Heavy primordial black holes from strongly clustered light black holes

TL;DR

This paper proposes a new mechanism where strongly clustered light black holes in the early universe can merge or evolve into heavy primordial black holes, potentially explaining supermassive black hole formation without accretion.

Contribution

It introduces a novel formation pathway for heavy primordial black holes through clustering of lighter ones, differing from standard models.

Findings

Heavy primordial black holes can form from lighter ones if strongly clustered.

This mechanism operates without the need for efficient accretion.

It offers new scenarios for the origin of supermassive black holes.

Abstract

We show that heavy primordial black holes may originate from much lighter ones if the latter are strongly clustered at the time of their formation. While this population is subject to the usual constraints from late-time universe observations, its relation to the initial conditions is different from the standard scenario and provides a new mechanism to generate massive primordial black holes even in the absence of efficient accretion, opening new scenarios, e.g. for the generation of supermassive black holes.