scholarly journals On the Trapped Surface Characterization of Black Hole Region in Vaidya Spacetime

2018 ◽  
Vol 10 (1) ◽  
pp. 59
Author(s):  
Mohammed Kumah ◽  
Francis T. Oduro
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Event Horizon ◽  
Surface Characterization ◽  
Local Approach ◽  
Null Infinity ◽  
Trapped Surfaces ◽  
Marginally Trapped Surfaces ◽  
Trapped Surface

Characterizing black holes by means of classical event horizon is a global concept because it depends on future null infinity. This means, to find black hole region and event horizon requires the notion of the entire spacetime which is a teleological concept. With this as a motivation, we use local approach as a complementary means of characterizing black holes. In this paper we apply Gauss divergence and covariant divergence theorems to compute the fluxes and the divergences of the appropriate null vectors in Vaidya spacetime and thus explicitly determine the existence of trapped and marginally trapped surfaces in its black hole region.

scholarly journals On the Trapped Surface Characterization of the Black Hole Region in Kerr Spacetime

2018 ◽  
Vol 10 (4) ◽  
pp. 24
Author(s):  
Mohammed Kumah ◽  
Francis Oduro
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Event Horizon ◽  
Surface Characterization ◽  
Local Approach ◽  
Kerr Spacetime ◽  
Trapped Surfaces ◽  
Trapped Surface ◽  
Future Direction

Black holes are classically characterized by event horizon which is the boundary of the region from which particles or photons can escape to infinity in the future direction. Unfortunately this characterization is a global concept as the knowledge of the whole spacetime is needed in order to locate a black hole region and the event horizon. It is therefore important to recognize black holes locally; this has motivated the need to use local approach to characterize black holes. Specifically, we apply covariant divergence and Gauss’s divergence theorems to compute the divergences and the fluxes of appropriate null vectors in the Kerr spacetime to actually determine the existence of trapped and marginally trapped surfaces in its black hole region.

scholarly journals The fate of Schwarzschild–de Sitter black holes in f(R) gravity

2016 ◽  
Vol 31 (09) ◽  
pp. 1650054 ◽  
Author(s):  
Andrea Addazi ◽  
Salvatore Capozziello
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Thermal Radiation ◽  
Black Hole Physics ◽  
Black Hole Horizon ◽  
De Sitter ◽  
Trapped Surfaces ◽  
Emission Time ◽  
Marginally Trapped Surfaces

The semiclassical effects of anti-evaporating black holes can be discussed in the framework of f(R) gravity. In particular, the Bousso–Hawking–Nojiri–Odinstov anti-evaporation instability of degenerate Schwarzschild–de Sitter black holes (the so-called Nariai spacetime) leads to a dynamical increasing of black hole horizon in f(R) gravity. This phenomenon causes the following transition: emitting marginally trapped surfaces (TS) become space-like surfaces before the effective Bekenstein–Hawking emission time. As a consequence, Bousso–Hawking thermal radiation cannot be emitted in an anti-evaporating Nariai black hole. Possible implications in cosmology and black hole physics are also discussed.

STRINGS FROM BLACK HOLES

1992 ◽  
Vol 01 (02) ◽  
pp. 355-361 ◽  
Author(s):  
ICHIRO ODA
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Event Horizon ◽  
Zero Mode ◽  
Center Of Mass ◽  
Two Dimensional ◽  
Null Infinity ◽  
Four Dimensions ◽  
Surface Fluctuation ◽  
Future Null Infinity

It is shown that surface fluctuation of the event horizon of black holes in four dimensions which have been previously studied by ’t Hooft can be understood in terms of the topological two-dimensional string. This interpretation is valid at the lowest order, with respect to the magnitude of the radial momentum per magnitude of the transverse momentum, when particles near the event horizon fall into the black hole and from which particles then emit to future null infinity, owing to the Hawking radiation. This implies that in such a kinematical regime only the zero mode, that is, the center-of-mass momentum of the Euclidean string, propagates on the surface of the event horizon.

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.

3. Extrasolar tests of gravity

2017 ◽  
pp. 35-45
Author(s):  
Timothy Clifton
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Gravitational Field ◽  
Solar System ◽  
Neutron Stars ◽  
Event Horizon ◽  
Gravitational Fields ◽  
Binary Pulsars ◽  
Tests Of Gravity ◽  
Triple Star

By studying objects outside our Solar System, we can observe star systems with far greater gravitational fields. ‘Extrasolar tests of gravity’ considers stars of different sizes that have undergone gravitational collapse, including white dwarfs, neutron stars, and black holes. A black hole consists of a region of space-time enclosed by a surface called an event horizon. The gravitational field of a black hole is so strong that anything that finds its way inside the event horizon can never escape. Other star systems considered are binary pulsars and triple star systems. With the invention of even more powerful telescopes, there will be more tantalizing possibilities for testing gravity in the future.

Entropy bound of horizons of some regular black holes

2020 ◽  
Vol 35 (10) ◽  
pp. 2050070
Author(s):  
Ujjal Debnath
Keyword(s):  
Black Holes ◽  
Heat Capacity ◽  
Black Hole ◽  
Specific Heat ◽  
Surface Area ◽  
Event Horizon ◽  
Specific Heat Capacity ◽  
Thermodynamic Quantities ◽  
Event Horizons ◽  
Regular Black Hole

We study the four-dimensional (i) modified Bardeen black hole, (ii) modified Hayward black hole, (iii) charged regular black hole and (iv) magnetically charged regular black hole. For modified Bardeen black hole and modified Hayward black hole, we found only one horizon (event horizon) and then we found some thermodynamic quantities like the entropy, surface area, irreducible mass, temperature, Komar energy and specific heat capacity on the event horizon. We here study the bounds of the above thermodynamic quantities for these black holes on the event horizon. Then, we examine the thermodynamics stability of the black holes with some conditions. Next, we studied the charged regular black hole and magnetically charged regular black hole and found two horizons (Cauchy and event horizons) of these black holes. Then, we found the entropy, surface area, irreducible mass, temperature, Komar energy and specific heat capacity on the Cauchy and event horizons. Then, we get some conditions for thermodynamic stability/instability of the black holes. We found the radius of the extremal horizon and Christodoulou–Ruffiini mass and then analyze the above thermodynamic quantities on the extremal horizon. We calculate the sum/subtraction, product, division and sum/subtraction of inverse of surface areas, entropies, irreducible masses, temperatures, Komar energies and specific heat capacities on both the horizons. From these, we found the bounds of the above quantities on the horizons.

More on extracting information about the initial state from the black hole radiation

2018 ◽  
Vol 33 (19) ◽  
pp. 1850108
Author(s):  
Hossein Ghaforyan ◽  
Somayyeh Shoorvazi ◽  
Alireza Sepehri ◽  
Tooraj Ghaffary
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Density Matrix ◽  
Quantum Entanglement ◽  
Event Horizon ◽  
Initial State ◽  
Black Hole Radiation ◽  
Total Information ◽  
Quantum Treatment ◽  
Collapse Process

Recently, some authors showed that a classical collapse scenario ignores this richness of information in the resulting spectrum and a consistent quantum treatment of the entire collapse process might allow us to retrieve much more information from the spectrum of the final radiation. We confirm these results and show that by considering the quantum entanglement between metrics, we can uncover information of black holes. In our model, a density matrix is defined for the spaces, both inside and outside of the event horizon. These inside and outside spaces of black holes are obtained by tracing from a bigger space. An observer that lives in this big space can recover total information regarding the inside and outside of black hole.

2. Navigating through spacetime

2015 ◽  
Author(s):  
Katherine Blundell
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Event Horizon ◽  
Light Cone ◽  
Mathematical Language ◽  
Theory Of Relativity ◽  
Left Behind ◽  
Physical Universe

Mathematics is the perfect language needed for describing how the theory of relativity applies to the physical Universe and all of spacetime, and that description includes the strange behaviour that occurs near black holes. ‘Navigating through spacetime’ explains some of the complicated mathematical language using spacetime diagrams. It describes world-lines—the path left behind as an object journeys through spacetime—and light cones. Black holes profoundly affect the orientations of the light cones. As a particle approaches a black hole, its future light cone tilts more and more towards the black hole. When the particle crosses the event horizon, all of its possible future trajectories end inside the black hole.

scholarly journals A Note on the Observational Evidence for the Existence of Event Horizons in Astrophysical Black Hole Candidates

2013 ◽  
Vol 2013 ◽  
pp. 1-4 ◽  
Author(s):  
Cosimo Bambi
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Electromagnetic Radiation ◽  
Event Horizon ◽  
Observational Evidence ◽  
Short Paper ◽  
Event Horizons ◽  
Internal Region ◽  
The Universe ◽  
Black Hole Candidates

Black holes have the peculiar and intriguing property of having an event horizon, a one-way membrane causally separating their internal region from the rest of the Universe. Today, astrophysical observations provide some evidence for the existence of event horizons in astrophysical black hole candidates. In this short paper, I compare the constraint we can infer from the nonobservation of electromagnetic radiation from the putative surface of these objects with the bound coming from the ergoregion instability, pointing out the respective assumptions and limitations.

Black hole fusion made easy

2016 ◽  
Vol 25 (12) ◽  
pp. 1644015
Author(s):  
Roberto Emparan ◽  
Marina Martínez
Keyword(s):  
Black Holes ◽  
General Relativity ◽  
Black Hole ◽  
Event Horizon ◽  
Critical Behavior ◽  
Equivalence Principle ◽  
The Other ◽  
Schwarzschild Solution ◽  
Null Geodesics ◽  
Light Rays

The fusion of two black holes — a signature phenomenon of General Relativity — is usually regarded as a process so complex that nothing short of a supercomputer simulation can accurately capture it. In this essay, we explain how the event horizon of the merger can be found in an exact analytic way in the limit where one of the black holes is much smaller than the other. Remarkably, the ideas and techniques involved are elementary: the equivalence principle, null geodesics in the Schwarzschild solution, and the notion of event horizon itself. With these, one can identify features such as the line of caustics at which light rays enter the horizon, and find indications of universal critical behavior when the two black holes touch.

Sign in / Sign up

Export Citation Format

Share Document