Hidden Universality in the Merger Rate Distribution in the Primordial Black Hole Scenario

Kocsis, Bence; Suyama, Teruaki; Tanaka, Takahiro; Yokoyama, Shuichiro

doi:10.3847/1538-4357/aaa7f4

Cited by 84 publications

(86 citation statements)

References 54 publications

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“…Such primordial black holes (PBHs) can account for all or part of the dark matter (DM) (e.g. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]). PBHs can be associated with a variety of astrophysical phenomena, including the recently discovered [21][22][23] gravitational waves (e.g.…”

Section: Introductionmentioning

confidence: 99%

Analytic description of primordial black hole formation from scalar field fragmentation

Cotner

Kusenko

Sasaki

et al. 2019

J. Cosmol. Astropart. Phys.

154

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Primordial black hole (PBH) formation is a more generic phenomenon than was once thought. The dynamics of a scalar field in inflationary universe can produce PBHs under mild assumptions regarding the scalar potential. In the early universe, light scalar fields develop large expectation values during inflation and subsequently relax to the minimum of the effective potential at a later time. During the relaxation process, an initially homogeneous scalar condensate can fragment into lumps via an instability similar to the gravitational (Jeans) instability, where the scalar self-interactions, rather than gravity, play the leading role. The fragmentation of the scalar field into lumps (e.g. Q-balls or oscillons) creates matter composed of relatively few heavy "particles", whose distribution is subject to significant fluctuations unconstrained by comic microwave background (CMB) observations and unrelated to the large-scale structure. If this matter component comes to temporarily dominate the energy density before the scalar lumps decay, PBHs can be efficiently produced during the temporary matter-dominated era. We develop a general analytic framework for description of PBH formation in this class of models. We highlight the differences between the scalar fragmentation scenario and other commonly considered PBH formation models. Given the existence of the Higgs field and the preponderance of scalar fields within supersymmetric and other models of new physics, PBHs constitute an appealing and plausible candidate for dark matter.

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Section: Introductionmentioning

confidence: 99%

Analytic description of primordial black hole formation from scalar field fragmentation

Cotner

Kusenko

Sasaki

et al. 2019

J. Cosmol. Astropart. Phys.

154

View full text Add to dashboard Cite

show abstract

“…This is the same reason why α does not depend on the initial mass distribution functions F. The only contributions to α come from powers of the total mass M . Hence, from (2.37), we have This leads to the prediction of a "hidden universality" in the merger rate [1], where the parameter α should be in the narrow range 0.97 α 1.05. (2.51)…”

Section: Universality In the Mass Dependence Of The Merger Ratesmentioning

confidence: 90%

“…This is in agreement with the analysis of Refs. [1,4]. Note that, even in the case m ∼ 1 the upper limit of the observational bound (2.39) satisfies the condition f f * only marginally.…”

Section: )mentioning

confidence: 92%

“…The overall numerical factor in this expression is determined by taking into consideration the time dependence in Eq. (2.5) as the binary forms [1,10,13,20]. Note that the average of γ over angle and mass distribution function is…”

Section: )mentioning

confidence: 99%

“…The observed merger rate [5][6][7][8][9] Γ ≈ 10 − 100 Gpc −3 yr −1 in the range ∼ 5 − 100M has recently been used in order to place limits on the PBH abundance [4,10]. In such estimates, it has been assumed that PBH are spatially uncorrelated at the time of formation, and that the dominant contribution to the orbital angular momentum of the binaries originates from tidal forces exerted by other black holes in the neighborhood, around the time when the binary decouples from the Hubble flow [1,12,13]. With these assumptions, the observational upper bound on the merger rate limits the fraction of PBHs in DM to f 1%.…”

Section: Introductionmentioning

confidence: 99%

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Enhanced cosmological perturbations and the merger rate of PBH binaries

Garriga

Triantafyllou

2019

J. Cosmol. Astropart. Phys.

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The rate of merger events observed by LIGO/Virgo can be used in order to probe the fraction f of dark mater in the form of primordial black holes (PBH). Here, we consider the merger rate of PBH binaries, accounting for the effect of cosmological perturbations on their initial eccentricity e. The torque on the binaries may receive significant contributions from a wide range of scales, that goes from the size of the horizon at the time when the binary forms, down to the co-moving size of the binary. Extrapolating the observed plateau in the power spectrum P Φ ≈ 10 −9 from cosmological scales down to the co-moving size of binaries, the torque from perturbations is small. In this case, for f 10 −2 , the distribution of eccentricities is dominated by tidal torques from neighboring PBHs. On the other hand, in scenarios where PBH are formed from adiabatic perturbations, it is natural to expect an enhancement of P Φ at small scales, where it is poorly constrained observationally. The effect can then be quite significant. For instance, a nearly flat spectrum with amplitude P Φ 10 −7 on scales smaller than ∼ 10M pc −1 gives a contribution j 2 ∼ 10 3 P Φ , where j = (1 − e 2 ) 1/2 is the dimensionless angular momentum parameter of the binaries. This contribution can dominate over tidal torques from neighboring PBHs for any value of f . Current constraints allow for a power spectrum as large as P Φ ∼ 10 −5 at the intermediate scales 10 3 − 10 5 M pc −1 , comparable to the co-moving size of the binaries at the time of formation. In particular, this can relax current bounds on the PBH abundance based on the observed LIGO/Virgo merger rate, allowing for a fraction f ∼ 10% of dark matter in PBH of mass ∼ 30M . We investigate the differential merger rate ∆Γ(m 1 , m 2 ), as a function of the masses of the binary components, and the corresponding "universality" coefficient [1] α = −(m 1 + m 2 ) 2 ∂ 2 ln ∆Γ/∂m 1 ∂m 2 . For an enhanced power spectrum with spectral index p we find that α ≈ 30/(32 − 7p) for 0 < p 2, and α ≈ 5/3 for p 2. Such values may lie well outside the narrow range α ≈ 1 ± 0.05 characteristic of tidal forces from neighboring PBHs. We conclude that, given a large enough sample of events, merger rates may provide valuable information on the spectrum of primordial cosmological perturbations at currently uncharted lengthscales.

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Dynamical Formation of Merging Stellar-Mass Binary Black Holes

Kocsis

2021

Handbook of Gravitational Wave Astronomy

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Hidden Universality in the Merger Rate Distribution in the Primordial Black Hole Scenario

Cited by 84 publications

References 54 publications

Analytic description of primordial black hole formation from scalar field fragmentation

Analytic description of primordial black hole formation from scalar field fragmentation

Enhanced cosmological perturbations and the merger rate of PBH binaries

Dynamical Formation of Merging Stellar-Mass Binary Black Holes

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