Browsing by Author "Capistrano A.J.S."

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Effective Perihelion Advance and Potentials in a Conformastatic Background with Magnetic Field
(Hindawi Limited, 2016) Capistrano A.J.S.; Gutiérrez-Piñeres A.C.
Exact solutions of the Einstein-Maxwell field equations for a conformastatic metric with magnetized sources are investigated. In this context, effective potentials are studied in order to understand the dynamics of the magnetic field in galaxies. We derive the equations of motion for neutral and charged particles in a spacetime background characterized by this class of solutions. In this particular case, we investigate the main physical properties of the equatorial circular orbits and related effective potentials. In addition, we obtain an effective analytic expression for the perihelion advance of test particles. Our theoretical predictions are compared with the observational data calibrated with the ephemerides of the planets of the solar system and the Moon (EPM2011). In general, we show that the magnetic punctual mass predicts values that are in better agreement with observations than the values predicted in Einstein's gravity alone. © 2016 Abraão J. S. Capistrano and Antonio C. Gutiérrez-Piñeres.
Exact galactic disk-haloes model in Einstein-Maxwell gravity
(World Scientific Publishing Co. Pte. Ltd., 2018) Gutiérrez-Piñeres A.C.; Capistrano A.J.S.; Ruffini R.; Bianchi M.; Ruffini R.; Jantzen R.T.
An exact model in Einstein-Maxwell gravity describing a magnetized galactic disk-halo system is presented. The description of properties of the stationary metric and its source are discussed. All the expressions are presented in terms of an Harmonic function. A “generalization” of the Kuzmin potential is used as a particular example. The solution obtained is asymptotically Minkowskian in general and turns out to be singularity free. All the relevant quantities show a reasonable physical behavior. Copyright © 2018 by the Editors.All rights reserved.
Exact relativistic magnetized haloes around rotating disks
(Hindawi Publishing Corporation, 2015) Gutiérrez-Piñeres A.C.; Capistrano A.J.S.
The study of the dynamics of magnetic fields in galaxies is one of important problems in formation and evolution of galaxies. In this paper, we present the exact relativistic treatment of a rotating disk surrounded by a magnetized material halo. The features of the halo and disk are described by the distributional energy-momentum tensor of a general fluid in canonical form. All the relevant quantities and the metric and electromagnetic potentials are exactly determined by an arbitrary harmonic function only. For instance, the generalized Kuzmin-disk potential is used. The particular class of solutions obtained is asymptotically flat and satisfies all the energy conditions. Moreover, the motion of a charged particle on the halo is described. As far as we know, this is the first relativistic model describing analytically the magnetized halo of a rotating disk. © 2015 Antonio C. Gutiérrez-Piñeres and Abraão J. S. Capistrano.
Motion of test particles in a magnetized conformastatic background
(World Scientific Publishing Co. Pte. Ltd., 2018) Gutiérrez-Piñeres A.C.; Capistrano A.J.S.; Ruffini R.; Bianchi M.; Jantzen R.T.
A class of exact conformastatic solutions of the Einstein-Maxwell field equations is presented in which the gravitational and electromagnetic potentials are completely determined by a harmonic function only. The motion of test particles is investigated in the background of a space-time characterized by this class of solutions. We focus on the study of circular stable and unstable orbits obtained by taking account particular harmonic functions defining the gravitational potential. We show that is possible to have repulsive force generated by the charge distribution of the source. As the space-time here considered is singularity free we conclude that this phenomena is not exclusive to the case of naked singularities. Additionally, we obtain an expression for the perihelion advance of the test particles in a general magnetized conformastatic space-time. Copyright © 2018 by the Editors.All rights reserved.
On classical thermal stability of black holes with a dynamical extrinsic curvature
(Academic Press Inc., 2017) Capistrano A.J.S.; Gutiérrez-Piñeres A.C.; Ulhoa S.C.; Amorim R.G.G.
We study the deformation caused by the influence of the extrinsic curvature on a vacuum spherically symmetric metric embedded in a five-dimensional bulk. We investigate the resulting black-holes obtaining general characteristics such as their masses, horizons, singularities and thermal properties by using a dynamical extrinsic curvature leading to different results as those from rigid embedded models. As a test, we also study the bending of light near such black-holes analyzing the movement of a test particle and the modification caused by extrinsic curvature on its movement. Accordingly, using the asymptotically conformal flat condition, we show that such black holes must be large and constrained by the allowed number range −1/2≤n≤1.8 for a set of n-scalar potentials. As a result, they are locally thermodynamically stable, but not globally preferred. © 2017 Elsevier Inc.
Test particles in a magnetized conformastatic spacetime
(American Physical Society, 2016) Gutiérrez-Piñeres A.C.; Capistrano A.J.S.; Quevedo H.
A class of exact conformastatic solutions of the Einstein-Maxwell field equations is presented in which the gravitational and electromagnetic potentials are completely determined by a harmonic function. We derive the equations of motion for neutral and charged particles in a spacetime background characterized by this class of solutions. As an example, we focus on the analysis of a particular harmonic function, which generates a singularity-free and asymptotically flat spacetime that describes the gravitational field of a punctual mass endowed with a magnetic field. In this particular case, we investigate the main physical properties of equatorial circular orbits. We show that due to the electromagnetic interaction, it is possible to have charged test particles which stay at rest with respect to a static observer located at infinity. Additionally, we obtain an analytic expression for the perihelion advance of test particles and the corresponding explicit value in the case of a punctual magnetic mass. We show that the analytical expressions obtained from our analysis are sufficient for being confronted with observations in order to establish whether such objects can exist in nature. © 2016 American Physical Society.