Ernesto F. Eiroa

Linearized stability of charged thin shell wormholes

The linearized stability of charged thin shell wormholes under spherically symmetric perturbations is analyzed. It is shown that the presence of a large value of charge provides stabilization to the system, in the sense that the constraints onto the equation of state are less severe than for non-charged wormholes.

Cylindrical thin shell wormholes

A general formalism for the dynamics of nonrotating cylindrical thin-shell wormholes is developed. The time evolution of the throat is explicitly obtained for thin-shell wormholes whose metric has the form associated with local cosmic strings. It is found that the throat collapses to zero radius, remains static, or expands forever, depending only on the sign of its initial velocity.

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.

Thin-shell wormholes in dilaton gravity

In this work we construct charged thin-shell Lorentzian wormholes in dilaton gravity. The exotic matter required for the construction is localized in the shell and the energy conditions are satisfied outside the shell. The total amount of exotic matter is calculated and its dependence with the parameters of the model is analyzed.

Shadow of a rotating braneworld black hole

We investigate the shadow cast by a rotating braneworld black hole, in the Randall-Sundrum scenario. In addition to the angular momentum, the tidal charge term deforms the shape of the shadow. For a given value of the rotation parameter, the presence of a negative tidal charge enlarges the shadow and reduces its deformation with respect to Kerr spacetime, while for a positive charge, the opposite effect is obtained. We also analyze the case in which the combination of the rotation parameter and the tidal charge results in a naked singularity. We discuss the observational prospects corresponding to the supermassive black hole at the Galactic center.

Stability of Chaplygin gas thin-shell wormholes

In this paper we construct spherical thin-shell wormholes supported by a Chaplygin gas. For a rather general class of geometries we introduce a new approach for the stability analysis of static solutions under perturbations preserving the symmetry. We apply this to wormholes constructed from Schwarzschild, Schwarzschild-de Sitter, Schwarzschild-anti-de Sitter, and Reissner-Nordstrom metrics. In the last two cases, we find that there are values of the parameters for which stable static solutions exist.

Shadow of a Kaluza-Klein rotating dilaton black hole

Fil: Amarilla, Leonardo. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico - CONICET - Cordoba. Instituto Multidisciplinario de Biologia Vegetal (p); Argentina;

Null geodesics and shadow of a rotating black hole in extended Chern-Simons modified gravity

The Chern-Simons modification to general relativity in four dimensions consists of adding to the Einstein-Hilbert term a scalar field that couples to the first-class Pontryagin density. In this theory, which has attracted considerable attention recently, the Schwarzschild metric persists as an exact solution, and this is why this model resists several observational constraints. In contrast, the spinning black hole solution of the theory is not given by the Kerr metric but by a modification of it, so far only known for slow rotation and small coupling constant. In the present paper, we show that, in this approximation, the null geodesic equation can be integrated, and this allows us to investigate the shadow cast by a black hole. We discuss how, in addition to the angular momentum of the solution, the coupling to the Chern-Simons term deforms the shape of the shadow.

Gravitational lensing by Einstein-Born-Infeld black holes

In this paper, charged black holes in general relativity coupled to Born-Infeld electrodynamics are studied as gravitational lenses. The positions and magnifications of the relativistic images are obtained using the strong deflection limit, and the results are compared with those corresponding to a Reissner-Nordstroem black hole with the same mass and charge. As numerical examples, the model is applied to the supermassive Galactic center black hole and to a small size black hole situated in the Galactic halo.

Braneworld black hole gravitational lens: Strong field limit analysis

In this paper, a braneworld black hole is studied as a gravitational lens, using the strong field limit to obtain the positions and magnifications of the relativistic images. Standard lensing and retrolensing situations are analyzed in a unified setting, and the results are compared with those corresponding to the Schwarzschild black hole lens. The possibility of observing the strong field images is discussed.