Generating Static Black Holes in Higher Dimensional Space-Times

In this article we extend to higher dimensional space-times a recent theorem proved by Salgado which characterizes a three-parameter family of static and spherically symmetric solutions to the Einstein Field Equations. As it happens in four dimensions, it is shown that the Schwarzschild, Reissner-Nordstrom and global monopole solutions in higher dimensions are particular cases from this family.Comment: LaTeX. 9 page

Two-dimensional Riemannian and Lorentzian geometries from second order ODEs

In this note we give an alternative geometrical derivation of the results recently presented by Garcia-Godinez, Newman and Silva-Ortigoza in [1] on the class of all two-dimensional riemannian and lorentzian metrics from 2nd order ODEs which are in duality with the two dimensional Hamilton-Jacobi equation. We show that, as it happens in the Null Surface Formulation of General Relativity, the Wuschmann-like condition can be obtained as a requirement of a vanishing torsion tensor. Furthermore, from these second order ODEs we obtain the associated Cartan connections.Comment: 9 pages, final version to appear in J. Math. Phy

Explicit expressions for optical scalars in gravitational lensing from general matter sources

We present explicit expressions for the optical scalars and the deection angle in terms of the energymomentum tensor components of matter distributions. Our work generalizes standard references in the literature where normally stringent assumptions are made on the sources.Comment: Talk presented at the Conference I COSMOSUL (2011) (COSMOLOGY AND GRAVITATION IN THE SOUTHERN CONE

Photon spheres in Einstein and Einstein-Gauss-Bonnet theories and circular null geodesics in axially-symmetric spacetimes

In this article we extend a recent theorem proven by Hod (Phys. Lett. B, {\bf 727}, 345--348, 2013) to $n$-dimensional Einstein and Einstein-Gauss-Bonnet theories, which gives an upper bound for the photon sphere radii of spherically symmetric black holes. As applications of these results we give a universal upper bound for the real part of quasinormal modes in the WKB limit and a universal lower bound for the position of the first relativistic image in the strong lensing regime produced by these type of black holes. For the axially-symmetric case, we also make some general comments (independent of the underlying gravitational theory) on the relation between circular null geodesics and the fastest way to circle a black hole.Comment: In this post-publisher version two typos were corrected: the signature of the metric in eq.(1) and a factor in eq.(102). We thanks Gary Gibbons and Chris Pope for bringing to our attention these typo

A Jacobian elliptic single-field inflation

In the scenario of single-field inflation, this field is done in terms of Jacobian elliptic functions. This approach provides, when constrained to particular cases, analytic solutions already known in the past, generalizing them to a bigger family of analytical solutions. The emergent cosmology is analysed using the Hamilton-Jacobi approach and then, the main results are contrasted with the recent measurements obtained from the Planck 2015 data.Comment: 7 pages, 5 figure

Higher dimensional conformal metrics from PDEs and Null Surface Formulation of GR

We analyze the relationship between $n$-dimensional conformal metrics and a certain class of partial differential equations (PDEs) that are in duality with the eikonal equation. In particular, we extend the Null Surface Formulation of General Relativity to higher dimensions and give explicit expressions for the components of the metric and the generalized W\"{u}nschmann-like metricity conditions. We also compute the equation that the conformal factor must satisfy in order the metric be a solution of the Einstein equations.Comment: 20 pages. Some clarifications and a new appendix added. To be published in Class. Quantum Gra

Cartan Normal Conformal Connections from Pairs of 2nd Order PDE's

We explore the different geometric structures that can be constructed from the class of pairs of 2nd order PDE's that satisfy the condition of a vanishing generalized W\"{u}nschmann invariant. This condition arises naturally from the requirement of a vanishing torsion tensor. In particular, we find that from this class of PDE's we can obtain all four-dimensional conformal Lorentzian metrics as well as all Cartan normal conformal O(4,2) connections. To conclude, we briefly discuss how the conformal Einstein equations can be imposed by further restricting our class of PDE's to those satisfying additional differential conditions.Comment: 39 page

El campo de la economía social y solidaria en Río Negro y Mendoza : políticas públicas y espacio en la construcción de alternativas socio-económicas al capital

El análisis de experiencias concretas en economía social y solidaria (ESS) puede realizarse desde diversas escalas espaciales. El nivel meso puede ser una posibilidad y tiene la particularidad de trascender los análisis sobre el funcionamiento de cada organización de la ESS propios de la microescala, buscando identificar asociaciones, vínculos e impactos sobre un determinado territorio. Además, en esta escala se agrega el ingrediente que aporta el Estado a través de sus diversas políticas públicas, que afectan ese espacio y por ende, las actividades de la ESS que allí se desarrollen. Tomando como sinónimo de análisis mesoescalar el estudio a nivel provincial de la temática, en el presente trabajo se intentará dar cuenta, de manera breve, de la conformación del campo de la ESS en Río Negro y Mendoza. Posteriormente, se identificará las políticas públicas para el sector en ambas provincias, haciendo hincapié en las leyes provinciales específicas en la temática y su enfoque territorial. Finalmente, se expondrán a modo de comparación entre ambas provincias, las similitudes y divergencias encontradas tanto en la conformación del sector de la ESS como en el espacio que se busca construir desde las políticas públicas.Fil: Gallo, Mahuén . Universidad Nacional de Quilmes.Fil: Jurado, Emanuel. Universidad de Buenos Aires

Slowly rotating Kerr metric derived from the Einstein equations in affine-null coordinates

Using a quasi-spherical approximation of an affine-null metric adapted to an asymptotic Bondi inertial frame, we present high order approximations of the metric functions in terms of the specific angular momentum for a slowly rotating stationary and axi-symmetric vacuum spacetime. The metric is obtained by following the procedure of integrating the hierarchy of Einstein equations in a characteristic formulation utilizing master functions for the perturbations. It is further verified its equivalence with the Kerr metric in the slowly rotation approximation by carrying out an explicit transformation between the Boyer-Lindquist coordinates to the employed affine-null coordinates