Running spectral index from shooting-star moduli

TL;DR

This paper proposes a multi-field inflationary model where different moduli dominate at different scales, producing a running spectral index and large non-Gaussianity, aligning with observational constraints.

Contribution

It introduces a novel multi-field inflation scenario with shooting-star moduli causing scale-dependent perturbations and spectral index running.

Findings

The model achieves a large non-Gaussianity with a running spectral index.

Different moduli dominate at different inflationary epochs, affecting the spectral index.

The transition between moduli influences the curvature perturbation spectrum.

Abstract

We construct an inflationary model that is consistent with both large non-Gaussianity and a running spectral index. The scenario of modulated inflation suggests that modulated perturbation can induce the curvature perturbation with a large non-Gaussianity, even if the inflaton perturbation is negligible. Using this idea, we consider a multi-field extension of the modulated inflation scenario and examine the specific situation where different moduli are responsible for the perturbation at different scales. We suppose that the additional moduli (shooting-star moduli) is responsible for the curvature perturbation at the earlier inflationary epoch and it generates the fluctuation with n>1 spectral index at this scale. After a while, another moduli (or inflaton) takes the place and generates the perturbation with n<1. At the transition point the two fluctuations are comparable with each other. We show how the spectral index is affected by the transition induced by the shooting-star moduli.