Radiative decays and the nature of heavy quarkonia

We argue that the photon spectra in radiative decays of various heavy quarkonium states provide important information on their nature. If two of these states are in the strong coupling regime, we are able to produce a parameter-free model independent formula, which holds at next-to-leading order and includes both direct and fragmentation contributions. When the formula is checked against recent CLEO data it favors Upsilon (2S) and Upsilon (3S) in the strong coupling regime and disfavors Upsilon (1S) in it.Comment: 5 pages, 3 figures. Clarifications introduced, including extra curve in plots. Journal versio

Semi-inclusive radiative decays of Upsilon 1S

We discuss in detail the photon spectrum of radiative Upsilon 1S decays taking into account a number of results that have recently appeared in the literature. In particular, we show how to consistently combine expressions which are valid in the upper end-point region, where NRQCD factorization breaks down, with those of the central region, where NRQCD factorization holds. An excellent description of data is achieved, but theoretical errors are large.Comment: 18 pages, 7 figures. Minor modifications. References added and corrected. Journal versio

The QCD static energy at NNNLL

We compute the static energy of QCD at short distances at next-to-next-to-next-to leading-logarithmic accuracy in terms of the three-loop singlet potential. By comparing our results with lattice data we extract the value of the unknown piece of the three-loop singlet potential.Comment: 25 pages, 16 figures. v2: Incorrect files for figure 7 replaced by the correct ones. One reference adde

A linear acoustic model for multi-cylinder IC engine intake manifolds including the effects of the intake throttle

This paper presents a linear acoustic model of a multi-cylinder intake manifold that can be used as part of a hybrid time/frequency domain method to calculate the intake wave dynamics of practical naturally aspirated engines. The method allows the user to construct a model of almost any manifold of complex geometry. The model is constructed as an assemblage of sub-models: (i) A model for a straight pipe with both ends open and through-flow. (ii) A model for an expansion chamber consisting of three lengths of pipe laid end-to-end: a narrow bore pipe expanding into a wide bore pipe contracting into a narrower bore pipe once more. (iii) A model of a side-branch, which includes a model for a straight pipe with one end closed and a model for the three way junction that joins the side-branch to a length of flow pipe. (iv) A model for an expansion with two (or more) side-branches, which combines the sub-models (i, ii, iii) into a multi-way (n-way) junction model. (v) A model for an intake throttle. Good agreement with measurement has been found for each sub-model when bench-tested in isolation and encouraging agreement has been found when many sub-models are used together to model a complex intake manifold on a running engine

Panel Data Stochastic Convergence Analysis of the Mexican Regions

The stochastic convergence amongst Mexican Federal entities is analyzed in panel data framework. The joint consideration of cross-section dependence and multiple structural breaks is required to ensure that the statistical inference is based on statistics with good statistical properties. Once these features are accounted for, evidence in favour of stochastic convergence is found. Since stochastic convergence is a necessary, yet insufficient condition for convergence as predicted by economic growth models, the paper also investigates whether beta-convergence process has taken place. We found that the Mexican states have followed either heterogeneous convergence patterns or divergence process throughout the analyzed period.Stochastic convergence, beta-convergence, non-stationarity panel data tests, cross-section dependence, multiple structural breaks.

Extraction of alpha_s from radiative Upsilon(1S) decays

We improve on a recent determination of alpha_s from Gamma(Upsilon(1S)-->X gamma)/Gamma(Upsilon(1S)-->X) with CLEO data by taking into account color octet contributions and avoiding any model dependence in the extraction. We obtain alpha_s(M_Upsilon(1S))= 0.184+0.015-0.014, which corresponds to alpha_s(M_Z)=0.119+0.006-0.005.Comment: 11 pages. v2: One reference added. v3: Minor modification in an error estimate. Journal versio

Influencia de la resolución de problemas por investigación ; en el pesamiento crítico, estrategias y calidad del aprendizaje

El presente trabajo, tiene por finalidad compartir las implicancias didácticas de una propuesta metodológica activa, basada en resolución de problemas y sus efectos en el: rendimiento académico, pensamiento crítico y estrategias de aprendizaje. El punto de partida es la presentación de un problema integrador de contenido, que es un desafió a resolver a lo largo del semestre. Este sirve de columna vertebral para desarrollar y abordar el programa de la asignatura, que favorezca la construcción del conocimiento compartiendo significado. A partir de éste problema se desprenden una serie de problema mas acotados y entramados entre si, que se abordan a lo largo del semestre y consideran actividades de aprendizaje a resolver en la clase