3,949 research outputs found

    Soliton solutions of Calogero model in harmonic potential

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    A classical Calogero model in an external harmonic potential is known to be integrable for any number of particles. We consider here reductions which play a role of "soliton" solutions of the model. We obtain these solutions both for the model with finite number of particles and in a hydrodynamic limit. In the latter limit the model is described by hydrodynamic equations on continuous density and velocity fields. Soliton solutions in this case are finite dimensional reductions of the hydrodynamic model and describe the propagation of lumps of density and velocity in the nontrivial background.Comment: 25 pages, 2 figure

    Political independence, accountability, and the quality of regulatory decision-making

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    Recent decades have seen a considerable increase in delegation to independent regulatory agencies, which has been justified by reference to the superior performance of these bodies relative to government departments. Yet, the hypothesis that more independent regulators do better work has hardly been tested. We examine the link using a comprehensive measure of the quality of work carried out by competition authorities in 30 Organisation for Economic Co-Operation and Development (OECD) countries, and new data on the design of these organizations. We find that formal independence has a positive and significant effect on quality. Contrary to expectations, though, formal political accountability does not boost regulatory quality, and there is no evidence that it increases the effect of independence by reducing the risk of slacking. The quality of work is also enhanced by increased staffing, more extensive regulatory powers, and spillover effects of a more capable bureaucratic system

    The scalars from the topcolor scenario and the spin correlations of the top pair production at the LHC

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    The topcolor scenario predicts the existences of some new scalars. In this paper, we consider the contributions of these new particles to the observables, which are related to the top quark pair (ttˉt\bar{t}) production at the LHC. It is found that these new particles can generate significant corrections to the ttˉt\bar{t} production cross section and the ttˉt\bar{t} spin correlations.Comment: 23 pages, 4 figures; discussions and references added; agrees with published versio

    Primordial Entropy Production and Lambda-driven Inflation from Quantum Einstein Gravity

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    We review recent work on renormalization group (RG) improved cosmologies based upon a RG trajectory of Quantum Einstein Gravity (QEG) with realistic parameter values. In particular we argue that QEG effects can account for the entire entropy of the present Universe in the massless sector and give rise to a phase of inflationary expansion. This phase is a pure quantum effect and requires no classical inflaton field.Comment: 12 pages, 4 figures, IGCG-07 Pun

    Constraints on SUSY Lepton Flavour Violation by rare processes

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    We study the constraints on flavour violating terms in low energy SUSY coming from several processes as li -> lj gamma, li -> lj lj lj and mu -> e in Nuclei. We show that a combined analysis of the processes allows us to extract additional information with respect to an individual analysis of all the processes. In particular, it makes possible to put bounds on sectors previously unconstrained by li -> lj gamma. We perform the analysis both in the mass eigenstate and in the mass insertion approximations clarifying the limit of applicability of these approximations.Comment: 23 pages, 15 figures. Typos corrected, several references and equations added. Results and conclusions completely unchanged. Accepted version for publication in JHE

    Some non perturbative calculations on spin glasses

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    Models of spin glasses are studied with a phase transition discontinuous in the Parisi order parameter. It is assumed that the leading order corrections to the thermodynamic limit of the high temperature free energy are due to the existence of a metastable saddle point in the replica formalism. An ansatz is made on the form of the metastable point and its contribution to the free energy is calculated. The Random Energy Model is considered along with the p-spin and the p-state Potts Models in their p < infinity expansion.Comment: 12 pages, LaTe

    Magnetization plateaux in the classical Shastry-Sutherland lattice

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    We investigated the classical Shastry-Sutherland lattice under an external magnetic field in order to understand the recently discovered magnetization plateaux in the rare-earth tetraborides compounds RB4_4. A detailed study of the role of thermal fluctuations was carried out by mean of classical spin waves theory and Monte-Carlo simulations. Magnetization quasi-plateaux were observed at 1/3 of the saturation magnetization at non zero temperature. We showed that the existence of these quasi-plateaux is due to an entropic selection of a particular collinear state. We also obtained a phase diagram that shows the domains of existence of different spin configurations in the magnetic field versus temperature plane.Comment: 4 pages, proceedings of HFM200

    Different Scenarios for Critical Glassy Dynamics

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    We study the role of different terms in the NN-body potential of glass forming systems on the critical dynamics near the glass transition. Using a simplified spin model with quenched disorder, where the different terms of the real NN-body potential are mapped into multi-spin interactions, we identified three possible scenarios. For each scenario we introduce a ``minimal'' model representative of the critical glassy dynamics near, both above and below, the critical transition lin e. For each ``minimal'' model we discuss the low temperature equilibrium dynamics.Comment: Completely revised version, 8 pages, 5 figures, typeset using EURO-LaTeX, Europhysics Letters (in press

    Scale-dependent metric and causal structures in Quantum Einstein Gravity

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    Within the asymptotic safety scenario for gravity various conceptual issues related to the scale dependence of the metric are analyzed. The running effective field equations implied by the effective average action of Quantum Einstein Gravity (QEG) and the resulting families of resolution dependent metrics are discussed. The status of scale dependent vs. scale independent diffeomorphisms is clarified, and the difference between isometries implemented by scale dependent and independent Killing vectors is explained. A concept of scale dependent causality is proposed and illustrated by various simple examples. The possibility of assigning an "intrinsic length" to objects in a QEG spacetime is also discussed.Comment: 52 page
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