Detectability of Primordial Black Hole Binaries at High Redshift
  We show that the gravitational wave signals from primordial black hole (PBH)
binaries at high redshift can be detected. The detectability of PBH binaries is
enhanced by redshift bias and more PBH binaries at high redshift. The initial
clustering of PBHs is also included and enhances the effectively detectable
mass ranges of PBHs at high redshift. Future observations on the gravitational
wave at high redshift by space-based detectors such as LISA and SKA can
constrain the fraction of PBHs in dark matter and PBHs initial distribution.
