Primordial black hole tower: Dark matter, earth-mass, and LIGO black holes

Abstract

We investigate a possibility of primordial black hole (PBH) formation with a hierarchical mass spectrum in multiple phases of inflation. As an example, we find that one can simultaneously realize a mass spectrum which has recently attracted a lot of attention: stellar-mass PBHs (∼ O(10)M ) as a possible source of binary black holes detected by LIGO/Virgo collaboration, asteroid-mass (∼ O(10 −12 )M ) as a main component of dark matter, and earth-mass (∼ O(10 −5 )M ) as a source of ultrashort-timescale events in Optical Gravitational Lensing Experiment microlensing data. The recent refined de Sitter swampland conjecture may support such a multi-phase inflationary scenario with hierarchical mass PBHs as a transition signal of each inflationary phase.

Scalar induced gravitational waves in inflation with gravitationally enhanced friction

“…However, the energy spectrum of GWs, which relates to the stellar-mass PBH production estimated by using the Press-Schechter approach with the Gaussian window function, fails to satisfy the current constraint from EPTA. Our result is in agreement with what was obtained in [36], and moreover, the authors there also point out that once the Press-Schechter approach with the real-space top-hat window function or the refined peak-theory approach to calculate the abundance of PBHs is adopted, the required curvature perturbations are relatively smaller and then the corresponding GWs will be consistent with the current EPTA constraint. Thus, we guess that the incompatibility between the predicted GWs from the GEF mechanism and the EPTA observation can also be avoided by using the real-space top-hat window function or the refined peak-theory approach for the PBH production.…”

“…It has been pointed in Ref. [36] that if one adopts the Press-Schechter approach with the real-space top-hat window function instead of the Gaussian window function or the refined peak-theory approach [52] to calculate the abundance of PBHs, the required curvature perturbations are relatively smaller and then the corresponding GWs are consistent with the current EPTA constraint. Thus, we guess that the scalar induced GW from the GEF mechanism can also be consistent with the EPTA if the real-space top-hat window function or the refined peak-theory approach is adopted.…”

“…The mechanisms of amplifying the small-scale curvature perturbations within the infla- 1 It is worthing pointing out that the scalar induced GWs are gauge independent [26][27][28]. tionary scenario have been extensively studied in recent years [29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45]. The most common mechanism is the single-field inflection-point inflation [38][39][40][41][42][43][44][45], which requires that the potential of the inflaton field has an approximate inflection point.…”

What if Planet 9 is a Primordial Black Hole?

“…where While an M ⊕ object is too light to be an astrophysical black hole formed by stellar collapse, PBHs arise from over densities in the early Universe [15,16] and as a result can be substantially lighter than M ⊙ . Formation of PBHs inferred from OGLE has been discussed in [17][18][19]. We note that PBHs arise from Oð1Þ density fluctuations during radiation domination, due to an increase in the primordial power spectrum.…”

Clustering of primordial black holes formed in a matter-dominated epoch

“…For the shot-noise contributions, we consider typical values of M PBH / f PBH = 10 −12 M , 10 −3 M , 10 4.5 M , and 10 10 M . These values correspond to the cases of all the dark matter ("DM": light green, M PBH = 10 −12 M , f PBH = 1) [74], excess events of OGLE observations ("OGLE": dark yellow, M PBH = 10 −5 M , f PBH = 10 −2 ) [11,75,76], the origin of binary black holes leading to the gravitational-wave events of LIGO/Virgo ("LIGO/Virgo": orange, M PBH = 10 1.5 M , f PBH = 10 −3 ) [2,4,5], and the seeds of supermassive black holes ("SMBH": red, M PBH = 10 3.5 M , f PBH = 10 −6.5 ) [12][13][14], respectively. These are just benchmark points, and the actual allowed region of M PBH is not a point but a band.…”