15,934 research outputs found

    Surface Tension in Kac Glass Models

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    In this paper we study a distance-dependent surface tension, defined as the free-energy cost to put metastable states at a given distance. This will be done in the framework of a disordered microscopic model with Kac interactions that can be solved in the mean-field limit.Comment: 13 pages, 6 figure

    Spin glass models with Kac interactions

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    In this paper I will review my work on disordered systems -spin glass model with two body and p>2p>2 body interactions- with long but finite interaction range RR. I will describe the relation of these model with Mean Field Theory in the Kac limit and some attempts to go beyond mean field.Comment: Proceedings of the Stat-phys23 conferenc

    A note on the Guerra and Talagrand theorems for Mean Field Spin Glasses: the simple case of spherical models

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    The aim of this paper is to discuss the main ideas of the Talagrand proof of the Parisi Ansatz for the free-energy of Mean Field Spin Glasses with a physicist's approach. We consider the case of the spherical pp-spin model, which has the following advantages: 1) the Parisi Ansatz takes the simple ``one step replica symmetry breaking form'', 2) the replica free-energy as a function of the order parameters is simple enough to allow for numerical maximization with arbitrary precision. We present the essential ideas of the proof, we stress its connections with the theory of effective potentials for glassy systems, and we reduce the technically more difficult part of the Talagrand's analysis to an explicit evaluation of the solution of a variational problem.Comment: 20 pages, 5 figures. Added references and minor language correction

    Metastable States, Relaxation Times and Free-energy Barriers in Finite Dimensional Glassy Systems

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    In this note we discuss metastability in a long-but-finite range disordered model for the glass transition. We show that relaxation is dominated by configuration belonging to metastable states and associate an in principle computable free-energy barrier to the equilibrium relaxation time. Adam-Gibbs like relaxation times appear naturally in this approach.Comment: 4 pages, 2 figures. Typos correcte

    Analytic determination of dynamical and mosaic length scales in a Kac glass model

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    We consider a disordered spin model with multi-spin interactions undergoing a glass transition. We introduce a dynamic and a static length scales and compute them in the Kac limit (long--but--finite range interactions). They diverge at the dynamic and static phase transition with exponents (respectively) -1/4 and -1. The two length scales are approximately equal well above the mode coupling transition. Their discrepancy increases rapidly as this transition is approached. We argue that this signals a crossover from mode coupling to activated dynamics.Comment: 4 pages, 4 eps figures. New version conform to the published on

    A simple stochastic model for the dynamics of condensation

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    We consider the dynamics of a model introduced recently by Bialas, Burda and Johnston. At equilibrium the model exhibits a transition between a fluid and a condensed phase. For long evolution times the dynamics of condensation possesses a scaling regime that we study by analytical and numerical means. We determine the scaling form of the occupation number probabilities. The behaviour of the two-time correlations of the energy demonstrates that aging takes place in the condensed phase, while it does not in the fluid phase.Comment: 8 pages, plain tex, 2 figure

    Series Expansion of the Off-Equilibrium Mode Coupling Equations

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    We show that computing the coefficients of the Taylor expansion of the solution of the off-equilibrium dynamical equations characterizing models with quenched disorder is a very effective way to understand the long time asymptotic behavior. We study the p=3p=3 spherical spin glass model, and we compute the asymptotic energy (in the critical region and down to T=0T=0) and the coefficients of the time decay of the energy.Comment: 9 pages, LaTeX, 3 uuencoded figure

    On chaos in mean field spin glasses

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    We study the correlations between two equilibrium states of SK spin glasses at different temperatures or magnetic fields. The question, presiously investigated by Kondor and Kondor and V\'egs\"o, is approached here constraining two copies of the same system at different external parameters to have a fixed overlap. We find that imposing an overlap different from the minimal one implies an extensive cost in free energy. This confirms by a different method the Kondor's finding that equilibrium states corresponding to different values of the external parameters are completely uncorrelated. We also consider the Generalized Random Energy Model of Derrida as an example of system with strong correlations among states at different temperatures.Comment: 19 pages, Late
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