Supermassive primordial black holes for nano-Hertz gravitational waves and high-redshift JWST galaxies

Abstract

Recently, observational hints for supermassive black holes have been accumulating, prompting the question: Can primordial black holes (PBHs) be supermassive, particularly with masses $M\gtrsim 10^{9}M_\odot$? A supercritical bubble, containing an inflating baby universe, that nucleated during inflation can evolve into a PBH in our observable Universe. We find that when the inflaton slowly transitions past a neighboring vacuum, the nucleation rate of supercritical bubbles inevitably peaks, leading to a mass distribution of multiverse PBHs with a peak mass up to $M\gtrsim 10^{11}M_\odot$. Thus, our mechanism naturally provides a primordial origin for supermassive black holes.