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arXiv 1004.4970gr-qchep-th
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高维快速旋转黑洞的条模不稳定性:广义相对论的数值模拟

Bar-mode instability of rapidly spinning black hole in higher dimensions: Numerical simulation in general relativity

Masaru Shibata, Hirotaka Yoshino

摘要:

利用数值相对论方法模拟了高维特殊对称时空中快速自旋黑洞的运动,时空维数为$6 \leq d \leq 8$。我们发现,高维黑洞,旋转足够快,对非轴对称的棒模变形是动态不稳定的,自发发射引力波,不考虑$d$的情况下$d=5$ \cite{SY09}。不稳定性开始的无量纲自旋参数的临界值是:$d=6$的$q:=a/μ^{1/(d-3)} \approx 0.74$,$d=7$的$\approx 0.73$,$d=8$的$\approx 0.77$,其中$μ$和$a$是质量和自旋参数。自旋小于这些临界值($q_{\rm crit}$)的黑洞似乎对任何扰动都是动态稳定的。长期模拟不稳定的BH也进行$d=6$和7。我们发现,它们的自旋作为引力波发射的结果,并随后解决到一个稳定的静态BH的自旋小于$q_{\rm crit}$。对于自旋更快的不稳定黑洞,达到新状态的时间尺度更短,自旋下降的分数更大。我们的研究结果意味着,一个具有$q > q_{\rm crit}$的高速旋转BH不可能是粒子加速器中的静止产物,即使它是TeV引力假设的结果。它的影响的现象学的一个小BH进行了讨论。

英文摘要:

Numerical-relativity simulation is performed for rapidly spinning black holes (BHs) in a higher-dimensional spacetime of special symmetries for the dimensionality $6 \leq d \leq 8$. We find that higher-dimensional BHs, spinning rapidly enough, are dynamically unstable against nonaxisymmetric bar-mode deformation and spontaneously emit gravitational waves, irrespective of $d$ as in the case $d=5$ \cite{SY09}. The critical values of a nondimensional spin parameter for the onset of the instability are $q:=a/μ^{1/(d-3)} \approx 0.74$ for $d=6$, $\approx 0.73$ for $d=7$, and $\approx 0.77$ for $d=8$ where $μ$ and $a$ are mass and spin parameters. Black holes with a spin smaller than these critical values ($q_{\rm crit}$) appear to be dynamically stable for any perturbation. Longterm simulations for the unstable BHs are also performed for $d=6$ and 7. We find that they spin down as a result of gravitational-wave emission and subsequently settle to a stable stationary BH of a spin smaller than $q_{\rm crit}$. For more rapidly spinning unstable BHs, the timescale, for which the new state is reached, is shorter and fraction of the spin-down is larger. Our findings imply that a highly rapidly spinning BH with $q > q_{\rm crit}$ cannot be a stationary product in the particle accelerators, even if it would be formed as a consequence of a TeV-gravity hypothesis. Its implications for the phenomenology of a mini BH are discussed.

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