Detectability of gravitational waves from the coalescence of massive primordial black holes with initial clustering

We show that the effect of initial non-Gaussian clustering can significantly enhance the event rate for primordial black hole (PBH) coalescence. The impact of such clustering is studied in a specific scenario of multistream inflation. Initial clustering enables the possibility of detecting massive PBH coalescence by space-based gravitational-wave interferometers such as LISA and DECIGO/BBO. The parameter regime for the ground-based detectors to detect PBH coalescence is also extended.