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Se encontraron 2733 resultados en recursos

Por: Rosa del Carmen Blandon Isanoha | Fecha: 2023

Abstract: The interaction of defects can lead to a phenomenon of erasure. During this process, a lower-dimensional object gets absorbed and dissolved by a higher-dimensional one. The phenomenon is very general and has a wide range of cosmological and fundamental implications. In particular, all types of strings, such as cosmic strings, QCD flux tubes, or fundamental strings, get erased when encountering a defect, either solitonic or a D-brane that deconfines their fluxes. This leads to a novel mechanism of cosmic string breakup, accompanied by gravitational and electromagnetic radiations. The arguments based on loss of coherence and the entropy count suggest that the erasure probability is very close to one, and strings never make it through the deconfining layer. We confirm this by a numerical simulation of the system, which effectively captures the essence of the phenomenon: a 2+1- dimensional problem of interaction between a Nielsen-Olesen vortex of a U(1) Higgs model and a domain wall, inside which the U(1) gauge group is un-Higgsed, and the magnetic flux is deconfined. In accordance with the entropy argument, in our simulation, the vortex never makes it across the wall.

Fuente: Biblioteca Virtual Banco de la República Formatos de contenido: Artículos

Temas:
Otros

Por: Nicole Brigette Castañeda Moreno | Fecha: 2023

Abstract: Vorticity has recently been suggested to be a property of highly-spinning black holes. The connection between vorticity and limiting spin represents a universal feature shared by objects of maximal microstate entropy, so-called saturons. Using QQ-ball-like saturons as a laboratory for black holes, we study the collision of two such objects and find that vorticity can have a large impact on the emitted radiation as well as on the charge and angular momentum of the final configuration. As black holes belong to the class of saturons, we expect that the formation of vortices can cause similar effects in black hole mergers, leading to macroscopic deviations in gravitational radiation. This could leave unique signatures detectable with upcoming gravitational-wave searches, which can thereby serve as a portal to macroscopic quantum effects in black holes. Note: ancillary video at https://youtu.be/t29WUvZM-io

Fuente: Biblioteca Virtual Banco de la República Formatos de contenido: Artículos

Temas:
Otros

Por: Germán Barragán Agudelo | Fecha: 2021

Abstract: Black holes are considered exceptional due to their time evolution and information processing. However, it was proposed recently that these properties are generic for objects, the so-called saturons, that attain the maximal entropy permitted by unitarity. The present paper verifies this connection within a renormalizable SU(N) invariant theory. We show that the spectrum of the theory contains a tower of bubbles representing bound states of SU(N) Goldstones. Despite the absence of gravity, a saturated bound state exhibits a striking correspondence with a black hole: Its entropy is given by the Bekenstein-Hawking formula; semiclassically, the bubble evaporates at a thermal rate with a temperature equal to its inverse radius; the information retrieval time is equal to Page’s time. The correspondence goes through a trans-theoretic entity of the Poincaré Goldstone. The black hole–saturon correspondence has important implications for black hole physics, both fundamental and observational.

Fuente: Biblioteca Virtual Banco de la República Formatos de contenido: Artículos

Temas:
Otros

Por: José Alirio Salinas Bustos | Fecha: 2023

Abstract: In this work, we study the annihilation of a pair of ‘t Hooft-Polyakov monopoles due to confinement by a string. We analyze the regime in which the scales of monopoles and strings are comparable. We compute the spectrum of the emitted gravitational waves and find it to agree with the previously calculated pointlike case for wavelengths longer than the system width and before the collision. However, we observe that in a head-on collision, monopoles are never recreated. Correspondingly, not even once the string oscillates. Instead, the system decays into waves of Higgs and gauge fields. We explain this phenomenon by the loss of coherence in the annihilation process. Due to this, the entropy suppression makes the recreation of a monopole pair highly improbable. We argue that in a similar regime, analogous behavior is expected for the heavy quarks connected by a QCD string. There too, instead of restretching a long string after the first collapse, the system hadronizes and decays in a high multiplicity of mesons and glueballs. We discuss the implications of our results.

Fuente: Biblioteca Virtual Banco de la República Formatos de contenido: Artículos

Temas:
Otros

Por: Stephanie Johana Pérez Quintero | Fecha: 2023

Abstract: We study the interactions between ’t Hooft-Polyakov magnetic monopoles and the domain walls formed by the same order parameter within an SU(2) gauge theory. We observe that the collision leads to the erasure of the magnetic monopoles, as suggested by Dvali et al. [Phys. Rev. Lett. 80, 2281 (1998)]. The domain wall represents a layer of vacuum with un-Higgsed SU(2) gauge symmetry. When the monopole enters the wall, it unwinds, and the magnetic charge spreads over the wall. We perform numerical simulations of the collision process and, in particular, analyze the angular distribution of the emitted electromagnetic radiation. As in the previous studies, we observe that erasure always occurs. Although not forbidden by any conservation laws, the monopole never passes through the wall. This is explained by entropy suppression. The erasure phenomenon has important implications for cosmology, as it sheds a very different light on the monopole abundance in postinflationary phase transitions and provides potentially observable imprints in the form of electromagnetic and gravitational radiation. The phenomenon also sheds light on fundamental aspects of gauge theories with coexisting phases, such as confining and Higgs phases.

Fuente: Biblioteca Virtual Banco de la República Formatos de contenido: Artículos

Temas:
Otros

Por: Javier Fernando García Botero | Fecha: 2023

Abstract: In this paper, we introduce and numerically simulate a quantum field theoretical phenomenon called the gauge ``slingshot"" effect and study its production of gravitational waves. The effect occurs when a source, such as a magnetic monopole or a quark, crosses the boundary between the Coulomb and confining phases. The corresponding gauge field of the source, either electric or magnetic, gets confined into a flux tube stretching in the form of a string (cosmic or a QCD type) that attaches the source to the domain wall, separating the two phases. The string tension accelerates the source towards the wall as sort of a slingshot. The slingshot phenomenon is also exhibited by various sources of other co-dimensionality, such as cosmic strings confined by domain walls or vortices confined by Z_2 strings. Apart from the field-theoretic value, the slingshot effect has important cosmological implications, as it provides a distinct source for gravitational waves. The effect is expected to be generic in various standard model extensions, such as grand unification.

Fuente: Biblioteca Virtual Banco de la República Formatos de contenido: Artículos

Temas:
Otros

Por: Carlos Eduardo Ortiz Escobar | Fecha: 2018

The present study seeks to establish the socioeconomic profile of the producer of specialty coffees in the department of Huila and the practices of social innovation that they implement around their production, in order to offer recommendations in the understanding of this interest group whose dynamic relations, in the public and the private, contribute significantly to the departmental economy and rural development. The research is framed within a quantitative approach, as its intervention is determined as a descriptive cross-sectional observational study. The sample consists of two subgroups, one consisting of 200 producers of specialty coffees and another of 72 standard coffee producers. The type of sampling was determined non-probabilistic of intentional selection. Among the obtained results, it was identified that there is no producer of special coffees, which can guarantee the totality of its production as special coffee. In addition, the development of social innovation is an atypical practice in coffee producers, evidenced exclusively in the producers of special coffee.

Fuente: Universidad Externado de Colombia Formatos de contenido: Otros

Temas:
Otros

Por: César Augusto Devia Ayala | Fecha: 2019

El presente trabajo aborda los resultados del estudio de caso del programa Bloqueras Solidarias que ejecutó la empresa CEMEX COLOMBIA SA en el municipio de Anapoima, Cundinamarca. El proyecto se desarrolló como parte de las estrategias de responsabilidad social de la Empresa bajo la modalidad de Negocio lnclusivo. El programa vinculó a familias de bajos ingresos y en condiciones de pobreza extrema del sector rural en la fabricación de bloques de concreto de los cuales el 50% se comercializó con las instituciones aliadas y el 50% restante se utilizó para la construcción y mejoramiento de sus viviendas. Los aspectos concernientes al proyecto se concretaron a partir del convenio directo entre la Fundación Cemex, la Fundación Lazos de Calandaima y el apoyo de la Administración Municipal de Anapoima. En el presente estudio de caso se presentan tanto los factores de éxito, así coma los retos y oportunidades de mejora siguiendo la "Metodología para ta Elaboración de Estudios de Caso Cualitativos en Responsabilidad Social Empresarial" de la Universidad Externado de Colombia.

Fuente: Universidad Externado de Colombia Formatos de contenido: Otros

Temas:
Otros

Por: Ana Lucía González García | Fecha: 2017

El presente caso de estudio es sobre los Institutos Técnicos Agropecuarios y Forestales implementados por la Fundación Smurfit Kappa Colombia, quienes brindan educación secundaria y media técnica a los jóvenes de El Tambo y Cajibio en el Cauca y Darien en el Valle del Cauca, municipios donde la Compania Smurfit Kappa Colombia opera su proyecto de reforestación comercial. A través de la aplicación de la Metodología de Ia Universidad Externado de Colombia, para la elaboración de estudios de caso cualitativos en responsabilidad social, se describe la organización Smurfit Kappa Colombia, su sector productivo y su entorno sociodemográfico, luego se describe Ia Fundacion Smurfit Kappa Colombia y con ella sus Institutos Técnicos Agropecuarios y Forestales, para posteriormente realizar una evolución a la luz del enfoque del continuo organizacional y se arrojan unas lecciones aprendidas.

Fuente: Universidad Externado de Colombia Formatos de contenido: Otros

Temas:
Otros
Tecnología

Por: Carlos A. Lasso | Fecha: 2017

Se confirma la presencia en el pasado de las especies de pez sierra (Pristis spp) en el mar Caribe de Colombia y Venezuela, a partir de la revisión de once extensiones rostrales exhibidas en establecimientos, museos y colecciones de particulares, así como la consulta bibliográfica, encuestas y el examen de material fotográfico disponible sobre avistamientos o capturas realizadas en ambos países. Se determinó que las especies presentes en el Caribe de Colombia y Venezuela eran Pristis pristis y Pristis pectinata, las cuales en la actualidad se encuentran probablemente extintas localmente.

Fuente: Instituto de Investigación de Recursos Biológicos Alexander von Humboldt