黑洞和裸奇点附近的近日点进动和阴影
Perihelion Precession and Shadows near Blackholes and Naked Singularities
摘要：
现在已知，除了黑洞之外，一些裸奇点也可以投射阴影，从而提供它们可能的可观察特征。我们在这里研究相关的问题，即如何根据进一步的物理签名来区分这些实体。我们指出，黑洞总是允许有正近日点进动的类时束缚轨道。此外，虽然带有光子球的裸奇点可以投射阴影，但它也可以允许这种轨道的正近日点进动，从而模仿黑洞。这表明具有光子球（阴影）的紧凑物体总是允许围绕它们的类时束缚轨道的正近日点进动。另一方面，没有光子球的裸奇点可以允许正负近日点进动，但不需要有阴影。本文构造了一个具有中心裸奇点但没有光子球的时空位形，它既能产生阴影又能产生负近日点进动。我们的结果意味着，而存在的阴影和一个积极的近日点岁差意味着要么是一个黑洞或裸奇点，阴影的存在和一个消极的近日点岁差同时将意味着一个裸奇点。我们讨论我们的结果的背景下，恒星运动（运动的“S”星）周围的Sgr-A* 银河系中心。
英文摘要：
It is now known that, apart from black holes, some naked singularities can also cast shadows which provide their possible observable signatures. We examine the relevant question here as to how to distinguish then these entities from each other, in terms of further physical signatures. We point out that black holes always admit timelike bound orbits having positive perihelion precession. Also, while a naked singularity with a photon sphere can cast a shadow, it could also admit positive perihelion precession for such orbits, thereby mimicking a black hole. This indicates that compact objects with photon spheres (shadows) always admit positive perihelion precession of timelike bound orbits around them. On the other hand, a naked singularity without a photon sphere could admit both positive and negative perihelion precession but need not have a shadow. In this paper, we construct a spacetime configuration which has a central naked singularity but no photon sphere, and it can give both shadow and a negative perihelion precession. Our results imply that, whereas the presence of a shadow and a positive perihelion precession implies either a black hole or a naked singularity, the presence of a shadow and a negative perihelion precession simultaneously would imply a naked singularity only. We discuss our results in the context of stellar motions (motion of the `S' stars) around the Sgr-A* galactic center.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
