Primordial SdS universe from a 5D vacuum: scalar field fluctuations on Schwarzschild and Hubble horizons

We study scalar field fluctuations of the inflaton field in an early inflationary universe on an effective 4D Schwarzschild-de Sitter (SdS) metric, which is obtained after make a planar coordinate transformation on a 5D Ricci-flat Schwarzschild-de Sitter (SdS) static metric. We obtain the important result that the spectrum of fluctuations at zeroth order is independent of the scalar field mass $M$ on Schwarzschild scales, while on cosmological scales it exhibits a mass dependence. However, in the first-order expansion, the spectrum depends of the inflaton mass and the amplitude is linear with the Black-Hole (BH) mass $m$.Comment: Final version to be published in JCA

The primordial explosion of a false white hole from a 5D vacuum

We explore the cosmological consequences of some possible big bang produced by a black-hole with mass $M$ in an 5D extended SdS. Under these particular circumstances, the effective 4D metric obtained by the use of a constant foliation on the extra coordinate is comported as a false white-hole (FWH), which evaporates for all unstable modes that have wavelengths bigger than the size of the FWH. Outside the white hole the repulsive gravitational field can be considered as weak, so that the dynamics for fluctuations of the inflaton field and the scalar perturbations of the metric can be linearized.Comment: Final version to be published in PLB. arXiv admin note: substantial text overlap with arXiv:1304.698

Gravitational waves from a Weyl-Integrable manifold: a new formalism

We study the variational principle over an Hilbert-Einstein like action for an extended geometry taking into account torsion and non-metricity. By extending the semi-Riemannian geometry, we obtain an effective energy-momentum tensor which can be interpreted as physical sources. As an application we develop a new manner to obtain the gravitational wave equations on a Weyl-integrable manifold taking into account the non-metricity and non-trivial boundary conditions on the minimization of the action, which can be identified as possible sources for the cosmological constant and provides two different equations for gravitational waves. We examine gravitational waves in a pre-inflationary cosmological model.Comment: Accepted in Physics of the Dark Univers

School Literary Canon and Teaching of Literature in Middle School: A Critical Analysis of High School Programs in El Salvador

Recibido 20 de marzo de 2013 • Corregido 14 de junio de 2013 • Aceptado 19 de junio de 2013 Este artículo analiza el modelo didáctico-pedagógico para la enseñanza de la literatura en la educación media salvadoreña. Es parte de un trabajo más amplio de tesis doctoral. El objetivo es caracterizar el proceso histórico de conformación de dicho modelo mediante un análisis crítico de las fuentes de canonización. Los hallazgos sugieren que la enseñanza de la literatura se realiza con base en un enfoque historicista, europeizante y masculino; entre las consecuencias de este tipo de enseñanza se encuentran la progresiva invisibilización de la mujer escritora y el estatus marginal que ocupa la literatura salvadoreña, pese al discurso reformista que postula la equidad de género y el fortalecimiento de la identidad nacional como políticas centrales del actual proyecto educativo. Doctor en Educación de la Universidad de Costa Rica. Máster en Derechos Humanos y Educación para la Paz. Licenciado en Letras. Investigador del Consejo de Investigaciones Científicas de la Universidad de El Salvador (CIC-UES). Actualmente labora como profesor de la Universidad de El Salvador, sede Facultad Multidisciplinaria de Occidente, Departamento de Santa Ana, en donde es catedrático de Teoría Literaria y Literatura Salvadoreña. Autor del Libro Las Huellas del delirio. Novela salvadoreña de posguerra.This article analyzes the pedagogical-didactic model for the teaching of Literature in Middle School in the Salvadoran Educational system. This is part of a larger work towards a PhD project. The main goal of this project is to characterize the historical process in the construction of this model through a critical analysis of canonization sources. The findings suggest that the teaching of Literature is performed based on a historicist, pro-European, male-based approach. Among the consequences of this type of education are progressive invisibility of women writers and the marginal status of the Salvadoran literature, despite the reformist discourse that postulates gender equality and strengthening of the national identity as central policies in the current educational project

An investigation on thermal performance characteristics of hollow-core vacuum insulated panels

As concerns over climate change stimulate legislation for performance improvement in the building industry, in an effort to mitigate embodied and operational carbon footprint, high performance insulating solutions are gaining attention and invite further research in this area. Hollow-core VIPs are an alternative vacuum insulating technology that can provide thin insulating cladding solutions while avoiding some vulnerabilities of high performance insulating materials such as fumed silica VIPs.This thesis aims to develop and evaluate the performance of a conceptual prototype of hollow-core VIPs. Initial simulations of a simplied model were used to evaluate desirable values for main parameters such as emissivity and panel thickness. Desirable panel thickness lies between 20 and 50mm to eliminate convection at a pressure of 0.01 Pa and emissivity lower than 0.1 is necessary to stifle radiation. A more detailed model representing a node within a full size VIP was developed and tested in a vacuum chamber and compared to transient simulations to study its thermal performance. Nodes with three structural array congurations were manufactured from stainless steel, PTFE and epoxy resin to analyse performance in different panel thicknesses (25 and 50mm) and with different internal surface emissivity

Present accelerated expansion of the universe from new Weyl-Integrable gravity approach

We investigate if a recently introduced formulation of general relativity on a Weyl-integrable geometry, contains cosmological solutions exhibiting acceleration in the present cosmic expansion. We derive the general conditions to have acceleration in the expansion of the universe and obtain a particular solution for the Weyl scalar field describing a cosmological model for the present time in concordance with the data combination Planck + WP + BAO + SN.Comment: Version to be published in Eur. Phys. J.