Business Cycle and Speculative Pressures in a Target Zone

In the past time, most economies have suffered cyclical fluctuations in their activity which may influence the optimal use of productive factors in long slow-growth phases or price stability in periods of fast growth. This paper focuses on the possible interrelationship between business cycles and exchange rate ‡uctuations. We have chosen the European Monetary System framework in the nineties, from June 1989 to December 1998, because the Peseta belonged to the EMS during that time. This sample is specially interesting because it includes the worst crisis of the System in 1992-93 and the following ones affecting emerging countries like Mexico, Brazil or Russia at the end of the decade. We use a Binary Dependent Variable Logit Model to estimate the readjustment probability inside a band for two currencies, the Peseta and the french Franc . We calculate the dependent variable values from a Markov-Switching Regime Model with constant transition probabilities. We prove that it is a suitable method and that it allows both real and monetary variables to be identified in order to explain speculative pressures.Readjustment Probability, Speculative Pressures, Economic Fluctuations.

Exponential localization of singular vectors in spatiotemporal chaos

In a dynamical system the singular vector (SV) indicates which perturbation will exhibit maximal growth after a time interval $\tau$. We show that in systems with spatiotemporal chaos the SV exponentially localizes in space. Under a suitable transformation, the SV can be described in terms of the Kardar-Parisi-Zhang equation with periodic noise. A scaling argument allows us to deduce a universal power law $\tau^{-\gamma}$ for the localization of the SV. Moreover the same exponent $\gamma$ characterizes the finite-$\tau$ deviation of the Lyapunov exponent in excellent agreement with simulations. Our results may help improving existing forecasting techniques.Comment: 5 page

Modelling of heat and moisture transfer in concrete at high temperature

Moisture diffusion and related fluid pressures play a key role in cracking and spalling of concrete subject to high temperatures. This paper describes recent developments of a mode for moisture and heat transfer in porous materials, to be combined with an existing and well tested meso-mechanical model for concrete. Liquid and gas flows are formulated separately, yet later they can be combined in terms of s single variable, Pv. The material pore distribution curve is taken as the basis for developing a new physically-based desorption isotherm alternative to the traditional Bazant & Thonguthai’s model. A simple academic example for temperatures between 27 and 800ºC is presented to show the behaviour of the model

Logarithmic bred vectors in spatiotemporal chaos: structure and growth

Bred vectors are a type of finite perturbation used in prediction studies of atmospheric models that exhibit spatially extended chaos. We study the structure, spatial correlations, and the growth- rates of logarithmic bred vectors (which are constructed by using a given norm). We find that, after a suitable transformation, logarithmic bred vectors are roughly piecewise copies of the leading Lyapunov vector. This fact allows us to deduce a scaling law for the bred vector growth rate as a function of their amplitude. In addition, we relate growth rates with the spectrum of Lyapunov exponents corresponding to the most expanding directions. We illustrate our results with simulations of the Lorenz '96 model.Comment: 8 pages, 8 figure

Revisiting the optical PTPT-symmetric dimer

Optics has proved a fertile ground for the experimental simulation of quantum mechanics. Most recently, optical realizations of $\mathcal{PT}$-symmetric quantum mechanics have been shown, both theoretically and experimentally, opening the door to international efforts aiming at the design of practical optical devices exploiting this symmetry. Here, we focus on the optical $\mathcal{PT}$-symmetric dimer, a two-waveguide coupler were the materials show symmetric effective gain and loss, and provide a review of the linear and nonlinear optical realizations from a symmetry based point of view. We go beyond a simple review of the literature and show that the dimer is just the smallest of a class of planar $N$-waveguide couplers that are the optical realization of Lorentz group in 2+1 dimensions. Furthermore, we provide a formulation to describe light propagation through waveguide couplers described by non-Hermitian mode coupling matrices based on a non-Hermitian generalization of Ehrenfest theorem.Comment: 25 pages, 12 figure

1/fα1/f^\alpha noise and integrable systems

An innovative test for detecting quantum chaos based on the analysis of the spectral fluctuations regarded as a time series has been recently proposed. According to this test, the fluctuations of a fully chaotic system should exhibit 1/f noise, whereas for an integrable system this noise should obey the 1/f^2 power law. In this letter, we show that there is a family of well-known integrable systems, namely spin chains of Haldane-Shastry type, whose spectral fluctuations decay instead as 1/f^4. We present a simple theoretical justification of this fact, and propose an alternative characterization of quantum chaos versus integrability formulated directly in terms of the power spectrum of the spacings of the unfolded spectrum.Comment: 5 pages, 3 figures, RevTe

A search for new hot subdwarf stars by means of Virtual Observatory tools

Hot subdwarf stars are faint, blue objects, and are the main contributors to the far-UV excess observed in elliptical galaxies. They offer an excellent laboratory to study close and wide binary systems, and to scrutinize their interiors through asteroseismology, as some of them undergo stellar oscillations. However, their origins are still uncertain, and increasing the number of detections is crucial to undertake statistical studies. In this work, we aim at defining a strategy to find new, uncatalogued hot subdwarfs. Making use of Virtual Observatory tools we thoroughly search stellar catalogues to retrieve multi-colour photometry and astrometric information of a known sample of blue objects, including hot subdwarfs, white dwarfs, cataclysmic variables and main sequence OB stars. We define a procedure to discriminate among these spectral classes, particularly designed to obtain a hot subdwarf sample with a low contamination factor. In order to check the validity of the method, this procedure is then applied to two test sky regions: the Kepler FoV and to a test region of around (RA:225, DEC:5) deg. As a result, we obtained 38 hot subdwarf candidates, 23 of which had already a spectral classification. We have acquired spectroscopy for three other targets, and four additional ones have an available SDSS spectrum, which we used to determine their spectral type. A temperature estimate is provided for the candidates based on their spectral energy distribution, considering two-atmospheres fit for objects with clear infrared excess. Eventually, out of 30 candidates with spectral classification, 26 objects were confirmed to be hot subdwarfs, yielding a contamination factor of only 13%. The high rate of success demonstrates the validity of the proposed strategy to find new uncatalogued hot subdwarfs. An application of this method to the entire sky will be presented in a forthcoming work.Comment: 13 pages, 7 figure

The fonds classification schedule of the Historical Provincial Archives: a new proposal

[Resumen] La primera propuesta de normalización para elaborar los cuadros de organización de fondos de los Archivos Históricos Provinciales fue presentada en 1980, y revisada en 1994. Pero, llegados a 2011, nos parece preciso reflexionar nuevamente sobre las necesidades de organización de estos centros, tomando en consideración el gran volumen de los documentos custodiados, los retos de la identificación y organización de fondos, y las necesidades de consulta por los usuarios. Nos parece evidente que es preciso incorporar a la praxis archivística nuevos criterios de clasificación, estrictamente funcionales, tomando como referencia no sólo la legislación de creación/reordenación de unidades administrativas, sino otros documentos organizativos de las administraciones, que permitiesen mantener criterios más estables en referencia a las unidades productoras de documentos. Además, no podemos olvidar las nuevas herramientas con que cuenta el archivero, (ISAD(G), ISAAR(CPF), ISDF, ISDIAH), que van a permitirnos incorporar estructuradamente datos no sólo descriptivos de los documentos, sino también relativos a los productores, a sus funciones, a los centros custodios, etc. En esta línea, presentamos una propuesta de cuadro de clasificación teórico que toma como base para la incorporación a la clasificación de fondos la estructura presupuestaria funcional de que se dotan a sí mismas las administraciones, tanto del Estado como la de la Comunidad Autónoma, en su caso, entendiendo que dota de estabilidad a la propia clasificación, y que nos va a permitir establecer criterios organizativos con vocación de permanencia, facilitándonos, además, una mayor coherencia y continuidad en la información.[Abstract] The first proposal to regulate the classification schedule of the Historical Provincial Archives in Spain was presented in 1980 and later reviewed in 1994. Now, in 2011, it seems necessary to reconsider the organisation of these centres taking into account the big amount of documents, the challenges of identification and organisation of fonds, and the requirements needed by users for consultation. It is clear that strictly, functional, new criteria must be added to the archival praxis. To achieve this, the reference source will be not only the legislation on creation and regulation of the agencies but also other documents related to their management, which will allow the producers of records to maintain more permanent criteria. On the other hand, we can?t ignore the new tools (ISAD (G), ISAAR (CPF), ISDF, ISDIAH) that give the archivist the possibility to include not only descriptive data of the records but also those related to the producers, their functions, the centres of keeping, etc. Following this procedure, we present a new proposal of a theoretical classification schedule based on the functional budgetary structure, provided either by the State or the Autonomous Communities, in order to add the fonds classification. On the whole, the own classification will become more steady allowing to establish more permanent criteria as well as providing more coherence and continuity in the information