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arXiv 2004.06525gr-qc
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无光子球的裸奇点的阴影

Shadow of a Naked Singularity without Photon Sphere

Ashok B. Joshi, Dipanjan Dey, Pankaj S. Joshi, Parth Bambhaniya

摘要:

一般认为,黑洞或裸奇点的阴影是由于光子球在这些时空中的发展而产生的。在这里,我们提出了一个新的球对称裸奇点时空的爱因斯坦方程的解决方案,没有光子球,我们表明,奇异投下的阴影,在没有光子球。我们讨论了这个阴影和类光测地线在这个时空中的一些新的功能。我们将这里的裸奇点阴影与史瓦西黑洞和第一种类型的Joshi-Malafarina-Narayan(JMN 1)裸奇点投射的阴影进行比较,在最后两个时空中,阴影是由于光子球的存在而形成的。特别是可以看到,奇点阴影的大小比黑洞的要小得多。我们的分析表明,这个裸奇点的阴影是区别于史瓦西黑洞和JMN 1裸奇点的阴影。这些结果是有用的和重要的背景下,最近的观测阴影的M87银河系中心。

英文摘要:

It is generally believed that the shadows of either a black hole or naked singularity arise due to photon spheres developing in these spacetimes. Here we propose a new spherically symmetric naked singularity spacetime solution of Einstein equations which has no photon sphere, and we show that the singularity casts a shadow in the absence of the photon sphere. We discuss some novel features of this shadow and the lightlike geodesics in this spacetime. We compare the shadow of the naked singularity here with shadows cast by Schwarzschild black hole and the first type of Joshi-Malafarina-Narayan (JMN1) naked singularity, where for the last two spacetimes the shadow is formed due to the presence of a photon sphere. It is seen, in particular, that the size of shadow of the singularity is considerably smaller than that of a black hole. Our analysis shows that the shadow of this naked singularity is distinguishable from the shadow of a Schwarzschild black hole and the JMN1 naked singularity. These results are useful and important in the context of recent observations of shadow of the M87 galactic center.

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