The universality of Martinez’s conjecture, which states that the quasilocal energy of a black hole at the outer horizon reduces to twice its irreducible mass, or equivalently, to √ A/4π (A is the area of the black hole), is investigated by calculating Brown-York quasilocal energies for stationary black holes in heterotic string theory, e. g., for the stationary Kaluza-Klein black hole, the rota...

The universality of Martinez’s conjecture, which states that quasilocal energy of a black hole at the outer horizon reduces to twice its irreducible mass, or equivalently, to √ A/4π (A is the area of the black hole), is investigated by calculating Brown-York quasilocal energies for stationary black holes in heterotic string theory, such as for the stationary Kaluza-Klein black hole, the rotatin...

Motivated by the recent interest on models with varying constants and whether black hole physics can constrain such theories, two-dimensional charged stringy black holes are considered. We exploit the role of two-dimensional stringy black holes as toy models for exploring paradoxes which may lead to constrains on a theory. A two-dimensional charged stringy black hole is investigated in two diff...

Black-hole physics mirrors thermodynamics in many respects. Inparticular, it is widely believed that a system consisting of ordinary matter interacting with a black hole will obey the generalized second law of thermodynamics. In this paper we challenge the validity of the law in a gedanken experiment in which an entropy-bearing rotating system falls into a stationary black hole. It is shown tha...

We derive and discuss black–hole solutions to the gravitating O(3) σ model in (2+1) dimensions. Three different kinds of static black holes are found. One of these resembles the static BTZ black hole, another is completely free of singularities, and the last type has the same Penrose diagram as the (3+1)–dimensional Schwarzschild black hole. We also construct static and dynamical multi–black ho...

The characteristic initial value problem has been successfully implemented as a robust computational algorithm (the PITT NULL CODE) to evolve 4-dimensional vacuum spacetimes. It has been applied to the calculation of gravitational waveforms emitted by black holes and to the event horizon structure in the merger of black holes. The characteristic code also has potential application to the binary...

or Does the 2D black hole have tachyonic or W–hair? Abstract We solve the equations of motion of the tachyon and the discrete states in the background of Witten's semiclassical black hole and in the exact 2D dilaton-graviton background of Dijkgraaf et al. We find the exact solutions for weak fields, leading to conclusions in disagreement with previous studies of tachyons in the black hole. Dema...

Classical black holes are defined by the property that things can go in, but don’t come out. However, Stephen Hawking calculated that black holes actually radiate quantum mechanical particles. The two important ingredients that result in back hole evaporation are (1) the spacetime geometry, in particular the black hole horizon, and (2) the fact that the notion of a “particle” is not an invarian...

It has been proposed that a black hole horizon should generate Hawking radiation. In order to test this theory, we have created a narrow, low density, very low temperature atomic Bose-Einstein condensate, containing an analog black hole horizon and an inner horizon, as in a charged black hole. We observe Hawking radiation emitted by the black hole. This is the output of the black hole laser. We...

We show that the Abelian Higgs field equations in the background of the four dimensional AdS-Schwarzschild black hole have a vortex line solution. This solution, which has axial symmetry, is a generalization of the AdS spacetime Nielsen-Olesen string. By a numerical study of the field equations, we show that black hole could support the Abelian Higgs field as its Abelian hair. Also, we conside ...