Hadron spectra from a non-relativistic model with confining harmonic potential

Hadron spectra and other properties of quark systems are studied in the framework of a non-relativistic spin-independent phenomenological model. The chosen confining potential is harmonic, which allowed us to obtain analytical solutions for both meson and baryon (of equal constituent quarks) spectra. The introduced parameters are fixed from the low-lying levels of heavy quark mesons. The requirement of flavor independence is imposed, and it restricts the possible choices of inter-quark potentials. The hyper-spherical coordinates are considered for the solution of the three-body problem.Comment: Revtex file, 8 figures, 18 pages. Content and references added, some tables changed by figure

EuCo2P2: A Model Molecular-Field Helical Heisenberg Antiferromagnet

The metallic compound EuCo2P2 with the body-centered tetragonal ThCr2Si2 structure containing Eu spins 7/2 was previously shown from single-crystal neutron diffraction measurements to exhibit a helical antiferromagnetic (AFM) structure below TN = 66.5 K with the helix axis along the c axis and with the ordered moments aligned within the ab-plane. Here we report crystallography, electrical resistivity, heat capacity, magnetization and magnetic susceptibility measurements on single crystals of this compound. We demonstrate that EuCo2P2 is a model molecular-field helical Heisenberg antiferromagnet from comparisons of the anisotropic magnetic susceptibility chi, high-field magnetization and magnetic heat capacity of EuCo2P2 single crystals at temperature T < TN with the predictions of our recent formulation of molecular field theory. Values of the Heisenberg exchange interactions between the Eu spins are derived from the data. The low-T magnetic heat capacity ~ T^3 arising from spin-wave excitations with no anisotropy gap is calculated and found to be comparable to the lattice heat capacity. The density of states at the Fermi energy of EuCo2P2 and the related compound BaCo2P2 are found from the heat capacity data to be large, 10 and 16 states/eV per formula unit for EuCo2P2 and BaCo2P2, respectively. These values are enhanced by a factor of ~2.5 above those found from DFT electronic structure calculations for the two compounds. The calculations also find ferromagnetic Eu-Eu exchange interactions within the ab-plane and AFM interactions between nearest- and next-nearest planes, in agreement with the MFT analysis of chi{ab}(T < TN).Comment: 20 pages, 17 figures, 3 tables, 46 references. This is an extended replacement of arXiv:1512.02958 with an additional coautho

Enhanced moments of Eu in single crystals of the metallic helical antiferromagnet EuCo2 yAs2

The compound EuCo{2-y}As2 with the tetragonal ThCr2Si2 structure is known to contain Eu{+2} ions with spin S = 7/2 that order below a temperature TN = 47 K into an antiferromagnetic (AFM) proper helical structure with the ordered moments aligned in the tetragonal ab plane, perpendicular to the helix axis along the c axis, with no contribution from the Co atoms. Here we carry out a detailed investigation of the properties of single crystals. Enhanced ordered and effective moments of the Eu spins are found in most of our crystals. Electronic structure calculations indicate that the enhanced moments arise from polarization of the d bands, as occurs in ferromagnetic Gd metal. Electrical resistivity measurements indicate metallic behavior. The low-field in-plane magnetic susceptibilities chi{ab}(T < TN) for several crystals are reported that are fitted well by unified molecular field theory (MFT), and the Eu-Eu exchange interactions Jij are extracted from the fits. High-field magnetization M data for magnetic fields H||ab reveal what appears to be a first-order spin-flop transition followed at higher field by a second-order metamagnetic transition of unknown origin, and then by another second-order transition to the paramagnetic (PM) state. For H||c, the magnetization shows only a second-order transition from the canted AFM to the PM state, as expected. The critical fields for the AFM to PM transition are in approximate agreement with the predictions of MFT. Heat capacity Cp measurements in zero and high H are reported. Phase diagrams for H||c and H||ab versus T are constructed from the high-field M(H,T) and Cp(H,T) measurements. The magnetic part Cmag(T, H = 0) of Cp(T, H = 0) is extracted and is fitted rather well below TN by MFT, although dynamic short-range AFM order is apparent in Cmag(T) up to about 70 K, where the molar entropy attains its high-T limit of R ln8.Comment: 29 pages, 30 figures including 62 subfigures, 8 tables, 84 reference

Non-affine geometrization can lead to nonphysical instabilities

Geometrization of dynamics consists of representing trajectories by geodesics on a configuration space with a suitably defined metric. Previously, efforts were made to show that the analysis of dynamical stability can also be carried out within geometrical frameworks, by measuring the broadening rate of a bundle of geodesics. Two known formalisms are via Jacobi and Eisenhart metrics. We find that this geometrical analysis measures the actual stability when the length of any geodesic is proportional to the corresponding time interval. We prove that the Jacobi metric is not always an appropriate parametrization by showing that it predicts chaotic behavior for a system of harmonic oscillators. Furthermore, we show, by explicit calculation, that the correspondence between dynamical- and geometrical-spread is ill-defined for the Jacobi metric. We find that the Eisenhart dynamics corresponds to the actual tangent dynamics and is therefore an appropriate geometrization scheme.Comment: Featured on the Cover of the Journal. 9 pages, 6 figures: http://iopscience.iop.org/1751-8121/48/7/07510

Una construcción del concepto de justicia a partir del desarrollo de un proceso de lectura y reflexión de tres cuentos cortos por parte de los estudiantes de 3° grado de la sede D del colegio Marco Tulio Fernández

El presente documento muestra una propuesta de integración de contenido y lengua extranjera en la asignatura de matemáticas, que se llevó a cabo en la sede D del colegio Marco Tulio Fernández (IED) de Bogotá, la cual tuvo como base la construcción de justicia por medio de la lectura y posterior reflexión de tres cuentos cortos. Existe una necesidad para las estudiantes de básica primaria de construir su realidad y de desarrollar sus habilidades en ese proceso de construcción de conocimientos propios, así como de un proceso educativo que gire en torno a ello. Ante el poco reconocimiento que se les da a los imaginarios de los estudiantes, así como de las construcciones propias realizadas por ellos, se desarrolló un proceso de lectura y reflexión de tres cuentos cortos, con base en la pedagogía dialogante, que se explicará en este documento. El objetivo del trabajo fue fortalecer la construcción de justicia que realizan los estudiantes de grado 3° de la sede D del colegio Marco Tulio Fernández a partir del desarrollo de un proceso de lectura y reflexión de tres cuentos cortos. La aplicación cobra importancia, ya que brinda a los estudiantes voz y voto en su proceso de enseñanza-aprendizaje a partir de sus apreciaciones a la hora de construir el conocimiento, a partir de allí, éstas se fortalecen en la medida en la que se generan espacios de lectura y reflexión que les permiten a los estudiantes apropiarse cada vez como mayor profundidad de las características encontradas en los textos. Por ende, se proyecta la idea de utilizar la literatura como un medio que brinde las herramientas necesarias para fortalecer esas construcciones propias que realizan los estudiantes, construcciones que, a su vez, hacen parte de lo que para el niño o la niña es su realidad. Para esta implementación, se referenciaron distintas investigaciones realizadas al respecto a nivel internacional, nacional y local; para tener un punto de partida en el diseño de la propuesta. El marco teórico de esta investigación está constituido por los siguientes constructos: Justicia, cuentos cortos, diálogo, pedagogía y sociedad y desarrollo moral, los cuales conformaron las bases para la planeación y ejecución del proyecto. Esta es una investigación acción, que está compuesta por cuatro etapas para la obtención de los resultados. Dichos pasos fueron: observación, planeación, acción y análisis de resultados; lo cual contribuyó posteriormente al análisis de datos. Los resultados obtenidos demuestran que la pedagogía dialogante contribuye al fortalecimiento de conceptos, construcciones y realidades propias de los estudiantes, como en este caso lo fue la justicia. Finalmente, se incluyen los resultados obtenidos, que dan muestra de las fortalezas y dificultades del desarrollo del proyecto de investigación.Universidad Libre Facultad de Ciencias de la Educación Programa Licenciatura en Educación Básica con énfasis en Humanidades e Idioma

Autoimmunity in dengue: Literature review

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