The Irrelevance of Primordial Black Hole Clustering in the LVK mass range

TL;DR

This paper demonstrates that primordial black hole clustering does not affect binary mergers detectable by current gravitational wave observatories, due to CMB constraints, though lighter masses might be an exception.

Contribution

It shows that realistic primordial black hole clustering is irrelevant for current gravitational wave signals, refining previous assumptions about their merger rates.

Findings

Clustering does not influence merger rates within the LIGO-Virgo-KAGRA mass range.

CMB distortion constraints limit the impact of primordial black hole clustering.

Lighter primordial black holes might still be affected by clustering in future observations.

Abstract

We show that in realistic models where primordial black holes are formed due to the collapse of sizeable inflationary perturbations, their initial spatial clustering beyond Poisson distribution does not play any role in the binary mergers, including sub-solar primordial black holes, responsible for the gravitational waves detectable by LIGO-Virgo-KAGRA. This is a consequence of the existing FIRAS CMB distortion constraints on the relevant scales. This conclusion might not hold for lighter masses potentially accessible by future gravitational wave observations.