scholarly journals Observing shadow of the Schwarzschild black hole in presence of a plasma

2016 ◽  
Vol 12 (S324) ◽  
pp. 351-352 ◽  
Author(s):  
Farruh Atamurotov
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Electromagnetic Radiation ◽  
Power Law ◽  
Density Profile ◽  
Particle Motion ◽  
Spherically Symmetric ◽  
Schwarzschild Black Hole ◽  
Plasma Environment ◽  
Symmetric Black Hole

AbstractWe have investigated particle motion around Schwarzschild black holes in the presence of a plasma with radial power-law density profile has been shown that the photon sphere around a spherically symmetric black hole is unchanged under the influence of the plasma; however, the Schwarzschild black hole shadow size is reduced due to the refraction of electromagnetic radiation in the plasma environment of the black hole.

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.

Universality of spectra of black holes

2014 ◽  
Vol 29 (36) ◽  
pp. 1450191 ◽  
Author(s):  
Xiao-Xiong Zeng ◽  
Qiang Li ◽  
Yi-Wen Han
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Area Spectrum ◽  
Spherically Symmetric ◽  
Action Variable ◽  
Intrinsic Properties ◽  
Entropy Spectrum ◽  
Symmetric Black Hole

Using exclusively an action variable, we quantize a static, spherically symmetric black hole. The spacings of the quantized entropy spectrum and area spectrum are found to be equal to the values given by Bekenstein. Interestingly, we find the spectra are independent of the hairs of the black holes and the mode of motion of a particle outside the spacetime, which depends only on the intrinsic properties of the gravity. Our result shows that the spectra are universal provided the spacetime owns a horizon.

scholarly journals Black hole thermodynamics and heat engines in conformal gravity

2017 ◽  
Vol 26 (13) ◽  
pp. 1750151 ◽  
Author(s):  
Hao Xu ◽  
Yuan Sun ◽  
Liu Zhao
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Black Hole Thermodynamics ◽  
Spherically Symmetric ◽  
Conformal Gravity ◽  
Extended Phase ◽  
Heat Engines ◽  
Equation Of States ◽  
Symmetric Black Hole ◽  
Black Hole Solutions

The extended phase-space thermodynamics and heat engines for static spherically symmetric black hole solutions of four-dimensional conformal gravity are studied in detail. It is argued that the equation of states (EOS) for such black holes is always branched, any continuous thermodynamical process cannot drive the system from one branch of the EOS into another branch. Meanwhile, the thermodynamical volume is bounded from above, making the black holes always super-entropic in one branch and may also be super-entropic in another branch in certain range of the temperature. The Carnot and Stirling heat engines associated to such black holes are shown to be distinct from each other. For rectangular heat engines, the efficiency always approaches zero when the rectangle becomes extremely narrow, and given the highest and lowest working temperatures fixed, there is always a maximum for the efficiency of such engines.

QUANTUM ERGOSPHERE AND HAWKING PROCESS

1999 ◽  
Vol 14 (28) ◽  
pp. 1951-1960 ◽  
Author(s):  
ZHONG-HENG LI
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Thermal Radiation ◽  
Radiation Spectrum ◽  
Spherically Symmetric ◽  
Field Equations ◽  
Stationary Black Hole ◽  
Symmetric Black Hole ◽  
Hawking Process ◽  
Nonstationary Black Hole

We study both spherically symmetric and rotating (Kerr) nonstationary black holes and discuss the radiation of these black holes via the Hawking process. We find that the thermal radiation spectrum of a nonstationary black hole is obviously dependent on the spin state of a particle and is different from the case of a stationary black hole. This effect originates from the quantum ergosphere. We also find that the field equations of spin s=0,1/2,1 and 2 can combine into a generalized Teukolsky-type master equation with sources for any spherically symmetric black hole.

scholarly journals Peculiar five-dimensional black holes

2019 ◽  
Vol 17 (1, spec.issue) ◽  
pp. 69-78
Author(s):  
Dejan Simic
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Semiclassical Approximation ◽  
Three Dimensions ◽  
Spherically Symmetric ◽  
Btz Black Hole ◽  
Lovelock Gravity ◽  
Zero Entropy ◽  
Symmetric Black Hole ◽  
Black Hole Solutions

In this article, we review two black hole solutions to the five-dimensional Lovelock gravity. These solutions are characterized by the non-vanishing torsion and the peculiar property that all their conserved charges vanish. The first solution is a spherically symmetric black hole with torsion, which also has zero entropy in the semiclassical approximation. The second solution is a black ring, which is the five-dimensional uplift of the BTZ black hole with torsion in three dimensions.

scholarly journals Thermodynamics of spherically symmetric black holes in scale-dependent gravity

2020 ◽  
Vol 80 (12) ◽  
Author(s):  
P. Bargueño ◽  
J. A. Miralles ◽  
J. A. Pons
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Spatial Variation ◽  
Gravitational Constant ◽  
Spherically Symmetric ◽  
Equilibrium Thermodynamics ◽  
First Law Of Thermodynamics ◽  
Symmetric Black Hole ◽  
Black Hole Solutions

AbstractIn this work we extend the first law of thermodynamics to spherically symmetric black hole solutions in the context of scale-dependent gravity. After deriving generalized expressions for both the entropy and energy due to the spatial variation of the gravitational constant we analize, by pointing out some relations between scale-dependent and f(R) theories, whether or not the former can be described using equilibrium thermodynamics.

scholarly journals Quasi-normal modes of near-extremal black holes in generalized spherically symmetric spacetime and strong cosmic censorship conjecture

2020 ◽  
Vol 80 (10) ◽  
Author(s):  
Piyabut Burikham ◽  
Supakchai Ponglertsakul ◽  
Taum Wuthicharn
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Normal Modes ◽  
Cosmic Censorship ◽  
Analytic Formula ◽  
Spherically Symmetric ◽  
Black Hole Background ◽  
Strong Cosmic Censorship ◽  
Black Hole Spacetime ◽  
Symmetric Black Hole

AbstractA number of near-extremal conditions are utilized to simplify the equation of motion of the neutral scalar perturbations in generalized spherically symmetric black hole background into a differential equation with the Pöschl–Teller potential. An analytic formula for quasinormal frequencies is obtained. The analytic formula is then used to investigate strong cosmic censorship conjectures (SCC) of the generalized black hole spacetime for the smooth initial data. The Christodoulou version of the SCC is found to be violated for certain regions of the black hole parameter space including the black holes in general relativity while the $$C^{1}$$ C 1 version of the SCC is always valid.

scholarly journals Black holes, moduli, and long-range forces

2020 ◽  
Vol 2020 (11) ◽  
Author(s):  
Ben Heidenreich
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Large Class ◽  
Large Distance ◽  
Arbitrary Number ◽  
Gauge Fields ◽  
Spherically Symmetric ◽  
Identical Pair ◽  
Symmetric Black Hole ◽  
Effective Theories

Abstract It is well known that an identical pair of extremal Reissner-Nordström black holes placed a large distance apart will exert no force on each other. In this paper, I establish that the same result holds in a very large class of two-derivative effective theories containing an arbitrary number of gauge fields and moduli, where the appropriate analog of an extremal Reissner-Nordström black hole is a charged, spherically symmetric black hole with vanishing surface gravity or vanishing horizon area. Analogous results hold for black branes.

scholarly journals Black Holes with Short Hair

1997 ◽  
Vol 06 (05) ◽  
pp. 563-573 ◽  
Author(s):  
J. David Brown ◽  
Viqar Husain
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Einstein Gravity ◽  
Spherically Symmetric ◽  
Short Hair ◽  
Anisotropic Matter ◽  
Symmetric Black Hole ◽  
Black Hole Solutions

We present spherically symmetric black hole solutions for Einstein gravity coupled to anisotropic matter. We show that these black holes have arbitrarily short hair, and argue for stability by showing that they can arise from dynamical collapse. We also show that a recent "no short hair" theorem does not apply to these solutions.

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