Departamento de Física da Universidade de Aveiro and CIDMA, Campus de Santiago, 3810-183 Aveiro, Portugal.
Departamento de Astronomía y Astrofísica, Universitat de València, Carrer del Dr. Moliner 50, 46100, Burjassot (València), Spain.
Phys Rev Lett. 2018 Sep 7;121(10):101102. doi: 10.1103/PhysRevLett.121.101102.
Extended scalar-tensor Gauss-Bonnet (ESTGB) gravity has been recently argued to exhibit spontaneous scalarization of vacuum black holes (BHs). A similar phenomenon can be expected in a larger class of models, which includes, e.g., Einstein-Maxwell scalar (EMS) models, where spontaneous scalarization of electrovacuum BHs should occur. EMS models have no higher curvature corrections, a technical simplification over ESTGB models that allows us to investigate, fully nonlinearly, BH scalarization in two novel directions. First, numerical simulations in spherical symmetry show, dynamically, that Reissner-Nordström (RN) BHs evolve into a perturbatively stable scalarized BH. Second, we compute the nonspherical sector of static scalarized BH solutions bifurcating from the RN BH trunk. Scalarized BHs form an infinite (countable) number of branches and possess a large freedom in their multipole structure. Unlike the case of electrovacuum, the EMS model admits static, asymptotically flat, regular on and outside the horizon BHs without spherical symmetry and even without any spatial isometries, which are thermodynamically preferred over the electrovacuum state. We speculate on a possible dynamical role of these nonspherical scalarized BHs.
扩展标量张量引力（ESTGB）最近被认为会导致真空黑洞（BH）的自发标量化。在更大的一类模型中也可以预期到类似的现象，例如爱因斯坦-麦克斯韦标量（EMS）模型，其中电真空 BH 应该会发生自发标量化。EMS 模型没有更高曲率的修正，相对于 ESTGB 模型来说是一种技术简化，这使得我们能够从两个新的方向全面地非线性地研究 BH 标量化。首先，球对称的数值模拟显示，Reissner-Nordström（RN）BH 动态地演变成了一个微扰稳定的标量化 BH。其次，我们计算了从 RN BH 主干分叉出来的静态标量化 BH 解的非球对称部分。标量化 BH 形成了无限个（可数个）分支，其多极结构有很大的自由度。与电真空的情况不同，EMS 模型允许存在没有球对称性、甚至没有任何空间等距性的静态、渐近平坦、在视界内外都规则的、热力学上优先于电真空态的 BH。我们推测了这些非球对称标量化 BH 的可能动力学作用。
