8,105 research outputs found

    Phase transitions and adiabatic preparation of a fractional Chern insulator in a boson cold atom model

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    We investigate the fate of hardcore bosons in a Harper-Hofstadter model which was experimentally realized by Aidelsburger et al. [Nature Physics 11 , 162 (2015)] at half filling of the lowest band. We discuss the stability of an emergent fractional Chern insulator (FCI) state in a finite region of the phase diagram that is separated from a superfluid state by a first-order transition when tuning the band topology following the protocol used in the experiment. Since crossing a first-order transition is unfavorable for adiabatically preparing the FCI state, we extend the model to stabilize a featureless insulating state. The transition between this phase and the topological state proves to be continuous, providing a path in parameter space along which an FCI state could be adiabatically prepared. To further corroborate this statement, we perform time-dependent DMRG calculations which demonstrate that the FCI state may indeed be reached by adiabatically tuning a simple product state.Comment: 7 pages, 7 figures, published versio

    Diffractive dissociation into KsK±ππK_sK^{\pm}\pi^{\mp}\pi^{-} final states

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    The COMPASS fixed-target experiment at CERN/SPS is dedicated to the study of hadron structure and spectroscopy, especially the search for spin-exotic states. After having started to study the existence of the spin-exotic π1(1600)\pi_1(1600) resonance in the 2004 pilot-run data, the new 2008/09 data will enable us to further clarify the situation. Apart from the π1(1600)\pi_1(1600) resonance, also a spin-exotic π1(2000)\pi_1(2000) was reported in the past in the f1(1285)πf_1(1285)\pi decay channel by the E852/BNL experiment, however, this state still lacks confirmation. We present a first event selection of the diffractively produced (KKˉππ)(K\bar{K}\pi\pi)^{-} system showing clean f1(1285)f_1(1285) and f1(1420)f_1(1420) resonances at competing statistics. A partial-wave analysis started on f1(1285)πf_1(1285)\pi and f1(1420)πf_1(1420)\pi decay channels will further complete the search for spin-exotics in the 2008/09 COMPASS data.Comment: 4 pages, 6 figures, Hadron2011 Conference Proceedings, to appear in the proceedings of the XIV International Conference on Hadron Spectroscopy: Hadron 2011, Munich, Germany, 13-17 June 201

    NLO QCD predictions for Z+γZ+\gamma + jets production with Sherpa

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    We present precise predictions for prompt photon production in association with a ZZ boson and jets. They are obtained within the Sherpa framework as a consistently merged inclusive sample. Leptonic decays of the ZZ boson are fully included in the calculation with all offshell effects. Virtual matrix elements are provided by OpenLoops and parton shower effects are simulated with a dipole parton shower. Thanks to the NLO QCD corrections included not only for inclusive ZγZ\gamma production but also for the ZγZ\gamma + 1-jet process we find significantly reduced systematic uncertainties and very good agreement with experimental measurements at s=8\sqrt{s}=8 TeV. Predictions at s=13\sqrt{s}=13 TeV are displayed including a study of theoretical uncertainties. In view of an application of these simulations within LHC experiments, we discuss in detail the necessary combination with a simulation of the ZZ + jets final state. In addition to a corresponding prescription we introduce recommended cross checks to avoid common pitfalls during the overlap removal between the two samples.Comment: 20 pages, 15 Figure

    Mutual information in classical spin models

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    The total many-body correlations present in finite temperature classical spin systems are studied using the concept of mutual information. As opposed to zero-temperature quantum phase transitions, the total correlations are not maximal at the phase transition, but reach a maximum in the high temperature paramagnetic phase. The Shannon and Renyi mutual information in both Ising and Potts models in 2 dimensions are calculated numerically by combining matrix product states algorithms and Monte Carlo sampling techniques

    Impact of Specialization on Health Outcomes – Evidence from U.S. Cancer Data

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    There have been many studies of the volume-outcome relationship. In all of these, the unit of analysis is the hospital or physician. However, this level of analysis is mostly limited to the use of in-hospital mortality rates and is particularly sensitive to selective referral. Moreover, the literature on agglomeration economies highlights the importance of information spillovers within regions (Glaeser, 2010). To overcome these problems, our study is the first that examines the volume-outcome relationship on a regional (county or cancer registry) level. Using data from the National Cancer Institute’s Surveillance, Epidemiology and End Results program we find that regions with relatively more of the same cancer type exhibit relatively better health outcomes.Specialization, experience, cancer, survival