Contemporary gravitational waves from primordial black holes
  Stochastic background of gravitational waves (GW) generated by the
interactions between primordial black holes (PBH) in the early universe and by
PBH evaporation is considered. If PBHs dominated in the cosmological energy
density prior to their evaporation, GWs from the earlier stages (e.g.
inflation) would be noticeably diluted. On the other hand, at the PBH dominance
period they could form dense clusters where PBH binary formation might be
significant. These binaries would be efficient sources of the gravitational
waves.
