论文标题
固定轴对称空间的光环的通用性能
Universal Properties of Light Rings for Stationary Axisymmetric Spacetimes
论文作者
论文摘要
光环（LRS）在引力波观测和黑洞照片中起重要作用。在本文中，我们研究了LRS在固定，轴对称，渐近平坦的空间中有或没有地平线的一般特征。对于非Xtremal黑洞，我们明确地表明，总是至少存在两个LR在相反方向传播的LR，其中最外面的LR径向不稳定。对于一个极端的黑洞，我们表明至少存在一个逆行LR。我们发现至少有一个LR具有角度稳定。稳定性分析不涉及任何能量条件。我们的方法也适用于无水平的空间，我们证明LR总是成对出现的。我们的证明中仅使用了一些自然和通用的假设。结果适用于一般相对论以及大多数修改的重力理论。与以前在此问题上的作品相反，我们采用更直接的方法获得了更强的结果。
Light rings (LRs) play an important role in gravitational wave observations and black hole photographs. In this paper, we investigate general features of LRs in stationary, axisymmetric, asymptotically flat spacetimes with or without horizons. For a nonextremal black hole, we show explicitly that there always exist at least two LRs propagating in opposite directions, where the outermost one is radially unstable. For an extremal black hole, we show that there exists at least one retrograde LR. We find that there is at least one LR which is angularly stable. The stability analysis does not involve any energy condition. Our method also applies to horizonless spacetimes and we prove that LRs always appear in pairs. Only some natural and generic assumptions are used in our proof. The results are applicable to general relativity as well as most modified theories of gravity. In contrast to previous works on this issue, we obtain much stronger results with a much more straightforward approach.
