Observable Aspects of Black Holes

Date

2026-1-22

Author

Tavlayan, Aydın

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In this thesis, some of the crucial observable aspects of black holes are investigated. The existence of the light rings around black holes in five dimensional spacetime is considered by using topological invariants. It is shown that the method is robust and can be also applied to higher dimensions. Some specific cases indicating the possible existence of the naked singularities are analyzed with the help of both null and timelike geodesics around it. The shadow and the accretion disc around this hypothetical naked singularity are examined. In addition to geodesic investigation, the black hole thermodynamics is also considered. A recently developed method of assigning entropy to some fixed volume in Einstein's gravity is generalized to the higher powers of curvature in three dimensions. Then, by using background Killing charges, the thermodynamic charges and their corresponding conjugates are redefined and checked whether they obey the laws of black hole thermodynamics and the geometrical relations of the corresponding spacetime. Finally, the instability of a particle around a black hole is investigated by considering the exponentially unstable motion it performs when perturbed and the corresponding Lyapunov exponents of this motion. A possible connection is proposed between the instability and the black hole thermodynamics. The importance of non-equatorial contributions to the shadow image is discussed.

Subject Keywords

Black Holes, Light Rings, Singularity, Black Hole Thermodynamics, Instability

URI

https://hdl.handle.net/11511/118480

Collections

Graduate School of Natural and Applied Sciences, Thesis