36 research outputs found
Thin-shell wormholes from charged black holes in generalized dilaton-axion gravity
This paper discusses a new type of thin-shell wormhole constructed by
applying the cut-and-paste technique to two copies of a charged black hole in
generalized dilaton-axion gravity, which was inspired by low-energy string
theory. After analyzing various aspects of this thin-shell wormhole, we discuss
its stability to linearized spherically symmetric perturbations.Comment: Minor changes, 6 pages, 4 figures. Accepted for publication in Gen.
Rel. Gra
Thin-shell wormholes from regular charged black holes
We investigate a new thin-shell wormhole constructed by surgically grafting
two regular charged black holes arising from the action using nonlinear
electrodynamics coupled to general relativity. The stress-energy components
within the shell violate the null and weak energy conditions but obey the
strong energy condition. We study the stability in two ways: (i) taking a
specific equation of state at the throat and (ii) analyzing the stability to
linearized spherically symmetric perturbations about a static equilibrium
solution. Various other aspects of this thin-shell wormhole are also analyzed.Comment: 8 pages and 19 figure
Thin-shell wormholes with a generalized Chaplygin gas in Einstein-Born-Infeld theory
We construct spherically symmetric thin-shell wormholes supported by a
generalized Chaplygin gas in Born-Infeld electrodynamics coupled to Einstein
gravity, and we analyze their stability under radial perturbations. For
different values of the Born-Infeld parameter and the charge, we compare the
results with those obtained in a previous work for Maxwell electrodynamics. The
stability region in the parameter space reduces and then disappears as the
value of the Born-Infeld parameter is modified in the sense of a larger
departure from Maxwell theory.Comment: 9 pages, 6 figures; v2: improved versio
Stability of Non-asymptotically flat thin-shell wormholes in generalized dilaton-axion gravity
We construct a new type of thin-shell wormhole for non-asymptotically flat
charged black holes in generalized dilaton-axion gravity inspired by low-energy
string theory using cut-and-paste technique. We have shown that this thin shell
wormhole is stable. The most striking feature of our model is that the total
amount of exotic matter needed to support the wormhole can be reduced as
desired with the suitable choice of the value of a parameter. Various other
aspects of thin-shell wormhole are also analyzed.Comment: 15 pages and 11 figures. Minor revisions have been done. Accepted in
Int.J.Theor.Phy
Thin-shell wormholes in Einstein-Maxwell theory with a Gauss-Bonnet term
We study five dimensional thin-shell wormholes in Einstein-Maxwell theory
with a Gauss-Bonnet term. The linearized stability under radial perturbations
and the amount of exotic matter are analyzed as a function of the parameters of
the model. We find that the inclusion of the quadratic correction substantially
widens the range of possible stable configurations, and besides it allows for a
reduction of the exotic matter required to construct the wormholes.Comment: 13 pages, 6 figures; v2: minor changes and new references added.
Accepted for publication in General Relativity and Gravitatio
Weak field limit of Reissner-Nordstrom black hole lensing
We study gravitational lensing by a Reissner-Nordstrom (RN) black hole in the
weak field limit. We obtain the basic equations for the deflection angle and
time delay and find analytical expressions for the positions and amplifications
of the primary and secondary images. Due to a net positive charge, the
separation between images increases, but no change in the total magnification
occurs.Comment: 8 pages, to appear in Phys. Rev.
Strong field limit analysis of gravitational retro-lensing
We present a complete treatment in the strong field limit of gravitational
retro-lensing by a static spherically symmetric compact object having a photon
sphere. The results are compared with those corresponding to ordinary lensing
in similar strong field situations. As examples of application of the
formalism, a supermassive black hole at the galactic center and a stellar mass
black hole in the galactic halo are studied as retro-lenses, in both cases
using the Schwarzschild and Reissner-Nordstrom geometries.Comment: 11 pages, 1 figure; v2: minor changes. Accepted for publication in
Physical Review
Thin-shell wormholes from black holes with dilaton and monopole fields
We provide a new type of thin-shell wormhole from the black holes with
dilaton and monopole fields. The dilaton and monopole that built the black
holes may supply fuel to construct the wormholes. Several characteristics of
this thin-shell wormhole have been discussed. Finally, we discuss the stability
of the thin-shell wormholes with a "phantom-like" equation of state for the
exotic matter at the throat.Comment: 6 pages and 3 figures, some typos are corrected and accepted in
Int.J.Theor.Phy
Particle motion and gravitational lensing in the metric of a dilaton black hole in a de Sitter universe
We consider the metric exterior to a charged dilaton black hole in a de
Sitter universe. We study the motion of a test particle in this metric.
Conserved quantities are identified and the Hamilton-Jacobi method is employed
for the solutions of the equations of motion. At large distances from the black
hole the Hubble expansion of the universe modifies the effective potential such
that bound orbits could exist up to an upper limit of the angular momentum per
mass for the orbiting test particle. We then study the phenomenon of strong
field gravitational lensing by these black holes by extending the standard
formalism of strong lensing to the non-asymptotically flat dilaton-de Sitter
metric. Expressions for the various lensing quantities are obtained in terms of
the metric coefficients.Comment: 8 pages, RevTex, 1 eps figures; discussion improved; typos corrected;
references adde
Strong Gravitational Lensing in a Charged Squashed Kaluza- Klein Black hole
In this paper we investigate the strong gravitational lensing in a charged
squashed Kaluza-Klein black hole. We suppose that the supermassive black hole
in the galaxy center can be considered by a charged squashed Kaluza-Klein black
hole and then we study the strong gravitational lensing theory and estimate the
numerical values for parameters and observables of it. We explore the effects
of the scale of extra dimension and the charge of black hole
on these parameters and observables.Comment: 17 pages, 10 figure