A topic review on probing primordial black hole dark matter with scalar induced gravitational waves

Abstract

Summary Primordial black holes (PBHs) might form from the collapse of over-densed regions generated by large scalar curvature perturbations in the radiation dominated era. Despite decades of various independent observations, the nature of dark matter (DM) remains highly puzzling. Recently, PBH DM have aroused interest since they provide an attracting explanation to the merger events of binary black holes discovered by LIGO/VIRGO and may play an important role on DM. During the formation of PBH, gravitational waves will be sourced by linear scalar perturbations at second-order, known as the scalar induced gravitational waves (SIGWs), which provides a new way to hunt for PBH DM. This topic review mainly focuses on the physics about SIGWs accompanying the formation of PBH DM.

Scalar induced gravitational waves review

“…[173][174][175][176]. A complementary review on induced GWs with more focus on the PBH counterpart is given by Yuan and Huang [177].…”

“…A more detailed and general analysis is necessary. It should be noted that if we include third order perturbation theory terms, the induced GW spectrum for a Dirac delta peak has three resonant peaks instead of one [141,177].…”

“…Although this may be a very complicated task, it is in principle possible. In this sense, there is no telling primordial non-gaussianity apart just from the induced GW spectrum [177]. Nevertheless, the story becomes more interesting when considering the PBH counterpart.…”

PBH formation from spherically symmetric hydrodynamical perturbations: a review

“…For an interesting historical review of the dark matter candidates, we refer the reader to [81]. About reviews that focus on gravitational waves applied to PBHs and the different constraints to account for the dark matter we have [1,[82][83][84][85][86][87][88]. Another interesting review with potential applications to PBHs is [89], which is focused on scenarios with deviations from radiation domination in the early Universe.…”

Quantum state evolution in an environment of cosmological perturbations

“…The scalar perturbations are measurable as temperature fluctuations in CMB [2] and as density fluctuations of galaxies [1] [28]. We assume that the detector can receive primordial perturbations from the inflationary stage of the Universe evolution (possibly as gravitational waves produced as the second order effect from scalar perturbations [29] [30]). After the radiation era and baryonic era the cosmological perturbations arrive us at the time interval when the metric can be approximated by a static (Minkowski) metric .…”