Primordial Black Hole Binaries: The Impact of Poisson Clustering

Poisson noise in the initial spatial distribution of primordial black holes (PBHs) leads to their active clustering in the early Universe. Using a simple model, this work examines the internal dynamics of clusters, the formation of binary black holes and their mergers. It is shown that PBH binaries formed at the radiation-dominated phase are actively perturbed and make a subdominant contribution to gravitational wave events compared to PBHs mergers in clusters.