Revealing the amplitude of primordial curvature perturbations on small scales from primordial black hole binaries for gravitational wave detection

Primordial black holes (PBHs) have been intensively investigated in cosmology as they are considered a potential candidate to be used as sources of the observed gravitational wave (GW) signals [1]. A substantial increase in primordial curvature perturbations on small scales is one of the natural methods to generate PBHs (smaller than a single Mpc)[2]. Hence, the PBH scenario of observed GW events by LIGO/VIRGO [3] offers an opportunity to analyze the primordial curvature perturbations on small scales, which have not yet been explored systematically because of lack of corresponding observations.