Primordial black holes and gravitational waves from resonant amplification during inflation

TL;DR

This paper proposes a two-stage inflation model with resonant amplification that produces primordial black holes and gravitational waves, with potential observational signatures in future gravitational wave detectors.

Contribution

It introduces a novel two-field inflation scenario with resonant effects that enhance small-scale perturbations, leading to black hole and gravitational wave production.

Findings

Significant peak in the primordial power spectrum on small scales.

Potential for primordial black hole formation.

Generation of detectable gravitational waves during inflation.

Abstract

We present a new realization of the resonant production of primordial black holes as well as gravitational waves in a two-stage inflation model consisting of a scalar field \phi with an axion-monodromy-like periodic structure in the potential that governs the first stage and another field \chi with a hilltop-like potential that dominates the second stage. The parametric resonance seeded by the periodic structure at the first stage amplifies the perturbations of both fields inside the Hubble radius. While the evolution of the background trajectory experiences a turn as the oscillatory barrier height increases, the amplified perturbations of \chi remain as they are and contribute to the final curvature perturbation. It turns out that the primordial power spectrum displays a significant resonant peak on small scales, which can lead to an abundant production of primordial black holes. Furthermore, gravitational waves are also generated from the resonantly enhanced field perturbations during inflation, the amplitude of which may be constrained by future gravitational wave interferometers.