Ruling out Initially Clustered Primordial Black Holes as Dark Matter

Abstract

Combining constraints from microlensing and Lyman-$\hat{I}\pm$ forest, we provide a simple argument to show that large spatial clustering of stellar-mass primordial black holes at the time of formation, such as the one induced by the presence of large non-Gaussianities, is ruled out. Therefore, it is not possible to evade existing constraints preventing stellar-mass primordial black holes to be a dominant constituent of the dark matter by boosting their initial clustering.

5 pages + supplementary material. 2 figures. v2: matching version published in PRL