Beauty is Distractive: Particle production during multifield inflation

TL;DR

This paper investigates how particle production during multifield inflation, triggered by encounters with Extra Species Points, can significantly influence curvature perturbations and generate observable non-Gaussianities, providing new insights into inflationary dynamics.

Contribution

It introduces a detailed model of particle production at ESPs during inflation, analyzing its effects on curvature perturbations and non-Gaussianities, and explores various scenarios including modulated couplings and extended loci.

Findings

Particle production at ESPs can dominate curvature perturbations.

Non-Gaussianities such as bispectrum and trispectrum are potentially detectable.

Inflaton interactions are constrained by current non-Gaussianity observations.

Abstract

We consider a two-dimensional model of inflation, where the inflationary trajectory is "deformed" by a grazing encounter with an Extra Species/Symmetry Point (ESP) after the observable cosmological scales have left the Hubble radius. The encounter entails a sudden production of particles, whose backreaction causes a bending of the trajectory and a temporary decrease in speed, both of which are sensitive to initial conditions. This "modulated" effect leads to an additional contribution to the curvature perturbation, which can be dominant if the encounter is close. We compute associated non-Gaussianities, the bispectrum and its scale dependence as well as the trispectrum, which are potentially detectable in many cases. In addition, we consider a direct modulation of the coupling to the light field at the ESP via a modulaton field, a mixed scenario whereby the modulaton is identified with a second inflaton, and an extended Extra Species Locus (ESL); all of these scenarios lead to similar additional contributions to observables. We conclude that inflaton interactions throughout inflation are strongly constrained if primordial non-Gaussianities remain unobserved in current experiments such as PLANCK. If they are observed, an ESP encounter leaves additional signatures on smaller scales which may be used to identify the model.