scholarly journals Quantum optics approach to radiation from atoms falling into a black hole

2018 ◽  
Vol 115 (32) ◽  
pp. 8131-8136 ◽  
Author(s):  
Marlan O. Scully ◽  
Stephen Fulling ◽  
David M. Lee ◽  
Don N. Page ◽  
Wolfgang P. Schleich ◽  
...  
Keyword(s):  
Black Hole ◽  
Quantum Optics ◽  
Initial Conditions ◽  
Principle Of Equivalence ◽  
Distant Observer ◽  
Insight Into

We show that atoms falling into a black hole (BH) emit acceleration radiation which, under appropriate initial conditions, looks to a distant observer much like (but is different from) Hawking BH radiation. In particular, we find the entropy of the acceleration radiation via a simple laser-like analysis. We call this entropy horizon brightened acceleration radiation (HBAR) entropy to distinguish it from the BH entropy of Bekenstein and Hawking. This analysis also provides insight into the Einstein principle of equivalence between acceleration and gravity.

scholarly journals Unruh acceleration radiation revisited

2019 ◽  
Vol 34 (28) ◽  
pp. 1941005 ◽  
Author(s):  
J. S. Ben-Benjamin ◽  
M. O. Scully ◽  
S. A. Fulling ◽  
D. M. Lee ◽  
D. N. Page ◽  
...  
Keyword(s):  
Black Hole ◽  
Correlation Function ◽  
Energy Spectrum ◽  
Ground State ◽  
Hawking Radiation ◽  
Initial Conditions ◽  
Vacuum State ◽  
Principle Of Equivalence ◽  
Thermal Correlation ◽  
Insight Into

When ground-state atoms are accelerated and the field with which they interact is in its normal vacuum state, the atoms detect Unruh radiation. We show that atoms falling into a black hole emit acceleration radiation which, under appropriate initial conditions (Boulware vacuum), has an energy spectrum which looks much like Hawking radiation. This analysis also provides insight into the Einstein principle of equivalence between acceleration and gravity. The Unruh temperature can also be obtained by using the Kubo–Martin–Schwinger (KMS) periodicity of the two-point thermal correlation function, for a system undergoing uniform acceleration; as with much of the material in this paper, this known result is obtained with a twist.

Numerical simulation of the disk dynamics around the black hole: Bondi–Hoyle accretion

2014 ◽  
Vol 29 (21) ◽  
pp. 1450115
Author(s):  
Fahrettin Koyuncu ◽  
Orhan Dönmez
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Mach Number ◽  
Initial Conditions ◽  
Outer Boundary ◽  
Compact Objects ◽  
Adiabatic Index ◽  
Computational Domain ◽  
X Rays ◽  
Flip Flop

We have solved the General Relativistic Hydrodynamic (GRH) equations using the high resolution shock capturing scheme (HRSCS) to find out the dependency of the disk dynamics to the Mach number, adiabatic index, the black hole rotation parameter and the outer boundary of the computational domain around the non-rotating and rotating black holes. We inject the gas to computational domain at upstream and downstream regions at the same time with different initial conditions. It is found that variety of the mass accretion rates and shock cone structures strongly depend on Mach number and adiabatic index of the gas. The shock cones on the accretion disk are important physical mechanisms to trap existing oscillation modes, thereupon these trapped modes may generate strong X-rays observed by different X-ray satellites. Besides, our numerical approach also show that the shock cones produces the flip–flop oscillation around the black holes. The flip–flop instabilities which are monitored in our simulations may explain the erratic spin behavior of the compact objects (the black holes and neutron stars) seen from observed data.

scholarly journals To see the invisible: Image of the event horizon within the black hole shadow

2019 ◽  
Vol 28 (13) ◽  
pp. 1941005 ◽  
Author(s):  
Vyacheslav Dokuchaev
Keyword(s):  
Black Hole ◽  
Event Horizon ◽  
Cross Section ◽  
Milky Way ◽  
Distant Observer ◽  
Luminous Matter ◽  
Hot Matter ◽  
Per Se ◽  
Celestial Sphere ◽  
Shadow Projection

How the supermassive black hole SgrA* in the Milky Way Center looks like for a distant observer? It depends on the black hole highlighting by the surrounding hot matter. The black hole shadow (the photon capture cross-section) would be viewed if there is a stationary luminous background. The black hole event horizon is invisible directly (per se). Nevertheless, a more compact (with respect to black hole shadow) projection of the black hole event horizon on the celestial sphere may be reconstructed by detecting the highly redshifted photons emitted by the nonstationary luminous matter plunging into the black hole and approaching the event horizon. It is appropriate to call this reconstructed projection of the event horizon on the celestial sphere for a distant observer as the “lensed event horizon image”, or simply the “event horizon image”. This event horizon image is placed on the celestial sphere within the position of black hole shadow. Amazingly, the event horizon image is a gravitationally lensed projection on the celestial sphere of the whole surface of the event horizon globe. As a result, the black holes may be viewed at once from both the front and back sides. The lensed event horizon image may be considered as a genuine silhouette of the black hole. For example, a dark northern hemisphere of the event horizon image is the simplest model for a black hole silhouette in the presence of a thin accretion disk.

scholarly journals Population synthesis of black hole binary mergers from star clusters

2020 ◽  
Vol 492 (2) ◽  
pp. 2936-2954 ◽  
Author(s):  
Fabio Antonini ◽  
Mark Gieles
Keyword(s):  
Black Hole ◽  
Globular Clusters ◽  
Initial Conditions ◽  
Star Clusters ◽  
Population Synthesis ◽  
Wide Range ◽  
Binary Mergers ◽  
Cluster Properties ◽  
Black Hole Binary ◽  
Merger Rate

ABSTRACT Black hole (BH) binary mergers formed through dynamical interactions in dense star clusters are believed to be one of the main sources of gravitational waves (GWs) for Advanced LIGO and Virgo. Here, we present a fast numerical method for simulating the evolution of star clusters with BHs, including a model for the dynamical formation and merger of BH binaries. Our method is based on Hénon’s principle of balanced evolution, according to which the flow of energy within a cluster must be balanced by the energy production inside its core. Because the heat production in the core is powered by the BHs, one can then link the evolution of the cluster to the evolution of its BH population. This allows us to construct evolutionary tracks of the cluster properties including its BH population and its effect on the cluster and, at the same time, determine the merger rate of BH binaries as well as their eccentricity distributions. The model is publicly available and includes the effects of a BH mass spectrum, mass-loss due to stellar evolution, the ejection of BHs due to natal and dynamical kicks, and relativistic corrections during binary–single encounters. We validate our method using direct N-body simulations, and find it to be in excellent agreement with results from recent Monte Carlo models of globular clusters. This establishes our new method as a robust tool for the study of BH dynamics in star clusters and the modelling of GW sources produced in these systems. Finally, we compute the rate and eccentricity distributions of merging BH binaries for a wide range of cluster initial conditions, spanning more than two orders of magnitude in mass and radius.

scholarly journals Numerical relativity and high energy physics: Recent developments

2016 ◽  
Vol 25 (09) ◽  
pp. 1641022 ◽  
Author(s):  
Emanuele Berti ◽  
Vitor Cardoso ◽  
Luis C. B. Crispino ◽  
Leonardo Gualtieri ◽  
Carlos Herdeiro ◽  
...  
Keyword(s):  
Black Hole ◽  
High Energy Physics ◽  
Numerical Relativity ◽  
Compact Object ◽  
High Energy ◽  
Gravity Models ◽  
Black Hole Binaries ◽  
Recent Developments ◽  
Insight Into ◽  
Energy Physics

We review recent progress in the application of numerical relativity techniques to astrophysics and high-energy physics. We focus on recent developments regarding the spin evolution in black hole binaries, high-energy black hole collisions, compact object solutions in scalar–tensor gravity, superradiant instabilities, hairy black hole solutions in Einstein’s gravity coupled to fundamental fields, and the possibility to gain insight into these phenomena using analog gravity models.

scholarly journals New closed analytical solutions for geometrically thick fluid tori around black holes

2018 ◽  
Vol 614 ◽  
pp. A75 ◽  
Author(s):  
V. Witzany ◽  
P. Jefremov
Keyword(s):  
Black Hole ◽  
Initial Conditions ◽  
Rest Mass ◽  
Decisive Role ◽  
Rotational Instability ◽  
Asymptotic State ◽  
Rotation Curves ◽  
Perfect Fluids ◽  
Order Of Magnitude ◽  
Orbital Periods

Context. When a black hole is accreting well below the Eddington rate, a geometrically thick, radiatively inefficient state of the accretion disk is established. There is a limited number of closed-form physical solutions for geometrically thick (nonselfgravitating) toroidal equilibria of perfect fluids orbiting a spinning black hole, and these are predominantly used as initial conditions for simulations of accretion in the aforementioned mode. However, different initial configurations might lead to different results and thus observational predictions drawn from such simulations. Aims. We aim to expand the known equilibria by a number of closed multiparametric solutions with various possibilities of rotation curves and geometric shapes. Then, we ask whether choosing these as initial conditions influences the onset of accretion and the asymptotic state of the disk. Methods. We have investigated a set of examples from the derived solutions in detail; we analytically estimate the growth of the magneto-rotational instability (MRI) from their rotation curves and evolve the analytically obtained tori using the 2D magneto-hydrodynamical code HARM. Properties of the evolutions are then studied through the mass, energy, and angular-momentum accretion rates. Results. The rotation curve has a decisive role in the numerical onset of accretion in accordance with our analytical MRI estimates: in the first few orbital periods, the average accretion rate is linearly proportional to the initial MRI rate in the toroids. The final state obtained from any initial condition within the studied class after an evolution of ten or more orbital periods is mostly qualitatively identical and the quantitative properties vary within a single order of magnitude. The average values of the energy of the accreted fluid have an irregular dependency on initial data, and in some cases fluid with energies many times its rest mass is systematically accreted.

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