Single-field inflation, anomalous enhancement of superhorizon fluctuations, and non-Gaussianity in primordial black hole formation

TL;DR

This paper demonstrates how a Coleman-Weinberg potential in single-field inflation can lead to double inflation and primordial black hole formation, with enhanced superhorizon fluctuations and minor non-Gaussian effects.

Contribution

It introduces a novel mechanism for PBH formation via anomalous fluctuation enhancement in a Coleman-Weinberg inflation model, including effects of non-Gaussianity.

Findings

Primordial black holes can form in specific mass ranges depending on model parameters.

Superhorizon fluctuations are anomalously enhanced at the transition between two inflation phases.

Non-Gaussian effects on PBH abundance are found to be small.

Abstract

We show a text-book potential for single-field inflation, namely, the Coleman-Weinberg model can induce double inflation and formation of primordial black holes (PBHs), because fluctuations that leave the horizon near the end of first inflation are anomalously enhanced at the onset of second inflation when the time-dependent mode turns to a growing mode rather than a decaying mode. The mass of PBHs produced in this mechanism lies in several discrete ranges depending on the model parameters. We also calculate the effects of non-Gaussian statistics due to higher-order interactions on the abundance of PBHs, which turns out to be small.