Brahma Suddhasattwa, Chen Che-Yu, Yeom Dong-Han
Department of Physics, McGill University, Montréal QC H3A 2T8, Canada.
Institute of Physics, Academia Sinica, Taipei 11529, Taiwan.
Phys Rev Lett. 2021 May 7;126(18):181301. doi: 10.1103/PhysRevLett.126.181301.
The lack of rotating black hole models, which are typically found in nature, in loop quantum gravity (LQG) substantially hinders the progress of testing LQG from observations. Starting with a nonrotating LQG black hole as a seed metric, we construct a rotating spacetime using the revised Newman-Janis algorithm. The rotating solution is nonsingular everywhere and it reduces to the Kerr black hole asymptotically. In different regions of the parameter space, the solution describes (1) a wormhole without event horizon (which, we show, is almost ruled out by observations), (2) a black hole with a spacelike transition surface inside the event horizon, or (3) a black hole with a timelike transition region inside the inner horizon. It is shown how fundamental parameters of LQG can be constrained by the observational implications of the shadow cast by this object. The causal structure of our solution depends crucially only on the spacelike transition surface of the nonrotating seed metric, while being agnostic about specific details of the latter, and therefore captures universal features of an effective rotating, nonsingular black hole in LQG.
在圈量子引力（LQG）中缺乏自然界中常见的旋转黑洞模型，这在很大程度上阻碍了从观测检验LQG的进展。我们以一个非旋转的LQG黑洞作为种子度规开始，使用修正的纽曼 - 贾尼斯算法构建一个旋转时空。该旋转解在任何地方都是非奇异的，并且渐近地简化为克尔黑洞。在参数空间的不同区域，该解描述了：（1）一个没有事件视界的虫洞（我们表明，观测几乎排除了这种情况），（2）一个在事件视界内有类空过渡面的黑洞，或者（3）一个在内视界内有类时过渡区域的黑洞。展示了LQG的基本参数如何受到该物体阴影的观测结果的约束。我们解的因果结构关键仅取决于非旋转种子度规的类空过渡面，而与后者的具体细节无关，因此捕捉了LQG中有效旋转、非奇异黑洞的普遍特征。
