Related papers: Extremal Limits and Kerr Spacetime
We consider collision of two massive particles in the equatorial plane of an axially symmetric stationary spacetime that produces two massless particles afterwards. It is implied that the horizon is absent but there is a naked singularity…
We investigate the near horizon geometry of the simplest representative of the class of axisymmetric space-times: the Kerr Vaidya metrics. Kerr Vaidya metrics can be derived from the Vaidya metric by the complex coordinate transformation…
We present a systematic construction of the Penrose coordinates and plane wave limits of spacetimes for which both the null Hamilton-Jacobi and geodesic equations separate. The method is illustrated for the Kerr-NUT-(A)dS four-dimensional…
Some problems have been found as to the definition of entropy of black hole being applied to the extremal Kerr-Newman case, which has conflicts with the third law of thermodynamics. We have proposed a new modification for the near extremal…
We study the conformal symmetry described by $SL(2,R)_L \times SL(2,R)_R$ in the nonextremal Kerr black hole case. We calculate the central charges $c_{L,R}$ separately on a stretched horizon by the Hamiltonian gravity. In order to get two…
We analyze the near horizon structure of the extremal spacelike stretched black holes, exact solutions of topologically massive gravity. We show that the algebra of improved canonical generator is realized as a single centrally extended…
We describe the Kerr black hole in the ingoing and outgoing Kerr-Schild horizon penetrating coordinates. Starting from the null vector naturally defined in these coordinates, we construct the null tetrad for each case, as well as the…
We review the basic definitions and properties of trapped surfaces and discuss them in the context of Kerr-Vaidya line-element. Our study shows that the apparent horizon does not exist in general for axisymmetric space-times. The reason…
Metrics representing black holes in General Relativity may exhibit naked singularities for certain values of their parameters. This is the case for super-extremal ($J^2 > M>0$) Kerr and super-extremal ($|Q|>M>0$) Reissner-N\"ordstrom…
We investigate here the particle acceleration and collisions with extremely large center of mass energies in a perfectly regular spacetime containing neither singularity nor an event horizon. The ultra-high energy collisions of particles…
We study hidden symmetries, the symmetries associated with the Killing tensors, of the near horizon geometry of odd-dimensional Kerr-AdS-NUT black hole in two limits: generic extremal and extremal vanishing horizon (EVH) limits. Starting…
We establish the black-hole Meissner effect for extremal Kerr--Bertotti--Robinson (Kerr--BR) black holes, which are exact solutions of the Einstein--Maxwell equations describing a rotating black hole immersed in a uniform Bertotti--Robinson…
A modified version of the Schwarzschild geometry is proposed. The source of curvature comes from an anisotropic fluid with $p_{r} = -\rho$ and fluctuating tangential pressures. The event horizon has zero surface gravity but the invariant…
The requirement that a trapped spacetime domain forms in finite time for distant observers is logically possible and sometimes unavoidable, but its consequences are not yet fully understood. In spherical symmetry, the characterization of…
We study 5-dimensional black holes in Einstein-Maxwell-Chern-Simons theory with free Chern-Simons coupling parameter. We consider an event horizon with spherical topology, and both angular momenta of equal magnitude. In particular, we study…
In General Relativity, the spacetimes of black holes have three fundamental properties: (i) they are the same, to lowest order in spin, as the metrics of stellar objects; (ii) they are independent of mass, when expressed in geometric units;…
We consider null geodesics in the exterior region of a subextremal Kerr spacetime. We show that most well-known fundamental properties of null geodesics can be represented on one plot. In particular, one can see immediately that the…
Bearing the final fate of gravitational collapse in mind, we study the asymptotic structures at timelike infinity in four dimensions. Assuming that spacetimes are asymptotically stationary, we will examine the asymptotic structure of…
We clarify the relation between gravitational entropy and the area of horizons. We first show that the entropy of an extreme Reissner-Nordstr\"om black hole is $zero$, despite the fact that its horizon has nonzero area. Next, we consider…
We study extremal surfaces in the Schwarzschild de Sitter spacetime with real mass parameter. We find codim-2 timelike extremal surfaces stretching between the future and past boundaries that pass through the vicinity of the cosmological…