Gravitational waves induced by the local-type non-Gaussian curvature perturbations

The current observational constraints still leave a substantial mass window similar to[10(-16), 10(-14)] boolean OR [10(-13), 10(12)]M-circle dot for primordial black holes (PBHs) representing all of dark matter (DM) in our Universe. The gravitational waves (GWs) induced by the curvature perturbations are inevitably generated during the formation of these PBHs, and fall in the frequency band of LISA. Such scalar induced gravitational waves (SIGWs) are supposed to be definitely detected by LISA even when the second-order local-type non-Gaussianity characterized by the parameter F-NL is taken into account. In this letter, we give a comprehensive analysis of the GWs induced by the local-type non-Gaussian curvature perturbations up to the third-order denoted by the non-linear parameter G(NL), and we find that a log-dependent slope of SIGWs in the infrared region is generically predicted and the amplitude of SIGWs can be further suppressed by several orders of magnitude. As a result, the null-detection of SIGWs by LISA cannot rule out the possibility of PBHs making up all of DM. (C) 2021 The Author(s). Published by Elsevier B.V.

Automated summary

The study suggests that primordial black holes may represent a significant portion of dark matter in the universe, with gravitational waves induced by curvature perturbations potentially detectable within the range of LISA. Even when accounting for second-order local-type non-Gaussianity, the gravitational waves caused by local-type non-Gaussian curvature perturbations could still be detected.