Elastic Scattering of Cosmological Gravitational Wave Backgrounds: Primordial Black Holes and Stellar Objects

TL;DR

This paper explores how primordial black holes and stellar objects scatter cosmological gravitational waves, causing spectral distortions that could inform dark matter research, with potential detectability depending on background spectrum understanding.

Contribution

It demonstrates that primordial black holes can induce measurable spectral distortions in gravitational wave backgrounds, highlighting a new method to probe dark matter candidates.

Findings

Black holes cause up to 5% spectral distortions in gravitational waves.

Stellar objects induce much smaller distortions.

Detectability hinges on understanding the unperturbed background spectrum.

Abstract

Primordial black holes (PBHs) are plausible dark matter candidates that formed from the gravitational collapse of primordial density fluctuations. Current observational constraints allow asteroid-mass PBHs to account for all of the cosmological dark matter. We show that elastic scattering of a cosmological gravitational wave background, these black holes generate spectral distortions on the background of 0.3% for cosmologically relevant frequencies without considering coherent scattering and 5% when the coherent enhancement is included. Scattering from stellar objects induce much smaller distortions. Detectability of this signal depends on our ultimate understanding of the unperturbed background spectrum.