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Search Results: 1 - 10 of 194627 matches for " D. Alvarez "
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El Caribe colombiano que nos une
Arturo Alvarez D'Armas
Memorias: Revista Digital de Historia y Arqueología desde el Caribe , 2007,
Abstract:
Exotic Newton-Hooke group, noncommutative plane and superconformal symmetry
Pedro D. Alvarez
Physics , 2009,
Abstract: In this thesis some systems with exotic symmetries, which are a peculiarity in 2+1 space-time dimensions, are studied. Coded in the exotic structure, there appear noncommutative coordinates and a phases structure. This kind of systems has attracted attention from different areas of physics independently. Among them, we can mention: theory of ray representations of Lie groups, anyon physics, some condensed matter systems, for instance the quantum Hall effect, planar gauge and gravitation theories, noncommutative field theory, noncommutative geometry, and noncommutative quantum mechanics. We focus our study in some topics on exotic nonrelativistic symmetries, such as the exotic Newton-Hooke group, the relation between such systems and the noncommutative Landau problem, the symmetries of noncommutative Landau problem, and of its supersymmetric extension. The exotic Newton-Hooke group corresponds to the nonrelativistic limit of the de Sitter groups, and has as a particular, flat limit the exotic Galilei group. For the exotic Newton-Hooke symmetry, we construct a free particle action, and realize a complete study of its classical and quantum properties. The Newton-Hooke system is intimately related with the noncommutative Landau problem, which we study apart. We show that the inclusion of spin degrees of freedom in the noncommutative Landau problem produces a natural integration of the exotic Newton-Hooke group with the conformal symmetry and supersymmetry.
The Fire Station as an Essential Tool in Urban Community Development: The Case of Chepo, Panama  [PDF]
Jeffrey S. Smith, Jorge D. Coromac, Victor Raul Alvarez
Current Urban Studies (CUS) , 2016, DOI: 10.4236/cus.2016.43020
Abstract: As the world’s population becomes increasingly urban, efforts to improve the quality of life among the impoverished must turn to cities. The literature asserts that the most successful programs in the fight against poverty are those that are implemented and managed by local community members. Moreover, the personnel in charge of distributing aid must have: 1) the trust and confidence of the community, 2) experience with community outreach, 3) a record of disseminating useful information, and 4) a clear understanding of local cultural traditions. The fire department is an often overlooked community resource that fulfills these requirements. Within the city of Chepo, Panama the fire station has successfully by-passed the thick layers of bureaucracy and is effectively reaching the city’s urban poor. Fire departments in other cities throughout the Global South might consider emulating the example set by Chepo.
Preda??o de ninhos artificiais em uma ilha na Mata Atlantica: testando o local e o tipo de ovo
Alvarez, Ariane D.;Galetti, Mauro;
Revista Brasileira de Zoologia , 2007, DOI: 10.1590/S0101-81752007000400018
Abstract: experiments on artificial nests are usually used to test ecological hypothesis and behavioural that affects the predation of natural bird nests. it is has been discussed about the size of the egg, texture and color affecting predation rate, but a few studies evaluate which egg type is more appropriate to simulate nest predation in tropical areas. the objective of this work was to compare the predation of different models of eggs (coturnix coturnix, plasticine and serinus canarius) on the ground and understory in a island with high abundance of nest predators. the study was carry out in october 2004 at anchieta island, ubatuba, s?o paulo, brazil. the nests on the ground showed a statistical significance difference in the predation of quail eggs, plasticine and canary eggs. however, we did not find differences between plasticine and canaries eggs. the nests in the understory had a different pattern on the ground of quail eggs (25%) and plasticine (28%) and there was a difference when we compare canary eggs with plasticine and quail eggs. our work pointed out that different eggs may have different predation rates. therefore, studies that evaluate reproductive fitness of the bird community based on artificial nests must considered different egg types and strata.
Tipos de ansiedad frente a la donación hipotética de embriones para investigación. una aproximación desde la perspectiva de género
Jorge Alberto Alvarez Díaz
Salud mental , 2006,
Abstract: Un artículo publicado recientemente exploró los tipos de ansiedad que presentan las parejas que han sido tratadas con técnicas de fecundación asistida de alta complejidad, frente a la donación hipotética de embriones para investigación. Los tipos de ansiedad más frecuentes, de acuerdo con la metodología de Gottschalk y cols., fueron la ansiedad de culpa y la ansiedad de separación. En este trabajo se pretende dar una reflexión a modo de ensayo acerca de las probables relaciones entre el género y estos tipos de ansiedad. Ansiedad en medicina reproductiva Los aspectos emocionales y psicológicos, en general han sido poco estudiados en la población de las parejas que tienen problemas de fertilidad. Suele aceptarse que los problemas reproductivos causan repercusiones en la esfera psicológica, pero aún se discute que el factor psicológico pueda ser causa de problemas de fertilidad. Al iniciar este tipo de estudios, se sugirió que las mujeres con un rol femenino tradicional se muestran más ansiosas que los varones. Sin embargo, en buena medida lo anterior dependerá de las concepciones que se establezcan en torno a la relación entre masculinidad y paternidad, feminidad y maternidad. Perspectiva de género La perspectiva de género hace referencia a la concepción académica, ilustrada y científica que sintetiza la teoría, la filosofía y la política liberadoras, creadas por las mujeres en la cultura feminista. El análisis de género feminista es detractor del orden patriarcal, contiene de manera específica una crítica a los aspectos nocivos, destructivos, opresivos y enajenantes que se producen por la organización genérica originada en la desigualdad, la injusticia, y la jerarquía política de las personas basadas en el género. La categoría de cautiverio para el género femenino y la de dominio para el masculino no pueden escapar al ámbito de la medicina reproductiva y a la posibilidad teórica, cada vez más real, de utilizar embriones humanos con fines de investigación. La ansiedad de culpa La ansiedad de culpa se puede asociar con la visión de desaprobación que tiene el cristianismo en occidente respecto de la medicina reproductiva en general y de la donación de embriones en particular, independientemente de si el fin es reproductivo o no. Se podría situar un primer momento del dominio patriarcal a través de la Iglesia y el control ejercido en la sexualidad y la reproductividad en la Familia, y un segundo momento de dominio patriarcal cuando, al no ser suficiente lo anterior, utiliza la medicina reproductiva como agente de dominio sobre el cautiverio femenino: el cauti
Decoherence induced by Smith-Purcell radiation
Ezequiel Alvarez,Francisco D. Mazzitelli
Physics , 2007, DOI: 10.1103/PhysRevA.77.032113
Abstract: The interaction between charged particles and the vacuum fluctuations of the electromagnetic field induces decoherence, and therefore affects the contrast of fringes in an interference experiment. In this article we show that if a double slit experiment is performed near a conducting grating, the fringe visibility is reduced. We find that the reduction of contrast is proportional to the number of grooves in the conducting surface, and that for realistic values of the parameters it could be large enough to be observed. The effect can be understood in terms of the Smith-Purcell radiation produced by the surface currents induced in the conductor.
Exactly Solvable Potentials and Romanovski Polynomials in Quantum Mechanics
D. E. Alvarez-Castillo
Physics , 2008,
Abstract: Orthogonal Polynomials in Quantum Mechanics. Exact solutions of the Schrodinger equation with the hyperbolic Scarf potential (Scarf II) in terms of Romanovski polynomials. Among the applications included is the solution of the problem of an electron within a particular potential leading to the definition of new non-spherical angular functions.
Covariant perturbation theory and the Randall-Sundrum picture
Ezequiel Alvarez,Francisco D. Mazzitelli
Physics , 2000, DOI: 10.1016/S0370-2693(01)00322-7
Abstract: The effective action for quantum fields on a $d$-dimensional spacetime can be computed using a non local expansion in powers of the curvature. We show explicitly that, for conformal fields and up to quadratic order in the curvature, the non local effective action is equivalent to the $d+1$ action for classical gravity in $AdS_{d+1}$ restricted to a $d-1$-brane. This generalizes previous results about quantum corrections to the Newtonian potential and provides an alternative method for making local a non-local effective action. The equivalence can be easily understood by comparing the Kallen-Lehmann decomposition of the classical propagator with the spectral representation of the non local form factors in the quantum effective action.
Mixed phase effects on high-mass twin stars
D. E. Alvarez-Castillo,D. Blaschke
Physics , 2014, DOI: 10.1134/S1063779615050032
Abstract: Recently it has been found that a certain class of hybrid star equations of state with a large latent heat (strong first order phase transition obtained by a Maxwell construction) between stiff hadronic hadronic and stiff quark matter phases allows for the appearance of a third family of compact stars (including "twins") at high mass of $\sim 2 M_\odot$. We investigate how robust this high-mass twin phenomenon is against a smoothing of the transition which would occur, e.g., due to pasta structures in the mixed phase. To this end we propose a simple construction of a pasta-like equation of state with a parameter that quantifies the degree of smoothing of the transition and could eventually be related to the surface tension of the pasta structures. It is interesting to note that the range of energy densities for the transition as well as the pressure at the onset of the transition of this class of hybrid star matter at zero temperature corresponds well to values of the same quantities found in finite temperature lattice QCD simulations for the 1 $\sigma$ region at the pseudocritical temperature $T_c=154 \pm 9$ MeV. The pattern of the speed of sound as a function of energy density is very different.
Proving the CEP with compact stars?
D. E. Alvarez-Castillo,D. Blaschke
Physics , 2013,
Abstract: We present a model for hybrid compact stars composed of a quark core and a hadronic mantle with an abrupt first order phase transition at the interface and in accordance with the latest astrophysical measurements of two 2 M_sun pulsars. We demonstrate the possibility of a disconnected mass-radius sequence (third family) of high-mass pulsars as a distinct feature due to a large jump $\Delta \epsilon$ in the energy density of the first order phase transition setting in at $\epsilon_{\rm crit}\approx 500$ MeV/fm$^3$ and fulfilling $\Delta \epsilon/\epsilon_{\rm crit} > 0.6$. We conclude that the measurement of so called \textit{twin} compact stars at high mass (~ 2 M_sun) would support the existence of a first order phase transition in symmetric matter at zero temperature entailing the existence of a critical end point (CEP) in the QCD phase diagram.
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