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Rediscussion of charged dilaton-axion black hole entropy

100%
Wang C., Gui Y.
Open Physics
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2009
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vol. 7
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issue 3
521-526
EN
We rediscuss the entropy of a charged dilaton-axion black hole for both the asymptotically flat and non-flat cases by using the thin film brick-wall model. This improved method avoids some drawbacks in the original brick-wall method such as the small mass approximation, neglecting the logarithm term, and taking the term L 3 as the contribution of the vacuum surrounding the black hole. The entropy we obtain turns out to be proportional to the horizon area of the black hole, conforming to the Bekenstein-Hawking area-entropy formula for black holes.
2
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Localization of energy for a regular black hole solution in an asymptotically de Sitter spacetime geometry

100%
Radinschi I., Grammenos T., Spanou A.
Open Physics
|
2011
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vol. 9
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issue 5
1173-1181
EN
The energy and momentum distributions of a regular black hole in a four-dimensional, asymptotically de Sitter spacetime geometry are computed, whereby the Einstein, Landau-Lifshitz, Weinberg and Møller energy-momentum complexes are utilized. It is found, for all prescriptions applied, that the momentum distribution vanishes, while the energy distribution depends on the mass parameter M, the electric charge Q, and the cosmological constant Λ. In addition, various limiting cases are discussed.
3
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“Mass inflation” with lightlike branes

100%
Guendelman E., Kaganovich A., Nissimov E., Pacheva S.
Open Physics
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2009
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vol. 7
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issue 4
668-676
EN
We discuss properties of a new class of p-brane models, describing intrinsically lightlike branes for any world-volume dimension, in various gravitational backgrounds of interest in the context of black hole physics. One of the characteristic features of these lightlike p-branes is that the brane tension appears as an additional nontrivial dynamical world-volume degree of freedom. Codimension one lightlike brane dynamics requires that bulk space with a bulk metric of spherically symmetric type must possess an event horizon which is automatically occupied by the lightlike brane while its tension evolves exponentially with time. The latter phenomenon is an analog of the well known “mass inflation” effect in black holes.
4
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Extreme gravitational lensing in vicinity of Schwarzschild-de Sitter black holes

84%
Bakala P., Čermák P., Hledík S., Stuchlík Z., Truparová K.
Open Physics
|
2007
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vol. 5
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issue 4
599-610
EN
We have developed a realistic, fully general relativistic computer code to simulate optical projection in a strong, spherically symmetric gravitational field. The standard theoretical analysis of optical projection for an observer in the vicinity of a Schwarzschild black hole is extended to black hole spacetimes with a repulsive cosmological constant, i.e, Schwarzschild-de Sitterspacetimes. Influence of the cosmological constant is investigated for static observers and observers radially free-falling from the static radius. Simulations include effects of the gravitational lensing, multiple images, Doppler and gravitational frequency shift, as well as the intensity amplification. The code generates images of the sky for the static observer and a movie simulations of the changing sky for the radially free-falling observer. Techniques of parallel programming are applied to get a high performance and a fast run of the BHC simulation code.
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