Viscosity near phase transitions

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

Proyecto de emprendimiento para la creación de una empresa de servicios personalizados de condctores a personas particulares

Rigth es una solución para los ciudadanos bogotanos que carecen posibilidad de poder conducir su propio vehículo por razones jurídicas, personales o éticas. Este es un servicio que se le prestará a toda persona que necesite desplazarse en su propio vehículo y no pueda o no desee realizar dicha tarea. Las principales razones por la cual Mr. Rigthes una solución ideal para el ciudado bogotano son: la inseguridad, problemas físicos o mentales, y caos de la movilidad.Ingeniero (a) IndustrialPregrad

Heavy Quark Fluorescence

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

D-meson diffusion in hadronic matter

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

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

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

Memoria y olvido: una aproximación al conflicto armado en Colombia y sus estrategias de afrontamiento desde la memoria histórica y la prohibición del olvido en los Montes de María

360 páginas y anexosThis research aims to problematize the relationship between historical memory and oblivion, understanding that any intention that involves recall is mediated by complex phenomena that are not only based on recoverable information, they also understand that this information is part of an individual, collective and historical selection that makes it possible to give meaning to existence. Therefore, thanks to the tension between memory and oblivion, it is intended to enable scenarios in which peace has not been considered, as is the right to forget and forget by remembering, through an integral process in which the communities that have witnessed the armed conflict are not labeled, guaranteeing emotional well-being; that is related to the dynamism and the resignification. The current production of Historical Memory as a pillar in the country's public policy calls for groups in different fields of action; art, music and dance have been transversal tools for the mediation of the armed conflict both for the elaboration of memories and forgetfulness.Esta investigación pretende problematizar la relación entre la memoria histórica y el olvido, entendiendo que toda intención que implique rememorar se encuentra mediada por fenómenos complejos que no solo se basan en la información recuperable, además, entienden que dicha información hace parte de una selección individual, colectiva e histórica que posibilita darle sentido a la existencia. Por lo tanto, gracias a la tensión entre memoria y olvido se pretende posibilitar escenarios en los que la paz no ha sido considerada, como lo es el derecho a olvidar y olvidar recordando, mediante un proceso integral en el que las comunidades que han presenciado el conflicto armado no sean etiquetadas, garantizando el bienestar emocional; que se encuentra relacionado con el dinamismo y la resignificación. La producción actual de la Memoria Histórica como pilar en la política pública del país convoca colectivos en distintos campos de acción; el arte, música y danza han sido herramientas transversales para la mediación del conflicto armado tanto para la elaboración,de memorias como olvidos.Psicologo(a)Pregrad

Modelos multinomiales: un análisis de sus propiedades

En el presente trabajo se desarrolla un análisis de las propiedades de los modelos Multinomiales a través de distintos procesos de simulación; lo anterior se realizó asumiendo tanto el cumplimiento de los supuestos subyacentes de los mecanismos de estimación como el incumplimiento de los mismos. Igualmente se analizó el comportamiento de los estimadores bajo diferentes escenarios de tamaño muestral. Se encontró que bajo un modelo correctamente especificado y tamaños muestrales superiores a 200 observaciones, se cumplen las propiedades de insesgadez y consistencia, mientras que la incorrecta especificación de la distribución del proceso lleva a estimaciones sesgadas e inconsistentes; de igual forma se encontró que en tamaños muestrales pequeños y bajo modelos Condicionales se pierden las propiedades que una buena especificación del proceso suele generar, hallándose aún más inestabilidad cuando la estimación es llevada a cabo con la metodología Probit.This paper develops an analysis of Multinomial models through simulation; this was done under correct and incorrect assumptions on the data generating process. Also, it was analyzed the performance of the models under different sample sizes. It was found that a correct specified model with samples of 200 or more observations achieves estimators which are unbiased and consistent, while incorrect assumptions about the data generating process causes biased and inconsistent estimators. On the other hand, conditional models with small sample sizes imply bad statistical properties, especially when Probit models are estimated