scholarly journals Remark on near-horizon geometry of extreme regular black holes

2018 ◽  
Vol 33 (34) ◽  
pp. 1850197
Author(s):  
Sergei Filyukov
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Black Hole Solution ◽  
Einstein Gravity ◽  
Nonlinear Electrodynamics ◽  
Regular Black Hole ◽  
Regular Black Holes ◽  
Horizon Geometry

It is shown that the near-horizon geometry of a generic extreme regular black hole solution of Einstein gravity coupled to nonlinear electrodynamics is described by the AdS2 × S2 spacetime.

scholarly journals Mimicking Black Holes in General Relativity

2021 ◽  
Author(s):  
Thomas Berry
Keyword(s):  
Black Holes ◽  
General Relativity ◽  
Black Hole ◽  
Thin Shell ◽  
Classical General Relativity ◽  
Regular Black Hole ◽  
Regular Black Holes ◽  
Traversable Wormholes ◽  
Hole Model ◽  
Linearised Stability

<p><b>The central theme of this thesis is the study and analysis of black hole mimickers. The concept of a black hole mimicker is introduced, and various mimicker spacetime models are examined within the framework of classical general relativity. The mimickers examined fall into the classes of regular black holes and traversable wormholes under spherical symmetry. The regular black holes examined can be further categorised as static spacetimes, however the traversable wormhole is allowed to have a dynamic (non-static) throat. Astrophysical observables are calculated for a recently proposed regular black hole model containing an exponential suppression of the Misner-Sharp quasi-local mass. This same regular black hole model is then used to construct a wormhole via the "cut-and-paste" technique. The resulting wormhole is then analysed within the Darmois-Israel thin-shell formalism, and a linearised stability analysis of the (dynamic) wormhole throat is undertaken. Yet another regular black hole model spacetime is proposed, extending a previous work which attempted to construct a regular black hole through a quantum "deformation" of the Schwarzschild spacetime. The resulting spacetime is again analysed within the framework of classical general relativity. </b></p><p>In addition to the study of black hole mimickers, I start with a brief overview of the theory of special relativity where a new and novel result is presented for the combination of relativistic velocities in general directions using quaternions. This is succeed by an introduction to concepts in differential geometry needed for the successive introduction to the theory of general relativity. A thorough discussion of the concept of spacetime singularities is then provided, before analysing the specific black hole mimickers discussed above.</p>

scholarly journals REGULAR BLACK HOLES IN AN ASYMPTOTICALLY DE SITTER UNIVERSE

2008 ◽  
Vol 23 (40) ◽  
pp. 3377-3392 ◽  
Author(s):  
JERZY MATYJASEK ◽  
DARIUSZ TRYNIECKI ◽  
MARIUSZ KLIMEK
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Nonlinear Electrodynamics ◽  
Spherically Symmetric ◽  
De Sitter ◽  
Coupled Equations ◽  
Sitter Universe ◽  
De Sitter Universe ◽  
Horizon Geometry ◽  
Interesting Solution

A regular solution of the system of coupled equations of the nonlinear electrodynamics and gravity describing static and spherically-symmetric black holes in an asymptotically de Sitter universe is constructed and analyzed. Special emphasis is put on the degenerate configurations (when at least two horizons coincide) and their near horizon geometry. It is explicitly demonstrated that approximating the metric potentials in the region between the horizons by simple functions and making use of a limiting procedure one obtains the solutions constructed from maximally symmetric subspaces with different absolute values of radii. Topologically they are AdS2×S2 for the cold black hole, dS2×S2 when the event and cosmological horizon coincide, and the Plebański–Hacyan solution for the ultraextremal black hole. A physically interesting solution describing the lukewarm black holes is briefly analyzed.

scholarly journals Remarks on regular black holes

2018 ◽  
Vol 15 (02) ◽  
pp. 1850018 ◽  
Author(s):  
Piero Nicolini ◽  
Anais Smailagic ◽  
Euro Spallucci
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Einstein Equations ◽  
Curvature Singularity ◽  
Physical Content ◽  
Regular Black Hole ◽  
Regular Black Holes ◽  
Black Hole Solutions

Recently, it has been claimed by Chinaglia and Zerbini that the curvature singularity is present even in the so-called regular black hole solutions of the Einstein equations. In this brief note, we show that this criticism is devoid of any physical content.

scholarly journals Energy Distribution of a Regular Black Hole Solution in Einstein-Nonlinear Electrodynamics

2015 ◽  
Vol 2015 ◽  
pp. 1-12 ◽  
Author(s):  
I. Radinschi ◽  
F. Rahaman ◽  
Th. Grammenos ◽  
A. Spanou ◽  
Sayeedul Islam
Keyword(s):  
Black Hole ◽  
Positive Integer ◽  
Energy Distribution ◽  
Black Hole Solution ◽  
Mass Function ◽  
Nonlinear Electrodynamics ◽  
Radial Coordinate ◽  
Regular Black Hole ◽  
Limiting Behavior ◽  
Special Case

A study about the energy momentum of a new four-dimensional spherically symmetric, static and charged, regular black hole solution developed in the context of general relativity coupled to nonlinear electrodynamics is presented. Asymptotically, this new black hole solution behaves as the Reissner-Nordström solution only for the particular valueμ=4, whereμis a positive integer parameter appearing in the mass function of the solution. The calculations are performed by use of the Einstein, Landau-Lifshitz, Weinberg, and Møller energy momentum complexes. In all the aforementioned prescriptions, the expressions for the energy of the gravitating system considered depend on the massMof the black hole, its chargeq, a positive integerα, and the radial coordinater. In all these pseudotensorial prescriptions, the momenta are found to vanish, while the Landau-Lifshitz and Weinberg prescriptions give the same result for the energy distribution. In addition, the limiting behavior of the energy for the casesr→∞,r→0, andq=0is studied. The special caseμ=4andα=3is also examined. We conclude that the Einstein and Møller energy momentum complexes can be considered as the most reliable tools for the study of the energy momentum localization of a gravitating system.

scholarly journals 4D Einstein-Gauss-Bonnet Gravity Coupled with Nonlinear Electrodynamics

2020 ◽  
Author(s):  
Sergey Kruglov
Keyword(s):  
Black Holes ◽  
Heat Capacity ◽  
Black Hole ◽  
Phase Transitions ◽  
Black Hole Solution ◽  
Hawking Temperature ◽  
Nonlinear Electrodynamics ◽  
Nonlinearity Parameter ◽  
Spherically Symmetric ◽  
Bonnet Gravity

An exact spherically symmetric and magnetically charged black hole solution in 4D Einstein-Gauss-Bonnet gravity coupled to nonlinear electrodynamics (NED) is obtained. The NED Lagrangian is given by ${\cal L}_{NED} = -{\cal F}/(1+\sqrt[4]{2\beta{\cal F}})$, where ${\cal F}$ is the field invariant. We study the thermodynamics calculating the Hawking temperature and the heat capacity of the black hole. The phase transitions take place when the Hawking temperature has an extremum and the heat capacity is singular. We demonstrate that black holes are thermodynamically stable in some range of event horizon radii where the heat capacity is positive. The BH shadow radii are calculated. It is shown that when increasing the nonlinearity parameter $\beta$ the BH shadow radius is decreased.

scholarly journals A note on Reissner–Nordström black holes in the inverse electrodynamics model

2021 ◽  
pp. 2150155
Author(s):  
S. Habib Mazharimousavi
Keyword(s):  
Black Holes ◽  
General Relativity ◽  
Black Hole ◽  
General Class ◽  
Black Hole Solution ◽  
Energy Momentum Tensor ◽  
Momentum Tensor ◽  
Nonlinear Electrodynamics ◽  
Nonlinear Electrodynamic ◽  
Electric And Magnetic Fields

Recently, the inverse electrodynamics model (IEM) was introduced and applied to find Reissner–Nordström black holes in the context of the general relativity coupled minimally with the nonlinear electrodynamics. The solution consists of both electric and magnetic fields as of the dyonic solutions. Here, in this note, we show that the IEM model belongs to a more general class of the nonlinear electrodynamics with [Formula: see text]. Here, [Formula: see text] is the energy momentum tensor of the nonlinear electrodynamic Lagrangian. Naturally, such a dyonic RN black hole solution is the solution for this general class.

scholarly journals Traversable Wormholes, Regular Black Holes, and Black-Bounces

2021 ◽  
Author(s):  
◽  
Alexander Simpson
Keyword(s):  
Black Holes ◽  
General Relativity ◽  
Black Hole ◽  
Einstein Equations ◽  
Time Dependent ◽  
Alternative Theories Of Gravity ◽  
Regular Black Hole ◽  
Traversable Wormhole ◽  
Regular Black Holes ◽  
Traversable Wormholes

<p>Various spacetime candidates for traversable wormholes, regular black holes, and ‘black-bounces’ are presented and thoroughly explored in the context of the gravitational theory of general relativity. All candidate spacetimes belong to the mathematically simple class of spherically symmetric geometries; the majority are static (time-independent as well as nonrotational), with a single dynamical (time-dependent) geometry explored. To the extent possible, the candidates are presented through the use of a global coordinate patch – some of the prior literature (especially concerning traversable wormholes) has often proposed coordinate systems for desirable solutions to the Einstein equations requiring a multi-patch atlas. The most interesting cases include the so-called ‘exponential metric’ – well-favoured by proponents of alternative theories of gravity but which actually has a standard classical interpretation, and the ‘black-bounce’ to traversable wormhole case – where a metric is explored which represents either a traversable wormhole or a regular black hole, depending on the value of the newly introduced scalar parameter a. This notion of ‘blackbounce’ is defined as the case where the spherical boundary of a regular black hole forces one to travel towards a one-way traversable ‘bounce’ into a future reincarnation of our own universe. The metric of interest is then explored further in the context of a time-dependent spacetime, where the line element is rephrased with a Vaidya-like time-dependence imposed on the mass of the object, and in terms of outgoing/ingoing EddingtonFinkelstein coordinates. Analysing these candidate spacetimes extends the pre-existing discussion concerning the viability of non-singular black hole solutions in the context of general relativity, as well as contributing to the dialogue on whether an arbitrarily advanced civilization would be able to construct a traversable wormhole.</p>

scholarly journals Exact charged black hole solutions in D-dimensions in f(R) gravity

2021 ◽  
Vol 81 (4) ◽  
Author(s):  
Zi-Yu Tang ◽  
Bin Wang ◽  
Eleftherios Papantonopoulos
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
General Solution ◽  
Constant Curvature ◽  
Black Hole Solution ◽  
Einstein Gravity ◽  
Charged Black Hole ◽  
Spherically Symmetric ◽  
Spherically Symmetric Metric ◽  
Black Hole Solutions

AbstractWe consider Maxwell-f(R) gravity and obtain an exact charged black hole solution with dynamic curvature in D-dimensions. Considering a spherically symmetric metric ansatz and without specifying the form of f(R) we find a general black hole solution in D-dimensions. This general black hole solution can reduce to the Reissner–Nordström (RN) black hole in D-dimensions in Einstein gravity and to the known charged black hole solutions with constant curvature in f(R) gravity. Restricting the parameters of the general solution we get polynomial solutions which reveal novel properties when compared to RN black holes. Specifically we study the solution in $$(3+1)$$ ( 3 + 1 ) -dimensions in which the form of f(R) can be solved explicitly giving a dynamic curvature and compare it with the RN black hole. We also carry out a detailed study of its thermodynamics.

scholarly journals Photon Spheres, ISCOs, and OSCOs: Astrophysical Observables for Regular Black Holes with Asymptotically Minkowski Cores

Universe ◽  
2020 ◽  
Vol 7 (1) ◽  
pp. 2
Author(s):  
Thomas Berry ◽  
Alex Simpson ◽  
Matt Visser
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Circular Orbit ◽  
Schwarzschild Black Hole ◽  
Circular Orbits ◽  
Regular Black Hole ◽  
Astrophysical Interest ◽  
Regular Black Holes ◽  
Recent Advances ◽  
Classical Black Holes

Classical black holes contain a singularity at their core. This has prompted various researchers to propose a multitude of modified spacetimes that mimic the physically observable characteristics of classical black holes as best as possible, but that crucially do not contain singularities at their cores. Due to recent advances in near-horizon astronomy, the ability to observationally distinguish between a classical black hole and a potential black hole mimicker is becoming increasingly feasible. Herein, we calculate some physically observable quantities for a recently proposed regular black hole with an asymptotically Minkowski core—the radius of the photon sphere and the extremal stable timelike circular orbit (ESCO). The manner in which the photon sphere and ESCO relate to the presence (or absence) of horizons is much more complex than for the Schwarzschild black hole. We find situations in which photon spheres can approach arbitrarily close to (near extremal) horizons, situations in which some photon spheres become stable, and situations in which the locations of both photon spheres and ESCOs become multi-valued, with both ISCOs (innermost stable circular orbits) and OSCOs (outermost stable circular orbits). This provides an extremely rich phenomenology of potential astrophysical interest.

Slowly rotating black holes with nonlinear electrodynamics in five dimensions

2014 ◽  
Vol 23 (11) ◽  
pp. 1450095 ◽  
Author(s):  
S. H. Hendi ◽  
M. Sepehri Rad
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Einstein Gravity ◽  
Rotation Parameter ◽  
Nonlinear Electrodynamics ◽  
Five Dimensions ◽  
Angular Momenta ◽  
Static Black Hole ◽  
Rotating Black Holes ◽  
Black Hole Solutions

Employing linear order perturbation theory with the rotation parameter as the perturbative parameter, we obtain asymptotically AdS slowly rotating black hole solutions in the Einstein gravity with Born–Infeld (BI) type nonlinear electrodynamics (NED). We start from asymptotically AdS static black hole solutions coupled to BI type NED in five dimensions. Then, we consider the effect of adding a small amount of angular momenta to the seed solutions. Finally, we investigate the geometry and thermodynamic properties of the solutions.

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