333 research outputs found

    Viscosity near phase transitions

    Full text link
    Probably the most enticing observation in theoretical physics during the last decade was the discovery of the great amount of consequences obtained from the AdS/CFT conjecture put forward by Maldacena. In this work we review how this correspondence can be used to address hydrodynamic properties such as the viscosity of some strongly interacting systems. We also employ the Boltzmann equation for those systems closer to low-energy QCD, and argue that this kind of transport coefficients can be related to phase transitions, in particular the QGP/hadronic phase transition studied in heavy ion collisions.Comment: 9 pages, 1 figure. Contribution to the Gribov-80 Memorial Workshop. ICTP Trieste, Italy, May 26-28, 201

    Heavy Quark Fluorescence

    Get PDF
    Heavy hadrons containing heavy quarks (for example, Upsilon-mesons) feature a scale separation between the heavy quark mass (about 4.5 GeV for the b-quark) and the QCD scale (about 0.3 GeV}) that controls effective masses of lighter constituents. Therefore, as in ordinary molecules, the de-excitation of the lighter, faster degrees of freedom leaves the velocity distribution of the heavy quarks unchanged, populating the available decay channels in qualitatively predictable ways. Automatically an application of the Franck-Condon principle of molecular physics explains several puzzling results of Upsilon(5S) decays as measured by the Belle collaboration, such as the high rate of Bs*-anti Bs* versus Bs*-anti Bs production, the strength of three-body B-anti B + pion decays, or the dip in B momentum shown in these decays. We argue that the data is showing the first Sturm-Liouville zero of the Upsilon(5S) quantum mechanical squared wavefunction, and providing evidence for a largely b-anti b composition of this meson.Comment: 4 pages, 4 figures, Figure 2 updated and some typos corrected. To be published in Physical Review Letter

    Conferencia: ¿En qué trabaja un pedagogo/a?. Presentación de una investigación

    Get PDF
    Conferencia en el marco de la asignatura Teoría y práctica de la investigación educativa del grado de Pedagogía de la Universidad de Barcelon

    Ethical Competence in Master’s Degrees: Definition and Shaping Factors

    Full text link
    The inclusion of ethical competence in the training of master’s degree students remains a challenge. It has important links to the professionalization process, but unevenness has been found in its development and implementation, and this appears to generate shortcomings in training processes. The aim of this study is to understand the meaning of ethical competence and to identify factors that facilitate its inclusion in master’s degree programs. A multicentre phenomenological study was carried out at universities in Spain and Argentina. Students and faculty from ten master’s degree programs in different subjects participated. Three broad overall categories emerged from our analysis: competencies related to the professional profile; factors in the professionalizing process; and training in ethical competence. These categories suggest that ethical competence is a core rather than an added value for any professional, thereby stressing the need to address its pedagogical importance in education

    Minimum of η/s\eta/s and the phase transition of the Linear Sigma Model in the large-N limit

    Get PDF
    We reexamine the possibility of employing the viscosity over entropy density ratio as a diagnostic tool to identify a phase transition in hadron physics to the strongly coupled quark-gluon plasma and other circumstances where direct measurement of the order parameter or the free energy may be difficult. It has been conjectured that the minimum of eta/s does indeed occur at the phase transition. We now make a careful assessment in a controled theoretical framework, the Linear Sigma Model at large-N, and indeed find that the minimum of eta/s occurs near the second order phase transition of the model due to the rapid variation of the order parameter (here the sigma vacuum expectation value) at a temperature slightly smaller than the critical one.Comment: 22 pages, 19 figures, v2, some references and several figures added, typos corrected and certain arguments clarified, revised for PR

    D-meson diffusion in hadronic matter

    Get PDF
    We present effective-field-theory results with unitarized interactions on the D-meson transport coefficients in a gas populated by light mesons and baryons at finite temperature and baryochemical potential. The Fokker-Planck equation is used to compute the drag force, the relaxation time and the diffusion coefficients of D mesons for collisions at FAIR. At finite baryochemical potential, the combined effect of net baryonic density and sizable meson-baryon interaction makes the D mesons to relax more efficiently than in the case at zero baryochemical potential. We also describe the connection with the quark-gluon plasma phase in adiabatic trajectories on the phase diagram at both zero and finite baryochemical potential.Comment: 5 pages, 4 figures. Contribution to the FAIRNESS 2013 - Workshop for young scientists with research interests focused on FAIR physics. 15-21 September 2013, Berlin (Germany

    Transición y orientación: Interrelaciones, estrategias y recomendaciones desde la investigación

    Get PDF
    La investigación centrada en los problemas de la transición ha motivado a los autores de este ensayo a compartir con sus colegas nacionales e internacionales sus hallazgos y sus innovaciones. El artículo revisa el concepto de transición desde una perspectiva múltiple y sintetiza varias investigaciones desarrolladas durante esta última década por el equipo Transiciones Académicas y Laborales (TRALS), algunas centradas en transiciones convencionales y otras, en problemas no tan convencionales. El análisis de las investigaciones más significativas expone los objetivos, la metodología, las características y las fuentes de cada trabajo. Las repercusiones de distintas investigaciones relacionadas con la política educativa global para la evitación del abandono escolar y académico, se ven complementadas con una serie de sugerencias en torno a la intervención psicopedagógica para orientar a personas en transición, siguiendo modelos didácticos y psicológicos de autores clásicos en el tema
    • …