417 research outputs found
Strong gravitational lensing in a rotating Kaluza-Klein black hole with squashed horizons
We have investigated the strong gravitational lensing in a rotating squashed
Kaluza-Klein (KK) black hole spacetime. Our result show that the strong
gravitational lensings in the rotating squashed KK black hole spacetime have
some distinct behaviors from those in the backgrounds of the four-dimensional
Kerr black hole and of the squashed KK G\"{o}del black hole. In the rotating
squashed KK black hole spacetime, the marginally circular photon radius
, the coefficient , , the deflection angle
in the direction and the corresponding observational
variables are independent of whether the photon goes with or against the
rotation of the background, which is different with those in the usual
four-dimensional Kerr black hole spacetime. Moreover, we also find that with
the increase of the scale of extra dimension , the marginally circular
photon radius and the angular position of the relativistic images
first decreases and then increases in the rotating squashed KK
black hole for fixed rotation parameter , but in the squashed KK G\"{o}del
black hole they increase for the smaller global rotation parameter and
decrease for the larger one. In the extremely squashed case , the
coefficient in the rotating squashed KK black hole increases
monotonously with the rotation parameter, but in the squashed KK G\"{o}del
black hole it is a constant and independent of the global rotation of the
G\"{o}del Universe.Comment: 20 pages; 7 figures. Accepted for publication in JHEP. arXiv admin
note: substantial text overlap with arXiv:1102.008
Black hole entropy arising from massless scalar field with Lorentz violation induced by the coupling to Einstein tensor
We have investigated quantum entropy of a static black hole arising from the
massless scalar field with Lorentz violation induced by the coupling to
Einstein tensor. Our results show that the coupled massless scalar field
contributes to the classical Bekenstein-Hawking term in the black hole entropy.
The corrected classical Bekenstein-Hawking entropy is not one quarter of the
event horizon area of the original background black hole, but of a
corresponding effective metric related to the coupling. It means that the
classical Bekenstein-Hawking entropy depends not only on the black hole
parameter, but also on the coupling which reduces Lorentz violation.Comment: 5 pages, no figure. Accepted by PLB for publicatio
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