scholarly journals Extreme black hole anabasis

2021 ◽  
Vol 2021 (3) ◽  
Author(s):  
Shahar Hadar ◽  
Alexandru Lupsasca ◽  
Achilleas P. Porfyriadis
Keyword(s):  
Boundary Condition ◽  
Black Hole ◽  
Spherically Symmetric ◽  
Asymptotically Flat ◽  
Flat Region ◽  
Extreme Black Hole ◽  
Condition Change ◽  
Birkhoff's Theorem ◽  
Birkhoff’S Theorem

Abstract We study the SL(2) transformation properties of spherically symmetric perturbations of the Bertotti-Robinson universe and identify an invariant μ that characterizes the backreaction of these linear solutions. The only backreaction allowed by Birkhoff’s theorem is one that destroys the AdS2× S2 boundary and builds the exterior of an asymptotically flat Reissner-Nordström black hole with $$ Q=M\sqrt{1-\mu /4} $$ Q = M 1 − μ / 4 . We call such backreaction with boundary condition change an anabasis. We show that the addition of linear anabasis perturbations to Bertotti-Robinson may be thought of as a boundary condition that defines a connected AdS2×S2. The connected AdS2 is a nearly-AdS2 with its SL(2) broken appropriately for it to maintain connection to the asymptotically flat region of Reissner-Nordström. We perform a backreaction calculation with matter in the connected AdS2× S2 and show that it correctly captures the dynamics of the asymptotically flat black hole.

scholarly journals HOW TO BYPASS BIRKHOFF THROUGH EXTRA DIMENSIONS: A SIMPLE FRAMEWORK FOR INVESTIGATING THE GRAVITATIONAL COLLAPSE IN VACUUM

2006 ◽  
Vol 15 (12) ◽  
pp. 2217-2222 ◽  
Author(s):  
PIOTR BIZOŃ ◽  
BERND G. SCHMIDT
Keyword(s):  
Gravitational Collapse ◽  
Einstein Equations ◽  
Dimensional System ◽  
Spherically Symmetric ◽  
Asymptotically Flat ◽  
Spherical Collapse ◽  
Geometric Setting ◽  
Birkhoff's Theorem ◽  
Birkhoff’S Theorem ◽  
Odd Dimensions

It is fair to say that our current mathematical understanding of the dynamics of gravitational collapse to a black hole is limited to the spherically symmetric situation and, in fact, even in this case much remains to be learned. The reason is that Einstein's equations become tractable only if they are reduced to a (1 + 1)-dimensional system of partial differential equations. Owing to this technical obstacle, very little is known about the collapse of pure gravitational waves because by Birkhoff's theorem there is no spherical collapse in vacuum. In this essay, we describe a new cohomogeneity-two symmetry reduction of the vacuum Einstein equations in five and higher odd dimensions which evades Birkhoff's theorem and admits time-dependent asymptotically flat solutions. We argue that this model provides an attractive (1 + 1)-dimensional geometric setting for investigating the dynamics of gravitational collapse in vacuum.

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 Testing Generalized Einstein-Cartan-Kibble-Sciama Gravity Using Weak Deflection Angle and Shadow Cast

2020 ◽  
Author(s):  
Ali Övgün ◽  
İzzet Sakallı
Keyword(s):  
Black Hole ◽  
Gravitational Lensing ◽  
Symmetric Solution ◽  
Deflection Angle ◽  
Spherically Symmetric ◽  
Plasma Medium ◽  
Asymptotically Flat ◽  
Spherically Symmetric Solution ◽  
Shadow Cast ◽  
Bonnet Theorem

In this paper, we use a new asymptotically flat and spherically symmetric solution in the generalized Einstein-Cartan-Kibble-Sciama (ECKS) theory of gravity to study the weak gravitational lensing and its shadow cast. To this end, we first compute the weak deflection angle of generalized ECKS black hole using the Gauss–Bonnet theorem in plasma medium and in vacuum. Next by using the Newman-Janis algorithm without complexification, we derive the rotating generalized ECKS black hole and in the sequel study its shadow. Then, we discuss the effect of the ECKS parameter on the shadow of the black hole and weak deflection angle. In short, the goal of this paper is to give contribution to the ECKS theory and look for evidences to understand how the ECKS parameter effects the gravitational lensing.

Super-Penrose process for extremal charged white holes

2020 ◽  
pp. 2150020
Author(s):  
O. B. Zaslavskii
Keyword(s):  
Black Hole ◽  
Turning Points ◽  
The Other ◽  
White Hole ◽  
Asymptotically Flat ◽  
Flat Region ◽  
Angular Momenta ◽  
Penrose Process ◽  
New Particles

We consider collision of two particles 1 and 2 near the horizon of the extremal Reissner–Nordström (RN) black hole that produces two other particles 3 and 4. There exists such a scenario that both new particles fall into a black hole. One of them emerges from the white hole horizon in the asymptotically flat region, and the other one oscillates between turning points. However, the unbounded energies [Formula: see text] at infinity (super-Penrose process (SPP)) turn out to be impossible for any finite angular momenta [Formula: see text]. In this sense, the situation for such a white hole scenarios is opposite to the black hole ones, where the SPP is found earlier to be possible for the RN metric even for all [Formula: see text]. However, if [Formula: see text] themselves are unbounded, the SPP does exist for white holes.

scholarly journals TOPOLOGICAL BLACK HOLES OF EINSTEIN–YANG–MILLS DILATON GRAVITY

2010 ◽  
Vol 19 (03) ◽  
pp. 293-303 ◽  
Author(s):  
M. H. DEHGHANI ◽  
A. BAZRAFSHAN
Keyword(s):  
Black Hole ◽  
Naked Singularity ◽  
Dilaton Gravity ◽  
De Sitter ◽  
Asymptotically Flat ◽  
Four Dimensions ◽  
Yang Mills ◽  
First Law Of Thermodynamics ◽  
Extreme Black Hole ◽  
Mills Field

We present the topological solutions of Einstein dilaton gravity in the presence of a non-Abelian Yang–Mills field. In four dimensions, we consider the So(3) and So(2, 1) semisimple group as the Yang–Mills gauge group, and introduce the black hole solutions with spherical and hyperbolic horizons, respectively. The solution in the absence of dilaton potential is asymptotically flat and exists only with a spherical horizon. Contrary to the nonextreme Reissner–Nordstrom black hole, which has two horizons with a timelike and avoidable singularity, here the solution may present a black hole with a null and unavoidable singularity with only one horizon. In the presence of dilaton potential, the asymptotic behavior of the solutions is neither flat nor anti–de Sitter. These solutions contain a null and avoidable singularity, and may present a black hole with two horizons, an extreme black hole or a naked singularity. We also calculate the mass of the solutions through the use of a modified version of the Brown–York formalism, and consider the first law of thermodynamics.

scholarly journals Near-$$AdS_2$$ perturbations and the connection with near-extreme Reissner–Nordstrom

2019 ◽  
Vol 79 (10) ◽  
Author(s):  
Achilleas P. Porfyriadis
Keyword(s):  
Black Hole ◽  
Direct Product ◽  
Electromagnetic Waves ◽  
Scattering Matrix ◽  
Spherically Symmetric ◽  
Asymptotically Flat ◽  
Flat Part ◽  
Connection Problem ◽  
Symmetric Black Hole ◽  
Electromagnetic Perturbation

Abstract The geometry very near the horizon of a near-extreme Reissner–Nordstrom black hole is described by the direct product of a near-$$AdS_2$$AdS2 spacetime with a two-sphere. While near-$$AdS_2$$AdS2 is locally diffeomorphic to $$AdS_2$$AdS2 the two connect differently with the asymptotically flat part of the geometry of (near-)extreme Reissner–Nordstrom. In previous work, we solved analytically the coupled gravitational and electromagnetic perturbation equations of $$AdS_2\times S^2$$AdS2×S2 and the associated connection problem with extreme Reissner–Nordstrom. In this paper, we give the solution for perturbations of near-$$AdS_2\times S^2$$AdS2×S2 and make the connection with near-extreme Reissner–Nordstrom. Our results here may also be thought of as computing the classical scattering matrix for gravitational and electromagnetic waves which probe the region very near the horizon of a highly charged spherically symmetric black hole.

scholarly journals New spherically symmetric solutions in the Einstein–Yang–Mills–Higgs model

2010 ◽  
Vol 88 (3) ◽  
pp. 189-200 ◽  
Author(s):  
Junji Jia
Keyword(s):  
Black Hole ◽  
Boundary Conditions ◽  
Parameter Space ◽  
Numerical Solutions ◽  
Classical Solutions ◽  
Spherically Symmetric ◽  
Regular Solutions ◽  
Asymptotically Flat ◽  
Yang Mills ◽  
Black Hole Solutions

We study classical solutions in the SU(2) Einstein–Yang–Mills–Higgs theory. The spherically symmetric ansatz for all fields are given, and the equations of motion are derived as a system of ordinary differential equations. The asymptotics and the boundary conditions at the space origin for regular solutions and at the event horizon for black hole solutions are studied. Using the shooting method, we found numerical solutions to the theory. For regular solutions, we find two new sets of asymptotically flat solutions. Each of these sets contains continua of solutions in the parameter space spanned by the shooting parameters. The solutions bifurcate along these parameter curves, and the bifurcations are argued to be due to the internal structure of the model. Both sets of the solutions are asymptotically flat, but one is exponentially so and the other is so with oscillations. For black holes, a new set of boundary conditions is studied, and it is found that there also exists a continuum of black hole solutions in parameter space and similar bifurcation behavior is also present to these solutions. The SU(2) charges of these solutions are found to be zero, and these solutions are proven to be unstable.

scholarly journals Thermodynamics of graviton condensate

2021 ◽  
Vol 81 (10) ◽  
Author(s):  
Jorge Alfaro ◽  
Robinson Mancilla
Keyword(s):  
Black Hole ◽  
Line Element ◽  
Topological Defect ◽  
Einstein Condensate ◽  
Thermodynamic Quantities ◽  
Spherically Symmetric ◽  
Asymptotically Flat ◽  
Formal Equivalence ◽  
Bose Einstein Condensate ◽  
Bose Einstein

AbstractIn this work, we present the thermodynamic study of a model that considers the black hole as a condensate of gravitons. In this model, the spacetime is not asymptotically flat because of a topological defect that introduces an angle deficit in the spacetime like in Global Monopole solutions. We have obtained a correction to the Hawking temperature plus a negative pressure associated with the black hole of mass M. In this way, the graviton condensate, which is assumed to be at the critical point defined by the condition $$\mu _{ch}=0,$$ μ ch = 0 , has well-defined thermodynamic quantities P, V, $$T_{h}$$ T h , S, and U as any other Bose–Einstein condensate (BEC). In addition, we present a formal equivalence between the Letelier spacetime and the line element that describes the graviton condensate. We also discuss the Kiselev black hole, which can parametrize the most well-known spherically symmetric black holes. Finally, we present a new metric, which we will call the BEC–Kiselev solution, that allows us to extend the graviton condensate to the case of solutions with different matter contents.

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