Mostrando recursos 81 - 100 de 3.334

  1. Anderson localization in Euclidean random matrices

    Ciliberti, S.; Grigera, T.S.; Martín Mayor, Víctor; Parisi, G.; Verrocchio, P.
    We study the spectra and localization properties of Euclidean random matrices defined on a random graph. We introduce a powerful method to find the density of states and the localization threshold in topologically disordered soff-latticed systems. We solve numerically an equation sexact on the random graphd for the probability distribution function of the diagonal elements of the resolvent matrix, with a population dynamics algorithm sPDAd. We show that the localization threshold can be estimated by studying the stability of a population of real resolvents under the PDA. An application is given in the context of the instantaneous normal modes of...

  2. Rejuvenation and memory in model spin glasses in three and four dimensions

    Jiménez, S.; Martín Mayor, Víctor; Pérez Gaviro, S.
    We numerically study aging for the Edwards-Anderson model in three and four dimensions using different temperature-change protocols. In D=3, time scales a thousand times larger than in previous work are reached with the Spin Update Engine SUE machine. Deviations from cumulative aging are observed in the nonmonotonic time behavior of the coherence length. Memory and rejuvenation effects are found in a temperature-cycle protocol, revealed by vanishing effective waiting times. Similar effects are reported for the D=3 site-diluted ferromagnetic Ising model without chaos. However, rejuvenation is reduced if off-equilibrium corrections to the fluctuation-dissipation theorem are considered. Memory and rejuvenation are quantitatively...

  3. Wilson loops in the Higgs phase of large-N field theories on the conifold

    Cáceres, Elena; Hernández Redondo, Rafael
    We study the quark-antiquark interaction in the large N limit of the superconformal field theory on D-3branes at a Calabi-Yau conical singularity. We compute the Wilson loop in the AdS_(5) × T^(11) supergravity background for the SU(2 N ) × SU(2 N) theory. We also calculate the Wilson loop for the Higgs phase where the gauge group is broken to SU ( N ) × SU ( N ) × SU_(D) ( N). This corresponds to a two center configuration with some of the branes at the singularity and the rest of them at a smooth point. The calculation exhibits...

  4. Glueball masses for the deformed conifold theory

    Cáceres, Elena; Hernández Redondo, Rafael
    We obtain the spectrum of glueball masses for the N = 1 non-conformal cascade theory whose supergravity dual was recently constructed by Klebanov and Strassler. The glueball masses are calculated by solving the supergravity equations of motion for the dilaton and the two-form in the deformed conifold background.

  5. Supersymmetric quantum mechanics from wrapped branes

    Hernández Redondo, Rafael; Sfetsos, Konstadinos
    We explicitly construct a solution of eight-dimensional gauged supergravity representing D6-branes wrapped on six-cycles inside Calabi–Yau fourfolds. The solution preserves two supercharges and asymptotically is a cone with the coset space SU(2)^(4)/U(1)^(3) as its base. It is shown to correspond to an M-theory compactification on a Calabi–Yau manifold with SU(5) holonomy and we discuss in detail its geometrical and topological features. We also construct a family of related higherdimensional metrics having SU(n + 1) holonomy, which of course have no brane interpretation.

  6. S-duality and the Calabi-Yau interpretation of the N=4 to N=2 flow

    Gómez, César; Hernández Redondo, Rafael; López, Esperanza
    The action of the S-duality Sl(2,Z) group on the moduli of the Calabi-Yau manifold WIP^(12)_(11226) appearing in the rank two dual pair (K3 × T 2/WIP^(12)_(11226)) is defined by interpreting the N = 4 to N = 2 flow, for SU(2) supersymmetric YangMills, in terms of the Calabi-Yau moduli. The different singularity loci are mapped in a one to one way, and the (N = 2 limit/point particle limit) is obtained in both cases by the same type of blow up. Moreover, it is shown that the S-duality group permutes the different singularity loci of the moduli of WIP^(12)_(11226). We...

  7. K3 fibrations and softly broken N=4 supersymmetric gauge theories

    Gómez, César; Hernández Redondo, Rafael; López, Esperanza
    Global geometry of K3-fibration Calabi-Yau threefolds, with Hodge number h_(2,1) = r+1, is used to define N =4 softly broken SU(r+1) gauge theories, with the bare coupling constant given by the dual heterotic dilaton, and the mass of the adjoint hypermultiplet given by the heterotic string tension. The U(r+1) Donagi-Witten integrable model is also derived from the K3-fibration structure, with the extra U(1) associated to the heterotic dilaton. The case of SU(2) gauge group is analyzed in detail. String physics beyond the heterotic point particle limit is partially described by the N =4 softly broken theory.

  8. M and F theory instantons, N=1 supersymmetry and fractional topological charge

    Gómez, César; Hernández Redondo, Rafael
    We analize instanton generated superpotentials for three dimensional N = 2 supersymmetric gauge theories obtained by compactifying on S^(1) N = 1 four dimensional theories. For SU(2) with N_(f) = 1, we find that the vacua in the decompactification limit is given by the singular points of the Coulomb branch of the N = 2 four dimensional theory (we also consider the massive case). The decompactification limit of the superpotential for pure gauge theories without chiral matter is interpreted in terms of ‘t Hooft’s fractional instanton amplitudes.

  9. M-theory, torons and confinement

    Gómez, C.; Hernández Redondo, Rafael
    We study the decompactification limit of M-theory superpotentials for N = 1 four dimensional supersymmetric gauge theories. These superpotentials can be interpreted as generated by toron configurations. The connection with the confinement picture in the maximal abelian gauge is discussed.

  10. Calibrated geometries and non-perturbative superpotentials in M-theory

    Hernández Redondo, Rafael
    We consider non-perturbative effects in M-theory compactifications on a seven-manifold of G_(2) holonomy arising from membranes wrapped on supersymmetric three-cycles. When membranes are wrapped on associative submanifolds they induce a superpotential that can be calculated using calibrated geometry. This superpotential is also derived from compactification on a seven-manifold, to four dimensional anti-de Sitter spacetime, of eleven dimensional supergravity with non-vanishing expectation value of the four-form field strength.

  11. Branes wrapped on coassociative cycles

    Hernández Redondo, Rafael
    We obtain a supergravity solution arising when D6-branes are wrapped on coassociative four-cycles of constant curvature in seven manifolds of G_(2) holonomy. The solutions preserve two supercharges and thus represent supergravity duals of three dimensional Yang-Mills with N = 1 supersymmetry. When uplifted to eleven dimensions our solution describes M-theory on the background of an eight manifold with Spin(7) holonomy.

  12. An eight-dimensional approach to G(2) manifolds

    Hernández Redondo, Rafael; Sfetsos, Konstadinos
    We develop a systematic approach to G_(2) holonomy manifolds with an SU(2) × SU(2) isometry using maximal eight-dimensional gauged supergravity to describe D6-branes wrapped on deformed three-spheres. A quite general metric ansatz that generalizes the celebrated Bryant–Salamon metric involves nine functions. We show that only six of them are the independent ones and derive the general first order system of differential equations that they obey. As a byproduct of our analysis, we generalize the notion of the twist that relates the spin and gauge connections in a way that involves non-trivially the scalar fields.

  13. Branes with fluxes wrapped on spheres

    Hernández Redondo, Rafael; Sfetsos, Konstadinos
    Following an eight-dimensional gauged supergravity approach we construct the most general solution describing D6-branes wrapped on a Kähler four-cycle taken to be the product of two spheres of different radii. Our solution interpolates between a Calabi–Yau four-fold and the spaces S^(2) × S^(2) × S^(2) × IR^(2) or S^(2) × S^(2) × IR^(4) , depending on generic choices for the parameters. Then we turn on a background four-form field strength, corresponding to D2-branes, and show explicitly how our solution is deformed. For a particular choice of parameters it represents a flow from a Calabi–Yau four-fold times the three-dimensional Minkowski space-time...

  14. 1501-18 MATEMATICA Derivadas

    Rosito, Mirta; Godino, Patricia
    Material de estudio para alumnos de 5º año - Área Matemática.

  15. 1301-18 MATEMATICA Proporcionalidad- Semejanza-Razones trigonométricas

    Bue, Juan Carlos; Lagreca, Noemí; Martínez, María del Luján; Candio, Daniela
    Material de estudio para alumnos de 3º año - Área Matemática.

  16. 1201-18 MATEMÁTICA - Números Reales

    Napolitano, Mónica; Napoli, Carla
    Material de estudio para alumnos de 2º año - Área Matemática.

  17. 1101-18 MATEMÁTICA Conjunto - Reales no negativos - Volumen

    Filotti, Verónica; Martínez, María del Luján
    Material de estudio para alumnos de 1º año - Área Matemática.

  18. Evaluación de distintos métodos para estimar la temperatura de operación de módulos fotovoltaicos y estimación de las pérdidas de energía por efecto de la temperatura

    Battioni, Mario; Risso Patrón, Gustavo N.; Cutrera, Miriam; Schmidt, Javier
    Debido a la incidencia de la temperatura de un panel fotovoltaico en su rendimiento energético, se compararon distintos modelos matemáticos que predicen en forma aceptable la temperatura final de un panel en función de las variables climáticas. Para ello se utilizaron los datos experimentales de una instalación fotovoltaica ubicada en la ciudad de Rosario, aplicando cinco modelos conocidos y evaluando cuál es el que mejor ajusta los valores reales medidos. Una vez elegido el modelo más adecuado, se hizo el cálculo de temperatura de operación de un panel en distintos puntos de la Provincia de Santa Fe para los cuales...

  19. Discalculia: contributo do Geogebra nas crianças com NEE

    Pimenta, Nélia José
    Hoje em dia os alunos têm inúmeras dificuldades na disciplina de Matemática, nomeadamente na resolução de problemas e em certas competências envolvendo cálculos. Em particular, a Discalculia traduz um caso extremo deste tipo de dificuldades, sendo uma Necessidade Educativa Especial (NEE) classificada como Dificuldade de Aprendizagem Específica (DAE). A escola e toda a comunidade educativa têm-se mostrado preocupados com o insucesso dos alunos, sobretudo os que revelam dificuldades na aprendizagem das operações matemáticas e falhas no raciocinio lógico-matemático, derivadas de desordens de caráter neuro-processológico, sendo que estes, em termos de inteligência, apresentam parâmetros considerados normais, podendo até sobressair noutras áreas. É...

  20. El aprendizaje de las matemáticas financieras

    Pérez Briceño , Juan Carlos; Iñiguez Ortega , Andrea; León Pineda , Sergio Mauricio
    Este artículo se enmarca en el aprendizaje de las Matemáticas Financieras en los alumnos que se encuentran cursando sus estudios en la Universidad Nacional de Loja. Realizando una ligera reseña histórica, que indica la necesaria aplicación de las matemáticas en el campo de las finanzas y la formación en este ámbito, se lleva a cabo un análisis de la situación actual, se conceptualiza y analiza la importancia que tienen para otras asignaturas, se realiza una revisión de los contenidos y fórmulas más importantes de la misma, para así poder llegar a concluir el por qué estudiar Matemáticas Financieras, no sólo...

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