New Shapes of Primordial Non-Gaussianity from Quasi-Single Field Inflation with Multiple Isocurvatons

Abstract

We study a simple extension of quasi-single field inflation in which the inflaton interacts with multiple extra massive scalars known as isocurvatons. Due to the breaking of time translational invariance by the inflaton background, the theory includes kinetic mixings among the inflaton and isocurvatons. These mixings give rise to novel new features in the primordial non-Gaussianities of the scalar curvature perturbation. A noteworthy feature is the amplitude of the squeezed bispectrum can grow nearly as $(k_s/k_l)^{-3}$ while oscillating as ${\rm \cos\gamma \log}(k_s/k_l)$, where $k_s/k_l$ is the ratio of the lengths of the short and long wavevectors. Observation of such a shape would provide evidence for the existence of multiple isocurvatons during inflation. In addition, we consider the effects of these non-Gaussianities on large-scale structure.