Slowly rotating Kerr black hole as a solution of Einstein-Cartan gravity extended by a Chern-Simons term

We consider the nondynamical Chern-Simons (CS) modification to General Relativity (GR) in the framework of the Einstein-Cartan formulation, as providing a way to incorporate a slowly rotating Kerr black hole in the space of solutions. Our proposal lies on considering the CS term as a source of torsion and on an iterative procedure to look for vacuum solutions of the system, by expanding the tetrad, the connection and the embedding parameter, in powers of a dimensionless small parameter $\beta$ which codifies the CS coupling. Starting from a torsionless zeroth-order vacuum solution we derive the second-order differential equation for the $\mathcal{O}(\beta)$ corrections to the metric, for an arbitrary embedding parameter. Furthermore we can show that the slowly rotating Kerr metric is an $\mathcal{O}(\beta)$ solution of the system either in the canonical or the axial embeddings.Comment: "Presented at the Fifth Meeting on CPT and Lorentz Symmetry, Bloomington, Indiana, June 28-July 2, 2010

Lorentz-violating photons with a mass term

Perturbative calculations in quantum field theory often require the regularization of infrared divergences. In quantum electrodynamics, such a regularization can for example be accomplished by a photon mass introduced via the Stueckelberg method. The present work extends this method to the QED limit of the Lorentz- and CPT-violating Standard-Model Extension.Comment: 4 pages, presented at the Sixth Meeting on CPT and Lorentz Symmetry, Bloomington, Indiana, June 17-21, 201

Electro and magneto statics of topological insulators as modeled by planar, spherical and cylindrical θ\theta boundaries: Green function approach

The Green function (GF) method is used to analyze the boundary effects produced by a Chern Simons (CS) extension to electrodynamics. We consider the electromagnetic field coupled to a $\theta$ term that is piecewise constant in different regions of space, separated by a common interface $\Sigma$, the $\theta$ boundary, model which we will refer to as $\theta$ electrodynamics ($\theta$ ED). This model provides a correct low energy effective action for describing topological insulators (TI). In this work we construct the static GF in $\theta$ ED for different geometrical configurations of the $\theta$ boundary, namely: planar, spherical and cylindrical $\theta$ interfaces. Also we adapt the standard Green theorem to include the effects of the $\theta$ boundary. These are the most important results of our work, since they allow to obtain the corresponding static electric and magnetic fields for arbitrary sources and arbitrary boundary conditions in the given geometries. Also, the method provides a well defined starting point for either analytical or numerical approximations in the cases where the exact analytical calculations are not possible. Explicit solutions for simple cases in each of the aforementioned geometries for $\theta$ boundaries are provided. The adapted Green theorem is illustrated by studying the problem of a point like electric charge interacting with a planar TI with prescribed boundary conditions. Our generalization, when particularized to specific cases, is successfully compared with previously reported results, most of which have been obtained by using the methods of images.Comment: 24 pages, 4 figures, accepted for publication in PRD. arXiv admin note: text overlap with arXiv:1511.0117

Green's function approach to Chern-Simons extended electrodynamics: an effective theory describing topological insulators

Boundary effects produced by a Chern-Simons (CS) extension to electrodynamics are analyzed exploiting the Green's function (GF) method. We consider the electromagnetic field coupled to a $\theta$-term in a way that has been proposed to provide the correct low energy effective action for topological insulators (TI). We take the $\theta$-term to be piecewise constant in different regions of space separated by a common interface $\Sigma$, to be called the $\theta$-boundary. Features arising due to the presence of the boundary, such as magnetoelectric effects, are already known in CS extended electrodynamics and solutions for some experimental setups have been found with specific configuration of sources. In this work we illustrate a method to construct the GF that allows to solve the CS modified field equations for a given $\theta$-boundary with otherwise arbitrary configuration of sources. The method is illustrated by solving the case of a planar $\theta$-boundary but can also be applied for cylindrical and spherical geometries for which the $\theta$-boundary can be characterized by a surface where a given coordinate remains constant. The static fields of a point-like charge interacting with a planar TI, as described by a planar discontinuity in $\theta$, are calculated and successfully compared with previously reported results. We also compute the force between the charge and the $\theta$-boundary by two different methods, using the energy momentum tensor approach and the interaction energy calculated via the GF. The infinitely straight current-carrying wire is also analyzed

Acero alternativo resistente a la corrosión

Tesis (Ingeniero Constructor)La factibilidad en la utilización de aceros alternativos en ambientes agresivos respecto de los aceros ferríticos, desde un punto de vista económico, se respalda necesariamente con el aporte técnico recabado desde la ingeniería de producción y experimentación entregada por fabricantes, proveedores e investigadores entre otros. La metodología utilizada para este fin consiste en fusionar esta información precisa junto con los valores actuales de los aceros, asunto condicionado en forma directa por la creciente demanda internacional del producto afectando directamente en cualquier decisión de inversión relacionados con la materialidad de un proyecto influyendo así en el flujo relacionado a éste en el corto, mediano y largo plazo. Los avances tecnológicos en la investigación y producción de acero, han logrado hoy en día poder contar con una variada gama de productos tanto en aceros al carbono como en inoxidables pudiendo así entregar al mercado la posibilidad de utilizar el acero preciso respecto de su composición química (aleación), propiedades y valor en el mercado. Un análisis recabado respecto de los materiales a utilizar en un proyecto incide directamente en el costo directo de éste y darán necesariamente las directrices para determinar la viabilidad de ejecutarlo.The feasibility in using alternative steels in aggressive environments on ferritic steels, from an economic standpoint, are necessarily supported with technical input gathered from the production engineering and experimentation delivered by manufacturers, suppliers and researchers among others. The methodology used for this purpose is to merge this precise information along with the current values of steels, subject matter directly in the growing international demand for the product directly affecting in any investment decision related to the materiality of a project and influence in Linked to this f10w in the short, medium and long termo Technological advances in research and production of steel, have achieved today can count on a wide range of products both in carbon steels such as stainless market may well deliver to the possibility of using the steel needed on their chemical composition ( alloy), properties and market value. An analysis of materials collected with respect to use in a project has a direct impact on the direct cost of this will necessarily and guidelines to determine the feasibility of implementing it