Primordial Black Holes from Passive Density Fluctuations

TL;DR

This paper demonstrates that considering passive density fluctuations during single-field slow-roll inflation can lead to the formation of primordial black holes, which are light and likely evaporated, influencing early universe dynamics.

Contribution

It introduces a novel mechanism for PBH formation via passive fluctuations in inflation, highlighting their potential impact despite not being dark matter candidates.

Findings

Primordial black holes can form from passive fluctuations in inflation.

PBHs are light and likely evaporated, affecting early universe physics.

Passive fluctuations enhance the spectrum near the end of inflation.

Abstract

In this paper, we show that if passive fluctuations are considered, primordial black holes (PBHs) can be easily produced in the framework of single-field, slow-roll inflation models. The formation of PBHs is due to the blue spectrum of passive fluctuations and an enhancement of the spectral range which exits horizon near the end of inflation. Therefore the PBHs are light with masses $\lesssim 10^{15}g$ depending on the number of e-folds when the scale of our observable universe leaves horizon. These PBHs are likely to have evaporated and cannot be a candidate for dark matter but they may still affect the early universe.