scholarly journals Physical Properties of Schwarzschild–deSitter Event Horizon Induced by Stochastic Quantum Gravity

Entropy ◽  
2021 ◽  
Vol 23 (5) ◽  
pp. 511
Author(s):  
Claudio Cremaschini ◽  
Massimo Tessarotto
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Quantum Gravity ◽  
Event Horizon ◽  
Field Equations ◽  
Central Mass ◽  
Event Horizons ◽  
Covariant Quantum ◽  
Gravitational Fields ◽  
New Type

A new type of quantum correction to the structure of classical black holes is investigated. This concerns the physics of event horizons induced by the occurrence of stochastic quantum gravitational fields. The theoretical framework is provided by the theory of manifestly covariant quantum gravity and the related prediction of an exclusively quantum-produced stochastic cosmological constant. The specific example case of the Schwarzschild–deSitter geometry is looked at, analyzing the consequent stochastic modifications of the Einstein field equations. It is proved that, in such a setting, the black hole event horizon no longer identifies a classical (i.e., deterministic) two-dimensional surface. On the contrary, it acquires a quantum stochastic character, giving rise to a frame-dependent transition region of radial width δr between internal and external subdomains. It is found that: (a) the radial size of the stochastic region depends parametrically on the central mass M of the black hole, scaling as δr∼M3; (b) for supermassive black holes δr is typically orders of magnitude larger than the Planck length lP. Instead, for typical stellar-mass black holes, δr may drop well below lP. The outcome provides new insight into the quantum properties of black holes, with implications for the physics of quantum tunneling phenomena expected to arise across stochastic event horizons.

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.

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.

Quantum probing of singularities at event horizons of black holes

2021 ◽  
pp. 2150147
Author(s):  
V. P. Neznamov
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Quantum Mechanics ◽  
Event Horizon ◽  
Stationary States ◽  
Coordinate Transformations ◽  
Event Horizons ◽  
Schwarzschild Metric

It is proved that coordinate transformations of the Schwarzschild metric to new static and stationary metrics do not eliminate the mode of a particle “fall” to the event horizon of a black hole. This mode is unacceptable for the quantum mechanics of stationary states.

scholarly journals PRECURSORS SEE INSIDE BLACK HOLES

2003 ◽  
Vol 12 (09) ◽  
pp. 1693-1698 ◽  
Author(s):  
VERONIKA E. HUBENY
Keyword(s):  
Field Theory ◽  
Black Holes ◽  
Black Hole ◽  
Quantum Gravity ◽  
Black Hole Horizon ◽  
Information Paradox ◽  
Event Horizons ◽  
Global Nature ◽  
Singularity Resolution ◽  
Nonlocal Nature

We consider, within a string theoretic context, the accessibility of events inside a black hole horizon. We present a gedankenexperiment which uses the nonlocal nature of precursors in the AdS/CFT correspondence, as well as the global nature of event horizons, to argue that the dual field theory does contain information about physics inside black holes. This alleviates the causal obstacles to accessing behind-the-horizon physics, thereby rendering more tractable certain long-standing questions of quantum gravity, such as the information paradox and possibly even singularity resolution.

scholarly journals BLACK HOLES WITHOUT BOUNDARIES

2008 ◽  
Vol 17 (13n14) ◽  
pp. 2359-2366 ◽  
Author(s):  
ALEX B. NIELSEN
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Quantum Gravity ◽  
Hawking Radiation ◽  
Information Loss ◽  
Black Hole Thermodynamics ◽  
Event Horizons ◽  
Central Singularity ◽  
Trapping Horizon ◽  
Trapping Horizons

We discuss some of the drawbacks of using event horizons to define black holes and suggest ways in which black holes can be described without event horizons, using trapping horizons. We show that these trapping horizons give rise to thermodynamic behavior and possibly Hawking radiation too. This raises the issue of whether the event horizon or the trapping horizon should be seen as the true boundary of a black hole. This difference is important if we believe that quantum gravity will resolve the central singularity of the black hole and clarifies several of the issues associated with black hole thermodynamics and information loss.

A SCHRÖDINGER BLACK HOLE AND ITS ENTROPY

2002 ◽  
Vol 17 (15n17) ◽  
pp. 1047-1057 ◽  
Author(s):  
DANIEL SUDARSKY
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Quantum Gravity ◽  
Event Horizon ◽  
Black Hole Entropy ◽  
A Value ◽  
The Future ◽  
Quantum Event ◽  
Quantum Variable ◽  
The Given

We discuss the conditions under which one can expect to have the usual identification of black hole entropy with the area of the horizon. We then construct an example in which the actual presence of the event horizon on a given hypersurface depends on a quantum event in which a certain quantum variable acquires a value and which occurs in the future of the given hypersurface. This situation indicates that there is something fundamental that is missing in the most popular of the current approaches towards the construction of a theory of quantum gravity, or, alternatively, that there is something fundamental that we do not understand about entropy in general, or at least in its association with black holes.

Supermassive Black Holes

2019 ◽  
pp. 151-158
Author(s):  
Nicholas Mee
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Event Horizon ◽  
Supermassive Black Holes ◽  
Radio Telescopes ◽  
Event Horizons ◽  
Supermassive Black Hole

The Event Horizon Telescope (EHT) is aiming to image the event horizon of the supermassive black hole at the centre of our galaxy. Andrea Ghez has mapped out the orbits of stars around this supermassive black hole and deduced it has a mass of four million Suns. An even bigger supermassive black hole of six billion solar masses lies at the centre of the M87 Galaxy. Shep Doeleman has marshalled several of the world’s radio telescopes to form the EHT with the aim of imaging the event horizons of these black holes.

scholarly journals Driven black holes: from Kolmogorov scaling to turbulent wakes

2021 ◽  
Vol 2021 (7) ◽  
Author(s):  
Tomas Andrade ◽  
Christiana Pantelidou ◽  
Julian Sonner ◽  
Benjamin Withers
Keyword(s):  
Nonlinear Dynamics ◽  
Black Holes ◽  
General Relativity ◽  
Black Hole ◽  
Strong Field ◽  
De Sitter ◽  
Event Horizons ◽  
Binary Mergers ◽  
Tidal Deformations ◽  
Proof Of Principle

Abstract General relativity governs the nonlinear dynamics of spacetime, including black holes and their event horizons. We demonstrate that forced black hole horizons exhibit statistically steady turbulent spacetime dynamics consistent with Kolmogorov’s theory of 1941. As a proof of principle we focus on black holes in asymptotically anti-de Sitter spacetimes in a large number of dimensions, where greater analytic control is gained. We focus on cases where the effective horizon dynamics is restricted to 2+1 dimensions. We also demonstrate that tidal deformations of the horizon induce turbulent dynamics. When set in motion relative to the horizon a deformation develops a turbulent spacetime wake, indicating that turbulent spacetime dynamics may play a role in binary mergers and other strong-field phenomena.

scholarly journals Gaseous Disks in the Nuclei of Elliptical Galaxies

1997 ◽  
Vol 163 ◽  
pp. 620-625 ◽  
Author(s):  
H. Ford ◽  
Z. Tsvetanov ◽  
L. Ferrarese ◽  
G. Kriss ◽  
W. Jaffe ◽  
...  
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Angular Momentum ◽  
Accretion Disks ◽  
Large Scale ◽  
Elliptical Galaxies ◽  
Central Mass ◽  
Massive Black Holes ◽  
Radio Jets

AbstractHST images have led to the discovery that small (r ~ 1″ r ~ 100 – 200 pc), well-defined, gaseous disks are common in the nuclei of elliptical galaxies. Measurements of rotational velocities in the disks provide a means to measure the central mass and search for massive black holes in the parent galaxies. The minor axes of these disks are closely aligned with the directions of the large–scale radio jets, suggesting that it is angular momentum of the disk rather than that of the black hole that determines the direction of the radio jets. Because the disks are directly observable, we can study the disks themselves, and investigate important questions which cannot be directly addressed with observations of the smaller and unresolved central accretion disks. In this paper we summarize what has been learned to date in this rapidly unfolding new field.

Sign in / Sign up

Export Citation Format

Share Document