Primordial [tag:black_hole]black holes[/tag]: cracking the [tag:gravitational_waves]gravitational hum[/tag] ⚡ экспресс
The stochastic gravitational wave background (GWB) amplitude measured by pulsar timing arrays and JWST's detection of overmassive supermassive black holes at high redshifts challenge formation models. We investigated whether primordial black holes (PBHs) in halos could boost the GWB signal. PBHs introduce an isocurvature component to the power spectrum, accelerating dark matter halo formation and mergers. Black holes sink to the center via dynamical friction, and the central object grows through hierarchical mergers in addition to gas accretion. The calculated GWB amplitude was compared with 15-year NANOGrav data using Bayesian analysis; the prediction agrees with observations. The model requires only 0.09–0.12% of the halo mass to fall to the center, compatible with a PBH dark matter fraction f_pbh~0.1, assuming stellar PBHs (about 1% of the population) account for the observed supermassive black holes at z~6–10. Thus, the PBH scenario simultaneously explains both the early quasar population and the gravitational wave background.
Gravitational wave detectors pick up a low-frequency hum, like the sound of a distant waterfall. The Webb telescope finds galaxies in the early universe with black holes that seem too massive for such a young age.
If these invisible objects make up dark matter (as thought by Zwicky and Rubin), then every galaxy contains an uncountable number of them. Like pebbles in a stream, they are slowed by gas and stars, gradually sinking toward the center. There, clumping together, they produce waves that create the hum. Even a drop in the bucket—a mere fraction of a percent of the total mass—changes the tune, much like a handful of pebbles transforms a river’s sound. Calculations match years of observations by the NANOGrav project. Moreover, this model also explains the early giants: ordinary black holes, caught in this flow, grow rapidly. Thus, one simple idea connects three great cosmic mysteries.
🎯 Unlike stellar [tag:black_hole]black holes[/tag], [tag:black_hole]primordial ones[/tag] have no lower mass limit: some could weigh less than the Moon yet be no bigger than a pea.