PLANE SYMMETRIC GENERAL SOLUTION TO EINSTEIN-MAXWELL EQUATIONS IN HIGHER DIMENSIONS

The solutions of the Dirac equation Dear the black hole event horizon and the univers horizon in Vaidya-Schwarzschild-de Sitter space-time are given in this paper. Both the temperature of the Hawking radi-ation and the location of the evaporating black hole horizon and the universe horizon are determined exactly.     

HAWKING EFFECT OF DIRAC PARTICLES IN VAIDYA-SCHWARZSCHILD-DE SITTER SPACE-TIME

The solutions of the Dirac equation near the black hole event horizon and the universe horizon in the Vaidya-Schwarzschild-de Sitter space-time are given in this paper. Both the temperature of the Hawking radiation and the location of the evaporating black hole horizon and the universe horizon are determined exactly.     

The fate of magnetically charged black holes

The magnetically charged Reissner-Nordström black hole solutions of Maxwell-Einstein theory cannot evaporate completely, because their Hawking temperature tends to zero as their mass to charge ratio approaches unity. This situation changes when these solutions are considered in the context of a non-Abelian gauge theory containing nonsingular magnetic monopoles. If the horizon is sufficiently small, the Reissner-Nordström solution develops a classical instability and evolves into a new type of magnetically charged black hole solution. The temperature of these new solutions increases monotonically as the horizon contracts, so that there is no obstacle to the complete evaporation of a magnetically charged black hole.     

Asymptotically FRW black holes

Special solutions of the LTB family representing collapsing over-dense regions corresponding to asymptotically closed, open, or flat FRW models are found. These solutions may be considered as representing dynamical mass condensations leading to black holes immersed in a FRW universe. We study the dynamics of the collapsing region, and its density profile. The question of the strength of the central singularity and its nakedness, as well as the existence of an apparent horizon and an event horizon is dealt with in detail, shedding light to the notion of cosmological black holes. Differences to the Schwarzschild black hole are addressed.     

Quantum thermal effects of a radiating rotating charged black hole

Asymptotic solutions of the Klein-Gordon equation in a region near the event horizon of a radiating rotating charged black hole are obtained by using generalized tortoise coordinates. The location of the event horizon and the Hawking temperature of the black hole are given. Both the horizon and the temperature depend on the angle and time, due to radiation. However, they are independent of the angle if either rotation or radiation vanishes. The treatment encompasses as special cases the results on a number of well-known black holes.     

On EVH black hole solution in heterotic string theory

We study the near horizon geometry of charged rotating black holes in toroidal compactifications of heterotic string theory. We analyze the extremal vanishing horizon (EVH) limit for these black hole solutions and we will show that the near horizon geometry develops an AdS₃ throat. Furthermore, we will show that the near horizon limit of near EVH black holes has a BTZ factor. We also comment on the CFT dual to this near horizon geometry.     

Area and Entropy Spectrum of Gauss-Bonnet Gravity in de Sitter Space-Times for Black Hole Event Horizon

In this paper, we use the modified Hod's treatment and the Kunstatter's method to study the horizon area spectrum and entropy spectrum in Gauss-Bonnet de-Sitter space-time, which is regarded as the natural generalization of Einstein gravity by including higher derivative correction terms to the original Einstein-Hilbert action. The horizon areas have some properties that are very different from the vacuum solutions obtained from the frame of Einstein gravity. With the new physical interpretation of quasinormal modes, the area/entropy spectrum for the event horizon for nearextremal Gauss-Bonnet de Sitter black holes are obtained. Meanwhile, we also extend the discussion of area/entropy quantization to the non-extremal black holes solutions.     

Charged boson stars and black holes

We consider boson stars and black holes in scalar electrodynamics with a V-shaped scalar potential. The boson stars come in two types, having either ball-like or shell-like charge density. We analyze the properties of these solutions and determine their domains of existence. When mass and charge become equal, the space–times develop a throat. The shell-like solutions need not be globally regular, but may possess a horizon. The space–times then consist of a Schwarzschild-type black hole in the interior, surrounded by a shell of charged matter, and thus a Reissner–Nordström-type space–time in the exterior. These solutions violate black hole uniqueness. The mass of the black hole solutions is related to the mass of the regular shell-like solutions by a mass formula of the type first obtained within the isolated horizon framework.     

Hawking effect in Vaidya-de Sitter space-time

The solutions of both the Klein-Gordon equation and the Dirac equation near the event horizons are given in the Vaidya-de Sitter space-time. With a new method the locations of the black hole event horizon and universe horizon, as well as their Hawking temperatures, are shown automatically and easily.     

Are all static black hole solutions spherically symmetric?

The static black hole solutions to the Einstein-Maxwell equations are all spherically symmetric, as are many of the recently discovered black hole solutions in theories of gravity coupled to other forms of matter. However, counterexamples demonstrating that static black holes need not be spherically symmetric exist in theories, such as the standard electroweak model, with electrically charged massive vector fields. In such theories, a magnetically charged Reissner-Nordström solution with sufficiently small horizon radius is unstable against the development of a nonzero vector field outside the horizon. General arguments show that, for generic values of the magnetic charge, this field cannot be spherically symmetric. Explicit construction of the solution shows that it in fact has no rotational symmetry at all.This essay received the second award from the Gravity Research Foundation, 1995-Ed.     

Inner mechanics of three-dimensional black holes

We investigate properties of the inner horizons of certain black holes in higher-derivative three-dimensional gravity theories. We focus on Ba?ados-Teitelboim-Zanelli and spacelike warped anti-de Sitter black holes, as well as on asymptotically warped de Sitter solutions exhibiting both a cosmological and a black hole horizon. We verify that a first law is satisfied at the inner horizon, in agreement with the proposal of Castro and Rodriguez [arXiv:1204.1284]. We then show that, in topologically massive gravity, the product of the areas of the inner and outer horizons fails to be independent on the mass, and we trace this to the diffeomorphism anomaly of the theory.     

New cosmology

We propose a model of our universe as a 3-sphere resting on the surface of a black hole which exists in a spacetime consisting of four space dimensions and one time dimension. The matter and energy within our universe exist as stationary solutions to the field equations in the Rindler coordinates just above the horizon of the black hole. Each solution may be though of as a standing wave consisting of a wave propagating toward the horizon superposed with its time-reversed twin propagating away from the horizon. As matter and energy from the greater five-dimensional spacetime fall into the black hole, its radius increases and our universe expands. This mechanism of expansion allows the model to describe a universe which is older than its oldest stars and homogeneous without inflation. It also predicts galaxy counts at high redshift which agree with observation.     

EVH black hole solutions with higher derivative corrections

We analyze the effect of higher derivative corrections to the near horizon geometry of the extremal vanishing horizon (EVH) black hole solutions in four dimensions. We restrict ourselves to a Gauss–Bonnet correction with a dilation dependent coupling in an Einstein–Maxwell-dilaton theory. This action may represent the effective action as it arises in tree level heterotic string theory compactified to four dimensions or the K3 compactification of type II string theory. We show that EVH black holes, in this theory, develop an AdS₃ throat in their near horizon geometry.     

Curvature-corrected dilatonic black holes and black hole—string transition

We investigate extremal charged black hole solutions in the four-dimensional string frame Gauss-Bonnet gravity with the Maxwell field and the dilaton. Without curvature corrections, the extremal electrically charged dilatonic black holes have singular horizon and zero Bekenstein entropy. When the Gauss-Bonnet term is switched on, the horizon radius expands to a finite value provided curvature corrections are strong enough. Below a certain threshold value of the Gauss-Bonnet coupling the extremal black hole solutions cease to exist. Since decreasing Gauss-Bonnet coupling corresponds to decreasing string coupling g _s , the situation can tentatively be interpreted as classical indication on the black hole—string transition. Previously the extremal dilaton black holes were studied in the Einstein-frame version of the Gauss-Bonnet gravity. Here we work in the string frame version of the theory with the S-duality symmetric dilaton function as required by the heterotic string theory. The article is published in the original.     

On the ‘Stationary Implies Axisymmetric’ Theorem for Extremal Black Holes in Higher Dimensions

All known stationary black hole solutions in higher dimensions possess additional rotational symmetries in addition to the stationary Killing field. Also, for all known stationary solutions, the event horizon is a Killing horizon, and the surface gravity is constant. In the case of non-degenerate horizons (non-extremal black holes), a general theorem was previously established [24] proving that these statements are in fact generally true under the assumption that the spacetime is analytic, and that the metric satisfies Einstein’s equation. Here, we extend the analysis to the case of degenerate (extremal) black holes. It is shown that the theorem still holds true if the vector of angular velocities of the horizon satisfies a certain “diophantine condition,” which holds except for a set of measure zero.     

Five-dimensional Kaluza-Klein black holes coupled to massive scalar particles

Spherically symmetric solutions coupled to massive scalar particles in five-dimensional Kaluza-Klein theory are obtained. The solutions contain two event horizons. The inner horizon corresponds to the Schwarzschild black hole and the outer one is a new horizon which is produced by the massive scalar particles. It is found that the massive modes contribute an effective cosmological constant to the four-dimensional Einstein theory.     

Quantum electron levels in the field of a charged black hole

Stationary solutions of the Dirac equation in the metric of the charged Reissner–Nordstrom black hole are found. In the case of an extremal black hole, the normalization integral of the wave functions is finite, and the regular stationary solution is physically self-consistent. The presence of quantum electron levels under the Cauchy horizon can have an impact on the final stage of the Hawking evaporation of the black hole, as well as on the particle scattering in the field of the black hole.     

Thermodynamics and phase transition of topological dS black holes with a nonlinear source

We discuss black hole solutions of Einstein-Λ gravity in the presence of nonlinear electrodynamics in d S spacetime. Considering the correlation of the thermodynamic quantities respectively corresponding to the black hole horizon and cosmological horizon of dS spacetime and taking the region between the two horizons as a thermodynamic system, we derive effective thermodynamic quantities of the system according to the first law of thermodynamics, and investigate the thermodynamic properties of the system under the influence of nonlinearity parameter α. It is shown that nonlinearity parameter α influences the position of the black hole horizon and the critical state of the system, and along with electric charge has an effect on the phase structure of the system,which is obvious, especially as the effective temperature is below the critical temperature. The critical phase transition is proved to be second-order equilibrium phase transition by using the Gibbs free energy criterion and Ehrenfest equations.     

Bouncing cosmological solutions due to the self-gravitational corrections and their stability

In this paper we consider the bouncing braneworld scenario, in which the bulk is given by a five-dimensional AdS black hole spacetime with matter field confined in a 3D brane. Exploiting the CFT/FRW-cosmology relation, we consider the self-gravitational corrections to the first Friedmann-like equation which is the equation of the brane motion. The self-gravitational corrections act as a source of stiff matter contrary to standard FRW cosmology, where the charge of the black hole plays this role. Then we study the stability of solutions with respect to homogeneous and isotropic perturbations. Specifically, if we do not consider the self-gravitational corrections, the AdS black hole with zero ADM mass and open horizon is an attractor, while, if we consider the self-gravitational corrections, the AdS black hole with zero ADM mass and flat horizon is a repeller.     

(2 + 1)-Dimensional Solutions in F(R) Gravity

Motivated by the well-known charged BTZ black holes, we look for (2 + 1)-dimensional solutions of F(R) gravity. At first we investigate some near horizon solutions and after that we obtain asymptotically Lifshitz black hole solutions. Finally, we discuss about rotating black holes with exponential form of F(R) theory.