José P. S. Lemos

Three dimensional black holes and cylindrical general relativity

A black hole solution of Einsteins field equations with cylindrical symmetry is found. Using the Hamiltonian formulation one is able to define mass and angular momentum for the cylindrical black hole through the corresponding and equivalent three dimensional theory. The causal structure is analyzed. Comments: revised version.Abstract A black string solution of the four dimensional Einstein-Hilbert action, S = 1 16πG ∫ d 4X −g (R−2Λ) , in a cylindrical spacetime is found. The three dimensional dilaton-gravity theory obtained through dimensional reduction, with action S = 1 2π ∫ d 3 x −ge (R − 2Θ) , contains the corresponding three dimensional black hole solution. In this three dimensional theory one is able to define mass and angular momentum for the black hole using the Hamiltonian formulation. The causal structure is analyzed and the temperature of the black hole is computed.

Quasinormal modes of Schwarzschild anti-de Sitter black holes: Electromagnetic and gravitational perturbations

We study the quasi-normal modes (QNM) of electromagnetic and gravitational perturbations of a Schwarzschild black hole in an asymptotically Anti-de Sitter (AdS) spacetime. Some of the electromagnetic modes do not oscillate, they only decay, since they have pure imaginary frequencies. The gravitational modes show peculiar features: the odd and even gravitational perturbations no longer have the same characteristic quasinormal frequencies. There is a special mode for odd perturbations whose behavior differs completely from the usual one in scalar and electromagnetic perturbation in an AdS spacetime, but has a similar behavior to the Schwarzschild black hole in an asymptotically flat spacetime: the imaginary part of the frequency goes as 1 r+ , where r+ is the horizon radius. We also investigate the small black hole limit showing that the imaginary part of the frequency goes as r2 +. These results are important to the AdS/CFT conjecture since according to it the QNMs describe the approach to equilibrium in the conformal field theory. E-mail: vcardoso@fisica.ist.utl.pt E-mail: lemos@kelvin.ist.utl.pt

Rotating charged black strings and three-dimensional black holes.

Einstein-Maxwell equations with a cosmological constant are analyzed in a four dimensional stationary spacetime admitting in addition a two dimensional group

Quasinormal frequencies of Schwarzschild black holes in anti-de Sitter space-times: A Complete study on the asymptotic behavior

G_2

Morris-Thorne wormholes with a cosmological constant

of spatial isometries. Charged rotating open and closed black string solutions are found.

Quasinormal modes of the near extremal Schwarzschild-de Sitter black hole

We present a thorough analysis of the quasinormal (QN) behavior associated with the decay of scalar, electromagnetic, and gravitational perturbations of Schwarzschild black holes in anti\char21{}de Sitter (AdS) spacetimes. As is known, the AdS QN spectrum crucially depends on the relative size of the black hole to the AdS radius. There are three different types of behavior depending on whether the black hole is large, intermediate, or small. The results of previous works, concerning lower overtones for large black holes, are completed here by obtaining higher overtones for all three black hole regimes. There are two major conclusions that one can draw from this work: First, asymptotically for high overtones, all the modes are evenly spaced, and this holds for all three types of regime, large, intermediate, and small black holes, independently of l, where l is the quantum number characterizing the angular distribution; second, the spacing between modes is apparently universal in that it does not depend on the field; i.e., scalar, electromagnetic, and gravitational QN modes all have the same spacing for high overtones. We are also able to prove why scalar and gravitational perturbations are isospectral, asymptotically for high overtones, by introducing appropriate superpartner potentials.

Gravitational radiation in D-dimensional space-times

First, the ideas introduced in the wormhole research field since the work of Morris and Thorne are reviewed, namely, the issues of energy conditions, wormhole construction, stability, time machines and astrophysical signatures. Then, spherically symmetric and static traversable Morris-Thorne wormholes in the presence of a generic cosmological constant

Two-dimensional black holes and planar general relativity

\ensuremath{\Lambda}

Electrically charged compact stars and formation of charged black holes

are analyzed. A matching of an interior solution to the unique exterior vacuum solution is done using directly the Einstein equations. The structure as well as several physical properties and characteristics of traversable wormholes due to the effects of the cosmological term are studied. Interesting equations appear in the process of matching. For instance, one finds that for asymptotically flat and anti\char21{}de Sitter spacetimes the surface tangential pressure

Plane symmetric thin-shell wormholes: Solutions and stability

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