REVIEW
Reducing orbital eccentricity in binary black hole simulations
General Relativity and Quantum Cosmology · Submitted 20 Feb 2007 · 41 references
Pith's verdict: A real, cheap methodological extension — radial velocity in quasi-equilibrium initial data — with a working tuning loop and an honestly stated ceiling on the headline overlap number.
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Referee report
The paper
The paper claims
Adding tunable radial velocities to quasi-equilibrium binary black hole initial data reduces orbital eccentricity by about a factor of ten, and the resulting gravitational waveforms overlap the eccentric ones at roughly 0.99.
The reading
Extended reading notes
Core claim
The central claim is that the eccentricity inherent in quasi-circular initial data does not materially change the gravitational waveform over the last roughly five orbits before merger: 'The gravitational waveforms, which contain ~8 cycles in the dominant l=m=2 mode, are largely unaffected by the eccentricity of the quasi-circular initial data. The overlap between the dominant mode in the quasi-circular evolution and the same mode in the low-eccentricity evolution is about 0.99' (abstract; Table 2 reports 0.998 for l=m=2 at both medium and high resolution). If correct, groups using zero-radial-velocity initial data were not injecting a significant waveform systematic over this inspiral length.
Load-bearing premise
The 0.99 overlap rests on comparing h(t) obtained by double-integrating Psi4 with two integration constants C_lm and D_lm that are unknown for a truncated waveform and are fixed by an arbitrary convention (Eq. 35: zero mean and zero first moment over [t1,t2]). Appendix B shows this makes every quoted overlap an upper bound, with a systematic of order 12/(pi N_cyc)^2, about 0.02 for the m=2 modes, which the authors state exceeds the actual mismatch. The headline number is therefore a ceiling rather than a measurement, and the true agreement could sit near 0.97.
Original abstract
Binary black hole simulations starting from quasi-circular (i.e., zero radial velocity) initial data have orbits with small but non-zero orbital eccentricities. In this paper the quasi-equilibrium initial-data method is extended to allow non-zero radial velocities to be specified in binary black hole initial data. New low-eccentricity initial data are obtained by adjusting the orbital frequency and radial velocities to minimize the orbital eccentricity, and the resulting ($\sim 5$ orbit) evolutions are compared with those of quasi-circular initial data. Evolutions of the quasi-circular data clearly show eccentric orbits, with eccentricity that decays over time. The precise decay rate depends on the definition of eccentricity; if defined in terms of variations in the orbital frequency, the decay rate agrees well with the prediction of Peters (1964). The gravitational waveforms, which contain $\sim 8$ cycles in the dominant l=m=2 mode, are largely unaffected by the eccentricity of the quasi-circular initial data. The overlap between the dominant mode in the quasi-circular evolution and the same mode in the low-eccentricity evolution is about 0.99.
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
Binary black hole simulations starting from quasi-circular (i.e., zero radial velocity) initial data have orbits with small but non-zero orbital eccentricities. In this paper the quasi-equilibrium initial-data method is extended to allow non-zero radial velocities to be specified in binary black hole initial data. New low-eccentricity initial data are obtained by adjusting the orbital frequency and radial velocities to minimize the orbital eccentricity, and the resulting ($\sim 5$ orbit) evolutions are compared with those of quasi-circular initial data. Evolutions of the quasi-circular data clearly show eccentric orbits, with eccentricity that decays over time. The precise decay rate depends on the definition of eccentricity; if defined in terms of variations in the orbital frequency, the decay rate agrees well with the prediction of Peters (1964). The gravitational waveforms, which contain $\sim 8$ cycles in the dominant l=m=2 mode, are largely unaffected by the eccentricity of the quasi-circular initial data. The overlap between the dominant mode in the quasi-circular evolution and the same mode in the low-eccentricity evolution is about 0.99.
background contribution method result interpretation main claim
| # | sentence | role | the authors' own work | states the main conclusion | strength |
|---|---|---|---|---|---|
| s0 | Binary black hole simulations starting from quasi-circular (i.e., zero radial velocity) initial data have orbits with small but non-zero orbital eccentricities. | background 1.00 | 0.23 | 0.04 | asserted 1.00 |
| s1 | In this paper the quasi-equilibrium initial-data method is extended to allow non-zero radial velocities to be specified in binary black hole initial data. | contribution 0.62 | 0.92 | 0.07 | asserted 1.00 |
| s2 | New low-eccentricity initial data are obtained by adjusting the orbital frequency and radial velocities to minimize the orbital eccentricity, and the resulting ($\sim 5$ orbit) evolutions are compared with those of quasi-circular initial data. | method 0.70 | 0.96 | 0.26 | asserted 1.00 |
| s3 | Evolutions of the quasi-circular data clearly show eccentric orbits, with eccentricity that decays over time. | result 0.99 | 0.89 | 0.08 | asserted 1.00 |
| s4 | The precise decay rate depends on the definition of eccentricity; if defined in terms of variations in the orbital frequency, the decay rate agrees well with the prediction of Peters (1964). | result 0.82 | 0.79 | 0.07 | asserted 0.80 |
| s5 | The gravitational waveforms, which contain $\sim 8$ cycles in the dominant l=m=2 mode, are largely unaffected by the eccentricity of the quasi-circular initial data. | result 0.98 | 0.92 | 0.21 | asserted 1.00 |
| s6 | The overlap between the dominant mode in the quasi-circular evolution and the same mode in the low-eccentricity evolution is about 0.99. | result 0.99 | 0.95 | 0.25 | asserted 1.00 |
What was examined, and what was not
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Figures
Figures reproduced from arXiv:gr-qc/0702106 by the authors.
References
How later papers used it
73 later papers cite it
5 later papers by other authors are listed below: 5 used its method or tool. 5 more papers by the same authors are listed: 5 used its method or tool.
Uses its method or tool 10 of 40 papers with this label · 5 by the same authors
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Reduced the eccentricity of the numerical binary by adding small changes to the initial inspiral rate and orbital frequency using the techniques of this paper.
Inspiraling black-hole binary spacetimes: Challenges in transitioning from analytical to numerical techniques (2015) · 1.00 · paraphrased: the licence does not allow quoting
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Specifically, we fit for the binary BS coordinate separation $d(t)$ using [equation] and correspondingly for the binary's radial velocity using the fit [equation] Based on this parameterization, the initial orbital frequency $Ω_0$ and initial radial velocity $v_r$ are corrected by [ref] [equation] at each eccentricity iteration step, where $d_0=A_-1$[Note, in general $d_0≠D_0$, as we show below explicitly.].
Generic initial data for binary boson stars (2023) · Eccentricity reduction · 0.99
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Estimated the eccentricity with the method described in this paper or in the Appendix of another work, finding a maximum eccentricity after the first orbit of 0.005 except in the 0.3 case.
General relativistic simulations of the quasi-circular inspiral and merger of charged black holes: GW150914 and fundamental physics implications (2020) · 1.00 · paraphrased: the licence does not allow quoting
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Reduced the eccentricity by adjusting the initial orbital frequency and radial velocity using the iterative method in this paper, measuring the eccentricity using the puncture tracks.
Conformally curved initial data for charged, spinning black hole binaries on arbitrary orbits (2022) · 1.00 · paraphrased: the licence does not allow quoting
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Estimated the residual eccentricity following this paper by fitting the time derivative of the coordinate separation of the two black holes with a function of the given form.
Numerical-relativity simulations of the quasi-circular inspiral and merger of non-spinning, charged black holes: methods and comparison with approximate approaches (2021) · 1.00 · paraphrased: the licence does not allow quoting
By the same authors
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Tuned its initially guessed radial velocity and orbital frequency using the iterative scheme described in Sec. 4 of this paper to reduce the eccentricity of the SBS data.
Reducing spurious gravitational radiation in binary-black-hole simulations by using conformally curved initial data (2008) (same authors) · 1.00 · paraphrased: the licence does not allow quoting
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Achieved initial eccentricities of at most 5e-4 following this paper, computing initial conditions as in another work.
Effects of neutron-star dynamic tides on gravitational waveforms within the effective-one-body approach (2016) (same authors) · 1.00 · paraphrased: the licence does not allow quoting
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Adjusted its values following the eccentricity reduction method developed by Pfeiffer et al. in this paper.
Binary Neutron Stars with Arbitrary Spins in Numerical Relativity (2015) (same authors) · 1.00 · paraphrased: the licence does not allow quoting
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Iteratively adjusted the initial angular and radial velocity of the neutron stars to reduce the initial eccentricity of the orbits to at most 0.002 utilizing the methods of this paper.
Gravitational Waves from Binary Neutron Star Mergers with a Spectral Equation of State (2023) (same authors) · 1.00 · paraphrased: the licence does not allow quoting
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Obtained low eccentricity of at most 0.005 using the iterative method developed by Pfeiffer et al. in this paper.
Black hole-neutron star mergers for 10 solar mass black holes (2011) (same authors) · 0.99 · paraphrased: the licence does not allow quoting
How the literature uses it
65 arXiv papers cite this in 100 sentences
Papers citing it · 45 sentences without a confident label
Builds on it 1 paper
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First, one can adapt iterative eccentricity-reduction schemes, such as those described in [ref] for uncharged black holes, to systems with charge.
Numerical-relativity simulations of the quasi-circular inspiral and merger of non-spinning, charged black holes: methods and comparison with approximate approaches · Controlling the eccentricity · 0.89
Uses its method or tool 38 papers
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In addition, by adding small changes to the initial inspiral rate and orbital frequency, we significantly reduced the eccentricity of the numerical binary using the techniques of Ref. [ref] .
Inspiraling black-hole binary spacetimes: Challenges in transitioning from analytical to numerical techniques · Discussion · 1.00
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To handle the above difficulties, we have adopted an iterative method for producing quasicircular NR initial data [ref] : An initial guess is chosen for NR initial data parameters, the binary is evolved for a few orbits using NR and the eccentricity is measured from that evolution, and then the initial guess is updated so as to give smaller eccentricity for the next iteration.
Eccentricity Reduction for Quasicircular Binary Evolutions · Introduction · 0.91
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In particular, I use the eccentricity-reduction technique of [ref] (originally developed under the assumption of conformal flatness) so that sets CFMS and SBS both have very little orbital eccentricity.
Reducing spurious gravitational radiation in binary-black-hole simulations by using conformally curved initial data · Introduction · 0.99
Uses its data or values 1 paper
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Figure [ref] shows the properties of the two sets of NR data considered in this study [ref] in terms of inverse mass ratio $m_2/m_1= 1/q$, effective spin parameter $χ_eff$ and precessing spin parameter $χ_p$.
Effective-one-body waveforms for precessing coalescing compact binaries with post-newtonian Twist · Numerical relativity data · 0.98
Cites it as background 3 papers
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Additionally, significant effort has been put into generating binary compact object ID featuring low orbital eccentricities [ref] , or generalisations to arbitrary eccentricities [ref] .
A new public code for initial data of unequal-mass, spinning compact-object binaries · Introduction · 0.93
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Typically, statements of eccentricity in NR simulations are made through particular measures of coordinate eccentricity [ref] , although there has been some work on applying PN orbital parameterizations a posteriori to NR simulations [ref] .
Nature Abhors a Circle · Introduction · 0.93
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For more details see [ref] .
Gravitational waveforms for high spin and high mass-ratio binary black holes: A synergistic use of numerical-relativity codes · Introduction · 0.95
Discussion
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