On the spectrum of nonrelativistic AdS/CFT

We develop a Hamiltonian picture for a family of models of nonrelativistic AdS/CFT duality. The Schrodinger group is realized via the conformal quantum mechanics of De Alfaro, Fubini and Furlan in the holographic direction. We show that most physical requirements, including the introduction of harmonic traps, can be realized with exact AdS metrics, but without any need for exotic matter sectors in the bulk dynamics. This Hamiltonian picture can be used to compare directly with many-body spectra of fermions at unitarity on harmonic traps, thereby providing a direct physical interpretation of the holographic radial coordinate for these systems. Finally, we add some speculations on the dynamical generation of mass gaps in the AdS description, the resulting quasiparticle spectra, and the analog of `deconfining' phase transitions that may occur.Comment: 20 pages and 1 figure; typos corrected, references added; references added, minor changes matching published versio

The “Golden Chapel” of the convent of Calatrava la Nueva: Iconographic precisions and patronage

El comendador García de Padilla, miembro de un importante linaje y vinculado a la corte de Carlos V, planeó su enterramiento en el templo de la sede de la Orden Militar de Calatrava. Para ello consiguió la llamada “Capilla Dorada”, comprada al embajador don Francisco de Rojas, en la que se emprendieron diversas obras de ornamentación, destinadas no solo a reflejar un determinado programa iconográfico de tipo religioso, sino también a recordar perpetuamente los vínculos de Padilla con el emperador. El propósito principal de este trabajo es, por una parte, analizar la iconografía de dicha capilla, pero especialmente se pretende contribuir al estudio de los usos y actitudes ante la muerte entre las élites de la Edad Moderna, donde las obras de arte se convierten en portadoras de mensajes propagandísticos destinados en gran medida, a la exaltación del linajeThe knight commander (comendador) García de Padilla, a descent of an important lineage related to Carlos V court, planned his burial in the temple of the Calatrava fortress, headquarters of this Military Order. With this purpose in mind, he bought from the ambassador D. Francisco de Rojas the so-called “Golden chapel”, in which he undertook several ornamentation works. This decoration was aimed not only to represent a religious iconographic program, but a perpetual reminder of his relationship with the emperor. The aim of this paper is two-fold: first, to analyze the iconography of the above mentioned chapel and, more important, to increase our knowledge of the habits and attitudes towards death among Modern Age elites, where art conveys a propagandistic message, mainly aimed at the exaltation of their nobilit

Dependence in Credit Default Swap and Equity Markets: Dynamic Copula with Markov Switching

Theoretical credit risk models à la Merton (1974) predict a non-linear negative link between the default likelihood and asset value of a firm. This motivates us to propose a flexible empirical Markov-switching bivariate copula that allows for distinct time-varying dependence between credit default swap (CDS) spreads and equity prices in “crisis” and “tranquil” periods. The model identifies high-dependence regimes that coincide with the recent credit crunch and the European sovereign debt crises, and is supported by in-sample goodness-of-fit criteria relative to nested copula models that impose within-regime constant dependence or no regime-switching. Value-at-Risk forecasts that aim to set day-ahead trading limits for the hedging of CDS-equity portfolios reveal the economic relevance of the model from the viewpoints of both regulatory and asymmetric piecewise linear loss functions

Combining Nearest Neighbor Predictions and Model-Based Predictions of Realized Variance: Does it Pay?

The increasing availability of intraday financial data has led to improvements in daily volatility forecasting through long-memory models of realized volatility. This paper demonstrates the merit of the non-parametric Nearest Neighbor (NN) approach for S&P 100 realized variance forecasting. A priori the NN approach is appealing because it can reproduce complex dynamic dependencies while largely avoiding misspecification and parameter estimation uncertainty, unlike model-based methods. We evaluate the forecasts through straddle trading profitability metrics and using conventional statistical accuracy criteria. The ranking of individual forecasts confirms that statistical accuracy does not have a one-to-one mapping into profitability. In turbulent markets, the NN forecasts lead to higher risk-adjusted profitability even though the model-based forecasts are statistically superior. In both calm and turbulent market conditions, the directional combination of NN and model-based forecasts is more profitable than any of the individual forecasts

Compressibility and structural stability of ultra-incompressible bimetallic interstitial carbides and nitrides

We have investigated by means of high-pressure x-ray diffraction the structural stability of Pd2Mo3N, Ni2Mo3C0.52N0.48, Co3Mo3C0.62N0.38, and Fe3Mo3C. We have found that they remain stable in their ambient-pressure cubic phase at least up to 48 GPa. All of them have a bulk modulus larger than 330 GPa, being the least compressible material Fe3Mo3C, B0 = 374(3) GPa. In addition, apparently a reduction of compressibility is detected as the carbon content increased. The equation of state for each material is determined. A comparison with other refractory materials indicates that interstitial nitrides and carbides behave as ultra-incompressible materials.Comment: 14 pages, 3 figures, 1 tabl

Global associations between UVR exposure and current eczema prevalence in children from ISAAC Phase Three

We sought to examine the relationship globally between UV dose exposure and current eczema prevalences. ISAAC Phase Three provided data on eczema prevalence for 13-14 year-olds in 214 centres in 87 countries and for 6-7 year-olds in 132 centres in 57 countries. Linear and non-linear associations between (natural log transformed) eczema prevalence and the mean, maximum, minimum, standard deviation and range of monthly UV dose exposures were assessed using linear mixed-effects regression models. For the 13-14 year olds, the country-level eczema prevalence was positively and linearly associated with country-level monthly mean (prevalence ratio: 1.31, 95% confidence interval: [1.05, 1.63] per kJ/m2) and minimum (1.25 [1.06, 1.47] per kJ/m2) UV dose exposure. Linear and non-linear associations were also observed for other metrics of UV. Results were similar in trend, but non-significant, for the fewer centres with 6-7 year-olds (e.g. 1.24 [0.96, 1.59] per kJ/m2 for country-level monthly mean UV). No consistent within-country associations were observed (e.g. 1.05 [0.89, 1.23] and 0.92 [0.71, 1.18] per kJ/m2 for center-level monthly mean UV, for the 13-14 and 6-7 year-olds, respectively). These ecological results support a role for UV exposure in explaining some of the variation in global childhood eczema prevalence

User-Interface Modelling for Blind Users

The design of a user interface usable by blind people sets specific usability requirements that are unnecessary for sighted users. These requirements focus on task adequacy, dimensional trade-off, behaviour equivalence, semantic loss avoidance and device-independency. Consequently, the development of human-computer interfaces (HCI) that are based on task, domain, dialog, presentation, platform and user models has to be modified to take into account these requirements. This paper presents a user interface model for blind people, which incorporates these usability requirements into the above HCI models. A frame-work implementing the model has been developed and implemented in an electronic speaking bilingual software environment for blind or visually impaired people and in an educational system for children with special educational needs

Evaluating Conformance to WCAG 2.0: Open Challenges

Web accessibility for people with disabilities is a highly visible area of work in the field of ICT accessibility, including many policy activities in several countries. The commonly accepted guidelines for web accessibility (WCAG 1.0) were published in 1999 and have been extensively used by designers, evaluators and legislators. A new version of these guidelines (WCAG 2.0) was published in 2008. In this paper we point out the main challenges that WCAG 2.0 raises for web accessibility evaluators: the concept of "accessibility supported technologies"; success criteria testability; technique and failure openness, and the aggregation of partial results. We conclude the paper with some recommendations for the future

STUDY OF SENSITIVITY OF THE PARAMETERS OF A GENETIC ALGORITHM FOR DESIGN OF WATER DISTRIBUTION NETWORKS

The Genetic Algorithms (GAs) are a technique of optimization used for water distribution networks design. This work has been made with a modified pseudo genetic algorithm (PGA), whose main variation with a classical GA is a change in the codification of the chromosomes, which is made of numerical form instead of the binary codification. This variation entails a series of special characteristics in the codification and in the definition of the operations of mutation and crossover. Initially, the work displays the results of the PGA on a water network studied in the literature. The results show the kindness of the method. Also is made a statistical analysis of the obtained solutions. This analysis allows verifying the values of mutation and crossing probability more suitable for the proposed method. Finally, in the study of the analyzed water supply networks the concept of reliability in introduced. This concept is essential to understand the validity of the obtained results. The second part, starting with values optimized for the probability of crossing and mutation, the influence of the population size is analyzed in the final solutions on the network of Hanoi, widely studied in the bibliography. The aim is to find the most suitable configuration of the problem, so that good solutions are obtained in the less time

Some results on the eigenfunctions of the quantum trigonometric Calogero-Sutherland model related to the Lie algebra E6

The quantum trigonometric Calogero-Sutherland models related to Lie algebras admit a parametrization in which the dynamical variables are the characters of the fundamental representations of the algebra. We develop here this approach for the case of the exceptional Lie algebra E6.Comment: 17 pages, no figure