Primordial Gravitational Wave Background as a Probe of the Primordial Black Holes

TL;DR

This paper explores how primordial gravitational waves could lead to primordial black hole formation, consistent with recent PTA observations, and predicts detectable signals for future gravitational wave detectors.

Contribution

It demonstrates that the interpretation of PTA data as PGWs-induced PBHs is viable without overproducing black holes and derives amplitude constraints linking PGWs to observable SGWB signals.

Findings

PTA data interpretation as PGWs-induced PBHs remains viable.

Derived amplitude constraints on PGWs consistent with PBH abundance limits.

Predicted SGWB signals detectable by future observatories.

Abstract

We study the formation of primordial black holes (PBHs) from the collapse of density perturbations induced by primordial gravitational waves (PGWs). The PGWs' interpretation of the stochastic gravitational wave background (SGWB) detected by the Pulsar Timing Array (PTA) corresponds to PBHs formation in the mass range $[10^{-12}-10^{-3}] M_{\odot}$. Importantly, our analysis shows that PGWs' interpretation of recent PTA data remains viable, as it does not lead to PBH overproduction. We derive the amplitude of PGWs by leveraging existing constraints on the PBH abundance across a wide mass range. Notably, these constrained amplitudes predict SGWB signals that would be detectable by future gravitational wave observatories.