scholarly journals SURFACE GRAVITY AND HAWKING TEMPERATURE FROM ENTROPIC FORCE VIEWPOINT

2010 ◽  
Vol 25 (33) ◽  
pp. 2825-2830 ◽  
Author(s):  
CHANG-YOUNG EE ◽  
MYUNGSEOK EUNE ◽  
KYOUNGTAE KIMM ◽  
DAEHO LEE
Keyword(s):  
Black Holes ◽  
Event Horizon ◽  
Hawking Temperature ◽  
Surface Gravity ◽  
Entropic Force ◽  
Holographic Screen

We consider a freely falling holographic screen for the Schwarzschild and Reissner–Nordström black holes and evaluate the entropic force à la Verlinde. When the screen crosses the event horizon, the temperature of the screen agrees to the Hawking temperature and the entropic force gives rise to the surface gravity for both of the black holes.

scholarly journals Effects of bosonic and fermionic q-deformation on the entropic gravity

2019 ◽  
Vol 34 (31) ◽  
pp. 1950249
Author(s):  
Salih Kibaroğlu ◽  
Mustafa Senay
Keyword(s):  
Black Holes ◽  
Poisson Equation ◽  
Entropic Force ◽  
Fundamental Interaction ◽  
Field Equations ◽  
The Poisson Equation ◽  
Entropic Gravity ◽  
Holographic Screen ◽  
Fermion Gas ◽  
Law Of Gravity

In this paper, we study thermodynamical contributions to the theory of gravity under the q-deformed boson and fermion gas models. According to Verlinde’s proposal, the law of gravity is not based on a fundamental interaction but it emerges as an entropic force from the changes of entropy associated with the information on the holographic screen. In addition, Strominger shows that the extremal quantum black holes obey neither boson nor fermion statistics, but they obey deformed statistic. Using these notions, we find q-deformed entropy and temperature functions. We also present the contributions that come from the q-deformed model to the Poisson equation, Newton’s law of gravity and Einstein’s field equations.

Thermodynamics of charged Newman–Unti–Tamburino accelerating rotating black holes

2013 ◽  
Vol 91 (3) ◽  
pp. 236-241 ◽  
Author(s):  
M. Sharif ◽  
Wajiha Javed
Keyword(s):  
Black Holes ◽  
Heat Capacity ◽  
Black Hole ◽  
Hawking Temperature ◽  
Surface Gravity ◽  
Thermodynamic Quantities ◽  
Field Equations ◽  
First Law Of Thermodynamics ◽  
Rotating Black Holes ◽  
Black Hole Solutions

This paper is devoted to studying the thermodynamics of charged Newman–Unti–Tamburino black hole solutions to the field equations, including rotation and acceleration. We evaluate some thermodynamic quantities like surface gravity, Hawking temperature, the entropy–area relationship, heat capacity, and the first law of thermodynamics. These quantities reduce to the results already available in the literature for some particular cases. We also explore their graphical behavior.

scholarly journals Event Horizon Telescope observations of the jet launching and collimation in Centaurus A

2021 ◽  
Author(s):  
Michael Janssen ◽  
Heino Falcke ◽  
Matthias Kadler ◽  
Eduardo Ros ◽  
Maciek Wielgus ◽  
...  
Keyword(s):  
Black Holes ◽  
Event Horizon ◽  
Galactic Nuclei ◽  
Galactic Centre ◽  
Radio Jets ◽  
Long Baseline ◽  
Wide Range ◽  
Terahertz Frequencies ◽  
Source Structure ◽  
Centaurus A

AbstractVery-long-baseline interferometry (VLBI) observations of active galactic nuclei at millimetre wavelengths have the power to reveal the launching and initial collimation region of extragalactic radio jets, down to 10–100 gravitational radii (rg ≡ GM/c2) scales in nearby sources1. Centaurus A is the closest radio-loud source to Earth2. It bridges the gap in mass and accretion rate between the supermassive black holes (SMBHs) in Messier 87 and our Galactic Centre. A large southern declination of −43° has, however, prevented VLBI imaging of Centaurus A below a wavelength of 1 cm thus far. Here we show the millimetre VLBI image of the source, which we obtained with the Event Horizon Telescope at 228 GHz. Compared with previous observations3, we image the jet of Centaurus A at a tenfold higher frequency and sixteen times sharper resolution and thereby probe sub-lightday structures. We reveal a highly collimated, asymmetrically edge-brightened jet as well as the fainter counterjet. We find that the source structure of Centaurus A resembles the jet in Messier 87 on ~500 rg scales remarkably well. Furthermore, we identify the location of Centaurus A’s SMBH with respect to its resolved jet core at a wavelength of 1.3 mm and conclude that the source’s event horizon shadow4 should be visible at terahertz frequencies. This location further supports the universal scale invariance of black holes over a wide range of masses5,6.

scholarly journals Black Holes or an Objects without Event Horizon?

2021 ◽  
Author(s):  
Leonid Verozub
Keyword(s):  
Black Holes ◽  
Event Horizon ◽  
Fermi Gas ◽  
Einstein’S Equations ◽  
Einstein's Equations ◽  
Degenerate Fermi Gas

The paper substantiates the possibility that objects that we usually identify with black holes are self-gravitating, fully or partially degenerate Fermi gas. This follows from the modification of Einstein's equations, which is based on a mathematical fact that the author of the GR could not have known in his time.

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.

scholarly journals On the speed of a test particle inside the Schwarzschild event horizon and other kinds of black holes

2018 ◽  
Vol 50 (10) ◽  
Author(s):  
Andy T. Augousti ◽  
Paweł Gusin ◽  
Bartosz Kuśmierz ◽  
Jan Masajada ◽  
Andrzej Radosz
Keyword(s):  
Black Holes ◽  
Event Horizon ◽  
Test Particle

Change in event horizon surface area as the source of nonmetricity field

2018 ◽  
Vol 15 (06) ◽  
pp. 1850104
Author(s):  
Yuriy A. Portnov
Keyword(s):  
Black Holes ◽  
Surface Area ◽  
Event Horizon ◽  
Test Body ◽  
Body Motion ◽  
Motion Equations ◽  
Gravitational Source ◽  
Theory Of Gravitation ◽  
The Relationship ◽  
Over Time

This paper concerns the relationship between the nonmetricity 1-form and the change in entropy. Motion equations have been obtained for test bodies in a gravitational field created by a massive body with entropy varying over time. It has been shown that increasing entropy of the gravitational source will bring about an increase in the acceleration of the test body. Applied to the theory of gravitation with nonmetricity, black hole dynamics equations based on foundations laid by S. Hawking and J. Beckenstein, enabled identification of changes in black holes event horizon surface area as a putative source of nonmetricity field. The implication is that changes in event horizon area will affect test body motion. The latter property makes it possible to contemplate a completely new method for discovering short-lived microscopic black holes.

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 Launching proton-dominated jets from accreting Kerr Black Holes: the case of M87

2011 ◽  
Vol 1 (1) ◽  
pp. 4 ◽  
Author(s):  
Felix F. Brezinski ◽  
Ahmad A. Hujeirat
Keyword(s):  
Magnetic Field ◽  
Boundary Layer ◽  
Black Holes ◽  
Angular Momentum ◽  
Event Horizon ◽  
Accretion Disk ◽  
Lorentz Factor ◽  
Spin Parameter ◽  
Low Mass ◽  
Kerr Black Holes

A general relativistic model for the formation and acceleration of low mass-loaded jets from systems containing accreting black holes is presented. The model is based on previous numerical results and theoretical studies in the Newtonian regime, but modified to include the effects of space-time curvature in the vicinity of the event horizon of a spinning black hole. It is argued that the boundary layer between the Keplerian accretion disk and the event horizon is best suited for the formation and acceleration of the accretion-powered jets in active galactic nuclei and micro-quasars. The model presented here is based on matching the solutions of three different regions: i- a weakly magnetized Keplerian accretion disk in the outer part, where the transport of angular momentum is mediated through the magentorotational instability, ii- a strongly magnetized, advection-dominated and turbulent-free boundary layer (BL) between the outer cold accretion disk and the event horizon and where the plasma rotates sub-Keplerian and iii- a transition zone (TZ) between the BL and the overlying corona, where the electrons and protons are thermally uncoupled, highly dissipative and rotate super-Keplerian. In the BL, the gravitation-driven dynamical collapse of the plasma increases the strength of the poloidal magnetic field (PMF) significantly, subsequently suppressing the generation and dissipation of turbulence and turning off the primary source of heating. In this case, the BL appears much fainter than standard disk models so as if the disk truncates at a certain radius. The action of the PMF in the BL is to initiate torsional Alf`ven waves that transport angular momentum from the embedded plasma vertically into the TZ, where a significant fraction of the shear-generated toroidal magnetic field reconnects, thereby heating the protons up to the virial-temperature. Also, the strong PMF forces the electrons to cool rapidly, giving rise therefore to the formation of a gravitationally unbound two-temperature proton-dominated outflow. Our model predicts the known correlation between the Lorentz-factor and the spin parameter of the BH. It also shows that the effective surface of the BL, through which the baryons flow into the TZ, shrinks with increasing the spin parameter, implying therefore that low mass-loaded jets most likely originate from around Kerr black holes. When applying our model to the jet in the elliptical galaxy M87, we find a spin parameter <em>a ∈</em> [0.99, 0.998], a transition radius rtr ≈ 30 gravitational radii and a fraction of 0.05 − 0.1 of the mass accretion rate goes into the TZ, where the plasma speeds up its outward-oriented motion to reach a Lorentz factor Γ <em>∈</em> [2.5, 5.0] at rtr.

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