论文标题
静态和极端黑洞中的光环
Light rings in static and extremal black holes
论文作者
论文摘要
在这项工作中，我们建立了一些关于通过纽曼 - 奔驰形式主义的极端黑洞空间中外部光环存在的结果。具体而言，假设存在保形平，静态和无效的能量状况，我们表明，外部光环存在的足够条件是$ r <2 k_ {g} $，其中$ r $，$ r $，时空的曲率标量和$ k_ {g} $的曲率标量，$ k_ {g} $，均可评估的两种速度，这两个都可以在spacelike上进行评估，这两个始终是外在的，均可在外面的情况下，在范围内，均可在范围内进行。球形，双曲线或平面几何形状。我们的结果对于光子遵循无效测量学的任何度量重力理论都是有效的。
In this work we establish some results concerning the existence of external light rings in extremal black hole spacetimes through the Newman-Penrose formalism. Specifically, assuming conformal flatness, staticity and the null energy condition, we show that a sufficient condition for the existence of external light rings is $R < 2 K_{G}$, where $R$, the curvature scalar of the spacetime and $K_{G}$, the Gaussian curvature of a spacelike two-surface, are both evaluated at the outermost event horizon, which can be endowed with spherical, hyperbolic or planar geometry. Our results are valid for any metric gravity theory where photons follow null geodesics.
