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arXiv 1507.07079hep-thgr-qc
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Kerr膜的超辐射不稳定性

Superradiant instability of the Kerr brane

Akihiro Ishibashi, Paolo Pani, Leonardo Gualtieri, Vitor Cardoso

摘要:

我们考虑克尔膜的线性引力扰动,四维以上真空爱因斯坦方程的精确解和弦论的低能解。通过对横向Ricci平坦空间张量调和函数中的扰动进行分解,证明了Kerr膜的张量型和矢量型度量扰动分别满足四维Kerr空间上的质量Klein-Gordon方程和Proca方程,其中质量项与调和函数的本征值成正比.在克尔黑洞中,大质量玻色子场引发了一种著名的超辐射不稳定性。因此,我们建立了在$D\geq6$维的克尔膜是引力不稳定的,由于超辐射。这些解对于Gregory-Laflamme不稳定性来说也是不稳定的,我们讨论了两种不稳定性发生的条件以及它们相当不同的性质。当横向维度被紧化并且比克尔视界小得多时,只存在超辐射不稳定性,其时间尺度比动力学时间尺度长得多。利用四维黑洞线性微扰研究的最新进展,我们的形式也可以用来讨论其他类型的高维黑天体。

英文摘要:

We consider linear gravitational perturbations of the Kerr brane, an exact solution of vacuum Einstein's equations in dimensions higher than four and a low-energy solution of string theory. Decomposing the perturbations in tensor harmonics of the transverse Ricci-flat space, we show that tensor- and vector-type metric perturbations of the Kerr brane satisfy respectively a massive Klein-Gordon equation and a Proca equation on the four-dimensional Kerr space, where the mass term is proportional to the eigenvalue of the harmonics. Massive bosonic fields trigger a well-known superradiant instability on a Kerr black hole. We thus establish that Kerr branes in dimensions $D\geq6$ are gravitationally unstable due to superradiance. These solutions are also unstable against the Gregory-Laflamme instability and we discuss the conditions for either instability to occur and their rather different nature. When the transverse dimensions are compactified and much smaller than the Kerr horizon, only the superradiant instability is present, with a time scale much longer than the dynamical time scale. Our formalism can be also used to discuss other types of higher-dimensional black objects, taking advantage of recent progress in studying linear perturbations of four-dimensional black holes.

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