The irrelevance of primordial black hole clustering in the LVK mass range

We show that in common inflationary models where primordial black holes are formed due to the collapse of sizeable inflationary perturbations, their initial spatial clustering beyond the Poisson distribution does not affect 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. However, this conclusion may not hold for lighter masses potentially accessible by future gravitational wave observations and for multi-field inflation scenarios, where the curvature perturbation can acquire a large-scale modulation from a field that is not the primary source of the perturbation.