The spin glass transition of the three dimensional Heisenberg spin glass

It is shown, by means of Monte Carlo simulation and Finite Size Scaling analysis, that the Heisenberg spin glass undergoes a finite-temperature phase transition in three dimensions. There is a single critical temperature, at which both a spin glass and a chiral glass orderings develop. The Monte Carlo algorithm, adapted from lattice gauge theory simulations, makes possible to thermalize lattices of size L=32, larger than in any previous spin glass simulation in three dimensions. High accuracy is reached thanks to the use of the Marenostrum supercomputer. The large range of system sizes studied allow us to consider scaling corrections.Comment: 4 pages, 4 Postscript figures, version to be published in Physical Review Letter

Paisajes mineros en la Asturias Central. Un análisis de la arquitectura industrial y su relación con el paisaje asturiano

Este trabajo tratará de documentar gráfica y teóricamente el estado actual de una parte del paisaje minero e industrial de Asturias, aportando una visión arquitectónica sobre estos espacios degradados. Para ello se analiza en profundidad el contexto histórico y natural en el que se han desarrollado estas actividades mineras con la intención de extraer los argumentos necesarios para evitar su estado abandono, e impulsar por parte del organismo público, su conservación, mantenimiento y puesta en valor. Se analizan algunos casos concretos situados en el Valle del Río Nalón creando un marco de análisis crítico que pueda servir de base para posibles intervenciones futuras.This work will try to graphically and theoretically document the current state of a part of the mining and industrial landscape of Asturias, providing an architectural vision of these degraded landscapes. For this, the historical and natural context in which these mining activities have been developed is analyzed in depth with the intention of extracting the necessary arguments to avoid their state of abandonment, and promote their conservation, maintenance and enhancement by the public body. . Some specific cases located in the Nalón River Valley are analyzed, creating a critical analysis framework that can serve as a basis for possible future interventions.Departamento de Teoría de la Arquitectura y Proyectos ArquitectónicosGrado en Fundamentos de la Arquitectur

Nuevos modos de habitar / nuevos modelos de convivencia

El barrio de las villas es un reducto del sistema productivo de Valladolid de los siglos xix y xx. La urbanización y el crecimiento demográfico han destruido esta capacidad ecosistémica, relegando el suelo a orillas del Pisuerga a un uso especulativo y corrosivo con el medio ambiente. Se propone recuperar su antigua actividad agrícola de manera que fomente y refuerce los valores de la nueva comunidad. Parece que el futuro tal y como nos lo imaginábamos, modo Blade runner, tiene fecha de caducidad. El futuro que se aproxima a nuestros días es algo más hedonista, buscando alcanzar el bienestar ambiental y el desarrollo ecosostenible. El proyecto aborda la dicotomía campo / ciudad y difumina los bordes en los límites de la periferia através de conexiones territoriales blandas y usos agrarios productivos integrados en el tejido urbano.Departamento de Teoría de la Arquitectura y Proyectos ArquitectónicosMáster en Arquitectur

Spin and chirality orderings of the one-dimensional Heisenberg spin glass with the long-range power-law interaction

The ordering of the one-dimensional Heisenberg spin glass interacting via the long-range power-law interaction is studied by Monte Carlo simulations. Particular attention is paid to the possible occurrence of the ``spin-chirality decoupling'' for appropriate values of the power-law exponent \sigma. Our result suggests that, for intermediate values of $\sigma$, the chiral-glass order occurs at finite temperatures while the standard spin-glass order occurs only at zero temperature.Comment: Proceedings of the Highly Frustrated Magnetism (HFM2006) conference. To appear in a special issue of J. Phys. Condens. Matte

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© 2007 American Physical Society.Depto. de Física TeóricaFac. de Ciencias FísicasTRUEpu

New opportunities in trace elements structural characterization: high-energy X-ray absorption near-edge structure spectroscopy

Garnets in lower crustal mafic and ultramafic rocks usually contain rare-earth elements (REE) in trace concentrations. Direct characterization of REE at trace levels in natural garnets is not available in the literature because of the difficulty of obtaining structural information by means of conventional diffraction methods. Here, the characterization of Nd at trace levels (176-1029 p.p.m.) in a set of natural garnets performed by means of Nd K-edge X-ray absorption near-edge structure spectroscopy is presented, showing the capability of high-energy XANES for REE in trace structural determinations

JANUS: an FPGA-based System for High Performance Scientific Computing

This paper describes JANUS, a modular massively parallel and reconfigurable FPGA-based computing system. Each JANUS module has a computational core and a host. The computational core is a 4x4 array of FPGA-based processing elements with nearest-neighbor data links. Processors are also directly connected to an I/O node attached to the JANUS host, a conventional PC. JANUS is tailored for, but not limited to, the requirements of a class of hard scientific applications characterized by regular code structure, unconventional data manipulation instructions and not too large data-base size. We discuss the architecture of this configurable machine, and focus on its use on Monte Carlo simulations of statistical mechanics. On this class of application JANUS achieves impressive performances: in some cases one JANUS processing element outperfoms high-end PCs by a factor ~ 1000. We also discuss the role of JANUS on other classes of scientific applications.Comment: 11 pages, 6 figures. Improved version, largely rewritten, submitted to Computing in Science & Engineerin

Simulating spin systems on IANUS, an FPGA-based computer

We describe the hardwired implementation of algorithms for Monte Carlo simulations of a large class of spin models. We have implemented these algorithms as VHDL codes and we have mapped them onto a dedicated processor based on a large FPGA device. The measured performance on one such processor is comparable to O(100) carefully programmed high-end PCs: it turns out to be even better for some selected spin models. We describe here codes that we are currently executing on the IANUS massively parallel FPGA-based system.Comment: 19 pages, 8 figures; submitted to Computer Physics Communication