Detecting the gravitational wave background from primordial black hole dark matter

Merger rates in primordial black hole clusters without initial binaries

“…Recently, detections of gravitational waves (GWs) from merging black holes of 10−40 M by Advanced LIGO (Laser Interferometer Gravitational-wave Observatory) and Virgo have returned attention to stellar mass PBHs (Abbott et al 2016;Abbott et al 2018). Shortly after the first LIGO detection (GW150914) several authors suggested that it might have been the result of two PBHs capturing each other (e.g., Bird et al 2016;Clesse & García-Bellido 2016;Sasaki et al 2016;Ali-Haïmoud et al 2017). Assuming that stellar mass PBHs comprise all DM (or at least a significant fraction), Bird et al (2016) derive a capture rate that ranges between 10 −4 and 1400 Gpc −3 yr −1 depending on assumptions about how PBHs cluster in DM halos.…”

Primordial Black Hole Dark Matter and the LIGO/Virgo observations

“…[29] for a review). These constraints have been recently amended by limits on the PBH mass fraction contributing to dark matter, due to the observed BH binary coalescence rates form LIGO/Virgo data and from the non-observation of a gravitational stochastic wave background due to PBH mergers [30][31][32][33][34][35][36][37][38][39]. The verdict of the community [37,[40][41][42][43][44][45] is that solar mass PBHs can not constitute the bulk of the dark matter, mostly because they would greatly surpass the observed LIGO/Virgo rates.…”

“…[40,46] is highly suspect. Many authors [14,32,33,35,41,42,44,45,55] have used this distribution to draw conclusions.…”

“…2, we may compute the expected merger rates of pre-existing ∼ M ⊙ PBHs binaries to be M M⊙ ≈ 40 Gpc −3 yr −1 , to be compared to the LIGO/Virgo imposed upper limit of M < M⊙ ≈ 5.2 × 10 3 Gpc −3 yr −1 [55]. In fact, pre-existing binary properties get so efficiently modified by collisions in clusters, that the total merging rate is dominated by merging of single PBHs colliding at very low impact parameter [30,32,57] in presentday clusters (cf. SM section).…”

Exploring Primordial Black Holes from the Multiverse with Optical Telescopes

“…). It has also been suggested that they could play a central role in a variety of astrophysical phenomena, such as progenitors [24][25][26][27][28][29][30][31] for the LIGO gravitational wave events [32][33][34], seeds for formation of super-massive black holes [25,35,36] as well as the source of new signals [31,37,38] from compact star disruptions from PBH capture, among others.…”