scholarly journals Energy of test objects on black hole spacetimes: A brief review

2015 ◽  
Vol 24 (14) ◽  
pp. 1550103 ◽  
Author(s):  
Alejandro Corichi
Keyword(s):  
Black Hole ◽  
Asymptotic Region ◽  
Gravitational Potential Energy ◽  
De Sitter ◽  
Conservation Of Energy ◽  
Asymptotically Flat ◽  
Black Hole Spacetimes ◽  
Test Particles ◽  
Exterior Regions ◽  
Test Objects

In this paper, we review the issue of defining energy for test particles on a background stationary spacetime. We revisit different notions of energy as defined by different observers. As is well-known, the existence of a timelike isometry allows for the notion of total conserved energy to be well defined. We use this well-known quantity to show that a gravitational potential energy can be consistently defined. As examples, we study the case of the exterior regions of an asymptotically flat black hole and of the [Formula: see text] Schwarzschild–de Sitter (SdS) case, where an asymptotic region is not available. We then consider the situation in which the test particle is absorbed by the black hole and analyze the energetics in detail. In particular, we show that the notion of horizon energy as defined by the isolated horizons formalism provides a satisfactory notion of energy compatible with the particle’s total conserved energy. With these choices, there is a global conservation of energy. Finally, we comment on a recent proposal to define energy of the black hole as seen by a nearby observer at rest, for which this feature is lost.

scholarly journals Supermassive black holes surrounded by dark matter modeled as anisotropic fluid: epicyclic oscillations and their fitting to observed QPOs

2021 ◽  
Vol 2021 (11) ◽  
pp. 059
Author(s):  
Z. Stuchlík ◽  
J. Vrba
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Dark Matter ◽  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Supermassive Black Holes ◽  
Anisotropic Fluid ◽  
Physical Parameters ◽  
Black Hole Spacetimes ◽  
Test Particles

Abstract Recently introduced exact solution of the Einstein gravity coupled minimally to an anisotropic fluid representing dark matter can well represent supermassive black holes in galactic nuclei with realistic distribution of dark matter around the black hole, given by the Hernquist-like density distribution. For these fluid-hairy black hole spacetimes, properties of the gravitational radiation, quasinormal ringing, and optical phenomena were studied, giving interesting results. Here, using the range of physical parameters of these spacetimes allowing for their relevance in astrophysics, we study the epicyclic oscillatory motion of test particles in these spacetimes. The frequencies of the orbital and epicyclic motion are applied in the epicyclic resonance variant of the geodesic model of quasiperiodic oscillations (QPOs) observed in active galactic nuclei to demonstrate the possibility to solve the cases where the standard vacuum black hole spacetimes are not allowing for explanation of the observed data. We demonstrate that the geodesic model can explain the QPOs observed in most of the active galactic nuclei for the fluid-hairy black holes with reasonable halo parameters.

scholarly journals SOME ASPECTS OF SPHERICAL SYMMETRIC EXTREMAL DYONIC BLACK HOLES IN 4D N = 1 SUPERGRAVITY

2013 ◽  
Vol 28 (18) ◽  
pp. 1350084 ◽  
Author(s):  
BOBBY E. GUNARA ◽  
FREDDY P. ZEN ◽  
FIKI T. AKBAR ◽  
AGUS SUROSO ◽  
ARIANTO
Keyword(s):  
Black Hole ◽  
Scalar Potential ◽  
Local Existence ◽  
Scalar Fields ◽  
Asymptotic Region ◽  
De Sitter ◽  
Complex Scalar ◽  
Symmetric Black Hole ◽  
Scalar Potentials ◽  
Nonzero Scalar

In this paper, we study several aspects of extremal spherical symmetric black hole solutions of four-dimensional N = 1 supergravity coupled to vector and chiral multiplets with the scalar potential turned on. In the asymptotic region, the complex scalars are fixed and regular which can be viewed as the critical points of the black hole and the scalar potentials with vanishing scalar charges. It follows that the asymptotic geometries are of a constant and nonzero scalar curvature which are generally not Einstein. These spaces could also correspond to the near horizon geometries which are the product spaces of a two anti-de Sitter surface and the two sphere if the value of the scalars in both regions coincide. In addition, we prove the local existence of nontrivial radius dependent complex scalar fields which interpolate between the horizon and the asymptotic region. We finally give some simple ℂn-models with both linear superpotential and gauge couplings.

EXACT SOLUTIONS OF DILATON GRAVITY WITH (ANTI)-DE SITTER ASYMPTOTICS

2014 ◽  
Vol 29 (02) ◽  
pp. 1450010 ◽  
Author(s):  
S. MIGNEMI
Keyword(s):  
Black Hole ◽  
Exact Solutions ◽  
Maxwell Field ◽  
Spherically Symmetric ◽  
Dilaton Gravity ◽  
De Sitter ◽  
Asymptotically Flat ◽  
Black Hole Solutions

We present a technique for obtaining exact spherically symmetric asymptotically de Sitter (dS) or anti-de Sitter (adS) black hole solutions of dilaton gravity with generic coupling to Maxwell field, starting from asymptotically flat solutions and adding a suitable dilaton potential to the action.

scholarly journals Extreme gravitational lensing in vicinity of Schwarzschild-de Sitter black holes

Open Physics ◽  
2007 ◽  
Vol 5 (4) ◽  
Author(s):  
Pavel Bakala ◽  
Petr Čermák ◽  
Stanislav Hledík ◽  
Zdeněk Stuchlík ◽  
Kamila Truparová
Keyword(s):  
Black Hole ◽  
Cosmological Constant ◽  
Gravitational Lensing ◽  
High Performance ◽  
Computer Code ◽  
De Sitter ◽  
Simulation Code ◽  
Black Hole Spacetimes ◽  
Optical Projection ◽  
Free Falling

AbstractWe have developed a realistic, fully general relativistic computer code to simulate optical projection in a strong, spherically symmetric gravitational field. The standard theoretical analysis of optical projection for an observer in the vicinity of a Schwarzschild black hole is extended to black hole spacetimes with a repulsive cosmological constant, i.e, Schwarzschild-de Sitterspacetimes. Influence of the cosmological constant is investigated for static observers and observers radially free-falling from the static radius. Simulations include effects of the gravitational lensing, multiple images, Doppler and gravitational frequency shift, as well as the intensity amplification. The code generates images of the sky for the static observer and a movie simulations of the changing sky for the radially free-falling observer. Techniques of parallel programming are applied to get a high performance and a fast run of the BHC simulation code.

scholarly journals Dynamics and epicyclic motions of particles around the Schwarzschild–de Sitter black hole in perfect fluid dark matter

2021 ◽  
Vol 81 (8) ◽  
Author(s):  
Javlon Rayimbaev ◽  
Sanjar Shaymatov ◽  
Mubasher Jamil
Keyword(s):  
Black Hole ◽  
Dark Matter ◽  
Perfect Fluid ◽  
Matter Field ◽  
De Sitter ◽  
Circular Orbits ◽  
Test Particles ◽  
Remarkable Result ◽  
The Impact ◽  
Twin Peak

AbstractIn this paper, we investigate circular orbits for test particles around the Schwarzschild–de Sitter (dS) black hole surrounded by perfect fluid dark matter. We determine the region of circular orbits bounded by innermost and outermost stable circular orbits. We show that the impact of the perfect fluid dark matter shrinks the region where circular orbits can exist as the values of both innermost and outermost stable circular orbits decrease. We find that for specific lower and upper values of the dark matter parameter there exist double matching values for inner and outermost stable circular orbits. It turns out that the gravitational attraction due to the dark matter contribution dominates over cosmological repulsion. This gives rise to a remarkable result in the Schwarzschild–de Sitter black hole surrounded by dark matter field in contrast to the Schwarzschild–de Sitter metric. Finally, we study epicyclic motion and its frequencies with their applications to twin peak quasi-periodic oscillations (QPOs) for various models. We find the corresponding values of the black hole parameters which could best fit and explain the observed twin peak QPO object GRS 1915+109 from microquasars.

Geometry of Black Holes

2020 ◽  
Author(s):  
Piotr T. Chruściel
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Einstein Equations ◽  
De Sitter ◽  
Black Hole Spacetimes ◽  
Local Coordinates ◽  
The Subject ◽  
Basic Facts ◽  
Kaluza Klein

There exists a large scientific literature on black holes, including many excellent textbooks of various levels of difficulty. However, most of these prefer physical intuition to mathematical rigour. The object of this book is to fill this gap and present a detailed, mathematically oriented, extended introduction to the subject. The first part of the book starts with a presentation, in Chapter 1, of some basic facts about Lorentzian manifolds. Chapter 2 develops those elements of Lorentzian causality theory which are key to the understanding of black-hole spacetimes. We present some applications of the causality theory in Chapter 3, as relevant for the study of black holes. Chapter 4, which opens the second part of the book, constitutes an introduction to the theory of black holes, including a review of experimental evidence, a presentation of the basic notions, and a study of the flagship black holes: the Schwarzschild, Reissner–Nordström, Kerr, and Majumdar–Papapetrou solutions of the Einstein, or Einstein–Maxwell, equations. Chapter 5 presents some further important solutions: the Kerr–Newman–(anti-)de Sitter black holes, the Emperan–Reall black rings, the Kaluza–Klein solutions of Rasheed, and the Birmingham family of metrics. Chapters 6 and 7 present the construction of conformal and projective diagrams, which play a key role in understanding the global structure of spacetimes obtained by piecing together metrics which, initially, are expressed in local coordinates. Chapter 8 presents an overview of known dynamical black-hole solutions of the vacuum Einstein equations.

Further selected solutions

2020 ◽  
pp. 200-258
Author(s):  
Piotr T. Chruściel
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
De Sitter ◽  
Stationary Black Hole ◽  
Static Vacuum ◽  
Black Hole Spacetimes ◽  
Wide Range ◽  
Dimensional Black Hole ◽  
Horizon Topology ◽  
Basic Features

In previous chapters we presented the key notions associated with stationary black-hole spacetimes, as well as the minimal set of metrics needed to illustrate the basic features of the world of black holes. In this chapter we present some further black holes, selected because of their physical and mathematical interest. We start, in Section 5.1, with the Kerr–de Sitter/anti-de Sitter metrics, the cosmological counterparts of the Kerr metrics. Section 5.2 contains a description of the Kerr–Newman–de Sitter/anti-de Sitter metrics, which are the charged relatives of the metrics presented in Section 5.1. In Section 5.3 we analyse in detail the global structure of the Emparan–Reall ‘black rings’: these are five-dimensional black-hole spacetimes with R × S 1 × S 2-horizon topology. The Rasheed metrics of Section 5.4 provide an example of black holes arising in Kaluza–Klein theories. The Birmingham family of metrics, presented in Section 5.5, forms the most general class known of explicit static vacuum metrics with cosmological constant in all dimensions, with a wide range of horizon topologies.

scholarly journals Regular Bardeen Black Holes in Anti-de Sitter Spacetime versus Kerr Black Holes through Particle Dynamics

Galaxies ◽  
2021 ◽  
Vol 9 (3) ◽  
pp. 63
Author(s):  
Bakhtiyor Narzilloev ◽  
Javlon Rayimbaev ◽  
Ahmadjon Abdujabbarov ◽  
Bobomurat Ahmedov
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Magnetic Charge ◽  
Particle Dynamics ◽  
Kerr Metric ◽  
De Sitter Spacetime ◽  
De Sitter ◽  
Sitter Spacetime ◽  
Test Particles ◽  
Charge Parameter

In this work, test particle dynamics around a static regular Bardeen black hole (BH) in Anti-de Sitter spacetime has been studied. It has been shown for neutral test particles that parameters of a regular Bardeen black hole in Anti-de Sitter spacetime can mimic the rotation parameter of the Kerr metric up to the value a≈0.9 providing the same innermost stable circular orbit (ISCO) radius. We have also explored the dynamics of magnetized particles with a magnetic dipole moment around a magnetically charged regular Bardeen black hole in Anti-de Sitter spacetime. As a realistic astrophysical scenario of the study, we have treated neutron stars orbiting a supermassive black hole (SMBH), in particular, the magnetar PSR J1745-2900 orbiting Sgr A* with the parameter β=10.2, as magnetized test particles. The magnetized particles dynamics shows that the parameter β, negative values of cosmological constant and magnetic charge parameter of the central BH cause a decrease in the ISCO radius. We have compared the effects of the magnetic charge of the Bardeen BH with the spin of rotating Kerr BH and shown that magnetic charge parameter can mimic the spin in the range a/M≃(0,0.7896) when Λ=0 at the range of its values g/M≃(0,0.648).

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