Constraint on the abundance of primordial black holes in dark matter from Planck data

Abstract

We use Planck data released in 2015 to constrain the abundance of primordial black holes (PBHs) in dark matter in two different reionization models (one is the instantaneous reionization and the other is the asymmetric reionization), and significantly improve the existing upper limits on the abundance of PBHs by around two orders of magnitude. These new limits imply that the event rates of mergers of PBH binaries (Gpc −3 yr −1 ) are less than 0.002 for M pbh = 30M , 5 for M pbh = 10M and 2000 for M pbh = 2M at 95% confidence level (C.L.), and thus the gravitational-wave event GW150914 is very unlikely produced by the merger of a PBH binary.

Pulsar timing array constraints on the induced gravitational waves

“…LIGO/VIRGO have detected gravitational waves (GWs) from mergers of binary black holes (BBHs) and binary neutron stars [1][2][3][4][5][6]. It is possible that these black holes we observed are of the primordial origin [7][8][9][10][11][12][13][14][15][16][17][18][19][20], which are formed by gravitational collapse when the curvature perturbation is of O(1) at the horizon reentry [21][22][23][24][25]. During inflation, the primordial curvature perturbation R is generated by quantum fluctuations, which is then frozen when it is stretched outside the horizon by inflation, and finally seeds the temperature anisotropies and the large scale structure inhomogeneities on large scales observed today.…”

Log-dependent slope of scalar induced gravitational waves in the infrared regions

“…. From Eq (13),. the density parameter of SIGWs for such a power spectrum readsΩ GW,eq = k + k k − k dv min( k + k ,1+v) max( k − k ,|1−v|) duI(u, v)P φ (uk)P φ (vk),(16)In this letter, we focus on the behavior of Ω GW,eq in the infrared region, namely k k − , and then 1 k − /k < k + /k.…”

Detectability of gravitational waves from the coalescence of massive primordial black holes with initial clustering

“…Otherwise the quasar bound can apply. (3) CMB limits [27] (see also [46,47]). The effect of PBH accretion (which is an indirect limit depending on astrophysical assumptions) mainly affects the reionization history and thus modifies the temperature and polarization power spectra at low .…”