Factorization and Criticality in Finite XXZ Systems of Arbitrary Spin

We analyze ground state (GS) factorization in general arrays of spins si with XXZ couplings immersed in nonuniform fields. It is shown that an exceptionally degenerate set of completely separable symmetry-breaking GSs can arise for a wide range of field configurations, at a quantum critical point where all GS magnetization plateaus merge. Such configurations include alternating fields as well as zero-bulk field solutions with edge fields only and intermediate solutions with zero field at specific sites, valid for d-dimensional arrays. The definite magnetization-projected GSs at factorization can be analytically determined and depend only on the exchange anisotropies, exhibiting critical entanglement properties. We also show that some factorization-compatible field configurations may result in field-induced frustration and nontrivial behavior at strong fields.Fil: Cerezo, M. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; ArgentinaFil: Rossignoli, Raúl Dante. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; Argentina. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas; ArgentinaFil: Canosa, Norma Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; ArgentinaFil: Ríos, E.. Universidad Tecnológica Nacional; Argentin

Intrinsic point defects and volume swelling in ZrSiO4 under irradiation

The effects of high concentration of point defects in crystalline ZrSiO4 as originated by exposure to radiation, have been simulated using first principles density functional calculations. Structural relaxation and vibrational studies were performed for a catalogue of intrinsic point defects, with different charge states and concentrations. The experimental evidence of a large anisotropic volume swelling in natural and artificially irradiated samples is used to select the subset of defects that give similar lattice swelling for the concentrations studied, namely interstitials of O and Si, and the anti-site Zr(Si), Calculated vibrational spectra for the interstitials show additional evidence for the presence of high concentrations of some of these defects in irradiated zircon.Comment: 9 pages, 7 (color) figure

Continuum variational and diffusion quantum Monte Carlo calculations

This topical review describes the methodology of continuum variational and diffusion quantum Monte Carlo calculations. These stochastic methods are based on many-body wave functions and are capable of achieving very high accuracy. The algorithms are intrinsically parallel and well-suited to petascale computers, and the computational cost scales as a polynomial of the number of particles. A guide to the systems and topics which have been investigated using these methods is given. The bulk of the article is devoted to an overview of the basic quantum Monte Carlo methods, the forms and optimisation of wave functions, performing calculations within periodic boundary conditions, using pseudopotentials, excited-state calculations, sources of calculational inaccuracy, and calculating energy differences and forces

Usability Heuristics for Domain-Specific Languages (DSLs)

[Abstract] The usability of Domain-Specific Languages (DSLs) has been attracting considerable interest from researchers lately. In particular, our literature review found many usability studies that make use of subjective and empirical methods. However, we noted a lack of heuristic methods in the literature. In comparison, there exist several usability studies of Application Programming Interfaces (APIs) that have used heuristics with success, so we argue that this approach would be also useful for DSLs. Therefore, this paper proposes a set of usability heuristics for DSLs and illustrates the approach with a case study. We show how our heuristics helped us identify many actual usability problems, even for a simple DSL.Xunta de Galicia; GRC2014/035Xunta de Galicia; ED431G/0

Efficient excitation of cavity resonances of subwavelength metallic gratings

One dimensional rectangular metallic gratings enable enhanced transmission of light for specific resonance frequencies. Two kinds of modes participating to enhanced transmission have already been demonstrated : (i) waveguide modes and (ii) surface plasmon polaritons (SPP). Since the original paper of Hessel and Oliner \cite{hessel} pointing out the existence of (i), no progress was made in their understanding. We present here a carefull analysis, and show that the coupling between the light and such resonances can be tremendously improved using an {\it evanescent} wave. This leads to enhanced localisation of light in cavities, yielding, in particular, to a very selective light transmission through these gratings.Comment: 4 pages, 5 figures, submitted to Phys. Rev. Let

Interfaz gráfica como una herramienta en la simulación de propiedades de manganitas Re2/3A1/3MnO3 empleando el método de Monte Carlo y el modelo de Heisenberg

Las interfaces gráficas son útiles para especificar y examinar estructuras químicasy propiedades físicas de materiales. En este artículo se presenta el software SIMMON (Simulación de propiedades magnéticas de manganitas) como un programa de visualización cuyo objetivo es mostrar la magnetización, la susceptibilidad magnética, la energía, el calor específico, los ciclos de histéresis y la resistividad de materiales magnéticos. Estas propiedades pueden ser obtenidas a partir de la simulación de diferentes manganitas del tipo Re2/3A1/3MnO3, donde Re son iones de una tierra rarametálica como La, Nd y Pr con valencia 3+, los cuales se enlazan con iones Mn3+–3d4 y A es una tierra alcalina con valencia 2+ tal como Ba, Ca, Sr, entre otras, enlazadas con Mn4+–3d3. En estas simulaciones se emplea el método Monte Carlo combinado con el algoritmo de Metrópolis y el modelo de Heinsenberg

La ciència de la pintura, la pintura de la ciència

La ciència de la pintura, la pintura de la ciènci

An update to the surface ocean CO2 atlas (SOCAT version 2)

22 páginas, 9 figuras, 10 tablas.-- D. C. E. Bakker ... et al.-- This work is distributed under the Creative Commons Attribution 3.0 License.-- Proyecto CarbochangeThe Surface Ocean CO2 Atlas (SOCAT), an activity of the international marine carbon research community, provides access to synthesis and gridded fCO2 (fugacity of carbon dioxide) products for the surface oceans. Version 2 of SOCAT is an update of the previous release (version 1) with more data (increased from 6.3 million to 10.1 million surface water fCO2 values) and extended data coverage (from 1968–2007 to 1968–2011). The quality control criteria, while identical in both versions, have been applied more strictly in version 2 than in version 1. The SOCAT website (http://www.socat.info/) has links to quality control comments, metadata, individual data set files, and synthesis and gridded data products. Interactive online tools allow visitors to explore the richness of the data. Applications of SOCAT include process studies, quantification of the ocean carbon sink and its spatial, seasonal, year-to-year and longerterm variation, as well as initialisation or validation of ocean carbon models and coupled climate-carbon modelsSupport for SOCAT has been received from the University of East Anglia (UK), the Bjerknes Centre for Climate Research, the Geophysical Institute at the University of Bergen (Norway), the Climate Observation Division of the Climate Program Office of the US National Oceanic and Atmospheric Administration, the University of Washington, Oak Ridge National Laboratory (USA), PANGAEA ® Data Publisher for Earth and Environmental Data (Germany), the Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research (Germany), the National Institute for Environmental Studies (Japan), the Korean Institute of Ocean Science and Technology, the European Union projects CarboChange (FP7 264879) and GEO- CARBON (FP7 283080), the UK Ocean Acidification Research Programme (NE/H017046/1; funded by the Natural Environment Research Council, the Department for Energy and Climate Change and the Department for Environment, Food and Rural Affairs), the Research Council of Norway (CARBON-HEAT), the Scientific Committee on Oceanic Research (SCOR, US, OCE-0938349), the US National Science Foundation (OCE-1068958), Swedish Research Council projects (2009–2994; 2008–6228; 2009–2994) and the Swedish National Space Board (RESCUE project; REmote Sensing ocean Carbon UptakE).Peer reviewe

Building a business case for corporate fleets to adopt vehicle-to-grid technology (V2G) and participate in the regulation service market

Thesis (M. Eng. in Logistics)--Massachusetts Institute of Technology, Engineering Systems Division, 2011.Cataloged from PDF version of thesis.Includes bibliographical references (p. 95-98).Electric (EV) and Plug-in Hybrid Electric vehicles (PHEV) continue to gain attention and market share, not only as options for consumers but also for corporate fleets. EVs and PHEVs can contribute to lower operating costs through reduced maintenance requirements and enhanced fuel economy. In addition, a fleet of EVs or PHEVs, when parked and aggregated in a sizeable number, can provide regulation services to the grid through the electricity stored in the vehicle's batteries. This opportunity is known as Vehicle-to-grid technology (V2G). This thesis evaluates the economics for V2G-enabled fleets to participate in the regulation services market. In order to build a business case for fleet managers, we constructed a 10-year cash flow model that compares the operating, infrastructure, and capital costs, as well as the revenue opportunities for EVs, PHEVs, and ICEs. To quantify potential revenues, we adapted a tool that the ISO New England has used to simulate the revenues of participants in the regulation market for an alternative energy pilot. We show that ICEs, while having the lowest retail value, actually have the greatest NPV due to their high operating costs and inability to participate in the regulation services market. EVs have the highest retail value, but due to their large battery size are able to provide the most regulation services. The opportunity for V2G is critical for the attractiveness of the EV. PHEVs offer lower V2G revenue opportunity than the EVs but have greater operational flexibility. We determined that V2G revenue potential is driven by the charger capacity and battery size and there are tradeoffs associated with these components. A larger battery and charger will generate more money from regulation services, but their high investment cost may outweigh these benefits. The correct combination of charger capacity, battery size, and state of charge (SOC) is important. If the charger capacity is too large and SOC too high or low, a small battery can be charged or depleted too quickly, hindering its ability to provide regulation services.by Andrés De los Ríos Vergara and Kristen E. Nordstrom.M.Eng.in Logistic