标题： 超辐射散射在洛伦兹破坏引力中 显示英文标题

标题： Superradiant scattering in Lorentz-violating gravity

摘要： 在破坏洛伦兹对称性的引力理论中，黑洞具有类似于广义相对论中克尔解的双视界结构。 此外，当具有修改色散关系的标量场与这些背景耦合时，在视界之间的区域可能出现具有负能量的在壳模式。 这两个特性共同表明，即使时空是静态的，也可以通过波的散射从黑洞中提取能量。 在这里，我们在频域中明确地进行了这种散射，表明确实可以观察到一种超辐射效应，导致能量提取，对于球对称情况下的模式$l>0$来说如此。 特别是，我们表明对于某些破坏洛伦兹对称性的尺度值，模式$l=1$可以表现出超过700%的反射率。 这使我们推测这些时空对这类扰动是不稳定的，尽管天体物理尺寸的物体应该具有很长的寿命。 我们的结果不仅适用于破坏洛伦兹对称性的引力，还可以扩展到任何存在修改色散关系的情况，例如类似引力。 显示英文摘要

摘要： Black holes in Lorentz violating gravity enjoy a double horizon structure which resembles that of the Kerr solution in General Relativity. Moreover, when a scalar field with a modified dispersion relation is coupled to these backgrounds, an on-shell mode with negative energy becomes possible in the region in between the horizons. Both properties together call for the possibility of extracting energy from the black hole by scattering of waves, even if the space-time is stationary. Here, we perform such scattering explicitly in the frequency domain, showing that indeed, a superradiant effect, leading to energy extraction, can be observed for modes with $l>0$ in spherical symmetry. In particular, we show that the mode $l=1$ can display a reflectivity exceeding 700% for certain values of the Lorentz violating scale. This leads us to conjecture the instability of these space-times against such perturbations, although astrophysical size objects should have long life-times. Our results are not unique to Lorentz violating gravity and can be extended to any setting where modified dispersion relations are present, such as analogue gravity.