AI 中文总结
该研究针对LISA受限旋入波形，发现近等质量双黑洞的自旋反转情况与无自旋反转双黑洞在参考信噪比100时存在强简并性，需更完整波形检验简并能否打破。
AI 中文摘要
自旋反转现象出现在多个场景中。分析研究预测，不等质量的超大质量双黑洞旋入过程中会发生一次自旋翻转；而数值相对论和后牛顿计算则显示，等质量双黑洞会出现反复的“翻转-跳跃”运动。长期自旋演化理论还预测了由自旋诱导质量四极矩驱动的额外情况。这些效应能否在引力波数据中被区分，目前仍不明确。我们将长期自旋角方程与准圆形二阶后牛顿频率演化相结合，构建了一个受LISA天区平均灵敏度加权的受限波形。我们研究了5个近等质量注入信号，探测器帧总质量M=2×10^5M⊙，包括克尔翻转-跳跃情况和1个四极矩诱导情况。每个注入信号都与受约束的无轨道平面穿越的物理演化波形进行对比。我们搜索了全部4个无自旋反转扇区，调整了质量、自旋大小和初始自旋角，并对时间、相位和整体振幅进行最大化处理。在该受限模型中，大自旋运动本身并不会产生明显不同的波形：一个扫过133.26°的弱自旋在参考信号信噪比ρ★=100时留下的残余信噪比为0.806；两个自旋多次穿越轨道平面的情况留下最大残余信噪比1.641；四极矩情况的次级自旋范围为128.11°，包含5次穿越，但找到的最佳无自旋反转候选者仅留下残余信噪比0.454；所有找到的最大匹配值均超过0.999865。因此，在ρ★=100时，该受限模型中的自旋反转情况与无自旋反转双黑洞具有强简并性，需要更完整的波形（包括观测者帧进动调制、高阶谐波、独立偏振和完整LISA响应）来检验这种简并性能否被打破。
英文摘要
Spin inversions appear in several settings. Analytical work predicts a single spin flip during unequal-mass supermassive binary inspiral, while numerical relativity and post-Newtonian calculations show repeated flip-flop motion in comparable-mass binaries. Secular spin evolution also predicts additional cases driven by spin-induced mass quadrupoles. Whether these effects can be distinguished in gravitational-wave data is still unclear. We combine the secular spin angle equations with a quasi-circular second post-Newtonian frequency evolution and build a restricted waveform weighted by the sky-averaged LISA sensitivity. We study five near-equal-mass injections with detector-frame total mass $M=2\times10^5M_\odot$, including Kerr flip-flops and one quadrupole-induced case. Each injection is compared with physically evolving waveforms constrained to have no orbital-plane crossings. We search all four no-inversion sectors, vary the masses, spin magnitudes, and initial spin angles, and maximize over time, phase, and overall amplitude. Large spin motion does not by itself lead to a clearly different waveform in this restricted model. A weak spin that sweeps through $133.26^\circ$ leaves a residual SNR of $0.806$ at reference signal SNR $ρ_\star=100$. A case where both spins cross the orbital plane many times gives the largest residual, $1.641$. The quadrupole case has a secondary-spin range of $128.11^\circ$ with five crossings, yet the best no-inversion candidate found leaves a residual SNR of only $0.454$. All largest matches found exceed $0.999865$. Within this restricted model, the spin inversion cases are therefore strongly degenerate with no-inversion binaries at $ρ_\star=100$. More complete waveforms, including observer-frame precession modulations, higher harmonics, separate polarizations, and the full LISA response, are needed to test whether this degeneracy can be broken.
Comments20 pages, 4 figures. Submitted to Universe. Data and code: https://doi.org/10.5281/zenodo.22025538
