Inhomogenous loop quantum cosmology with matter

The linearly polarized Gowdy $T^3$ model with a massless scalar field with the same symmetries as the metric is quantized by applying a hybrid approach. The homogeneous geometry degrees of freedom are loop quantized, fact which leads to the resolution of the cosmological singularity, while a Fock quantization is employed for both matter and gravitational inhomogeneities. Owing to the inclusion of the massless scalar field this system allows us to modelize flat Friedmann-Robertson-Walker cosmologies filled with inhomogeneities propagating in one direction. It provides a perfect scenario to study the quantum back-reaction between the inhomogeneities and the polymeric homogeneous and isotropic background.Comment: 4 pages, Contribution to the proceedings of the Loops 11-Madrid conferenc

Approximation methods in Loop Quantum Cosmology: From Gowdy cosmologies to inhomogeneous models in Friedmann-Robertson-Walker geometries

We develop approximation methods in the hybrid quantization of the Gowdy model with linear polarization and a massless scalar field, for the case of three-torus spatial topology. The loop quantization of the homogeneous gravitational sector of the Gowdy model (according to the improved dynamics prescription) and the presence of inhomogeneities lead to a very complicated Hamiltonian constraint. Therefore, the extraction of physical results calls for the introduction of well justified approximations. We first show how to approximate the homogeneous part of the Hamiltonian constraint, corresponding to Bianchi I geometries, as if it described a Friedmann-Robertson-Walker (FRW) model corrected with anisotropies. This approximation is valid in the high-energy sector of the FRW geometry (concerning its contribution to the constraint) and for anisotropy profiles that are sufficiently smooth. In addition, for certain families of states associated to regimes of physical interest, with negligible effects of the anisotropies and small inhomogeneities, one can approximate the Hamiltonian constraint of the inhomogeneous system by that of an FRW geometry with a relatively simple matter content, and then obtain its solutions.Comment: 20 pages, 3 figures. Minor changes, matches published versio

Inclusion of matter in inhomogeneous loop quantum cosmology

We study the hybrid quantization of the linearly polarized Gowdy $T^3$ model with a massless scalar field with the same symmetries as the metric. For simplicity, we quantize its restriction to the model with local rotational symmetry. Using this hybrid approach, the homogeneous degrees of freedom of the geometry are quantized \`a la loop, leading to the resolution of the cosmological singularity. A Fock quantization is employed both for the matter and the gravitational inhomogeneities. Owing to the inclusion of the massless scalar field this system allows us to modelize flat Friedmann-Robertson-Walker cosmologies filled with inhomogeneities propagating in one direction, providing a perfect scenario to study the quantum back-reaction of the inhomogeneities on the polymeric homogeneous and isotropic background.Comment: 4 pages. Contribution to the Proceedings of Spanish Relativity Meeting ERE2011, Madrid 201

Vacuum ultraviolet photolysis of hydrogenated amorphous carbons. III. Diffusion of photo-produced H2 as a function of temperature

Hydrogenated amorphous carbon (a-C:H) has been proposed as one of the carbonaceous solids detected in the interstellar medium. Energetic processing of the a-C:H particles leads to the dissociation of the C-H bonds and the formation of hydrogen molecules and small hydrocarbons. Photo-produced H2 molecules in the bulk of the dust particles can diffuse out to the gas phase and contribute to the total H2 abundance. We have simulated this process in the laboratory with plasma-produced a-C:H and a-C:D analogs under astrophysically relevant conditions to investigate the dependence of the diffusion as a function of temperature. Plasma-produced a-C:H analogs were UV-irradiated using a microwave-discharged hydrogen flow lamp. Molecules diffusing to the gas-phase were detected by a quadrupole mass spectrometer, providing a measurement of the outgoing H2 or D2 flux. By comparing the experimental measurements with the expected flux from a one-dimensional diffusion model, a diffusion coefficient D could be derived for experiments carried out at different temperatures. Dependance on the diffusion coefficient D with the temperature followed an Arrhenius-type equation. The activation energy for the diffusion process was estimated (ED(H2)=1660+-110 K, ED(D2)=2090+-90 K), as well as the pre-exponential factor (D0(H2)=0.0007+0.0013-0.0004 cm2 s-1, D0(D2)=0.0045+0.005-0.0023 cm2 s-1) The strong decrease of the diffusion coefficient at low dust particle temperatures exponentially increases the diffusion times in astrophysical environments. Therefore, transient dust heating by cosmic rays needs to be invoked for the release of the photo- produced H2 molecules in cold PDR regions, where destruction of the aliphatic component in hydrogenated amorphous carbons most probably takes place

Las reglas explícitas y otros señuelos políticos

Sin resume

El feminismo contemporáneo: entre liberalismo e Ilustración

Sin resume

La puerta a la razón : de lo ideal a lo práctico en la propuesta

Este libro habla de una metodología, una manera de afrontar un proyecto de arquitectura desde un plano más filosófico o retórico. Siendo capaz de evadir la solución evidente para profundizar en la esencia del proyecto, y encaminarse hacia nuevas soluciones que hagan evolucionar los lugares donde vivimos. Para ello se plantean dos escenarios distintos, con los que se llegan a dos soluciones muy distintas entre si. Y finalmente veremos cómo ser capaz de extraer lo mejor de cada una de ellas para llegar a una solución final, o solución práctica

Espacio público e Islam transnacional: A propósito de la Jama’at at-Tabligh en Barcelona

Este artículo analiza el desequilibrio entre la escasa atención científica prestada al Tabligh y su notable influencia entre musulmanes en España. Una particular tradición de conocimiento sobre el Islam lo ha definido como opuesto a la emergencia del espacio público. Atrapados en la discusión sobre las contradicciones de la dicotomía religioso/secular, el Tabligh invita a pensar más allá de los términos que conforman ese irresoluble debate. Pero será necesario poner en suspenso metodologías etnográficas precedentes y contar con nuevos motivos de observación y discusión: la relación entre sujeto y objeto de la práctica religiosa y la dimensión transnacional del IslamThis paper focuses on the imbalance between the limited scientific attention paid to the Tablighi Jamaat and its broad influence among Muslims in Spain. A particular tradition of knowledge about Islam defines it as opposed to the emergence of public sphere. Caught in the discussion on the contradictions of the religious/secular dichotomy, the Tablighis invite to think beyond the terms that shape this unsolvable debate. But it will be necessary to rethink certain ethnographic methodologies and develop new conceptions about the relationship between subject and object of the religious practice and the transnational dimension of Isla

Pràctica religiosa i pràctica etnogràfica: la Ŷama'at at-Tabligh ad-Da'wa' i el Raval

El treball de camp a què es remet aquest text proposa l'observació i anàlisi de la pràctica religiosa i les representacions de la Ŷama'at at-Tabligh ad-Da'wa' a la ciutat de Barcelona partint de dos recorreguts paral·lels: d'una banda, la reconstrucció històrica de les trajectòries del moviment des del seu moment fundacional fins a la seva arribada a Barcelona a principis dels anys vuitanta, fins a consolidar-se aquí a dia d'avui; de l'altra, una reconstrucció tant de la història com de l'evolució urbanística de l'espai en què se situen la investigació i gran part dels espais associatius i d'oració, dels actors socials i de les accions que en configuren la pràctica religiosa, és a dir, el Raval i en particular l'«Illa Robadors». A partir d'aquí es proposa l'anàlisi de com els mateixos membres de la Ŷama'at at-Tabligh construeixen els marcs i espais d'interacció i presentació del Tabligh mitjançant la seva praxi religiosa comunitària i, a més, l'article convida a pensar com, arran de determinades lectures d'aquestes pràctiques i dels espais urbans concrets on es porten a terme, se'n deriven altres representacions del moviment i dels participants dels seus moments i marcs d'interacció. Així, el text tracta d'analitzar les condicions i els termes en què la investigació d'un fenomen religiós com aquest pot produir-se de manera situada.The fieldwork described in the article involves the observation and analysis of the religious practice and the representations of the Tablighi Jamaat in the city of Barcelona based on two parallel historical paths. Firstly, a historical reconstruction of the movement’s development, from its founding to its arrival and implantation in Barcelona, at the beginning of 1980s. And secondly, a reconstruction of both the history and urban evolution of the area where the research is carried out, namely the Raval neighbourhood, in particular the area around Carrer Robadors. This is where the majority of prayer and meeting places are located and where the social agents and actions of this religious practice come together. Subsequently we analyse how members of the movement build frameworks and spaces for interaction and we study the introduction of the Tabligh through the practice of the religious community. Moreover, the article invites readers to consider, through certain readings of such practices and of specific urban spaces where they are performed, how other representations of the movement, of the participants of the events and of the interaction spaces are derived. Thus the article attempts to analyse the terms and conditions in which research into a religious phenomenon such as this can occur in a specific location