暗物质到黑洞的超吸积作为超大质量克尔黑洞的自旋印记机制
Dark-to-black super-accretion as a spin-imprinting mechanism for supermassive Kerr black holes
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中文总结 AI 辅助
本研究提出暗物质到黑洞的超吸积机制，可先抹去克尔黑洞初始自旋，再将其重置为仅由玻色子质量和最终黑洞质量决定的特征值，解决高红移超大质量黑洞的自旋演化难题。
中文摘要 AI 辅助
高红移处存在质量$M\gtrsim10^9\\,M_{\odot}$且无量纲自旋$\chi\sim0.9-0.99$的超大质量黑洞，这对我们理解早期宇宙构成了挑战。本研究探讨被两个占据不同束缚态的极轻标量暗物质云环绕的克尔黑洞种子的绝热共演化，证明该结构可让黑洞成长至超大质量范围，同时留下特征性的最终自旋。演化分为两个阶段：第一阶段，$\ell=0$模描述的球形云通过失控的暗物质到黑洞吸积机制完全耗尽，对于玻色子质量$\mu\sim10^{-18}-10^{-17}\\,\mathrm{eV}$，该过程的时标为数亿年。由于吸积物质不携带角动量，黑洞自旋会普遍被驱动至$\chi\simeq0$，与其初始自旋无关。此阶段中，$\ell=m=1$模描述的第二个云始终处于超辐射 regime，演化可忽略不计。但第一阶段完成后，该云会过渡至吸积 regime，快速将质量和角动量转移给黑洞。从$\chi\simeq0$开始，黑洞自旋不断增加，直至演化在接近阈值$\chi_{\rm sat}$处自洽饱和，该阈值由条件$\Omega_H(\chi_{\rm sat})=\mu$定义，此过程的e折叠时标为数千年，比第一阶段短数个数量级。该最终饱和自旋在很大程度上独立于黑洞初始自旋和次级云质量，提供了一种自旋印记机制：原始自旋先被球形吸积抹去，随后被重置为仅由玻色子质量和最终黑洞质量决定的值。
英文摘要
The existence of supermassive black holes with masses $M\gtrsim10^9\,M_{\odot}$ and large dimensionless spins $χ\sim0.9-0.99$ at high redshift remains a challenge to our understanding of the early Universe. In this work, we study the adiabatic co-evolution of a Kerr black hole seed surrounded by two ultralight scalar dark matter clouds occupying different bound states, and show that this configuration allows the black hole to grow into the supermassive mass range while imprinting a characteristic final spin. The evolution proceeds through two stages. During the first stage, a spherical cloud described by the $\ell=0$ mode is completely depleted through a runaway dark-to-black accretion mechanism on a timescale of hundreds of millions of years for boson masses $μ\sim10^{-18}-10^{-17}\,\mathrm{eV}$. Since the accreted material does not carry angular momentum, the black hole spin is universally driven to $χ\simeq0$, independently of its initial spin. Throughout this stage, the second cloud, described by the $\ell=m=1$ mode, remains in the superradiant regime with negligible evolution. However, once the first stage is completed, this cloud transitions to the accreting regime, rapidly transferring both mass and angular momentum to the black hole. Starting from $χ\simeq0$, the black hole spin increases until the evolution self-consistently saturates close to the threshold $χ_{\rm sat}$, defined by the condition $Ω_H(χ_{\rm sat})=μ$, on an e-folding timescale of thousands of years, orders of magnitude shorter than the first stage. This final saturation spin is largely independent of both the initial black hole spin and the mass of the secondary cloud, providing a spin-imprinting mechanism in which the primordial spin is first erased by spherical accretion and then reset to a value determined only by the boson mass and the final black hole mass.
