1,299 research outputs found
Shadows and rings of a de Sitter-Schwarzschild black hole
We study the optical appearance of a de Sitter-Schwarzschild black hole and
its distinguishability from a Schwarzschild black hole. By exploring various
accretion models and emission profiles, we investigate the impact of different
parameters on the observed shadows and intensity profiles. Our analysis reveals
that the outer edge of the shadow, corresponding to the apparent radius of the
photon sphere, remains consistent regardless of the spherical accretion details
or the size of the black hole. However, subtle differences in the overall
brightness and intensity distribution can arise between these two black holes,
especially for emission models with sharp peaks near the event horizon. We find
that the de Sitter-Schwarzschild black hole tends to exhibit a slightly darker
appearance in certain scenarios, while in others, it can appear slightly
brighter than the Schwarzschild black hole. These distinctions become more
prominent as the radial emission decreases more rapidly. Nevertheless, the size
of the shadow alone is not sufficient to differentiate the potential
differences in the optical appearance between the de Sitter-Schwarzschild black
hole and the Schwarzschild black hole. Instead, distinctions may be observed in
the overall brightness of the image.Comment: 25 pages, 14 figure
On a Schwarzschild-type defect wormhole
We investigate a new type of Schwarzschild wormhole, which relies on a
3-dimensional spacetime defect with degenerate metrics. This particular
wormhole is a solution of the vacuum Einstein equations. We also study the
generalized Schwarzschild-type defect wormhole and discuss the Null Energy
Condition. In particular, we investigate the geodesics and geodesic congruences
of the generalized Schwarzschild-type defect wormhole. Additionally, we explore
the optical appearance of these wormholes, shedding light on their observable
features.Comment: 21 pages, 5 figure
Hawking radiation-quasinormal modes correspondence for large AdS black holes
It is well-known that the non-strictly thermal character of the Hawking
radiation spectrum generates a natural correspondence between Hawking radiation
and black hole quasinormal modes. This main issue has been analyzed in the
framework of Schwarzschild black holes, Kerr black holes and nonextremal
Reissner-Nordstrom black holes. In this paper, by introducing the effective
temperature, we reanalysis the non-strictly thermal character of large AdS
black holes. The results show that the effective mass corresponding to the
effective temperature is approximatively the average one in any dimension. And
the other effective quantities can also be obtained. Based on the known forms
of frequency in quasinormal modes, we reanalysis the asymptotic frequencies of
the large AdS black hole in three and five dimensions. Then we get the formulas
of the Bekenstein-Hawking entropy and the horizon's area quantization with
functions of the quantum "overtone" number .Comment: 6 page
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