Cosmological constant effect on charged and rotating black hole shadows

2021 ◽  
pp. 2150188
Author(s):  
A. Belhaj ◽  
M. Benali ◽  
A. El Balali ◽  
W. El Hadri ◽  
H. El Moumni
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Cosmological Constant ◽  
Moduli Space ◽  
Emission Rate ◽  
De Sitter ◽  
Naked Singularities ◽  
Rotating Black Holes ◽  
Rotation Parameters ◽  
Made In

Motivated by recent astrophysical observations, we investigate the shadow behaviors of four-dimensional charged rotating black holes with a cosmological constant. This study is made in terms of a reduced moduli space parameterized by the charge and the rotation parameters. For fixed observers, we analyse in some details the shadow behaviors and the corresponding naked singularities of Kerr–Newman and Kerr–Sen four-dimensional black holes in Anti-de Sitter backgrounds. Then, a comparative discussion is provided by computing the geometrical observables and the energy emission rate.

scholarly journals Estimating the Cosmological Constant from Shadows of Kerr–de Sitter Black Holes

Universe ◽  
2022 ◽  
Vol 8 (1) ◽  
pp. 52
Author(s):  
Misba Afrin ◽  
Sushant G. Ghosh
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Cosmological Constant ◽  
Parameter Space ◽  
Analytical Formula ◽  
Kerr Black Hole ◽  
De Sitter ◽  
Modified Gravity Theories ◽  
Rotating Black Holes ◽  
Astrophysical Observation

The Event Horizon Telescope collaboration has revealed the first direct image of a black hole, as per the shadow of a Kerr black hole of general relativity. However, other Kerr-like rotating black holes of modified gravity theories cannot be ignored, and they are essential as they offer an arena in which these theories can be tested through astrophysical observation. This motivates us to investigate asymptotically de Sitter rotating black holes wherein interpreting the cosmological constant Λ as the vacuum energy leads to a deformation in the vicinity of a black hole—new Kerr–de Sitter solution, which has a richer geometric structure than the original one. We derive an analytical formula necessary for the shadow of the new Kerr–de Sitter black holes and then visualize the shadow of black holes for various parameters for an observer at given coordinates (r0,θ0) in the domain (r0,rc) and estimate the cosmological constant Λ from its shadow observables. The shadow observables of the new Kerr–de Sitter black holes significantly deviate from the corresponding observables of the Kerr–de Sitter black hole over an appreciable range of the parameter space. Interestingly, we find a finite parameter space for (Λ, a) where the observables of the two black holes are indistinguishable.

scholarly journals BOUNDING THE GREYBODY FACTORS FOR NON-ROTATING BLACK HOLES

2013 ◽  
Vol 22 (09) ◽  
pp. 1350058 ◽  
Author(s):  
TRITOS NGAMPITIPAN ◽  
PETARPA BOONSERM
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Hawking Radiation ◽  
Extra Dimensions ◽  
Emission Rate ◽  
Matrix Formalism ◽  
De Sitter ◽  
Emit Radiation ◽  
Rotating Black Holes ◽  
Transfer Matrix Formalism

Semiclassical black holes emit radiation called Hawking radiation. Such radiation, as seen by an asymptotic observer far outside the black hole, differs from the original radiation near the horizon of the black hole by a redshift factor and the so-called "greybody factor." In this paper, we concentrate on the greybody factor; various bounds for the greybody factors of non-rotaging black holes are obtained, concentrating primarily on charged Reissner–Nordström (RN) and RN–de Sitter black holes. These bounds can be derived using a 2 × 2 transfer matrix formalism. It is found that the charges of black holes act as efficient barriers. Furthermore, adding extra dimensions to spacetime can shield Hawking radiation. Finally, it is also found that the cosmological constant can increase the emission rate of Hawking radiation.

scholarly journals Hawking radiation via tunneling from Born–Infeld AdS black hole

2016 ◽  
Vol 94 (12) ◽  
pp. 1369-1371 ◽  
Author(s):  
Gu-Qiang Li
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Emission Spectrum ◽  
Hawking Radiation ◽  
Emission Rate ◽  
De Sitter ◽  
Tunneling Radiation ◽  
Unitary Theory ◽  
Thermal Spectrum

The tunneling radiation of particles from Born–Infeld anti-de Sitter black holes is studied by using the Parikh–Wilczek method and the emission rate of a particle is calculated. It is shown that the emission rate is related to the change of the Bekenstein–Hawking entropy of the black hole and the emission spectrum deviates from the purely thermal spectrum but is consistent with an underlying unitary theory.

scholarly journals Extremal Cosmological Black Holes in Horndeski Gravity and the Anti-Evaporation Regime

Universe ◽  
2020 ◽  
Vol 6 (11) ◽  
pp. 210
Author(s):  
Ismael Ayuso ◽  
Diego Sáez-Chillón Gómez
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Cosmological Constant ◽  
Linear Order ◽  
Scalar Tensor Theory ◽  
De Sitter ◽  
Tensor Theory ◽  
Effective Cosmological Constant ◽  
Cosmological Black Holes ◽  
Extremal Black Holes

Extremal cosmological black holes are analysed in the framework of the most general second order scalar-tensor theory, the so-called Horndeski gravity. Such extremal black holes are a particular case of Schwarzschild-De Sitter black holes that arises when the black hole horizon and the cosmological one coincide. Such metric is induced by a particular value of the effective cosmological constant and is known as Nariai spacetime. The existence of this type of solutions is studied when considering the Horndeski Lagrangian and its stability is analysed, where the so-called anti-evaporation regime is studied. Contrary to other frameworks, the radius of the horizon remains stable for some cases of the Horndeski Lagrangian when considering perturbations at linear order.

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 Black hole shadows in M-theory scenarios

2021 ◽  
Vol 30 (04) ◽  
pp. 2150026
Author(s):  
A. Belhaj ◽  
M. Benali ◽  
A. El Balali ◽  
W. El Hadri ◽  
H. El Moumni ◽  
...  
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Event Horizon ◽  
Moduli Space ◽  
Emission Rate ◽  
Rotation Parameter ◽  
High Energies ◽  
Energy Emission ◽  
M Theory

We study the shadows of four-dimensional black holes in M-theory inspired models. We first inspect the influence of M2-branes on such optical aspects for nonrotating solutions. In particular, we show that the M2-brane number can control the circular shadow size. This geometrical behavior is distorted for rotating solutions exhibiting cardioid shapes in certain moduli space regions. Implementing a rotation parameter, we analyze the geometrical shadow deformations. Among others, we recover the circular behaviors for a large M2-brane number. Investigating the energy emission rate at high energies, we find, in a well-defined approximation, that the associated peak decreases with the M2-brane number. Moreover, we investigate a possible connection with observations (from Event Horizon Telescope or future devices) from a particular M-theory compactification by deriving certain constraints on the M[Formula: see text]-brane number in the light of the [Formula: see text] observational parameters.

scholarly journals Critical Phenomena of Charged AdS Black Holes in Rastall Gravity

2020 ◽  
Vol 2020 ◽  
pp. 1-9
Author(s):  
De-Cheng Zou ◽  
Ming Zhang ◽  
Chao Wu ◽  
Rui-Hong Yue
Keyword(s):  
Phase Transition ◽  
Black Holes ◽  
Black Hole ◽  
Phase Transitions ◽  
Cosmological Constant ◽  
De Sitter ◽  
Perfect Fluids ◽  
Large Black Hole ◽  
Ads Black Holes ◽  
Phantom Fields

We construct analytical charged anti-de Sitter (AdS) black holes surrounded by perfect fluids in four dimensional Rastall gravity. Then, we discuss the thermodynamics and phase transitions of charged AdS black holes immersed in regular matter like dust and radiation, or exotic matter like quintessence, ΛCDM type, and phantom fields. Surrounded by phantom field, the charged AdS black hole demonstrates a new phenomenon of reentrant phase transition (RPT) when the parameters Q, Np, and ψ satisfy some certain condition, along with the usual small/large black hole (SBH/LBH) phase transition for the surrounding dust, radiation, quintessence, and cosmological constant fields.

scholarly journals De sitter magnetic black hole dipole with a supersymmetric horizon

2021 ◽  
Vol 2021 (12) ◽  
Author(s):  
Davide Astesiano ◽  
S.L. Cacciatori
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Scalar Field ◽  
Cosmological Constant ◽  
The Other ◽  
Gauge Fields ◽  
Positive Pressure ◽  
Closed Universe ◽  
De Sitter ◽  
Extremal Black Holes

Abstract We find a new non BPS solution in N = 2 D = 4 gauged supergravity coupled to U(1) gauge fields and matter. It consists in a closed universe with two extremal black holes of equal size, surrounding two singularities. They have opposite magnetic charges (and no electric charges), but stay in static equilibrium thanks to the positive pressure of a cosmological constant. The geometry is perfectly symmetric under the exchange of the black holes and the flip of the sign of the charges. However the scalar field is non constant and non symmetric, with different values at the horizons, which depend on a real modulus. Remarkably we show that it satisfies the attractor mechanism and the entropy indeed depends only on the magnetic charges. At one of the horizons the solution becomes $$ \frac{1}{2} $$ 1 2 -BPS supersymmetric, while at the other one there is no supersymmetry, but the entropy remains independent from the scalar modulus.

scholarly journals “MODULI SPACE” OF ASYMPTOTICALLY ANTI-DE-SITTER SPACE-TIMES IN 2+1 DIMENSIONS

1995 ◽  
Vol 10 (29) ◽  
pp. 4139-4160 ◽  
Author(s):  
KIYOSHI EZAWA
Keyword(s):  
Black Holes ◽  
General Solution ◽  
Power Series ◽  
Cosmological Constant ◽  
Moduli Space ◽  
Three Dimensional ◽  
Einstein Equations ◽  
Quadratic Differentials ◽  
De Sitter ◽  
Inverse Radius

Setting an ansatz that the metric is expressible by a power series of the inverse radius and taking a particular gauge choice, we construct a “general solution” of (2+1)-dimensional Einstein equations with a negative cosmological constant in the case where the space-time is asymptotically anti-de-Sitter. Our general solution turns out to be parametrized by two centrally extended quadratic differentials on S1. In order to include three-dimensional black holes naturally in our general solution, it is necessary to exclude the region inside the horizon. We also discuss the relation of our general solution to the moduli space of flat [Formula: see text] connections.

scholarly journals NONSINGULAR BLACK HOLES FROM GRAVITY–MATTER-BRANE LAGRANGIANS

2010 ◽  
Vol 25 (08) ◽  
pp. 1571-1596 ◽  
Author(s):  
EDUARDO GUENDELMAN ◽  
ALEXANDER KAGANOVICH ◽  
EMIL NISSIMOV ◽  
SVETLANA PACHEVA
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Cosmological Constant ◽  
Radial Coordinate ◽  
De Sitter ◽  
Wormhole Solution ◽  
Interior Region ◽  
Exterior Region ◽  
Inner Horizon ◽  
Self Consistent

We consider self-consistent coupling of bulk Einstein–Maxwell–Kalb–Ramond system to codimension-one charged lightlikep-brane with dynamical (variable) tension (LL-brane). The latter is described by a manifestly reparametrization-invariant worldvolume action significantly different from the ordinary Nambu–Goto one. We show that the LL-brane is the appropriate gravitational and charge source in the Einstein–Maxwell–Kalb–Ramond equations of motion needed to generate a self-consistent solution describing nonsingular black hole. The latter consists of de Sitter interior region and exterior Reissner–Nordström region glued together along their common horizon (it is the inner horizon from the Reissner–Nordström side). The matching horizon is automatically occupied by the LL-brane as a result of its worldvolume Lagrangian dynamics, which dynamically generates the cosmological constant in the interior region and uniquely determines the mass and charge parameters of the exterior region. Using similar techniques we construct a self-consistent wormhole solution of Einstein–Maxwell system coupled to electrically neutral LL-brane, which describes two identical copies of a nonsingular black hole region being the exterior Reissner–Nordström region above the inner horizon, glued together along their common horizon (the inner Reissner–Nordström one) occupied by the LL-brane. The corresponding mass and charge parameters of the two black hole "universes" are explicitly determined by the dynamical LL-brane tension. This also provides an explicit example of Misner–Wheeler "charge without charge" phenomenon. Finally, this wormhole solution connecting two nonsingular black holes can be transformed into a special case of Kantowski–Sachs bouncing cosmology solution if instead of Reissner–Nordström we glue together two copies of the exterior Reissner–Nordström–de Sitter region with big enough bare cosmological constant, such that the radial coordinate becomes a timelike variable everywhere in the two "universes," except at the matching hypersurface occupied by the LL-brane.

Sign in / Sign up

Export Citation Format

Share Document