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arXiv 0804.4184gr-qc
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黑洞双星的高精度数值模拟:引力波能流的计算及与后牛顿近似的比较

High-accuracy numerical simulation of black-hole binaries: Computation of the gravitational-wave energy flux and comparisons with post-Newtonian approximants

Michael Boyle, Alessandra Buonanno, Lawrence E. Kidder, Abdul H. Mroué, Yi Pan, Harald P. Pfeiffer, Mark A. Scheel

摘要:

紧双星的引力波(GW)能流和质心能量的表达式是后牛顿(PN)波形的组成部分。在本文中,我们计算GW的能量通量和GW频率导数的高精度数值模拟的等质量,非旋转的黑洞二。我们还通过假设能量平衡来估计来自模拟的质心能量(的导数)。我们比较这些数量与各种PN近似(绝热泰勒和帕德模型,非绝热有效单体(EOB)模型)的预测。我们发现,Pade求和的能量通量并没有加速收敛的通量系列,然而,Pade通量是显着更接近的数值结果的整个范围内的模拟(约30 GW周期)。Taylor和Pade模型高估了合并附近通量和频率导数的增加,而EOB模型更忠实地再现了形状,更接近于数值通量,频率导数和能量导数。我们还比较了GW阶段的数值模拟与Pade和EOB模型。匹配数值和未调谐的3.5 PN阶波形,我们发现,直到$M ω= 0.1$累积的相位差对于Pade近似是-0.12弧度,并且对于具有开普勒(非开普勒)通量的EOB近似是0.50(0.45)弧度。我们在EOB模型中拟合自由参数,以最小化相位差,并确认这些参数之间的简并性。通过调整伪4PN阶系数的径向电位或磁通,或者,如果存在的话,在磁通中的极点的位置,我们发现,累积的相位差可以减少-如果需要的话-远小于估计的数值相位误差(0.02弧度)。

英文摘要:

Expressions for the gravitational wave (GW) energy flux and center-of-mass energy of a compact binary are integral building blocks of post-Newtonian (PN) waveforms. In this paper, we compute the GW energy flux and GW frequency derivative from a highly accurate numerical simulation of an equal-mass, non-spinning black hole binary. We also estimate the (derivative of the) center-of-mass energy from the simulation by assuming energy balance. We compare these quantities with the predictions of various PN approximants (adiabatic Taylor and Pade models; non-adiabatic effective-one-body (EOB) models). We find that Pade summation of the energy flux does not accelerate the convergence of the flux series; nevertheless, the Pade flux is markedly closer to the numerical result for the whole range of the simulation (about 30 GW cycles). Taylor and Pade models overestimate the increase in flux and frequency derivative close to merger, whereas EOB models reproduce more faithfully the shape of and are closer to the numerical flux, frequency derivative and derivative of energy. We also compare the GW phase of the numerical simulation with Pade and EOB models. Matching numerical and untuned 3.5 PN order waveforms, we find that the phase difference accumulated until $M ω= 0.1$ is -0.12 radians for Pade approximants, and 0.50 (0.45) radians for an EOB approximant with Keplerian (non-Keplerian) flux. We fit free parameters within the EOB models to minimize the phase difference, and confirm degeneracies among these parameters. By tuning pseudo 4PN order coefficients in the radial potential or in the flux, or, if present, the location of the pole in the flux, we find that the accumulated phase difference can be reduced - if desired - to much less than the estimated numerical phase error (0.02 radians).

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