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arxiv: 2210.01605 · v4 · submitted 2022-10-04 · 🌀 gr-qc · astro-ph.HE

Closed-form solutions of spinning, eccentric binary black holes at 1.5 post-Newtonian order

Pith reviewed 2026-05-24 10:26 UTC · model grok-4.3

classification 🌀 gr-qc astro-ph.HE
keywords binary black holespost-Newtonian dynamicsclosed-form solutionsgravitational waveseccentric orbitsspinning binariesHamiltonian systems
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The pith

This paper derives two closed-form solutions for the 1.5 post-Newtonian dynamics of binary black holes with arbitrary masses, spins, and eccentricity.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The work establishes two fully accurate closed-form solutions to the equations governing spinning eccentric binary black holes at 1.5PN order. Earlier methods left gaps when handling all parameters together, and the solutions close those gaps by direct combination of the approaches. Accurate closed-form expressions matter because they allow efficient generation of gravitational wave templates needed to detect and characterize signals from such systems.

Core claim

By merging the direct integration method without action-angle variables and the action-angle variable method, the paper obtains two distinct closed-form solutions for the 1.5PN binary black hole Hamiltonian that remain valid for arbitrary mass ratios, spin vectors, and orbital eccentricity.

What carries the argument

The 1.5PN binary black hole Hamiltonian, integrated via combined non-action-angle and action-angle techniques to yield explicit time-dependent solutions for orbital elements and spins.

If this is right

  • The solutions enable direct computation of gravitational waveforms from eccentric spinning binaries without numerical orbit integration.
  • Numerical agreement between the two solutions verifies the five action variables constructed in the action-angle framework.
  • The solutions provide an explicit starting point for applying canonical perturbation theory at the next order.
  • A public implementation allows immediate use and cross-checks against full numerical evolution of the same system.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • These expressions could reduce the computational cost of template banks for eccentric signals in current and future detectors.
  • Extending the same combination technique might systematically reach 2PN order without new conceptual obstacles.
  • The closed forms could serve as test cases for checking consistency of other post-Newtonian resummation schemes.

Load-bearing premise

That filling the identified gaps between the two earlier solution methods produces no missing interaction terms or inconsistencies precisely at 1.5PN order.

What would settle it

A high-precision numerical integration of the 1.5PN equations of motion that produces trajectories differing from either closed-form solution beyond numerical error.

Figures

Figures reproduced from arXiv: 2210.01605 by Leo C. Stein, Rickmoy Samanta, Sashwat Tanay.

Figure 1
Figure 1. Figure 1: FIG. 1: The non-inertial [PITH_FULL_IMAGE:figures/full_fig_p004_1.png] view at source ↗
Figure 0.1
Figure 0.1. Figure 0.1: Test 1 FIG. 1: The non-inertial (i ′ j ′k ′ ) frame (centered around Lˆ ≡ L/L ⃗ ) is displayed along with the inertial (ijk) frame (centered around Jˆ ≡ J/J ⃗ ). one orbital period. In Eqs. (29) and (30), F is the incom￾plete elliptic integral of the first kind, whereas sn and am are the Jacobi sin and amplitude functions respectively. Finally, the + sign in Eq. (21) is chosen if d cos κ1/dt > 0 at initi… view at source ↗
Figure 2
Figure 2. Figure 2: FIG. 2: Comparison of the analytical solutions with the numerical one. For a system with [PITH_FULL_IMAGE:figures/full_fig_p010_2.png] view at source ↗
Figure 3
Figure 3. Figure 3: FIG. 3: Difference between the numerical and analytical position vector [PITH_FULL_IMAGE:figures/full_fig_p010_3.png] view at source ↗
Figure 1
Figure 1. Figure 1: Test FIG. 3: Difference between the numerical and analytical position vector R⃗ being split in two perpendicular components. keeping sufficient numerical precision while constructing the numerical solution. Now, the R⃗ a − R⃗ n can be broken down into two com￾ponents: an in-plane component R⃗ a∥ − R⃗ n, and an out￾of-plane component R⃗ a − R⃗ a∥. The in-plane difference is brought about by an in-plane (per… view at source ↗
read the original abstract

The closed-form solution of the 1.5 post-Newtonian (PN) accurate binary black hole (BBH) Hamiltonian system has proven to be difficult to obtain for a long time since its introduction in 1966. Closed-form solutions of the PN BBH systems with arbitrary parameters (masses, spins, eccentricity) are required for modeling the gravitational waves (GWs) emitted by them. Accurate models of GWs are crucial for their detection by LIGO/Virgo and LISA. Only recently, two solution methods for solving the BBH dynamics were proposed in arXiv:1908.02927 (without using action-angle variables), and arXiv:2012.06586, arXiv:2110.15351 (action-angle based). This paper combines the ideas laid out in the above articles, fills the missing gaps and provides the two solutions which are fully 1.5PN accurate. We also present a public Mathematica package BBHpnToolkit which implements these two solutions and compares them with a fully numerical treatment. The level of agreement between these solutions provides a numerical verification for all the five actions constructed in arXiv:2012.06586, and arXiv:2110.15351. This paper hence serves as a stepping stone for pushing the action-angle-based solution to 2PN order via canonical perturbation theory.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

0 major / 3 minor

Summary. The manuscript claims to deliver two fully 1.5PN accurate closed-form solutions for the Hamiltonian dynamics of spinning, eccentric binary black holes with arbitrary masses by combining the non-action-angle method of arXiv:1908.02927 with the action-angle approaches of arXiv:2012.06586 and arXiv:2110.15351. It identifies and fills gaps in prior work, supplies a public Mathematica package BBHpnToolkit implementing the solutions, and demonstrates agreement with direct numerical integration of the 1.5PN system, thereby verifying the five actions constructed in the earlier action-angle papers.

Significance. If the closed-form expressions are correct at 1.5PN order, the work is significant for gravitational-wave astronomy as it enables analytic modeling of waveforms from eccentric, spinning binaries, which are relevant for LIGO/Virgo and future LISA detections. The provision of reproducible code and numerical verification constitutes a strength, offering an independent check on the completeness of the 1.5PN terms. This also lays groundwork for extending to 2PN via canonical perturbation theory.

minor comments (3)
  1. [Abstract] The abstract states that the solutions are 'fully 1.5PN accurate' but does not specify the exact functional form (e.g., whether the radial motion is expressed via elliptic integrals or other special functions) or the precise manner in which the two solutions differ.
  2. A dedicated section or table quantifying the maximum relative error between the closed-form solutions and the numerical integration (as a function of eccentricity, spin magnitude, and mass ratio) would strengthen the verification claim.
  3. [Introduction] The manuscript would benefit from an explicit statement, perhaps in the introduction, of which specific terms or cross terms were missing in each of the cited prior works and how they are now included.

Simulated Author's Rebuttal

0 responses · 0 unresolved

We thank the referee for their positive assessment of the manuscript and for recommending minor revision. We appreciate the recognition of the work's significance for gravitational-wave astronomy, the value of the public BBHpnToolkit package, and its role in verifying the actions from prior papers.

Circularity Check

0 steps flagged

No significant circularity identified

full rationale

The paper constructs its closed-form solutions by combining the known 1.5PN Hamiltonian with methods from cited prior works (arXiv:1908.02927 and the action-angle papers), explicitly filling gaps, and then validates the results via direct comparison to independent numerical integration of the full 1.5PN system using a public Mathematica package. This numerical check is external and falsifiable. The agreement is presented as verification of the prior actions rather than an assumption, and no step reduces by construction to a self-definition, fitted input renamed as prediction, or load-bearing self-citation chain. The derivation remains self-contained against external benchmarks.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

The work rests on the standard post-Newtonian Hamiltonian at 1.5PN order and on the validity of the two cited solution frameworks; no new free parameters, ad-hoc axioms, or invented entities are introduced.

axioms (1)
  • domain assumption The 1.5PN Hamiltonian for spinning eccentric binary black holes is correctly given by the expressions in the cited prior literature.
    The paper takes the Hamiltonian as input and solves its dynamics; any error in that input would propagate directly into the claimed solutions.

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Forward citations

Cited by 2 Pith papers

Reviewed papers in the Pith corpus that reference this work. Sorted by Pith novelty score.

  1. Analytical Solution of Spinning, Eccentric Binary Black Hole Dynamics at the Second Post-Newtonian Order

    gr-qc 2026-03 unverdicted novelty 6.0

    An analytical 2PN solution is constructed for the orbital and spin dynamics of eccentric, arbitrarily spinning binary black holes, with spin oscillations retained only at 1.5PN accuracy.

  2. Action-angle variables of a binary black hole with arbitrary eccentricity, spins, and masses at 1.5 post-Newtonian order

    gr-qc 2021-10 unverdicted novelty 6.0

    Derives the fifth action for 1.5PN BBH with arbitrary eccentricity, spins, and masses, completing action-angle variables for analytical dynamics solution.

Reference graph

Works this paper leans on

49 extracted references · 49 canonical work pages · cited by 2 Pith papers · 13 internal anchors

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    Re-present the solution of Ref. [17] but with the 1PN terms included. We will call it the Standard Solution

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    Present a systematic procedure to construct the AA- based solution. As we will see later, the construction of the AA-based solution requires the Standard Solution as one of the inputs

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    Makeavailable BBHpnToolkit, apublic Mathemat- ica package [21] which (1) implements the Standard Solution, the AA-based solution, and the numerical solution (2) gives the numerical values of all five frequencies (rate of increase of the angle variables) of a given BBH system, (3) computes the Poisson brackets (PBs) between any two functions of the phase-s...

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    Next we compute the angleϕoffset, which is defined as ϕoffset = arcsin L(t) r(t)p(t) if ⃗ p·ˆr> 0, ϕoffset =π−arcsin L(t) r(t)p(t) if ⃗ p·ˆr< 0. (75)

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    Now it is a simple matter to see that the azimuthal angle that⃗ pmakes with thex-axis of the NIF is ϕ+ϕoffset, whereϕis the azimuthal angle of⃗ rin the NIF andϕoffset is the relative azimuthal angle between⃗ rand ⃗ p. This completes the specification of ⃗P. IV. ACTION-ANGLE BASED SOLUTION We devote this section to explaining our construction of an alterna...

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    The phase space of the 1.5PN system is 10 di- mensional (since spin magnitudes are constants) and has five mutually commuting constants, resulting in an integrable system. These constants are ⃗C = {J,Jz,L,H,S eff·L}. We thus have five action variables ⃗J = {J1 =J,J2 =Jz,J3 =L,J4,J5}, which can be found in Refs. [18] and [19]; their notations and defi- nit...

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    As shown in Sec VI-B of Ref. [19], the angleθi can be increased by a certain amount if we flow under the corresponding actionJi by the same amount. Therefore the problem becomes that of flowing under the actionsJi by amountsωit′(starting from the⃗V0 configuration). The order of flows does not matter because just like all the members of⃗C, all the actions ...

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