REVIEW
Black Hole Binary Formation in the Expanding Universe --- Three Body Problem Approximation ---
Astrophysics · Submitted 2 Jul 1998 · 32 references
Pith's verdict: Real three-body numerics that confirm rather than overturn the 1997 estimate; the rate's error bar is a stack of worst cases, not a propagated uncertainty.
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The paper
The paper claims
Numerical three-body calculations confirm that black-hole MACHO binaries form with semimajor axes and eccentricities close to earlier order-of-magnitude estimates, giving a coalescence rate of about 0.05 events per year per galaxy.
The reading
Extended reading notes
Core claim
The coalescence rate of black hole MACHO binaries is about 5 x 10^-2 x 2^(+/-1) events per year per galaxy, implying at least several coalescences per year within 15 Mpc detectable by the first LIGO/VIRGO interferometers (abstract; Sections 5B and 8). If correct, the MACHO dark matter is made of black holes and gravitational-wave detectors will see a guaranteed source population.
Load-bearing premise
The binary population is generated by Eq. 5.1, P(x,y) = 9 x^2 y^2 / xbar^6 exp(-y^3/xbar^3), which assumes black holes form at rest with respect to the Hubble flow, at random uncorrelated positions, with a delta-function mass function and Omega = Omega_BHM (Sections 2 and 5A). The entire event rate scales with the number of binaries this distribution produces; clustering or a broad mass function would change it by more than the quoted factor of two. The authors acknowledge this in Section 8 and sketch an unequal-mass extension in Appendix A but do not compute it.
Original abstract
We study black hole MACHO binary formation through three-body interactions in the early universe at $t\sim 10^{-5}$s. The probability distribution functions of the eccentricity and the semimajor axis of binaries as well as of the coalescence time are obtained assuming that the black holes are randomly formed in space. We confirm that the previous order-of-magnitude estimate for the binary parameters is valid within $\sim 50%$ error. We find that the coalescence rate of the black hole MACHO binaries is $\sim 5 \times 10^{-2} \times 2^{\pm 1}$ events/year/galaxy taking into consideration several possible factors which may affect this estimate. This suggests that the event rate of coalescing binary black holes will be at least several events per year within 15 Mpc. The first LIGO/VIRGO interferometers in 2001 will be able to verify whether the MACHOs are black holes or not.
The compiled record
The paper's own sentences, arranged, kept beside the review and separate from it. Each label is drawn from a closed vocabulary; the number beside it is the probability the classifier gave that label. Numbers in the tables are the authors', checked by code. No sentence in this record was written by a model.
The abstract, sentence by sentence
We study black hole MACHO binary formation through three-body interactions in the early universe at $t\sim 10^{-5}$s. The probability distribution functions of the eccentricity and the semimajor axis of binaries as well as of the coalescence time are obtained assuming that the black holes are randomly formed in space. We confirm that the previous order-of-magnitude estimate for the binary parameters is valid within $\sim 50%$ error. We find that the coalescence rate of the black hole MACHO binaries is $\sim 5 \times 10^{-2} \times 2^{\pm 1}$ events/year/galaxy taking into consideration several possible factors which may affect this estimate. This suggests that the event rate of coalescing binary black holes will be at least several events per year within 15 Mpc. The first LIGO/VIRGO interferometers in 2001 will be able to verify whether the MACHOs are black holes or not.
background contribution method result interpretation main claim
| # | sentence | role | the authors' own work | states the main conclusion | strength |
|---|---|---|---|---|---|
| s0 | We study black hole MACHO binary formation through three-body interactions in the early universe at $t\sim 10^{-5}$s. | contribution 1.00 | 0.89 | 0.05 | asserted 0.87 |
| s1 | The probability distribution functions of the eccentricity and the semimajor axis of binaries as well as of the coalescence time are obtained assuming that the black holes are randomly formed in space. | method 0.42 | 0.91 | 0.06 | asserted 0.98 |
| s2 | We confirm that the previous order-of-magnitude estimate for the binary parameters is valid within $\sim 50%$ error. | result 0.96 | 0.87 | 0.11 | asserted 1.00 |
| s3 | We find that the coalescence rate of the black hole MACHO binaries is $\sim 5 \times 10^{-2} \times 2^{\pm 1}$ events/year/galaxy taking into consideration several possible factors which may affect this estimate. | result 1.00 | 0.94 | 0.45 | asserted 1.00 |
| s4 | This suggests that the event rate of coalescing binary black holes will be at least several events per year within 15 Mpc. | interpretation 0.98 | 0.72 | 0.32 | hedged possibility 1.00 |
| s5 | The first LIGO/VIRGO interferometers in 2001 will be able to verify whether the MACHOs are black holes or not. | future work 0.81 | 0.09 | 0.07 | hedged possibility 0.67 |
What was examined, and what was not
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Figures
Showing 2 of the paper's 5 figures. See all figures in the PDF ↗ Figures reproduced from arXiv:astro-ph/9807018 by the authors.
References
How later papers used it
93 later papers cite it
3 later papers by other authors are listed below: 1 used its method or tool and 2 used its data or values.
Uses its method or tool 1 of 8 papers with this label
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Used this paper's expression for the probability of finding the relevant distances in given intervals, assuming a random distribution of PBHs.
Multi-messenger signal from QCD-Axion Ultracompact Minihalos (2026) · 0.84 · paraphrased: the licence does not allow quoting
Uses its data or values 2 of 4 papers with this label
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Adopted c1=0.4 and c2=0.8 in alignment with this paper.
Gravitational Waves From More Attractive Dark Binaries (2023) · 0.95 · paraphrased: the licence does not allow quoting
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Adopted c1 = 0.4 from this paper's numerical simulations of the gravity-only case.
Gravitational Waves From Dark Binaries With Finite-Range Dark Forces (2024) · 1.00 · paraphrased: the licence does not allow quoting
How the literature uses it
83 arXiv papers cite this in 143 sentences
Papers citing it · 96 sentences without a confident label
Builds on it 3 papers
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= ∫t aμ[ 1/2𝐫̇^2 + ä/2a𝐫^2 + a m_12 /r - 1/2𝐫 ·𝐓 ·𝐫 ], can be derived along the lines of [ref] but by using the evolving mass [ref] instead of a constant one.
Cosmological black holes are not described by the Thakurta metric: LIGO-Virgo bounds on PBHs remain unchanged · Binary dynamics with growing mass · 0.91
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Our analysis generalises the previous studies [ref] , as we consider extended PBH mass functions and estimate the effect of PBH clustering.
Gravitational Waves from Primordial Black Hole Mergers · Introduction · 0.98
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To calculate the merger rate, we update the treatment in [ref] (although see further refinements in [ref] ) to account for radiation due to dQED, which dominates the gravitational radiation.
Primordial Extremal Black Holes as Dark Matter · Appendix I: binary merger rate · 0.94
Uses its method or tool 6 papers
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The probability that a pair of black holes with unequal masses $M_1$ and $M_2=qM_1$, $q≤1$, coalesce within the time interval (t,t+dt) can be written as [ref] (see also [ref] ) [equation] In this model, the formation of a binary BH with masses $M_1, M_2$ is assisted by the collision with third BH $M_3$. $F(M)$ is the BH mass function which we assume to be of log-normal form ([ref]) that follows from the physical model suggested by [ref] , Eq. ([ref]).
On mass distribution of coalescing black holes · The model of binary PBH coalescences · 0.84
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We followed the picture detailed in [ref] .
Detecting the gravitational wave background from primordial black hole dark matter · Synthetizing a population of PBH binaries · 0.99
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We compute it following the derivation of [ref] , which builds on several earlier works [ref] .
Dancing in the dark: detecting a population of distant primordial black holes · Primordial black holes · 0.96
Uses its data or values 4 papers
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Numerical 3-body calculations (for a static mass) indicate that $α≈0.4$ and $β≈0.8$ [ref] are suitable corrections for the semi-analytic approximation here.
Eliminating the LIGO bounds on primordial black hole dark matter · Introduction · 0.96
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We adopt $c_1=0.4$ and $c_2=0.8$, in alignment with [ref] .
Gravitational Waves From More Attractive Dark Binaries · Merger Rate and Stochastic GW Spectrum · 0.95
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A detailed investigation of the dynamics of the binary formation suggests $A=0.4$ and $B=0.8$ [ref] .
Effects of the merger history on the merger rate density of primordial black hole binaries · Single-merger events · 0.99
Compares with it 6 papers
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The decoupling condition, Eq.([ref]), is very similar to the one used previously [ref] , but differs in one important aspect: it involves the approximate time-dependent Misner-Sharp mass, $ma=m/(1+z)$, instead of the static ADM mass $m$.
Eliminating the LIGO bounds on primordial black hole dark matter · Introduction · 0.84
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Solving the equation ([ref]) and ([ref]) for any $x$ (different values of $y$ are taken into account in ([ref]) by the scaling of $ξ$) and comparing with ([ref]), we obtain the following correction factors in ([ref]) [equation] In our calculations these factors are independent of $x$ with high accuracy, however [ref] obtained $α≃0.4$, $β≃0.8$ and weak dependence on the fraction $x/y$.
Gravitational waves from primordial black holes collisions in binary systems · The evolution of binaries at the stage of radiation domination · 0.98
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This implies an angular momentum j ≈1.5 x^3/y^3 (x̂ ·ŷ) (x̂ ×ŷ), with magnitude $j ≈0.8 (x/y)^3 sin(2 θ)$, where $θ$ is the angle between $x̂$ and $ŷ$, consistent with the results of Ref. [ref] .
The merger rate of primordial-black-hole binaries · Torques by other PBHs · 0.95
Cites it as support 2 papers
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The coalescence of PBH binaries can successfully explain this merger rate if PBHs constitute a small fraction of dark matter [ref] .
Implications for Dark Matter Direct Detection in the Presence of LIGO-Motivated Primordial Black Holes · Introduction · 0.98
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Indeed, it was shown that this process typically takes place before the matter-radiation equality and it is due to gravitational attraction leading to PBH pairs decoupling from the Hubble flow [ref] .
Constraining high-redshift stellar-mass primordial black holes with next-generation ground-based gravitational-wave detectors · Primordial Black Hole mergers · 0.96
Cites it as background 20 papers
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Binary PBHs can be formed in the early Universe (early formation channel) or at the matter-dominated stage due to dynamical interactions (late formation stage) [ref] .
Effect of post-recombination accretion on primordial binary black hole mergers within virialized dark matter halos · Introduction · 0.98
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Merger rate of primordial black hole binaries.— We give a brief overview of the formation mechanism of the binary PBH mergers proposed in Ref. [ref] and revisited by Refs. [ref] to study the merger rate of PBH binaries and the SGWB from PBH binary merger.
Constraints on the Primordial Black Hole Abundance from the First Advanced LIGO Observation Run Using the Stochastic Gravitational-Wave Background · Introduction · 0.91
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In this scenario, PBHs are not clustered at formation [ref] and primordial BBHs are assembled via gravitational decoupling from the Hubble flow before the matter-radiation equality [ref] (see [ref] for reviews).
Searching for a subpopulation of primordial black holes in LIGO/Virgo gravitational-wave data · Introduction · 0.87
Discussion
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