标题： 旋转黑洞作为宇宙弦的工厂 显示英文标题

标题： Spinning black holes as cosmic string factories

摘要： 我们考虑了一个宇宙弦环被一个质量大得多且更紧凑的黑洞捕获后的演化过程。 我们展示，在经历了几次产生较小环状物弹射的重新连接后，仍然与黑洞绑定的环状物沿几乎周期性的非自相交轨迹移动，即“轨道”。 由于环状物和旋转黑洞之间的能量和角动量交换，轨道会演化。 我们展示这种演化在数学上等价于三维空间中辅助闭合曲线的一种特定连续变形；对于零黑洞自旋，这种变形是曲线缩短，已由数学家广泛研究过。 演化特征包括通过超辐射提取黑洞自旋能量而产生的环状物增长效应，以及因运动的弦摩擦事件视界而产生的环状物衰减效应。 辅助曲线的自相交对应于黑洞捕获新的弦段，从而增加一个新的被捕获的环。 这种演化可能的渐近状态显示出强烈的引力波发射。 重新连接是否阻止达到渐近状态仍有待探索。 此外，由于引力波的发射和黑洞的反冲改变了轨道并可能导致自相交，轨道的形状也发生演化。 我们认为，在无量纲张力 $\mu$ 的显著范围内，弦环会被位于星系中心的超大质量黑洞捕获。 这强烈激励进一步研究弦环与黑洞之间的相互作用，特别是这一过程对黑洞自旋降低以及在星系核中产生的字符串所发出的引力波的影响。 我们还讨论了原始黑洞可能的环状物捕获。 显示英文摘要

摘要： We consider the evolution of a cosmic string loop that is captured by a much more massive and compact black hole. We show that after several reconnections that produce ejections of smaller loops, the loop that remains bound to the black hole moves on a nearly-periodic non-self-intersecting trajectory, "the orbit". The orbit evolves due to an energy and angular momentum exchange between the loop and the spinning black hole. We show that such evolution is mathematically equivalent to a certain continuous deformation of an auxiliary closed curve in a 3-dimensional space; for zero black-hole spin this deformation is curve-shortening that has been extensively studied by mathematicians. The evolution features competing effects of loop growth by the superradiant extraction of the black-hole spin energy, and loop decay by the friction of the moving string against the horizon. A self-intersection of an auxiliary curve corresponds to a capture by the black hole of a new string segment and thus an addition of a new captured loop. Possible asymptotic states of such evolution are shown to be strong emitters of gravitational waves. Whether reconnections prevent reaching the asymptotic states remains to be explored. Additionally, the orbit's shape also evolves due to an emission of gravitational waves, and a recoil of the black hole that changes the orbit and likely leads to self-intersections. We argue that for a significant range of the dimensionless tension $\mu$, string loops are captured by supermassive black holes at the centers of galaxies. This strongly motivates further study of interaction between string loops and black holes, especially the influence of this process on the black hole spindown and on the production of gravitational waves by strings created in galactic nuclei. We also discuss potential loop captures by primordial black holes.