Oscillatory power spectrum and strongly $k$-dependent $r$ in hybrid inflation

TL;DR

This paper analyzes the curvature perturbation power spectrum in hybrid inflation, revealing oscillations in the scalar spectrum during the waterfall phase, with potential implications for observational signatures.

Contribution

It provides the first detailed calculation of the power spectrum including entropic modes during the waterfall in hybrid inflation, highlighting oscillatory features.

Findings

Oscillations in the scalar power spectrum during waterfall phase

No features observed in the tensor power spectrum

Potential for developing observational templates for these oscillations

Abstract

For the original hybrid inflation model, we calculate the power spectrum of curvature perturbations generated during the waterfall, taking into account the contribution of entropic modes. We study the regime where the potential is very flat, and in which inflation continues for more than about 60 e-folds. Results show oscillations in the scalar power spectrum, qualitatively similar to that of a single field axion monodromy potential; however no feature is displayed in the tensor power spectrum. Directions to develop a template for this power spectrum are also discussed.