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Sep 18, 2013
09/13

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Francisco Frutos-Alfaro

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The gravitational lens equation for the tilted Plummer family of models can be reduced to a one-dimensional non-linear equation. For certain values of the slope of the radial profile it can be reduced to a polynomial form. Both forms are advantageous to find the roots, i.e. the images for a given model. The critical curve equations can also be reduced to a non-linear or polynomial form, and therefore it is useful to find the caustics. This lens model family has ample use in gravitational lens...

Source: http://arxiv.org/abs/0806.1086v1

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Sep 20, 2013
09/13

by
Francisco Frutos-Alfaro

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Gravitational lenses are presently playing an important role in astrophysics. By means of these lenses the parameters of the deflector such as its mass, ellipticity, etc. and Hubble's constant can be determined. Using C, Xforms, Mesa and Imlib a computer program to visualize this lens effect has been developed. This program has been applied to generate sequences of images of a source object and its corresponding images. It has also been used to visually test different models of gravitational...

Source: http://arxiv.org/abs/astro-ph/0204513v1

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Jun 28, 2018
06/18

by
Francisco Frutos-Alfaro

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A new approximate metric representing the spacetime of a rotating deformed body is obtained by perturbing the Kerr metric to include til the second order of the quadrupole moment. It has a simple form, because is Kerr-like. Its Taylor expansion form coincides with second order quadrupole metrics with slow rotation already found. Moreover, it can be transformed to an improved Hartle-Thorne metric, this guarantees its validity to be useful in studying compact object, and that it is possible to...

Topic: General Relativity and Quantum Cosmology

Source: http://arxiv.org/abs/1509.03698

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2.0

Jun 30, 2018
06/18

by
Francisco Frutos-Alfaro

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A new Kerr-like metric with quadrupole moment is obtained by means of perturbing the Kerr spacetime. By comparison with the exterior Hartle-Thorne metric, it is showed that it could be matched to an interior solution. This metric may represent the spacetime of an astrophysical object.

Topics: Astrophysics, General Relativity and Quantum Cosmology, Cosmology and Nongalactic Astrophysics

Source: http://arxiv.org/abs/1401.0866

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8.0

Jun 25, 2018
06/18

by
Rodrigo Carboni; Francisco Frutos-Alfaro

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Computer simulations of plasmas are relevant nowadays, because it helps us understand physical processes taking place in the sun and other stellar objects. We developed a program called PCell which is intended for displaying the evolution of the magnetic field in a 2D convective plasma cell with perfect conducting walls for different stationary plasma velocity fields. Applications of this program are presented. This software works interactively with the mouse and the users can create their own...

Topics: Solar and Stellar Astrophysics, Astrophysics

Source: http://arxiv.org/abs/1501.00598

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2.0

Jun 29, 2018
06/18

by
Francisco Frutos-Alfaro; Michael Soffel

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Among the known exact solutions of Einsteins vacuum field equations the Manko-Novikov and the Quevedo-Mashhoon metrics might be suitable ones for the description of the exterior gravitational field of some real non-collapsed body. By means of the Fodor-Hoenselaers-Perjes formalism we computed the lowest ten relativistic multipole moments of these metrics. Corresponding moments were derived for the static vacuum solutions of Gutsunayev-Manko and Hernandez-Martin. A direct comparison between the...

Topic: General Relativity and Quantum Cosmology

Source: http://arxiv.org/abs/1606.07173

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7.0

Jun 28, 2018
06/18

by
Francisco Frutos-Alfaro; Michael Soffel

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The Hartle-Thorne metric defines a reliable spacetime for most astrophysical purposes, for instance for the simulation of slowly rotating stars. Solving the Einstein field equations, we added terms of second order in the quadrupole moment to its post-linear version in order to compare it with solutions found by Blanchet in the frame of the multi-polar post-Minkowskian framework. We first derived the extended Hartle-Thorne metric in harmonic coordinates and then showed agreement with the...

Topic: General Relativity and Quantum Cosmology

Source: http://arxiv.org/abs/1507.04264

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3.0

Jun 29, 2018
06/18

by
Francisco Frutos-Alfaro; Paulo Montero-Camacho

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The Kerr metric is known to present issues when trying to find an interior solution. In this work we continue in our efforts to construct a more realistic exterior metric for astrophysical objects. A new approximate metric representing the spacetime of a charged, rotating and slightly-deformed body is obtained by perturbing the Kerr-Newman metric to include the mass-quadrupole and quadrupole-quadrupole orders. It has a simple form, because is Kerr-Newman-like. Its post-linear form without...

Topic: General Relativity and Quantum Cosmology

Source: http://arxiv.org/abs/1609.00102

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8.0

Jun 26, 2018
06/18

by
Francisco Frutos-Alfaro; Rodrigo Carboni-Mendez

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A program to generate codes in Fortran and C of the full Magnetohydrodynamic equations is shown. The program used the free computer algebra system software REDUCE. This software has a package called EXCALC, which is an exterior calculus program. The advantage of this program is that it can be modified to include another complex metric or spacetime. The output of this program is modified by means of a LINUX script which creates a new REDUCE program to manipulate the MHD equations to obtain a...

Topics: Instrumentation and Methods for Astrophysics, Astrophysics, Solar and Stellar Astrophysics

Source: http://arxiv.org/abs/1502.06666

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3.0

Jun 30, 2018
06/18

by
Francisco Frutos-Alfaro; Hernando Quevedo; Pedro Sánchez

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We investigate the properties of static and axisymmetric vacuum solutions of Einstein equations which generalize the Schwarzschild spherically symmetric solution to include a quadrupole parameter. We test all the solutions with respect to elementary and asymptotic flatness and curvature regularity. Analyzing their multipole structure, according to the relativistic invariant Geroch definition, we show that all of them are equivalent up to the level of the quadrupole. We conclude that the...

Topic: General Relativity and Quantum Cosmology

Source: http://arxiv.org/abs/1704.06734

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2.0

Jun 30, 2018
06/18

by
Paulo Montero-Camacho; Francisco Frutos-Alfaro; Carlos Gutierrez-Chaves

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A new rotation version of the Curzon-Chazy metric is found. This new metric was obtained by means of a perturbation method, in order to include slow rotation. The solution is then proved to fulfill the Einstein field equations using a REDUCE program. Furthermore, the applications of this new solution are discussed.

Topics: Astrophysics, General Relativity and Quantum Cosmology, Cosmology and Nongalactic Astrophysics

Source: http://arxiv.org/abs/1405.2899

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2.0

Jun 30, 2018
06/18

by
Carlos Gutierrez-Chavez; Francisco Frutos-Alfaro; Ivan Cordero-Garcia

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A REDUCE code for the Newman-Janis algorithm is described. This algorithm is intended to include rotation into nonrotating solutions of the Einstein field equations with spherically symmetry or perturbed spherically symmetry and has been successfully applied to many spacetimes. The applicability of the code is restricted to metrics containing potentials of the form 1/r.

Topics: Astrophysics, General Relativity and Quantum Cosmology, Cosmology and Nongalactic Astrophysics

Source: http://arxiv.org/abs/1405.3008

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3.0

Jun 30, 2018
06/18

by
Francisco Frutos-Alfaro; Frank Grave; Thomas Mueller; Daria Adis

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We investigate the light propagation by means of simulations of wavefronts and light cones for Kerr spacetimes. Simulations of this kind give us a new insight to better understand the light propagation in presence of massive rotating black holes. A relevant result is that wavefronts are back scattered with winding around the black hole. To generate these visualizations, an interactive computer program with a graphical user interface, called JWFront, was written in Java.

Topic: General Relativity and Quantum Cosmology

Source: http://arxiv.org/abs/1412.8068

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Sep 18, 2013
09/13

by
Francisco Frutos-Alfaro; Edwin Retana-Montenegro; Iván Cordero-García; Javier Bonatti González

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A metric representing a slowly rotating object with quadrupole moment is obtained using a perturbation method to include rotation into the weak limit of the Erez-Rosen metric. This metric is intended to tackle relativistic astrometry and gravitational lensing problems in which a quadrupole moment has to be taken into account.

Source: http://arxiv.org/abs/1209.6126v2

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2.0

Jun 30, 2018
06/18

by
Francisco Frutos-Alfaro; Paulo Montero-Camacho; Miguel Araya-Arguedas; Javier Bonatti-Gonzalez

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A new Kerr-like metric with quadrupole moment is obtained by means of perturbing the Kerr spacetime. The form of this new metric is simple as the Kerr metric. By comparison with the exterior Hartle-Thorne metric, it is shown that it could be matched to an interior solution. This approximate metric may represent the spacetime of a real astrophysical object with any Kerr rotation parameter a and slightly deformed.

Topics: Astrophysics, General Relativity and Quantum Cosmology, Cosmology and Nongalactic Astrophysics

Source: http://arxiv.org/abs/1405.1776

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3.0

Jun 27, 2018
06/18

by
Guillermo Andree Oliva-Mercado; Javier Bonatti-González; Iván Cordero-García; Francisco Frutos-Alfaro

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In this work we simulate null geodesics for the Bonnor massive dipole metric by implementing a symbolic-numerical algorithm in Sage and Python. This program is also capable of visualizing in 3D, in principle, the geodesics for any given metric. Geodesics are launched from a common point, collectively forming a cone of light beams, simulating a solid-angle section of a point source in front of a massive object with a magnetic field. Parallel light beams also were considered, and their bending...

Topics: Differential Geometry, General Relativity and Quantum Cosmology, Mathematics

Source: http://arxiv.org/abs/1504.04844