6,628 research outputs found

    Radion Assisted Gauge Inflation

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    We propose an extension to the recently proposed extranatural or gauge inflation scenario in which the radius modulus field around which the Wilson loop is wrapped assists inflation as it shrinks. We discuss how this might lead to more generic initial conditions for inflation.Comment: 10 pages, 2 figure

    Large N(c′)_(c'), chiral approach to M(n′)_(n') at finite temperature

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    We study the temperature dependence of the eta and eta[prime] meson masses within the framework of U(3)LĂ—U(3)R chiral perturbation theory, up to next-to-leading order in a simultaneous expansion in momenta, quark masses and number of colors. We find that both masses decrease at low temperatures, but only very slightly. We analyze higher order corrections and argue that large Nc suggests a discontinuous drop of Meta[prime] at the critical temperature of deconfinement Tc, consistent with a first order transition to a phase with approximate U(1)A symmetry

    Anomalous amplitudes in a thermal bath

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    I review the implications of the axial anomaly in a thermal bath. I assume that the Adler-Bardeen theorem applies at nonzero temperature, so that the divergence of the axial current remains is independent of temperature. Nevertheless, I argue that while the anomaly doesn't change with temperature, ``anomalous'' mesonic couplings do. This is verified by explicit calculations in a low temperature expansion, and near the chiral phase transition.Comment: 11 pages, PTPTeX, to appear in the Proceedings of YKIS '9

    Employment status and work-related problems of gastrointestinal cancer patients at diagnosis: a cross-sectional study

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    Objective To assess the employment status of patients with gastrointestinal cancer at diagnosis and to examine work-related problems of employed patients. Design New, consecutive patients were included at the Gastrointestinal Oncology Center Amsterdam, a one-stop, rapid access diagnostic assessment centre. Patients were interviewed on their employment status by a nurse. If (self-) employed, patients were asked to self-report on work-related problems, perceived distress (0-10), cancer-related problems, fatigue (MFI-20, range 4-20) and work ability (three WAI questions, range 0-10). Results Of all 333 included new consecutive patients (age range 32-89 years), 95 patients (28%) were (self-) employed at time of diagnosis, 179 (54%) were pensioners, and 59 were not working (18%). For the assessment of work-related problems, 45 (47%) of these 95 employed patients with cancer participated. Their mean age was 56 years, and patients had oesophageal/stomach (49%), colorectal (18%) or hepatic/pancreatic/biliary cancer (33%). Half of the employed patients (49%) were still at work, while 51% were on sick leave. The main reasons for sick leave were stress (35%), (scheduled) operation (26%), fatigue (17%) and pain (13%). Most patients on sick leave (70%) had no contact with their own occupational physician, although the majority (67%) would like to continue to work. Work-related problems were experienced by 73% of working patients. The mean work ability was 5.4, the mean general fatigue score was 11.5, and the mean distress score was 4.7. Employed patients on sick leave reported a lower work ability, more fatigue and higher distress but no more cancer-related problems compared with those still working. Conclusion A quarter of all patients with gastrointestinal cancer seen at an oncological centre are employed at time of diagnosis, and of these employed patients, 73% experience work-related problems. During diagnosis and treatment, information and support on work-related issues should be offered to patients with cancer as an essential part of high-quality oncological car

    Background reionization history from omniscopes

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    The measurements of the 21-cm brightness temperature fluctuations from the neutral hydrogen at the Epoch of Reionization (EoR) should inaugurate the next generation of cosmological observables. In this respect, many works have concentrated on the disambiguation of the cosmological signals from the dominant reionization foregrounds. However, even after perfect foregrounds removal, our ignorance on the background reionization history can significantly affect the cosmological parameter estimation. In particular, the interdependence between the hydrogen ionized fraction, the baryon density and the optical depth to the redshift of observation induce nontrivial degeneracies between the cosmological parameters that have not been considered so far. Using a simple, but consistent reionization model, we revisit their expected constraints for a futuristic giant 21-cm omniscope by using for the first time Markov Chain Monte Carlo (MCMC) methods on multiredshift full sky simulated data. Our results agree well with the usual Fisher matrix analysis on the three-dimensional flat sky power spectrum but only when the above-mentioned degeneracies are kept under control. In the opposite situation, Fisher results can be inaccurate. We show that these conditions can be fulfilled by combining cosmic microwave background measurements with multiple observation redshifts probing the beginning of EoR. This allows a precise reconstruction of the total optical depth, reionization duration and maximal spin temperature. Finally, we discuss the robustness of these results in presence of unresolved ionizing sources. Although most of the standard cosmological parameters remain weakly affected, we find a significant degradation of the background reionization parameter estimation in presence of nuisance ionizing sources.Comment: 22 pages, 18 figures, uses RevTex. References added, matches published versio

    Invisible Higgs and Scalar Dark Matter

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    In this proceeding, we show that when we combined WMAP and the most recent results of XENON100, the invisible width of the Higgs to scalar dark matter is negligible(<10%), except in a small region with very light dark matter (< 10 GeV) not yet excluded by XENON100 or around 60 GeV where the ratio can reach 50% to 60%. The new results released by the Higgs searches of ATLAS and CMS set very strong limits on the elastic scattering cross section.Comment: 4 pages, 2 figures, proceeding TAUP2011 References adde

    Vacuum Structure and the Axion Walls in Gluodynamics and QCD with Light Quarks

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    Large N gluodynamics was shown to have a set of metastable vacua with the gluonic domain walls interpolating between them. The walls may separate the genuine vacuum from an excited one, or two excited vacua which are unstable at finite N (here N is the number of colors). One may attempt to stabilize them by switching on the axion field. We study how the light quarks and the axion affect the structure of the domain walls. In pure gluodynamics (with the axion field) the axion walls acquire a very hard gluonic core. Thus, we deal with a wall "sandwich" which is stable at finite N. In the case of the minimal axion, the wall "sandwich" is in fact a "2-pi" wall, i.e., the corresponding field configuration interpolates between identical hadronic vacua. The same properties hold in QCD with three light quarks and very large number of colors. However, in the realistic case of three-color QCD the phase corresponding to the axion field profile in the axion wall is screened by a dynamical phase associated with the eta-prime, so that the gluon component of the wall is not excited. We propose a toy Lagrangian which models these properties and allows one to get exact solutions for the domain walls.Comment: 22 pages Latex, no figure

    Dashen's phenomenon in gauge theories with spontaneously broken chiral symmetries

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    We examine Dashen’s phenomenon in the Leutwyler-Smilga regime of QCD with any number of colors and quarks in either the fundamental or adjoint representations of the gauge group. In this limit, the theories only depend on simple combinations of quark masses, the volume, chiral condensate and vacuum angle. Based upon this observation, we derive simple expressions for the chiral condensate and the topological density and show that they are in fact related. By examining the zeros of the various partition functions, we elucidate the mechanism leading to Dashen’s phenomena in QCD

    New Physics at the LHC. A Les Houches Report: Physics at TeV Colliders 2009 - New Physics Working Group

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    We present a collection of signatures for physics beyond the standard model that need to be explored at the LHC. First, are presented various tools developed to measure new particle masses in scenarios where all decays include an unobservable particle. Second, various aspects of supersymmetric models are discussed. Third, some signatures of models of strong electroweak symmetry are discussed. In the fourth part, a special attention is devoted to high mass resonances, as the ones appearing in models with warped extra dimensions. Finally, prospects for models with a hidden sector/valley are presented. Our report, which includes brief experimental and theoretical reviews as well as original results, summarizes the activities of the "New Physics" working group for the "Physics at TeV Colliders" workshop (Les Houches, France, 8-26 June, 2009).Comment: 189 page
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