Comparison between self-force and post-Newtonian dynamics: Beyond circular orbits
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PhysRevD.91.124014.pdf
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Author(s)
Akcay, Sarp
Le Tiec, Alexandre
Barack, Leor
Sago, Norichika
Warburton, Niels J
Date Issued
June 2015
Journal
Physical Review D
Publisher
American Physical Society
Citation
Akcay, Sarp, Alexandre Le Tiec, Leor Barack, Norichika Sago, and Niels Warburton. “Comparison Between Self-Force and Post-Newtonian Dynamics: Beyond Circular Orbits.” Phys. Rev. D 91, no. 12 (June 2015). © 2015 American Physical Society
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Final published version
Abstract
The gravitational self-force (GSF) and post-Newtonian (PN) schemes are complementary approximation methods for modeling the dynamics of compact binary systems. Comparison of their results in an overlapping domain of validity provides a crucial test for both methods and can be used to enhance their accuracy, e.g. via the determination of previously unknown PN parameters. Here, for the first time, we extend such comparisons to noncircular orbits—specifically, to a system of two nonspinning objects in a bound (eccentric) orbit. To enable the comparison we use a certain orbital-averaged quantity ⟨U⟩ that generalizes Detweiler’s redshift invariant. The functional relationship ⟨U⟩(Ω[subscript r],Ω[subscript ϕ]), where Ω[subscript r] and Ω[subscript ϕ] are the frequencies of the radial and azimuthal motions, is an invariant characteristic of the conservative dynamics. We compute ⟨U⟩(Ω[subscript r],Ω[subscript ϕ]) numerically through linear order in the mass ratio q, using a GSF code which is based on a frequency-domain treatment of the linearized Einstein equations in the Lorenz gauge. We also derive ⟨U⟩(Ω[subscript r],Ω[subscript ϕ]) analytically through 3PN order, for an arbitrary q, using the known near-zone 3PN metric and the generalized quasi-Keplerian representation of the motion. We demonstrate that the O(q) piece of the analytical PN prediction is perfectly consistent with the numerical GSF results, and we use the latter to estimate yet unknown pieces of the 4PN expression at O(q).
MIT Department
MIT Kavli Institute for Astrophysics and Space Research
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DOI of Published Version
https://doi.org/10.1103/PhysRevD.91.124014
