2022MNRAS.510.6218M

Primordial black holes (PBHs) are dark matter candidates that span broad mass ranges from 10^–17 M_☉ to ∼100 M_☉. We show that the stochastic gravitational wave background can be a powerful window for the detection of subsolar mass PBHs and shed light on their formation channel via third-generation gravitational wave detectors such as Cosmic Explorer and the Einstein Telescope. By using the mass distribution of the compact objects and the redshift evolution of the merger rates, we can distinguish astrophysical sources from PBHs and will be able to constrain the fraction of subsolar mass PBHs <=1 M_☉ in the form of dark matter f_PBH≤1 per cent at 68 per cent C.L. even for a pessimistic value of a binary suppression factor. In the absence of any suppression of the merger rate, constraints on f_PBH will be less than 0.001 per cent. Furthermore, we will be able to measure the redshift evolution of the PBH merger rate with about 1 per cent accuracy, making it possible to uniquely distinguish between the Poisson and clustered PBH scenarios.