Spectrum oscillations from features in the potential of single-field inflation

TL;DR

This paper investigates how step-like features in single-field inflation potentials cause oscillations and enhancements in the power spectrum, affecting primordial black hole formation and producing detectable gravitational wave signatures.

Contribution

It provides analytical and numerical analysis of the impact of potential features on inflationary perturbations and primordial black hole production, highlighting observable signatures.

Findings

Power spectrum enhancement by several orders of magnitude.

Oscillatory patterns in curvature and tensor spectra.

Primordial black hole production depends on the universe's dominant energy component.

Abstract

We study single-field inflationary models with steep step-like features in the potential that lead to the temporary violation of the slow-roll conditions during the evolution of the inflaton. These features enhance the power spectrum of the curvature perturbations by several orders of magnitude at certain scales and also produce prominent oscillatory patterns. We study analytically and numerically the inflationary dynamics. We describe quantitatively the size of the enhancement, as well as the profile of the oscillations, which are shaped by the number and position of the features in the potential. The induced tensor power spectrum inherits the distinctive oscillatory profile of the curvature spectrum and is potentially detectable by near-future space interferometers. The enhancement of the power specrtum by step-like features, though significant, may be insufficient to trigger the production of a sizeable number of primordial black holes if radiation dominates the energy density of the early universe. However, it can result in sufficient black hole production if the universe is dominated by non-relativistic matter. For the latter scenario, we find that deviations from the standard monochromatic profile of the mass spectrum of primordial black holes are possible because of the multiple-peak structure of the curvature power spectrum.