[论文解读] Signature of horizon dynamics in binary black hole gravitational waveforms

Ssohrab Borhanian, K. G. Arun+2 more|arXiv (Cornell University)|Jan 1, 2019

Pulsars and Gravitational Waves Research被引用 3

一句话总结

本研究通过将数值 relativity 模拟与后牛顿理论预测进行比较，识别出在双黑洞并合过程中对强场视界动力学最敏感的引力波模态。在非自旋和自旋双黑洞中，(3,2) 模态均表现出与后牛顿行为最大的偏差，使其成为探测引力波形中视界尺度物理现象的首选候选模态。

ABSTRACT

Gravitational waves from merging binary black holes carry the signature of the strong field dynamics of the newly forming common horizon. This signature presents itself in the amplitudes and phases of various spherical harmonic modes as deviations from the point particle description provided by post-Newtonian theory. Understanding the nature of these departures will aid in (a) formulating better models of the emitted waveforms in the strong field regime of the dynamics, and (b) relating the waveforms observed at infinity to the common horizon dynamics. In this work we have used a combination of numerical relativity simulations and post-Newtonian theory to search for the modes of radiation whose amplitude is most affected by the strong field phase of the evolution. These modes are identified to carry the signature of the strong field regime due to significant deviations of the numerical data from the leading order post-Newtonian predictions. We find that modes with large amplitudes or with spherical harmonic indices $\ell=m$ are least modified from their dominant post-Newtonian behavior, while the weaker $\ell eq m$ modes are modified to the greatest extent. The addition of spins to the binary components only affects the current-multipole modes with $\ell + m= ext{odd}$ at the order of interest and does seem to stabilize some of these modes, the $(\ell, m)=(3,2)$ mode being the exception. This mode is the most promising candidate to observe the signature of strong field dynamics as it shows the deviations from post-Newtonian behavior equally for binaries with non-spinning and aligned spinning black holes.

研究动机与目标

• 识别双黑洞并合过程中携带强场视界动力学特征的引力波模态。
• 理解后牛顿预测的偏差如何揭示共同视界形成与演化过程中的信息。
• 确定哪些模态对双黑洞并合的非线性强场阶段最为敏感。
• 评估黑洞自旋对强场效应导致特定波形模态改变的影响。

提出的方法

• 结合数值 relativity 模拟与后牛顿理论，计算双黑洞并合全过程的引力波形。
• 分析引力辐射的球谐模态，重点关注振幅与相位相对于一阶后牛顿预测的偏差。
• 将数值波形与后牛顿估计值进行比较，量化偏差，尤其关注较弱的 ℓ≠m 模态。
• 通过研究共线自旋双黑洞及其对 ℓ+m 为奇数的电流多极模态的影响，分析自旋的作用。
• 识别出(3,2)模态在非自旋和自旋情况下均最显著地偏离后牛顿行为。
• 采用逐模态比较方法，隔离受强场动力学影响最大的模态，表明其在探测视界尺度物理方面的潜力。

实验结果

研究问题

• RQ1 在双黑洞并合的强场阶段，哪些引力波模态与后牛顿预测的偏差最大？
• RQ2 黑洞自旋在多大程度上影响强场视界动力学对特定波形模态的修改？
• RQ3 为何(3,2)模态相较于其他 ℓ≠m 模态对强场效应特别敏感？
• RQ4 ℓ+m 为奇数的电流多极模态在自旋效应下表现出何种增强的稳定性或偏差？
• RQ5 (3,2)模态是否可在非自旋和自旋双星系统中均作为共同视界动力学的可靠探测工具？

主要发现

• (3,2)模态在非自旋和自旋双黑洞构型中均表现出与后牛顿预测最大的偏差，表明其对强场视界动力学具有高度敏感性。
• ℓ=m 或振幅较大的模态从后牛顿行为中变化最小，表明它们对强场效应的信息量较低。
• 较弱的 ℓ≠m 模态受强场动力学影响最为显著，使其成为探测非线性视界物理的理想候选模态。
• 自旋仅影响 ℓ+m 为奇数的电流多极模态，且该影响并未使所有此类模态趋于稳定。
• (3,2)模态因其在非自旋和共线自旋情况下均保持一致的显著偏差，仍是观测强场特征的最有力候选模态。