2,657 research outputs found

    Unparticle contribution to the hydrogen atom ground state energy

    Get PDF
    In the present work we study the effect of unparticle modified static potentials on the energy levels of the hydrogen atom. By using Rayleigh-Schr\"odinger perturbation theory, we obtain the energy shift of the ground state and we compare it with experimental data. Bounds on the unparticle energy scale ΛU\Lambda_\mathcal{U} as a function of the scaling dimension dUd_\mathcal{U} and the coupling constant λ\lambda are derived. We show that there exists a parameter region where bounds on ΛU\Lambda_\mathcal{U} are stringent, signalling that unparticles could be tested in atomic physics experiments.Comment: 11 pages, 3 figure

    Minimal Scales from an Extended Hilbert Space

    Full text link
    We consider an extension of the conventional quantum Heisenberg algebra, assuming that coordinates as well as momenta fulfil nontrivial commutation relations. As a consequence, a minimal length and a minimal mass scale are implemented. Our commutators do not depend on positions and momenta and we provide an extension of the coordinate coherent state approach to Noncommutative Geometry. We explore, as toy model, the corresponding quantum field theory in a (2+1)-dimensional spacetime. Then we investigate the more realistic case of a (3+1)-dimensional spacetime, foliated into noncommutative planes. As a result, we obtain propagators, which are finite in the ultraviolet as well as the infrared regime.Comment: 16 pages, version which matches that published on CQ

    Inclusive Safety at School: How to Train Teachers

    Get PDF
    The paper presents the activities proposed last year during the first edition of the course \u201cSafety at school\u201d, organized by the University of Macerata and S.E.T.A. (Safety Education Training Agency) Association. Six workshops held by uni\uadversity professors and other experts, focused on the topic of inclusive safety both at school and in the city in order to provide the opportunity of exchanging ideas and field experiences. The idea of the course came up after the earthquakes that stroke the cent\uadral Italy, to offer new conceptual and practical instruments to face the topic of safety at school. As a conclusion, the first edition of the course was a satisfying pilot to move forward to the next step. The exit questionnaire showed a high level of satisfaction from participants

    Spinning Loop Black Holes

    Full text link
    In this paper we construct four Kerr-like spacetimes starting from the loop black hole Schwarzschild solutions (LBH) and applying the Newman-Janis transformation. In previous papers the Schwarzschild LBH was obtained replacing the Ashtekar connection with holonomies on a particular graph in a minisuperspace approximation which describes the black hole interior. Starting from this solution, we use a Newman-Janis transformation and we specialize to two different and natural complexifications inspired from the complexifications of the Schwarzschild and Reissner-Nordstrom metrics. We show explicitly that the space-times obtained in this way are singularity free and thus there are no naked singularities. We show that the transformation move, if any, the causality violating regions of the Kerr metric far from r=0. We study the space-time structure with particular attention to the horizons shape. We conclude the paper with a discussion on a regular Reissner-Nordstrom black hole derived from the Schwarzschild LBH and then applying again the Newmann-Janis transformation.Comment: 18 pages, 18 figure

    Diagnosing numerical Cherenkov instabilities in relativistic plasma simulations based on general meshes

    Full text link
    Numerical Cherenkov radiation (NCR) or instability is a detrimental effect frequently found in electromagnetic particle-in-cell (EM-PIC) simulations involving relativistic plasma beams. NCR is caused by spurious coupling between electromagnetic-field modes and multiple beam resonances. This coupling may result from the slow down of poorly-resolved waves due to numerical (grid) dispersion and from aliasing mechanisms. NCR has been studied in the past for finite-difference-based EM-PIC algorithms on regular (structured) meshes with rectangular elements. In this work, we extend the analysis of NCR to finite-element-based EM-PIC algorithms implemented on unstructured meshes. The influence of different mesh element shapes and mesh layouts on NCR is studied. Analytic predictions are compared against results from finite-element-based EM-PIC simulations of relativistic plasma beams on various mesh types.Comment: 31 pages, 20 figure

    Alternatives to Transplantation in the Treatment of Heart Failure: New Diagnostic and Therapeutic Insights

    Get PDF
    none4siThe aim of our current special issue was to present a series of original researches and reviews on recent advances in the diagnosis, medical therapy, and surgical approaches of heart failure. As reported in the introductive review of Agnetti et al., cardiovascular disease is the leading cause of mortality in the US and in westernized countries with ischemic heart disease accounting for the majority of these deaths. Paradoxically, the improvements in the medical and surgical treatments of acute coronary syndromes are leading to an increasing number of “survivors” who are then developing heart failure. Despite considerable advances in its management, the gold standard for the treatment of end-stage heart failure patients remains heart transplantation. Nevertheless, this procedure can be o ered only to a small percentage of patients who could bene t from a new heart due to the limited availability of donor organs. e authors reported in this comprehensive review the evaluation of the safety and e cacy of innovative approaches in the diagnosis and treatment of patients refrac- tory to standard medical therapy and excluded from cardiac transplantation lists.mixedNicolini, Francesco; Piepoli, Massimo F.; Agnetti, Giulio; Siniscalchi, GiuseppeNicolini, Francesco; Piepoli, Massimo F.; Agnetti, Giulio; Siniscalchi, Giusepp

    New Insights in the Diagnosis and Treatment of Heart Failure

    Get PDF
    Cardiovascular disease is the leading cause of mortality in the US and in westernized countries with ischemic heart disease accounting for the majority of these deaths. Paradoxically, the improvements in the medical and surgical treatments of acute coronary syndrome are leading to an increasing number of "survivors" who are then developing heart failure. Despite considerable advances in its management, the gold standard for the treatment of end-stage heart failure patients remains heart transplantation. Nevertheless, this procedure can be offered only to a small percentage of patients who could benefit from a new heart due to the limited availability of donor organs. The aim of this review is to evaluate the safety and efficacy of innovative approaches in the diagnosis and treatment of patients refractory to standard medical therapy and excluded from cardiac transplantation lists

    A criterion for optimal management of water distribution networks

    Get PDF
    The management of water supply systems is based on fundamental principles, set by international and national legislations; the general target for water utilities is to offer a reliable and effective service following efficiency criteria. In this context, losses in distribution networks are one of the main problems to tackle: their reduction implies a general decrease in operational costs and in the need for a limited resource such as water. Numerous solutions have been proposed to reduce non revenue water, from simple leak detection to structural interventions on distribution systems, based on new design criteria which favour district-based networks over redundant ones. The present work proposes a new procedure to restructure a water supply network starting from its hydraulic model, comparing different types of intervention and evaluating their feasibility, limits and effectiveness in terms of the global system efficiency, as measured by the infrastructure leakage index (ILI). The possibility to use excessive pressure in specific parts of a network for the production of electricity is also examined, as it offers an additional resource to improve the system performance. The procedure has been tested for the water network in the municipalities of Tarcento and Magnano in Riviera, near Udine in Italy. Thanks to a specific hydraulic model, simulations were performed to identify the optimal interventions on the system aimed at reducing water losses and improving performances and efficiency
    corecore