2,992 research outputs found

    Different Scenarios for Critical Glassy Dynamics

    Full text link
    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

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

    Full text link
    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

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

    Get PDF
    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

    Gravitating defects of codimension-two

    Get PDF
    Thin gravitating defects with conical singularities in higher codimensions and with generalized Israel matching conditions are known to be inconsistent for generic energy-momentum. A way to remove this inconsistency is proposed and is realized for an axially symmetric gravitating codimension-two defect in six dimensional Einstein gravity. By varying with respect to the brane embedding fields, alternative matching conditions are derived, which are generalizations of the Nambu-Goto equations of motion of the defect, consistent with bulk gravity. For a maximally symmetric defect the standard picture is recovered. The four-dimensional perfect fluid cosmology coincides with conventional FRW in the case of radiation, but for dust it has rho^{4/3} instead of rho. A four-dimensional black hole solution is presented having the Schwarzschild form with a short-distance correction r^{-2}.Comment: Minor changes, to appear in Classical and Quantum Gravit

    S-particles at their naturalness limits

    Full text link
    We draw attention on a particular configuration of supersymmetric particle masses, motivated by naturalness and flavour considerations. All its relevant phenomenological properties for the LHC are described in terms of a few physical parameters, irrespective of the underlying theoretical model. This allows a simple characterization of its main features, useful to define a strategy for its discovery.Comment: 13 pages, 8 figures, added reference

    Magnetization plateaux in the classical Shastry-Sutherland lattice

    Get PDF
    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

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

    Full text link
    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

    On nonlinear susceptibility in supercooled liquids

    Full text link
    In this paper, we discuss theoretically the behavior of the four point nonlinear susceptibility and its associated correlation length for supercooled liquids close to the Mode Coupling instability temperature TcT_c. We work in the theoretical framework of the glass transition as described by mean field theory of disordered systems, and the hypernetted chain approximation. Our results give an interpretation framework for recent numerical findings on heterogeneities in supercooled liquid dynamics.Comment: Proceedings of the Conference "Unifying Concepts in Glass Physics" ICTP, Trieste, 15 - 18 September 199
    • …
    corecore