arXiv subjects

Ernesto F. Eiroa

Publications and source records attributed to Ernesto F. Eiroa.

At least 19 recordsLinked to original sources

arXiv2026

Stability of spherical thin-shell wormholes in scalar-tensor theories

In this article, we construct a family of spherically symmetric thin-shell wormholes within scalar-tensor theories of gravity. In the case of wormholes symmetric across the throat, we study the matter content and analyze the stability of the static configurations under radial perturbations. We apply the formalism to a particular example involving Einstein-Maxwell gravity coupled to a conformally invariant scalar field. We show that stable configurations are possible for suitable values of the parameters involved.

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arXiv2026

Shadows cast by a class of rotating black bounces with an anisotropic fluid

In this work, we introduce a family of rotating black bounces with an anisotropic fluid obtained by using a modified Newman-Janis algorithm. We analyze the main features of these spacetimes and obtain the geodesics for photons, which admit the separation of the Hamilton-Jacobi equation. We then determine the shape of the shadow in terms of the parameters of the model. We present some relevant examples that exhibit some traits that distinguish these spacetimes from other related ones appearing in the literature.

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arXiv2025

Tides and energy conditions in Einstein-Gauss-Bonnet thin-shell wormholes

In this article we study spherical thin-shell wormholes in five-dimensional Einstein-Gauss-Bonnet gravity. We show that configurations supported by non-exotic matter, that is matter satisfying the weak energy condition, are possible at the same time that traversability problems associated with strong radial tides at the throat can be avoided when suitable values of the parameters are adopted. Our construction is performed in such a way that it also allows for the admissible behaviour of the geometry in the whole spacetime.

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arXiv2025

Charged thin shells in unimodular gravity

In this article, we construct a broad family of spacetimes with spherically symmetric thin shells in unimodular gravity. We present the framework for the analysis of the dynamical stability of the configurations under perturbations preserving the symmetry. In particular, we consider two different scenarios in which the non-conservation of the energy-momentum tensor is allowed; in both the spacetime has a thin shell with charge surrounding vacuum. Our constructions avoid the existence of event horizons and singularities. In both cases, we have obtained stable configurations for suitable values of the parameters. We compare our results with those corresponding to general relativity, finding some differences in the matter content and in the stability regions in the parameter space.

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arXiv2024

Dynamical and thermodynamical stability of a charged thin-shell wormhole

A study of the dynamical and thermodynamical stability of a charged thin-shell wormhole built by gluing two Reissner-Nordström geometries is presented. The charge on the shell is linearly related to the matter content. For the dynamical stability, a concise inequality is obtained, valid for any barotropic equation of state that relates the pressure with the energy density at the throat. A thermodynamical description of the system is introduced, which leads to the temperature and the electric potentials. Adopting a linear equation of state for the pressure and a definite form for the entropy function, the set of equilibrium configurations that are both dynamically and thermodynamically stable is found.

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arXiv2023

Shadows of rotating Einstein-Maxwell-dilaton black holes surrounded by a plasma

We consider rotating charged black holes with a scalar dilaton field and surrounded by plasma, with the purpose of studying their shadows. The corresponding metric has been previously obtained in the literature from the static solution by using the Newman-Janis algorithm. Assuming a well known form for the pressureless and nonmagnetized plasma distribution, which is suitable for the separation of the Hamilton-Jacobi equation for light, we derive an expression that determines the shape of the shadow. We present some examples of contours and we analyze their observable properties as functions of the charge and the dilaton coupling. We find that the presence of plasma introduces a dependency on the frequency, with the shadow becoming smaller as the frequency decreases.

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arXiv2022

Black hole solutions and thin shells in N-dimensional F(R) gravity with a conformally invariant Maxwell field

We present a generalization of the black hole solution with spherical symmetry already known in the literature for $N$-dimensional $F(R)$ gravity with a conformally invariant Maxwell field and constant scalar curvature $R$. This solution also includes a generalization of the one corresponding to general relativity as a special case. We introduce the formalism for the construction of a broad family of spherically symmetric thin shells in $F(R)$ theory. We use our generalized solution in order to provide examples of bubbles and thin layers of matter surrounding black holes. We analyze the stability of the constructions under perturbations preserving the symmetry, finding that stable configurations are possible for suitable values of the parameters. We show that the extension to higher dimensions does not alter the qualitative behavior of the thin shells found in four dimensions, with the main difference being a change of scale for the different values of $N$.

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arXiv2021

Shadow of a charged black hole surrounded by an anisotropic matter field

A certain type of matter with anisotropic pressures can add to the Reissner-Nordström metric a term proportional to a power of the radial coordinate. Using the standard method of separating variables for the Hamilton-Jacobi equation, we study the shadow of the corresponding rotating solution, obtained through the Newman-Janis algorithm. We define and calculate three observables in order to characterize the position, size and shape of the shadow.

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arXiv2021

Shadow of black holes with a plasma environment in 4D Einstein-Gauss-Bonnet gravity

We study the shadow cast by rotating black holes surrounded by plasma in the context of the 4D Einstein-Gauss-Bonnet theory of gravity. The metric for these black holes results from applying the Newman-Janis algorithm to a spherically symmetric solution. We obtain the contour of the shadow for a plasma frequency model that allows a separable Hamilton-Jacobi equation. We introduce three observables in order to characterize the position, size, and shape of the shadow.

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arXiv2021

Shadow of axisymmetric, stationary and asymptotically flat black holes in the presence of plasma

We study the shadow produced by a class of rotating black holes surrounded by plasma. The metric for these black holes arises by applying the Newman-Janis algorithm to a family of spherically symmetric spacetimes, which includes several well known geometries as special cases. We derive a general expression for the shape of the shadow in the case that the plasma frequency leads to a separable Hamilton-Jacobi equation for light. We present two examples in which we obtain the shadow contours and the observables resulting from them. In one, we analyze Kerr-Newman-like geometries, including braneworld and Horndeski gravity black holes, while in the other, we consider scalar-tensor 4D Einstein-Gauss-Bonnet gravity spacetimes. In both cases, we find that the presence of plasma leads to a smaller and less deformed shadow.

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arXiv2021

Circularly symmetric thin-shell wormholes in F(R) gravity with (2+1)-dimensions

Within the framework of $F(R)$ theories of gravity with (2+1)-dimensions and constant scalar curvature $R$, we construct a family of thin-shell wormholes with circular symmetry and we analyze the stability of the static configurations under radial perturbations. We show an example of asymptotically anti-de Sitter thin-shell wormholes with charge, finding that stable configurations with normal matter are possible for a suitable range of the parameters.

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arXiv2021

Thin-shell wormholes in (2+1)-dimensional F(R) theories

We construct a broad family of thin-shell wormholes with circular symmetry in (2+1)-dimensional F(R) theories of gravity, with constant scalar curvature R. We study the stability of the static configurations under perturbations preserving the symmetry. We present charged thin-shell wormholes as examples of spacetimes with a negative cosmological constant. We show that stable solutions are possible when suitable values of the parameters are taken.

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arXiv2021

Thin shells in (2+1)-dimensional F(R) gravity

We study thin shells of matter in (2+1)-dimensional F(R) theories of gravity with constant scalar curvature R. We consider a wide class of spacetimes with circular symmetry, in which a thin shell joins an inner region with an outer one. We analyze the stability of the static configurations under radial perturbations. As examples of spacetimes asymptotically anti-de Sitter, we present a charged bubble and a charged thin shell surrounding a non-charged black hole. In both cases, we show that stable solutions can be found for suitable values of the parameters.

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arXiv2020

Thin shells in F(R) gravity with non-constant scalar curvature

We introduce two classes of spherically symmetric spacetimes having a thin shell of matter, in non-quadratic F(R) theories of gravity with non-constant scalar curvature R. In the first, the thin shell joins an inner region with an outer one, while in the second it corresponds to the throat of a wormhole. In both scenarios, we analyze the stability of the static configurations under radial perturbations. As particular examples in spacetimes with a cosmological constant, we present charged thin shells surrounding a non-charged black hole and charged thin-shell wormholes. We show that in both cases stable solutions are possible for suitable values of the parameters.

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arXiv2020

Influence of an anisotropic matter field on the shadow of a rotating black hole

In this paper, we study the shadow produced by rotating black holes with charge in the presence of an anisotropic matter field. We obtain the apparent shape and the corresponding observables characterizing the size, oblateness, and deviation of the center, for different values of the parameters of the model. We compare the new results with those corresponding to the Kerr-Newmann spacetime and we also discuss the observational prospects in this case.

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arXiv2019

Thin shells associated to black string spacetimes

In this article, we study thin shells of matter connecting charged black string geometries with different values of the corresponding parameters. We analyze the matter content and the mechanical stability of the shells undergoing perturbations that preserve the cylindrical symmetry. Two different global configurations are considered: an interior geometry connected to an exterior one at the surface where the shell is placed, and two exterior geometries connected by a wormhole throat located at the shell position.

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arXiv2019

Thin shells surrounding black holes in F(R) gravity

In this article, we consider spherical thin shells of matter surrounding black holes in F(R) theories of gravity. We study the stability of the static configurations under perturbations that conserve the symmetry. In particular, we analyze the case of charged shells outside the horizon of non--charged black holes. We obtain that stable static thin shells are possible if the values of the parameters of the model are properly selected.

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arXiv2018

Spherical Skyrmion black holes as gravitational lenses

In this article, we extend the strong deflection limit to calculate the deflection angle for a class of geometries which are asymptotically locally flat. In particular, we study the deflection of light in the surroundings of spherical black holes in Einstein-Skyrme theory. We find the deflection angle in this limit, from which we obtain the positions and the magnifications of the relativistic images. We compare our results with those corresponding to the Schwarzschild and the global monopole (Barriola-Vilenkin) spacetimes.

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