The Berry-Tabor conjecture for spin chains of Haldane-Shastry type

According to a long-standing conjecture of Berry and Tabor, the distribution of the spacings between consecutive levels of a "generic'' integrable model should follow Poisson's law. In contrast, the spacings distribution of chaotic systems typically follows Wigner's law. An important exception to the Berry-Tabor conjecture is the integrable spin chain with long-range interactions introduced by Haldane and Shastry in 1988, whose spacings distribution is neither Poissonian nor of Wigner's type. In this letter we argue that the cumulative spacings distribution of this chain should follow the "square root of a logarithm'' law recently proposed by us as a characteristic feature of all spin chains of Haldane-Shastry type. We also show in detail that the latter law is valid for the rational counterpart of the Haldane-Shastry chain introduced by Polychronakos.Comment: LaTeX with revtex4, 6 pages, 6 figure

The timely overestimation of Spanish GDP in the great recession

The inefficient institutional design of the Euro allowed guaranteed bank liabilities to be converted into government debt, deepening the Great-Recession in Southern European countries. A recessive feedback process occurred through an increase in sovereign debt risk premiums in a cycle of global risk aversion. However, there was one fact that limited these negative effects. We refer to the overestimation of Spanish gross domestic product (GDP) in the public accounts for the period 2007–2013. We quantified the unexplained overestimation of Spain’s GDP for the period 2007–2013 using three different methodologies, which leads us to a similar conclusion: Spain’s GDP was overestimated by between 17% and 18%. We demonstrate that this overestimation allowed for significant savings in interest payments through a lower risk premium. This overestimation, unknown to investors, shows that markets are not efficient, and that information is incomplete. It is necessary to understand the role of debt under Hyman Minsky financial instability hypothesis

Delta-Vs and Design Reference Mission Scenarios for Mars Missions

Before setting out on any long journey, it is important to first have an idea about how to get there, how long it might take, and how much it will cost. Primarily, the answers depend upon where you are starting and where you wish to go. In the formulative stages of any mission to Mars, having quick estimates of answers to these basic questions will aid in the efficient exploration of the trade space. In this paper, we present a “mileage chart” of sorts illustrating the range of ΔV’s and times-of-flight (TOF) between various starting and stopping points between Earth and Mars. This paper expands upon a chart from a previous work by the authors. We discuss the methodologies used to calculate or estimate expected values and reasonable ranges, including some more detailed specific examples

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

Surface abundances of ON stars

Massive stars burn hydrogen through the CNO cycle during most of their evolution. When mixing is efficient, or when mass transfer in binary systems happens, chemically processed material is observed at the surface of O and B stars. ON stars show stronger lines of nitrogen than morphologically normal counterparts. Whether this corresponds to the presence of material processed through the CNO cycle or not is not known. Our goal is to answer this question. We perform a spectroscopic analysis of a sample of ON stars with atmosphere models. We determine the fundamental parameters as well as the He, C, N, and O surface abundances. We also measure the projected rotational velocities. We compare the properties of the ON stars to those of normal O stars. We show that ON stars are usually helium-rich. Their CNO surface abundances are fully consistent with predictions of nucleosynthesis. ON stars are more chemically evolved and rotate - on average - faster than normal O stars. Evolutionary models including rotation cannot account for the extreme enrichment observed among ON main sequence stars. Some ON stars are members of binary systems, but others are single stars as indicated by stable radial velocities. Hence, mass transfer is not a simple explanation for the observed chemical properties. We conclude that ON stars show extreme chemical enrichment at their surface, consistent with nucleosynthesis through the CNO cycle. Its origin is not clear at present.Comment: 18 pages, 10 figures (+ appendix). A&A accepte

Facies generadoras de carbón en el Westfaliense superior de la Cuenca Carbonífera Central Asturiana

La Cuenca Carbonífera Central Asturiana constituye una cuenca de antepais individualizada en la Zona Cantábrica durante el Carbonifero Superior coincidiendo con la máxima actividad de la orogenia Hercinica. Durante el Westfaliense, se acumularon en ella importantes volúmenes de material clástico procedentes de los relieves en elevación situados al W. Los abanicos aluviales costeros constituyeron unos sistemas deposicionales muy eficientes en la dispersión de estos materiales, generaron extensas cuñas clásticas en relación con las cuales se originaron capas de carbón explotables. En este trabajo se estudian varios litosomas de edad Westfaliense Superior que representan episodios progradantes de estos sistemas sobre ambientes marinos someros v de transición. El análisis e interpretación de sus facies y geometrías permite la reconstrucción de las condiciones ambientales en que se generaron las capas de carbón asociadas a cada una de las unidades estudiadas. Estas se desarrollaron: 1) en zonas marginales a los lóbulos progradantes y zonas interlóbulos y 2) sobre los mismos una vez que éstos fueron abandonados y previamente a su enterramiento

On the multiplicity of the zero-age main-sequence O star Herschel 36

We present the analysis of high-resolution optical spectroscopic observations of the zero-age main-sequence O star Herschel 36 spanning six years. This star is definitely a multiple system, with at least three components detected in its spectrum. Based on our radial-velocity (RV) study, we propose a picture of a close massive binary and a more distant companion, most probably in wide orbit about each other. The orbital solution for the binary, whose components we identify as O9 V and B0.5 V, is characterized by a period of 1.5415 +/- 0.0006 days. With a spectral type O7.5 V, the third body is the most luminous component of the system and also presents RV variations with a period close to 498 days. Some possible hypotheses to explain the variability are briefly addressed and further observations are suggested.Comment: 6 pages, 2 figure

Properties of massive stars in Galactic binary systems

En el marco del proyecto OWN, usamos datos espectroscópicos de alta resolución de la binaria masiva HD 54662 para medir velocidades radiales y desentramar los espectros de las dos componentes del sistema, que hemos clasificado como O6.5 Vz(n) y O7.5 Vz. Obtenemos una nueva solución orbital espectroscópica para el sistema, con un periodo de 5.50 ± 0.02 años. Usamos datos astrométricos publicados para calcular masas estelares absolutas de 24 ± 1 y 20 ± 1 M para las componentes A y B, respectivamente. Analizamos cuantitativamente los espectros desentramados con modelos fastwind de atmósferas estelares y calculamos masas evolutivas actuales usando la herramienta bonnsai. Obtenemos masas evolutivas demasiado altas, lo cual podría estar relacionado con el problema de discrepancia de masas.Within the OWN project, we use high resolution spectroscopic data of the massive binary system HD54662 to measure accurate radial velocities and disentangle the spectra of the two components, which we classify as O6.5Vz(n) and O7.5Vz. We obtain a new spectroscopic orbital solution of the system, with a period of P=5.500.02yr. We use published astrometric data to derive absolute stellar masses of 241 and 201M for components A and B, respectively. We analyze quantitatively the disentangled spectra using fastwind stellar atmosphere models and infer current evolutionary masses using the bonnsai tool. We find too high evolutionary masses, which could be related to the mass discrepancy problem.Fil: Sabín Sanjulián, C.. Universidad de La Serena; ChileFil: Barba, Rodolfo Héctor. Universidad de La Serena; ChileFil: Gamen, Roberto Claudio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; ArgentinaFil: Arias, J. A.. Universidad de La Serena; ChileSegunda Reunión Binacional de Asociación Argentina de Astronomía y Sociedad Chilena de AstronomíaLa SerenaChileUniversidad de La SerenaSociedad Chilena de Astronomí

Investigating Differences between Graphical and Textual Declarative Process Models

Declarative approaches to business process modeling are regarded as well suited for highly volatile environments, as they enable a high degree of flexibility. However, problems in understanding declarative process models often impede their adoption. Particularly, a study revealed that aspects that are present in both imperative and declarative process modeling languages at a graphical level-while having different semantics-cause considerable troubles. In this work we investigate whether a notation that does not contain graphical lookalikes, i.e., a textual notation, can help to avoid this problem. Even though a textual representation does not suffer from lookalikes, in our empirical study it performed worse in terms of error rate, duration and mental effort, as the textual representation forces the reader to mentally merge the textual information. Likewise, subjects themselves expressed that the graphical representation is easier to understand