Towards a theory of automated elliptic mesh generation

The theory of elliptic mesh generation is reviewed and the fundamental problem of constructing computational space is discussed. It is argued that the construction of computational space is an NP-Complete problem and therefore requires a nonstandard approach for its solution. This leads to the development of graph-theoretic, combinatorial optimization and integer programming algorithms. Methods for the construction of two dimensional computational space are presented

Bounds on OPE Coefficients from Interference Effects in the Conformal Collider

We apply the average null energy condition to obtain upper bounds on the three-point function coefficients of stress tensors and a scalar operator, $\langle TT {\cal O } \rangle,$ in general CFTs. We also constrain the gravitational anomaly of $U(1)$ currents in four-dimensional CFTs, which are encoded in three-point functions of the form $\langle TT J \rangle$. In theories with a large $N$ AdS dual we translate these bounds into constraints on the coefficient of a higher derivative bulk term of the form $\int \phi\hspace{.5mm} W^2$. We speculate that these bounds also apply in de-Sitter. In this case our results constrain inflationary observables, such as the amplitude for chiral gravity waves that originate from higher derivative terms in the Lagrangian of the form $\phi \hspace{.5mm}W W^*$.Comment: 46 pages, 3 figure

«The Idealist. The story of Baron Pierre de Coubertin», by George Hirthler: Comments and Reflections

En el año 2016 se publicó el libro «The Idealist». Es la historia novelesca del Barón Pierre de Coubertin, realizada por el escritor George Hirthler, muy familiarizado con el Movimiento Olímpico. El autor hace uso de la ficción histórica ya que afirma que ello le permitiría una mejor presentación. De acuerdo con éste, el uso de hechos reales permite crear un ambiente imaginativo de interpretaciones. En la obra, se mezclan personajes de la realidad con caracteres ficticios, aunque el autor añade que quiso permanecer lo más posible dentro de la realidad, manteniendo la mayoría de los eventos, en sus fechas y lugares, cuándo, cómo y dónde ocurrieron. Nuestro objetivo con la recensión de esta obra es ofrecer un breve recuento de esos hechos para añadir información interesante y útil para entender la figura del Barón Pierre de Coubertin y sus motivaciones para crear el Movimiento Olímpico Internacional como símbolo de paz y amistad entre personas y naciones, todo ello dentro del marco de la educación y el deporteIn the year 2016, writer George Hirthler, well versed in the Olympic Movement, published the book “The Idealist”. It is the fictionalized story of Baron Pierre de Coubertin, intermingling facts with characters and circumstances that may be fictitious. Emphasis is made in real events, places and dates. Our summary wishes to offer a brief narrative of its highlights in order to add interesting and useful information for a better understanding of Baron Pierre de Coubertin and his motivations to create the International Olympic Movement as a symbol of peace and friendship among people and nations, all within the scope of education and sport

How sensitive are Latin American exports to Chinese competition in the U.S. market ?

This paper estimates the elasticity of substitution of U.S. imports using detailed trade data over the 1990-2003 period. The authors use a two-stage least squares framework in order to identify the elasticity parameter of interest. The authors use the elasticity estimates to assess the extent to which Latin American and Chinese goods compete in the U.S. market by providing forecasts of how alternative policy scenarios may affect exports to the United States. The analysis considers the following scenarios: (i) currency revaluation in China; (ii) elimination of U.S. tariffs on Latin American exports under a hemispheric free trade agreement; and (iii) the elimination of quotas on apparel and textile exports under the Multi-Fiber Agreement. The findings show that a 20-percent appreciation of the renminbi reduces Chinese exports to the United States by a fifth, although since other regions increase sales to that market (0.5 percent for Latin America), U.S. imports decline by only 1.7 percent. Hemispheric free trade would increase Latin America's exports to the United States by around 3 percent. The removal of the quotas would lead to a sharp increase in Chinese sales to the United States (40 percent), but Latin America would see its share of the U.S. market decline by around 2 percent (2.5 percentage points). China's gains would come mainly at the expense of other regions of the world.Economic Theory&Research,Free Trade,Markets and Market Access,Trade Policy,Debt Markets

The incidence of graft on developing-country firms

This paper measures the extent to which firms in developing countries are the target of bribes. Using new firm-level survey data from 33 African and Latin American countries, we first show that perceptions adjust slowly tofirms'experience with corrupt officials and hence are an imperfect proxy for the true incidence of graft. We then construct an experience-based index that reflects the probability that a firm will be asked for a bribe in order to complete a specified set of business transactions. On average, African firms are three times as likely to be asked for bribes as are firms in Latin America, although there is substantial variation within each region. Last, we show that graft appears to be more prevalent in countries with excessive regulation and where democracy is weak. In particular, our results suggest that the incidence of graft in Africa would fall by approximately 85 percent if countries in the region had levels of democracy and regulation similar to those that exist in Latin America.Public Sector Corruption&Anticorruption Measures,Corruption&Anitcorruption Law,Crime and Society,E-Business,Access to Finance

The Globalization of Trade and Democracy, 1870-2000

We study whether international trade fosters democracy. The likely endogeneity between democracy and trade is addressed via the gravity model of trade, allowing us to obtain a measure of natural openness. This serves as our instrumental variable for actual trade openness à la Frankel and Romer (1999). We use this powerful instrument to obtain estimates of the causal impact of openness on democratization. A positive impact of openness on democracy is apparent from about 1895 onwards. Late nineteenth century trade globalization may have helped generate the "first wave" of democratization. Between 1920 and 1938 countries more exposed to international trade were less likely to become authoritarian. Finally, our post-World War II results suggest that a one standard deviation increase in trade with other countries could bring countries like Indonesia, Russia or Venezuela to be as democratic as the US, Great Britain or France. We also see some variation in the impact of openness by region and note that commodity exporters and petroleum producers do not seem to become more democratic by exporting more of such items.

On the use of machine learning algorithms in the measurement of stellar magnetic fields

Regression methods based in Machine Learning Algorithms (MLA) have become an important tool for data analysis in many different disciplines. In this work, we use MLA in an astrophysical context; our goal is to measure the mean longitudinal magnetic field in stars (H_ eff) from polarized spectra of high resolution, through the inversion of the so-called multi-line profiles. Using synthetic data, we tested the performance of our technique considering different noise levels: In an ideal scenario of noise-free multi-line profiles, the inversion results are excellent; however, the accuracy of the inversions diminish considerably when noise is taken into account. In consequence, we propose a data pre-process in order to reduce the noise impact, which consists in a denoising profile process combined with an iterative inversion methodology. Applying this data pre-process, we have found a considerable improvement of the inversions results, allowing to estimate the errors associated to the measurements of stellar magnetic fields at different noise levels. We have successfully applied our data analysis technique to two different stars, attaining by first time the measurement of H_eff from multi-line profiles beyond the condition of line autosimilarity assumed by other techniques.Comment: Accepted for publication in A&

Probing the Pulsar Wind Nebula of PSR B0355+54

We present XMM-Newton and Chandra X-ray observations of the middle-aged radio pulsar PSR B0355+54. Our X-ray observations reveal emission not only from the pulsar itself, but also from a compact diffuse component extending ~50'' in the opposite direction to the pulsar's proper motion. There is also evidence for the presence of fainter diffuse emission extending ~5' from the point source. The compact diffuse feature is well-fitted with a power-law, the index of which is consistent with the values found for other pulsar wind nebulae. The morphology of the diffuse component is similar to the ram-pressure confined pulsar wind nebulae detected for other sources. The X-ray emission from the pulsar itself is described well by a thermal plus power-law fit, with the thermal emission most likely originating in a hot polar cap.Comment: 9 pages (uses emulateapj.cls), 8 figures, 2 tables, accepted for publication in Ap

Аналіз текстури фрактографічних зображень на основі спектра фрактальних розмірностей Реньї

У статті досліджено застосування спектра фрактальних розмірностей Реньї для аналізу текстури фрактографічних зображень. Запропоновано використовувати цей підхід для класифікації типів зламів.В статье исследовано применение спектра фрактальных размерностей Реньи для анализа текстуры фрактографических изображений. Предложено использовать этот подход для классификации типов изломов.Investigated the use of the spectrum of fractal dimensions Renyi for texture analysis fraktohraphic images. Proposed to use this approach for the classification of types of fractures