Non-Gaussianity from violation of slow-roll in multiple inflation

TL;DR

This paper explores how sudden mass changes in the inflaton during multiple inflation cause oscillatory non-Gaussian signals in the primordial curvature perturbation, with potential detectability by Planck.

Contribution

It introduces a model linking phase transition oscillations during inflation to observable non-Gaussian features in the cosmic microwave background.

Findings

Non-Gaussianity characterized by oscillatory f_NL ~ 5-20.

Potential detectability of signals with future bispectrum estimators.

Derived a model-independent relation between phase transition oscillations and curvature perturbations.

Abstract

Multiple inflation is a model based on N=1 supergravity wherein there are sudden changes in the mass of the inflaton because it couples to 'flat direction' scalar fields which undergo symmetry breaking phase transitions as the universe cools. The resulting brief violations of slow-roll evolution generate a non-gaussian signal which we find to be oscillatory and yielding f_NL ~ 5-20. This is potentially detectable by e.g. Planck but would require new bispectrum estimators to do so. We also derive a model-independent result relating the period of oscillations of a phase transition during inflation to the period of oscillations in the primordial curvature perturbation generated by the inflaton.