scholarly journals Tidal-charge effects on the superradiance of rotating black holes

2020 ◽  
Vol 80 (11) ◽  
Author(s):  
Ednilton S. de Oliveira
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Massless Scalar ◽  
Charge Effects ◽  
Rotating Black Holes ◽  
Scalar Waves ◽  
Charge Intensity ◽  
Maximum Amplification ◽  
Extreme Black Holes ◽  
Considerable Enhancement

AbstractThe changes a (negative) tidal charge causes at the phenomenon of superradiance which occurs around rotating black holes are investigated. This is made by computing the amplification factors of massless scalar waves being scattered by the black hole. It is shown that the increase of the tidal-charge intensity leads to a considerable enhancement of energy extraction from near-extreme black holes. Such improvement results from the fact that extreme black holes with more negative tidal charges spin faster. Maximum amplification decreases with the increase of the tidal charge intensity if the angular momentum of the black hole per unit mass is fixed. The tidal charge may also change crucially the superradiance phenomenon of massless scalar waves causing maximum amplification to occur for $$m > 1$$ m > 1 differently from the case of Kerr black holes.

scholarly journals Black holes and magnetic fields

2006 ◽  
Vol 2 (S238) ◽  
pp. 139-144
Author(s):  
Jiří Bičák ◽  
Vladimír Karas ◽  
Tomáš Ledvinka
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Magnetic Fields ◽  
Magnetic Flux ◽  
Higher Dimensions ◽  
Meissner Effect ◽  
Maxwell Theory ◽  
Potential Threat ◽  
Rotating Black Holes ◽  
Extreme Black Holes

AbstractStationary axisymmetric magnetic fields are expelled from outer horizons of black holes as they become extremal. Extreme black holes exhibit Meissner effect also within exact Einstein–Maxwell theory and in string theories in higher dimensions. Since maximally rotating black holes are expected to be astrophysically most important, the expulsion of the magnetic flux from their horizons represents a potential threat to an electromagnetic mechanism launching the jets at the account of black-hole rotation.

scholarly journals Scattering by regular black holes: Planar massless scalar waves impinging upon a Bardeen black hole

2015 ◽  
Vol 92 (2) ◽  
Author(s):  
Caio F. B. Macedo ◽  
Ednilton S. de Oliveira ◽  
Luís C. B. Crispino
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Massless Scalar ◽  
Regular Black Holes ◽  
Scalar Waves

scholarly journals Black hole hair removal for N = 4 CHL models

2021 ◽  
Vol 2021 (2) ◽  
Author(s):  
Subhroneel Chakrabarti ◽  
Suresh Govindarajan ◽  
P. Shanmugapriya ◽  
Yogesh K. Srivastava ◽  
Amitabh Virmani
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Degrees Of Freedom ◽  
Microscopic Analysis ◽  
Flat Space ◽  
Special Care ◽  
Hair Removal ◽  
Partition Functions ◽  
Rotating Black Holes

Abstract Although BMPV black holes in flat space and in Taub-NUT space have identical near-horizon geometries, they have different indices from the microscopic analysis. For K3 compactification of type IIB theory, Sen et al. in a series of papers identified that the key to resolving this puzzle is the black hole hair modes: smooth, normalisable, bosonic and fermionic degrees of freedom living outside the horizon. In this paper, we extend their study to N = 4 CHL orbifold models. For these models, the puzzle is more challenging due to the presence of the twisted sectors. We identify hair modes in the untwisted as well as twisted sectors. We show that after removing the contributions of the hair modes from the microscopic partition functions, the 4d and 5d horizon partition functions agree. Special care is taken to present details on the smoothness analysis of hair modes for rotating black holes, thereby filling an essential gap in the literature.

The effect of dark matter on the weak cosmic censorship conjecture in the extended space

2021 ◽  
pp. 2150207
Author(s):  
Zi-Yu Fu ◽  
Bao-Qi Zhang ◽  
Chuan-Yin Wang ◽  
Hui-Ling Li
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Dark Matter ◽  
Second Law Of Thermodynamics ◽  
Cosmic Censorship ◽  
De Sitter ◽  
Extended Phase ◽  
Extended Space ◽  
Extreme Black Holes ◽  
Cosmic Censorship Conjecture

By analyzing the energy–momentum relationship of the absorbed fermions dropping into a Reissner–Nordstöm–anti-de Sitter black hole surrounded by dark matter, the laws of thermodynamic and weak cosmic censorship conjecture in the extended phase space are investigated. We find that the first law of thermodynamics is valid. However, the validity of the second law of thermodynamics depends on the density [Formula: see text] of the perfect fluid dark matter. In addition, we also find that when the fermions are absorbed, the structures of black hole surrounded by dark matter would not change. Therefore, weak cosmic censorship conjecture holds for the extreme black holes and the non-extreme black holes.

Hawking radiation of charged fermions from accelerating and rotating black holes with generalized uncertainty principle

2019 ◽  
Vol 28 (08) ◽  
pp. 1950102
Author(s):  
Muhammad Rizwan ◽  
Khalil Ur Rehman
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Uncertainty Principle ◽  
Hawking Radiation ◽  
Generalized Uncertainty Principle ◽  
Hawking Temperature ◽  
Black Hole Evaporation ◽  
Rotating Black Holes ◽  
Gravity Effects ◽  
Made In

By considering the quantum gravity effects based on generalized uncertainty principle, we give a correction to Hawking radiation of charged fermions from accelerating and rotating black holes. Using Hamilton–Jacobi approach, we calculate the corrected tunneling probability and the Hawking temperature. The quantum corrected Hawking temperature depends on the black hole parameters as well as quantum number of emitted particles. It is also seen that a remnant is formed during the black hole evaporation. In addition, the corrected temperature is independent of an angle [Formula: see text] which contradicts the claim made in the literature.

scholarly journals On-axis scalar absorption cross section of Kerr–Newman black holes: Geodesic analysis, sinc and low-frequency approximations

2018 ◽  
Vol 27 (11) ◽  
pp. 1843012 ◽  
Author(s):  
Carolina L. Benone ◽  
Luiz C. S. Leite ◽  
Luís C. B. Crispino ◽  
Sam R. Dolan
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Cross Section ◽  
Absorption Cross Section ◽  
Rotation Axis ◽  
Low Frequency ◽  
Massless Scalar ◽  
Massless Scalar Field ◽  
Absorption Cross ◽  
Newman Black Hole

We investigate null geodesics impinging parallel to the rotation axis of a Kerr–Newman black hole, and show that the absorption cross section for a massless scalar field in the eikonal limit can be described in terms of the photon orbit parameters. We compare our sinc and low-frequency approximations with numerical results, showing that they are in excellent agreement.

scholarly journals CHARGED ROTATING BLACK HOLES IN DILATON GRAVITY

2007 ◽  
Vol 22 (26) ◽  
pp. 4849-4858 ◽  
Author(s):  
A. SHEYKHI ◽  
N. RIAZI
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Angular Momentum ◽  
Dilaton Field ◽  
Dilaton Gravity ◽  
Charged Black Holes ◽  
Static Solutions ◽  
Rotating Black Holes ◽  
Small Rotation ◽  
Type Potential

We consider charged black holes with curved horizons, in five-dimensional dilaton gravity in the presence of Liouville-type potential for the dilaton field. We show how, by solving a pair of coupled differential equations, infinitesimally small angular momentum can be added to these static solutions to obtain charged rotating dilaton black hole solutions. In the absence of dilaton field, the nonrotating version of the solution reduces to the five-dimensional Reissner–Nordström black hole, and the rotating version reproduces the five-dimensional Kerr–Newman modification thereof for small rotation parameter. We also compute the angular momentum and the angular velocity of these rotating black holes which appear at the first order.

scholarly journals DISCUSSION ON SOME CHARACTERISTICS OF CHARGED BRANE-WORLD BLACK HOLES

2009 ◽  
Vol 24 (04) ◽  
pp. 719-739 ◽  
Author(s):  
M. KALAM ◽  
F. RAHAMAN ◽  
A. GHOSH ◽  
B. RAYCHAUDHURI
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Gravitational Field ◽  
Scalar Field ◽  
Brane World ◽  
Massless Scalar ◽  
Massless Scalar Field ◽  
Effective Potentials ◽  
Test Particles ◽  
Jacobi Formalism

Several physical natures of charged brane-world black holes are investigated. Firstly, the timelike and null geodesics of the charged brane-world black holes are presented. We also analyze all the possible motions by plotting the effective potentials for various parameters for circular and radial geodesics. Secondly, we investigate the motion of test particles in the gravitational field of the charged brane-world black holes using the Hamilton–Jacobi formalism. We consider charged and uncharged test particles and examine their behavior in both static and nonstatic cases. Thirdly, the thermodynamics of the charged brane-world black holes are studied. Finally, it is shown that there is no phenomenon of superradiance for an incident massless scalar field for such a black hole.

Numerical Study of Stationary Black Hole Magnetospheres-Toward Blandford-Znajek mechanism by fast rotating black holes-

2008 ◽  
Author(s):  
Yousuke Takamori ◽  
Hideki Ishihara ◽  
Masashi Kimura ◽  
Nakao Ken-ichi ◽  
Masaaki Takahashi ◽  
...  
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Numerical Study ◽  
Stationary Black Hole ◽  
Rotating Black Holes ◽  
Fast Rotating

scholarly journals Slowly Rotating Black Holes with Nonlinear Electrodynamics

2014 ◽  
Vol 2014 ◽  
pp. 1-7 ◽  
Author(s):  
S. H. Hendi ◽  
M. Allahverdizadeh
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Angular Momentum ◽  
Linear Order ◽  
Rotation Parameter ◽  
Nonlinear Electrodynamics ◽  
Nonlinearity Parameter ◽  
Static Solutions ◽  
Rotating Black Holes ◽  
Spherical Topology

We study charged slowly rotating black hole with a nonlinear electrodynamics (NED) in the presence of cosmological constant. Starting from the static solutions of Einstein-NED gravity as seed solutions, we use the angular momentum as the perturbative parameter to obtain slowly rotating black holes. We perform the perturbations up to the linear order for black holes in 4 dimensions. These solutions are asymptotically AdS and their horizon has spherical topology. We calculate the physical properties of these black holes and study their dependence on the rotation parameteraas well as the nonlinearity parameterβ. In the limitβ→∞, the solution describes slowly rotating AdS type black holes.

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