scholarly journals Timelike geodesics around a charged spherically symmetric dilaton black hole

2015 ◽  
pp. 41-48 ◽  
Author(s):  
C. Blaga
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Test Particle ◽  
Effective Potential ◽  
Equations Of Motion ◽  
Equation Of Motion ◽  
Qualitative Approach ◽  
Extremal Black Hole ◽  
Spherically Symmetric ◽  
Dilaton Black Hole

In this paper we study the timelike geodesics around a spherically symmetric charged dilaton black hole. The trajectories around the black hole are classified using the effective potential of a free test particle. This qualitative approach enables us to determine the type of orbit described by test particle without solving the equations of motion, if the parameters of the black hole and the particle are known. The connections between these parameters and the type of orbit described by the particle are obtained. To visualize the orbits we solve numerically the equation of motion for different values of parameters envolved in our analysis. The effective potential of a free test particle looks different for a non-extremal and an extremal black hole, therefore we have examined separately these two types of black holes.

scholarly journals Trajectory around a spherically symmetric non-rotating black hole

2011 ◽  
Vol 89 (6) ◽  
pp. 689-695 ◽  
Author(s):  
Sumanta Chakraborty ◽  
Subenoy Chakraborty
Keyword(s):  
Black Hole ◽  
Gravitational Field ◽  
Gravitational Potential ◽  
Test Particle ◽  
Effective Potential ◽  
Particle Motion ◽  
Spherically Symmetric ◽  
Rotating Black Hole

The trajectory of a test particle or a photon around a general spherical black hole is studied, and bending of the light trajectory is investigated. A pseudo-Newtonian gravitational potential describing the gravitational field of the black hole is determined and is compared with the related effective potential for test particle motion. As an example, results are presented for a Reissner–Nordström black hole.

scholarly journals PHANTOM ACCRETION BY FIVE-DIMENSIONAL CHARGED BLACK HOLE

2011 ◽  
Vol 26 (23) ◽  
pp. 1731-1736 ◽  
Author(s):  
M. SHARIF ◽  
G. ABBAS
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Equations Of Motion ◽  
Dynamical Behavior ◽  
Naked Singularity ◽  
Phantom Energy ◽  
Charge Ratio ◽  
Charged Black Hole ◽  
Spherically Symmetric ◽  
Symmetric Flow

This paper deals with the dynamical behavior of phantom field near five-dimensional charged black hole. We formulate equations of motion for steady-state spherically symmetric flow of phantom fluids. It is found that phantom energy accretes onto black holes for u < 0. Further, the location of critical point of accretion are evaluated that leads to mass to charge ratio for 5D charged black hole. This ratio implies that accretion cannot transform a black hole into a naked singularity. We would like to mention here that this work is an irreducible extension of 4D charged black hole.

scholarly journals Analytic study of superradiant stability of Kerr–Newman black holes under charged massive scalar perturbation

2021 ◽  
Vol 81 (5) ◽  
Author(s):  
Jun-Huai Xu ◽  
Zi-Han Zheng ◽  
Ming-Jian Luo ◽  
Jia-Hui Huang
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Effective Potential ◽  
Careful Analysis ◽  
Equation Of Motion ◽  
Analytic Study ◽  
Scalar Perturbation ◽  
Massive Scalar ◽  
Radial Equation ◽  
Newman Black Hole

AbstractThe superradiant stability of a Kerr–Newman black hole and charged massive scalar perturbation is investigated. We treat the black hole as a background geometry and study the equation of motion of the scalar perturbation. From the radial equation of motion, we derive the effective potential experienced by the scalar perturbation. By a careful analysis of this effective potential, it is found that when the inner and outer horizons of Kerr–Newman black hole satisfy $$\frac{r_-}{r_+}\leqslant \frac{1}{3}$$ r - r + ⩽ 1 3 and the charge-to-mass ratios of scalar perturbation and black hole satisfy $$ \frac{q}{\mu }\frac{Q}{ M}>1 $$ q μ Q M > 1 , the Kerr–Newman black hole and scalar perturbation system is superradiantly stable.

scholarly journals The statistical mechanics of near-extremal black holes

2021 ◽  
Vol 2021 (5) ◽  
Author(s):  
Luca V. Iliesiu ◽  
Gustavo J. Turiaci
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Partition Function ◽  
Gauge Field ◽  
Dimensional Reduction ◽  
Degrees Of Freedom ◽  
Energy Scale ◽  
Fixed Charge ◽  
Extremal Black Hole ◽  
Extremal Black Holes

Abstract An important open question in black hole thermodynamics is about the existence of a “mass gap” between an extremal black hole and the lightest near-extremal state within a sector of fixed charge. In this paper, we reliably compute the partition function of Reissner-Nordström near-extremal black holes at temperature scales comparable to the conjectured gap. We find that the density of states at fixed charge does not exhibit a gap; rather, at the expected gap energy scale, we see a continuum of states. We compute the partition function in the canonical and grand canonical ensembles, keeping track of all the fields appearing through a dimensional reduction on S2 in the near-horizon region. Our calculation shows that the relevant degrees of freedom at low temperatures are those of 2d Jackiw-Teitelboim gravity coupled to the electromagnetic U(1) gauge field and to an SO(3) gauge field generated by the dimensional reduction.

scholarly journals EXTREMAL BLACK HOLES AND ELEMENTARY STRING STATES

1995 ◽  
Vol 10 (28) ◽  
pp. 2081-2093 ◽  
Author(s):  
ASHOKE SEN
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Black Hole Entropy ◽  
Extremal Black Hole ◽  
Coupling Constant ◽  
Left Handed ◽  
Quantum Numbers ◽  
Independent Parameters ◽  
Elementary String ◽  
Extremal Black Holes

Some of the extremal black hole solutions in string theory have the same quantum numbers as the Bogomol’nyi saturated elementary string states. We explore the possibility that these black holes can be identified with elementary string excitations. It is shown that stringy effects could correct the Bekenstein-Hawking formula for the black hole entropy in such a way that it correctly reproduces the logarithm of the density of elementary string states. In particular, this entropy has the correct dependence on three independent parameters, the mass and the left-handed charge of the black hole, and the string coupling constant.

scholarly journals LUKEWARM BLACK HOLES IN QUADRATIC GRAVITY

2011 ◽  
Vol 26 (14) ◽  
pp. 999-1007 ◽  
Author(s):  
JERZY MATYJASEK ◽  
KATARZYNA ZWIERZCHOWSKA
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Event Horizon ◽  
Fourth Order ◽  
Spherically Symmetric ◽  
Cosmological Horizon ◽  
De Sitter ◽  
Quadratic Gravity ◽  
De Sitter Universe ◽  
Electrically Charged

Perturbative solutions to the fourth-order gravity describing spherically-symmetric, static and electrically charged black hole in an asymptotically de Sitter universe is constructed and discussed. Special emphasis is put on the lukewarm configurations, in which the temperature of the event horizon equals the temperature of the cosmological horizon.

Accretion onto a Black Hole

2014 ◽  
Author(s):  
Charles D. Bailyn
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Potential Energy ◽  
Gravitational Potential ◽  
Gas Flow ◽  
Gravitational Potential Energy ◽  
Spherically Symmetric ◽  
Potential Well ◽  
Accretion Flows ◽  
Flow Geometry

This chapter explores the ways that accretion onto a black hole produces energy and radiation. As material falls into a gravitational potential well, energy is transformed from gravitational potential energy into other forms of energy, so that total energy is conserved. Observing such accretion energy is one of the primary ways that astrophysicists pinpoint the locations of potential black holes. The spectrum and intensity of this radiation is governed by the geometry of the gas flow, the mass infall rate, and the mass of the accretor. The simplest flow geometry is that of a stationary object accreting mass equally from all directions. Such spherically symmetric accretion is referred to as Bondi-Hoyle accretion. However, accretion flows onto black holes are not thought to be spherically symmetric—the infall is much more frequently in the form of a flattened disk.

scholarly journals Shadow cast of noncommutative black holes in Rastall gravity

2020 ◽  
Vol 35 (20) ◽  
pp. 2050163 ◽  
Author(s):  
Ali Övgün ◽  
İzzet Sakallı ◽  
Joel Saavedra ◽  
Carlos Leiva
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Emission Rate ◽  
Model Parameters ◽  
Spherically Symmetric ◽  
Image Model ◽  
Schwarzschild Black Hole ◽  
Physical Validity ◽  
Shadow Cast ◽  
Noncommutative Parameter

We study the shadow and energy emission rate of a spherically symmetric noncommutative black hole in Rastall gravity. Depending on the model parameters, the noncommutative black hole can reduce to the Schwarzschild black hole. Since the nonvanishing noncommutative parameter affects the formation of event horizon, the visibility of the resulting shadow depends on the noncommutative parameter in Rastall gravity. The obtained sectional shadows respect the unstable circular orbit condition, which is crucial for physical validity of the black hole image model.

scholarly journals Distributions of extremal black holes in Calabi-Yau compactifications

2020 ◽  
Vol 2020 (10) ◽  
Author(s):  
George Hulsey ◽  
Shamit Kachru ◽  
Sungyeon Yang ◽  
Max Zimet
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Moduli Space ◽  
Black Hole Horizon ◽  
Extremal Black Hole ◽  
Vector Multiplet ◽  
Horizon Area ◽  
Extremal Black Holes

Abstract We study non-supersymmetric extremal black hole excitations of 4d $$ \mathcal{N} $$ N = 2 supersymmetric string vacua arising from compactification on Calabi-Yau threefolds. The values of the (vector multiplet) moduli at the black hole horizon are governed by the attractor mechanism. This raises natural questions, such as “what is the distribution of attractor points on moduli space?” and “how many attractor black holes are there with horizon area up to a certain size?” We employ tools developed by Denef and Douglas [1] to answer these questions.

scholarly journals Minimal Length Effects on Tunnelling from Spherically Symmetric Black Holes

2015 ◽  
Vol 2015 ◽  
pp. 1-8 ◽  
Author(s):  
Benrong Mu ◽  
Peng Wang ◽  
Haitang Yang
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Angular Momentum ◽  
Minimal Length ◽  
Jacobi Method ◽  
Spherically Symmetric ◽  
Infinite Time ◽  
Quantum Tunnelling ◽  
Zero Mass ◽  
Jacobi Equations

We investigate effects of the minimal length on quantum tunnelling from spherically symmetric black holes using the Hamilton-Jacobi method incorporating the minimal length. We first derive the deformed Hamilton-Jacobi equations for scalars and fermions, both of which have the same expressions. The minimal length correction to the Hawking temperature is found to depend on the black hole’s mass and the mass and angular momentum of emitted particles. Finally, we calculate a Schwarzschild black hole's luminosity and find the black hole evaporates to zero mass in infinite time.

Sign in / Sign up

Export Citation Format

Share Document