Alternative mechanism for black hole echoes
Alternative mechanism for black hole echoes
复制标题
黑洞回波的替代机制
DOI：
10.1103/physrevd.104.044012
复制
发表时间：
2021-08-05
影响因子：
5
通讯作者：
Yue，Rui-Hong
中科院分区：
文献类型：
--
作者：
Liu，Hang;Qian，Wei-Liang;Yue，Rui-Hong
来自黑洞的引力波回波被认为是探测视界附近时空的关键观测值。特别是，据推测，回声与奇异致密物体的特定特征密切相关，而且，可能提供了进入引力量子性质的途径。最近的研究表明，黑洞度规中的不连续实质上改变了准正态频率的渐近行为。在目前的研究中，我们进一步提出，在度规中植入不连续为黑洞回波提供了另一种机制。物理上，后者可能对应于周围光晕内部不均匀的物质分布。为了证明结果，我们首先用数值方法研究了具有非光滑有效势的黑洞周围标量扰动的时间演化。结果表明，即使在距离视界较远的地方，以相当小的强度定位不连续点，这种现象仍然存在。此外，我们还证明了该模型中的回波可以基于相关格林函数的修正极点结构进行解析推导。发现准正态模谱和回波的渐近特性密切相关，因为这两个特征可以归因于同一来源。特别是，时域$T$中回波的周期与频域$\Delta(\Re\omega)$中沿实轴的连续极点之间的渐近间距有关，通过一个简单的关系$\lim\limits_{\Re\omega\to+\infty}\Delta(\Re\omega) = 2\pi/T$。此外，我们还讨论了不同回声机制之间可能存在的区别。本文还讨论了本发现的潜在天体物理学意义。
Gravitational wave echoes from the black holes have been suggested as a crucial observable to probe the spacetime in the vicinity of the horizon. In particular, it was speculated that the echoes are closely connected with specific characteristics of the exotic compact objects, and moreover, possibly provide an access to the quantum nature of gravity. Recently, it was shown that the discontinuity in the black hole metric substantially modifies the asymptotical behavior of quasinormal frequencies. In the present study, we proceed further and argue that a discontinuity planted into the metric furnishes an alternative mechanism for the black hole echoes. Physically, the latter may correspond to an uneven matter distribution inside the surrounding halo. To demonstrate the results, we first numerically investigate the temporal evolution of the scalar perturbations around a black hole that possesses a nonsmooth effective potential. It is shown that the phenomenon persists even though the discontinuity can be located further away from the horizon with rather insignificant strength. Besides, we show that the echoes in the present model can be derived analytically based on the modified pole structure of the associated Green function. The asymptotical properties of the quasinormal mode spectrum and the echoes are found to be closely connected, as both features can be attributed to the same origin. In particular, the period of the echoes in the time domain $T$ is shown to be related to the asymptotic spacing between successive poles along the real axis in the frequency domain $\Delta(\Re\omega)$, by a simple relation $\lim\limits_{\Re\omega\to+\infty}\Delta(\Re\omega) = 2\pi/T$. Moreover, we discuss possible distinguishment between different echo mechanisms. The potential astrophysical implications of the present findings are also addressed.