Mostrando recursos 121 - 140 de 10.050

  1. Asymptotic aging in structural glasses

    Grigera, T.S.; Martín Mayor, Víctor; Parisi, G.; Verrocchio, P.
    Using a nonlocal Monte Carlo algorithm, we study the aging of a fragile glass, being able to follow it up to equilibrium, down to 0.89T_(MC) (T_(MC) is the mode-coupling temperature), and up to long waiting times at lower temperatures. We show that the fluctuation-dissipation ratio is independent of the dynamics chosen and is compatible with a phase transition and that the scaling behavior of the aging part of the correlation supports the full-aging scenario.

  2. Unimodular gravity and general relativity UV divergent contributions to the scattering of massive scalar particles

    González-Martín, S.; Pérez Martín, Carmelo
    We work out the one-loop and order κ 2m2 φ UV divergent contributions, coming from Unimodular Gravity and General Relativity, to the S matrix element of the scattering process φ+φ → φ+φ in a λφ4 theory with mass mφ . We show that both Unimodular Gravity and General Relativity give rise to the same UV divergent contributions in Dimension Regularization. This seems to be at odds with the known result that in a multiplicative MS dimensional regularization scheme the General Relativity corrections, in the de Donder gauge, to the beta function βλ of the λ coupling do not vanish, whereas...

  3. Chiral topological superconductors enhanced by long-range interactions

    Viyuela García, Óscar; Fu, Liang; Martin-Delgado Alcántara, Miguel Ángel
    We study the phase diagram and edge states of a two-dimensional p-wave superconductor with longrange hopping and pairing amplitudes. New topological phases and quasiparticles different from the usual short-range model are obtained. When both hopping and pairing terms decay with the same exponent, one of the topological chiral phases with propagating Majorana edge states gets significantly enhanced by longrange couplings. On the other hand, when the long-range pairing amplitude decays more slowly than the hopping, we discover new topological phases where propagating Majorana fermions at each edge pair nonlocally and become gapped even in the thermodynamic limit. Remarkably, these nonlocal...

  4. 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...

  5. 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...

  6. 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...

  7. 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.

  8. 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.

  9. 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...

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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...

  17. 7501-18 FISICA Oscilaciones Mecánicas

    Silva, Carlos; Farina, Juan
    Material de estudio para alumnos de 5º año - Área Física.

  18. 7101-18 FISICA - Estructura de la materia y fenómenos térmicos

    Godino, María Eugenia; Vettorel, Silvia; Marini, Silvana
    Material de estudio para alumnos de 1º año - Área Física.

  19. Estrutura e dinâmica do fitoplâncton em diferentes escalas temporais e espaciais em ambientes límnicos

    Bohnenberger, Juliana Elisa
    Este estudo teve como objetivo principal avaliar a estrutura e dinâmica do fitoplâncton em diferentes escalas temporais e espaciais em ambientes límnicos, verificando o padrão de distribuição da comunidade, a estrutura funcional e as principais variáveis ambientais correlacionadas, inclusive, em períodos perturbação. O primeiro estudo foi realizado na Lagoa Mangueira, uma lagoa costeira rasa, situada no sul do Rio Grande do Sul, Brasil, e se avaliou como as diferentes abordagens funcionais (formas de vida, máxima dimensão linear, grupos funcionais sensu Reynolds, grupos morfo-funcionais sensu Salmaso e Padisák e os grupos funcionais baseados na morfologia sensu Kruk), são correlacionadas com a...

  20. Análisis de las características mecánicas y físicas de la unidad de construcción ancestral, denominada putuco, situada en el altiplano peruano

    Gamio Felipa, Andrea Lissy
    Las zonas rurales del altiplano peruano, son afectadas por los fenómenos climatológicos de friajes y heladas. En la actualidad muchas de ellas no cuentan con la infraestructura necesaria para afrontarlos, aun cuando existen viviendas vernáculares como herencia de sus antepasados que les permitió resistir a las inclemencias climatológicas, entre ellas se tienen “Los putucos” en Puno. Los Putucos constituyen un sistema constructivo ancestral del altiplano peruano, que ha perdurado en el tiempo por el empírico conocimiento que utilizaron los pobladores, con el propósito de cubrir las necesidades básicas de protección contra los cambios climatológicos. El presente trabajo de fin de...

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