power law, thus offering a detailed cosmic spectroscopy of the particle content of inflation.