The possibility that primordial black hole binary mergers of stellar mass can explain the signals detected by the gravitational-wave interferometers has attracted much attention. In this scenario, primordial black holes can compose only part of the entire dark matter, say, of order 0.1%. This implies that most of the dark matter is accounted for by a different component, such as weakly interacting massive particles. We point out that in this situation, very compact dark matter minihalos, composed of the dominant component of the dark matter, are likely to be formed abundantly in the early universe, with their formation redshift and abundance depending on primordial non-Gaussianity. They may be detected in future experiments via pulsar observations.

• Received 20 May 2019

DOI:https://doi.org/10.1103/PhysRevD.99.123530