Spontaneous scalarisation of charged black holes: coupling dependence and dynamical features
Spontaneous scalarisation of charged black holes: coupling dependence and dynamical features
复制标题
DOI：
10.1088/1361-6382/ab23a1
复制
发表时间：
2019-02
影响因子：
3.5
通讯作者：
Pedro G S Fernandes;C. Herdeiro;Alexandre M. Pombo;E. Radu;N. Sanchis-Gual
中科院分区：
文献类型：
--
作者：
Pedro G S Fernandes;C. Herdeiro;Alexandre M. Pombo;E. Radu;N. Sanchis-Gual
带电的、渐近平坦的Reissner-Nordström黑洞（BH）的自发标量化最近被证明发生在Einstein-Maxwell-Scalar（EMS）模型中。这种现象是允许的标量场和麦克斯韦场之间的非最小耦合，并不需要非最小耦合的标量场曲率不变。EMS BH标度化提出了一种技术简化的BH标度化，已被证明是发生在扩展标量张量高斯-博内（eSTGB）模型。那么自然会问：（1）从EMS模型中得出的结论有多普遍？（2）这些结论对非最小耦合函数的选择有多大的依赖性？在这里，我们解决这些问题进行比较分析的几种不同形式的耦合函数，包括：指数，双曲，幂律和有理函数（分数）耦合。在所有这些，我们获得和研究域的存在的基本，球对称，标量BH和计算，特别是它们的熵。后者表明，标化的EMS BH总是熵优选的RN BH具有相同的总电荷质量比q。这与eSTGB的情况形成对比，其中对于相同的幂律耦合，基本标量化的球形BH在史瓦西解上不是熵优选的。此外，虽然在EMS模型的指数，双曲和幂律耦合的标度化的解决方案是非常相似的，有理函数耦合导致过渡域的存在，凭借一个极点的耦合功能，到一个区域的“异国情调”的解决方案，违反了弱能量条件。此外，完全非线性动力学演化的不稳定RN BH与不同的q值。这些显示：（1）对于足够小的q，标量化解具有（近似）相同的动态形式;（2）对于大的q，自发标量化明显降低q;因此演化是非保守的;（3）尽管存在非球形的静态标量化解，但在非球形扰动下不稳定RN BH的演化导致球形标量化BH。
Spontaneous scalarisation of electrically charged, asymptotically flat Reissner–Nordström black holes (BHs) has been recently demonstrated to occur in Einstein–Maxwell–Scalar (EMS) models. This phenomenon is allowed by a non-minimal coupling between the scalar and the Maxwell fields, and does not require non-minimal couplings of the scalar field to curvature invariants. EMS BH scalarisation presents a technical simplification over the BH scalarisation that has been conjectured to occur in extended scalar–tensor Gauss–Bonnet (eSTGB) models. It is then natural to ask: (1) how universal are the conclusions extracted from the EMS model? And (2) how much do these conclusions depend on the choice of the non-minimal coupling function? Here we address these questions by performing a comparative analysis of several different forms for the coupling function including: exponential, hyperbolic, power-law and a rational function (fraction) couplings. In all of them we obtain and study the domain of existence of fundamental, spherically symmetric, scalarised BHs and compute, in particular, their entropy. The latter shows that scalarised EMS BHs are always entropically preferred over the RN BHs with the same total charge to mass ratio q. This contrasts with the case of eSTGB, where for the same power-law coupling the spherical, fundamental scalarised BHs are not entropically preferred over the Schwarzschild solution. Also, while the scalarised solutions in the EMS model for the exponential, hyperbolic and power-law coupling are very similar, the rational function coupling leads to a transition in the domain of existence, by virtue of a pole in the coupling function, into a region of ‘exotic’ solutions that violate the weak energy condition. Furthermore, fully non-linear dynamical evolutions of unstable RN BHs with different values of q are presented. These show: (1) for sufficiently small q, scalarised solutions with (approximately) the same q form dynamically; (2) for large q, spontaneous scalarisation visibly decreases q; thus evolutions are non-conservative; (3) despite the existence of non-spherical, static scalarised solutions, the evolution of unstable RN BHs under non-spherical perturbations leads to a spherical scalarised BH.