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.

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 On the Identical Simulation of the Entire Universe

2016 ◽  
Author(s):  
Mesut Kavak
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Power Series ◽  
Event Horizon ◽  
Free Space ◽  
Irrational Number ◽  
Quadratic Equations ◽  
Entire Universe ◽  
The Universe ◽  
Irrational Values

A time ago, I published an article about deceleration of the universe. It was especially based on uncertainty, and it explains how does matter work. In this work, it was performed some analysis of the some specific subjects as an approach such as deceleration, uncertainty, possible particle formation, black hole, gravitation, energy, mass and light speed as the elements for identical simulation computations of the entire universe as the most sensitive as possible being related that article. There are some information about escaping from black holes, event horizon lengths, viscosity of free space, re-derivation of Planck constants and infrastructure of some basic laws of existence mathematically as matter is directly dependent of geometric rules. Also, some elements were given for the readers to solve some required constants as the most sensitive manner. As the constants are not enough in the name of engineering, also finally I found a working algorithm out which reduces process number of the power series to process number of the quadratic equations like calculating a root of an integer as an irrational number by solving equation; so also it can be used to calculate trigonometric values in the best manner for simulations of the entire universe besides physical constants as irrational values.

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.

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 Study of black hole as dissipative structure using negentropy

2016 ◽  
Vol 94 (10) ◽  
pp. 960-966
Author(s):  
Shripad P. Mahulikar ◽  
Pallavi Rastogi
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Event Horizon ◽  
Theoretical Investigation ◽  
Infinite Number ◽  
Dissipative Structure ◽  
Dissipative Structures ◽  
Area Theorem ◽  
Entropy Increase ◽  
The Universe

The area of the event horizon of a black hole (Aeh) is so far linked only with its entropy (SBH). In this theoretical investigation, it is shown that relating Aeh only to SBH is inadequate, because Aeh is linked to the black hole’s negentropy, which encompasses its entropy. Increasing Aeh of black holes that grow now follows from the negentropy theorem (NET) and also from the well-known area theorem. The decreasing Aeh of black holes that decay follows from the converse to NET and is not a violation of the area theorem. The corollary to NET is proved for the case when two dissipative structures merge, which is the basis for the coalescence of black holes. The converse of corollary to NET explains negentropy loss due to splitting of a dissipative structure. When applied to black hole explosion (i.e., splitting into an infinite number of parts), converse of corollary to NET reduces to converse of NET. The entropy/energy ratio of the exported Hawking radiance from black holes contributes to the entropy increase of the universe. These aspects justify the consideration of black holes as thermodynamic dissipative structures.

1. What is a black hole?

2015 ◽  
Author(s):  
Katherine Blundell
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Event Horizon ◽  
Albert Einstein ◽  
Escape Velocity ◽  
The Universe

A black hole is a region of space where the force of gravity is so strong that nothing, not even light, can travel fast enough to escape from its interior. ‘What is a black hole?’ outlines how they were first conceived by theoretical physicists such as John Michell, Henry Cavendish, Pierre-Simon Laplace, and Albert Einstein, and explains the concepts of singularity, escape velocity, the event horizon, and spacetime. Black holes have now been identified in the Universe in their hundreds and accounted for in their millions. Although invisible, these objects interact with and influence their surroundings in different ways depending on proximity relative to the black hole.

Black Hole Exotica

2014 ◽  
Author(s):  
Charles D. Bailyn
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Quantum Mechanics ◽  
Event Horizon ◽  
Hawking Radiation ◽  
The Universe

This chapter explores some of the predicted effects of black holes on people's lives and the possibility that they might someday be explored in fact as well as in fiction. These predicted effects include the Hawking radiation, wormholes, and multiverses. The Hawking radiation—in which the interaction between quantum mechanics and relativity has been explored with some success—is a process through which black holes are expected to emit energy and ultimately evaporate. Meanwhile, one of the most enticing possible effects associated with black holes is that they might form wormholes through which widely separated parts of the Universe can be closely connected. Lastly, one final suggestion that might be contemplated is that a separate universe might exist inside the event horizon of a black hole. This is one version of the multiverse concept, in which a variety of universes with a variety of characteristics exist.

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 DEVELOPMENT OF THE CONCEPT OF ENTROPY: FROM THERMODYNAMICS TO COSMOLOGY. PART 2. HYPOTHESIS OF ENTROPY IN COSMOLOGY AND ITS DEVELOPMENT

2021 ◽  
Vol 1 (54) ◽  
pp. 80-88
Author(s):  
Leonid A. SOSNOVSKIY ◽  
◽  
Sergei S. SHERBAKOV ◽  
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Energy Dissipation ◽  
Event Horizon ◽  
Fundamental Principle ◽  
Material World ◽  
Thermodynamic Entropy ◽  
Solid Bodies ◽  
The Universe ◽  
General Motion

In the work [7], the classical concepts of thermodynamic entropy are systematized and modern approaches to assessing the tribo-fatigue and mechanothermodynamic entropy of non-additive systems are outlined. In this article, the concept of the analogy of thermodynamics and mechanics of black holes is presented and analyzed, which made it possible to estimate their (thermodynamic) entropy. The insufficiency of this concept is that thermodynamic entropy is a characteristic of energy dissipation, whereas black holes are characterized by the absorption of energy and matter. In this regard, it is proposed to consider the event horizon as a hermodynamic medium, and a black hole as a tribo-fatigue object. And then the “black hole — event horizon” system is presented as a combined mechanothermodynamic non-additive multisystem. Methods for estimating the total (mechanothermodynamic) entropy and its components — tribo-fatigue and thermodynamic entropy in black hole mechanics are presented. With regard to individual (specific) zones and objects of the universe, the well-known theory of Zeldovich is accordingly modified: the universe is a thermodynamic medium with discretely distributed (scattered) dense and/or solid bodies (objects) — stars, galaxies, etc. Behavior of such a system (direct and back effects in the universe) are described. The peculiarity of the action of the medium on the stars and, conversely, the action of the cluster of stars on the interaction between them consists in the fact that it is non-Newtonian: action is not equal to reaction. It is the inequality of action against counteraction, which has radically different mechanisms and consequences (results), or, in other words, the imbalance of the universe that determine its general motion in space–time. The changing set of all states is the evolution of the universe. The analysis of possible strategies for the evolution of mechanothermodynamic systems is carried out on the basis of the fundamental principle: the damageability of everything that exists has no conceivable boundaries. This principle is formulated in mechanothermodynamics and used in philosophy to create a generalized theory of the evolution of the material world.

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.

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