Superradiant instabilities in astrophysical systems
Superradiant instabilities in astrophysical systems
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DOI：
10.1103/physrevd.87.043513
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发表时间：
2012-12
影响因子：
5
通讯作者：
Helvi Witek;V. Cardoso;A. Ishibashi;U. Sperhake
中科院分区：
文献类型：
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作者：
Helvi Witek;V. Cardoso;A. Ishibashi;U. Sperhake
光玻色子的自由度已经成为暗物质的重要候选者，暗物质似乎遍布我们整个宇宙。这些场在弯曲时空周围的演化尚不清楚，但预计会显示出有趣的效果。特别是，光玻色子场与超大质量黑洞（大多数星系中的关键角色）的相互作用，可以提供超辐射和非线性玻塞诺瓦状坍缩的丰富多彩的例子。反过来，对旋转黑洞的观测预计将对我们宇宙中假定的大质量玻色子场的质量施加严格的限制。我们在此的目的是对旋转黑洞附近线性化的大质量标量场和矢量场的演化进行全面的研究。一般初始数据的演化具有非常丰富的结构，这取决于场和黑洞的质量。在非常晚的时间里，伴随幂律尾巴的准正态衰荡或指数衰减是中间时间无质量场的一般特征。大型油田通常在早期就表现出向幂律尾巴的过渡。在一定的玻色子场质量范围内，玻色子场可以被困在视界外的势垒中，跃迁到束缚态。因为有许多这样的准边界状态，一般的结果是振幅调制的正弦信号，或跳动信号，其包络由两个最低的泛音很好地描述。我们认为，这种冲击的出现在过去没有被注意到，实际上被误认为是指数增长。信号的幅度调制很大程度上取决于泛音的相对激发，而泛音的相对激发又与束缚态的地理位置密切相关。对初始数据进行微调后，人们可以看到几乎纯束缚态模式的演化，这种模式在足够大的黑洞（BH）旋转时变得不稳定。这是我们第一次在一般黑洞背景下探索巨大的矢量场，在克尔背景下很难分离，如果不是不可能的话。我们的研究结果表明，旋转黑洞在大质量矢量场的作用下具有一般的强不稳定性。
Light bosonic degrees of freedom have become a serious candidate for dark matter, which seems to pervade our entire Universe. The evolution of these fields around curved spacetimes is poorly understood but is expected to display interesting effects. In particular, the interaction of light bosonic fields with supermassive black holes, key players in most galaxies, could provide colorful examples of superradiance and nonlinear bosenovalike collapse. In turn, the observation of spinning black holes is expected to impose stringent bounds on the mass of putative massive bosonic fields in our Universe. Our purpose here is to present a comprehensive study of the evolution of linearized massive scalar and vector fields in the vicinities of rotating black holes. The evolution of generic initial data has a very rich structure, depending on the mass of the field and of the black hole. Quasinormal ringdown or exponential decay followed by a power-law tail at very late times is a generic feature of massless fields at intermediate times. Massive fields generically show a transition to power-law tails early on. For a certain boson field mass range, the field can become trapped in a potential barrier outside the horizon and transition to a bound state. Because there are a number of such quasibound states, the generic outcome is an amplitude modulated sinusoidal, or beating, signal, whose envelope is well described by the two lowest overtones. We believe that the appearance of such beatings has gone unnoticed in the past, and in fact mistaken for exponential growth. The amplitude modulation of the signal depends strongly on the relative excitation of the overtones, which in turn is strongly tied to the bound state geography. A fine-tuning of the initial data allows one to see the evolution of the nearly pure bound state mode that turns unstable for sufficiently large black hole (BH) rotation. For the first time we explore massive vector fields in a generic black hole background that are difficult, if not impossible, to separate in the Kerr background. Our results show that spinning BHs are generically strongly unstable against massive vector fields.