Whispers from the Early Universe: The Ringdown of Primordial Black Holes

TL;DR

This paper explores the gravitational wave background from primordial black holes' ringdown phase, proposing it as a model-independent way to detect PBHs across multiple observational platforms.

Contribution

It introduces a numerical method to compute the SGWB from PBH ringdowns and assesses its detectability by future pulsar timing arrays and ground-based interferometers.

Findings

SGWB from PBH ringdowns could be detected by future PTAs.

Binary PBH mergers produce a detectable SGWB in next-generation interferometers.

The proposed method provides a model-independent probe of PBHs.

Abstract

We investigate the stochastic gravitational wave background (SGWB) generated by the ringdown phase of primordial black holes (PBHs) formed in the early universe. As the ringdown signal is independent of the PBH formation mechanism, the resulting SGWB offers a model-independent probe of PBHs. We numerically compute the ringdown waveform and derive the corresponding SGWB. We show that such a signal could be detected by future pulsar timing arrays (PTAs) for PBHs heavier than the solar mass. Additionally, we evaluate the SGWB from binary PBH mergers and demonstrate that it lies within the sensitivity bands of next-generation ground-based interferometers such as Cosmic Explorer and Einstein Telescope, suggesting a multi-band observational strategy for probing the PBH dark matter scenario.