16,987 research outputs found

    Three-Loop Calculation of the Anyonic Full Cluster Expansion

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    We calculate the perturbative correction to every cluster coefficient of a gas of anyons through second order in the anyon coupling constant, as described by Chern-Simons field theory.Comment: 10 pages, PlainTex with macro 'manumac', include

    Large lepton mixing and supernova 1987A

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    We reconsider the impact of νˉe↔νˉμ,τ\bar\nu_e \leftrightarrow \bar\nu_{\mu,\tau} neutrino oscillations on the observed νˉe\bar\nu_e signal of supernova SN 1987A. Performing a maximum-likelihood analysis using as fit parameters the released binding energy \Eb and the average neutrino energy \Ee, we find as previous analyses that νˉe↔νˉμ,τ\bar\nu_e \leftrightarrow \bar\nu_{\mu,\tau} oscillations with large mixing angles have lower best-fit values for \Ee than small-mixing angle (SMA) oscillations. Moreover, the inferred value of \Ee is already in the SMA case lower than those found in simulations. This apparent conflict has been interpreted as evidence against the large mixing oscillation solutions to the solar neutrino problem. In order to quantify the degree to which the experimental data favour the SMA over the large mixing solutions we use their likelihood ratios as well as a Kolmogorov-Smirnov test. We find within the range of SN parameters predicted by simulations regions in which the LMA-MSW solution is either only marginally disfavoured or favoured compared to the SMA-MSW solution. We conclude therefore that the LMA-MSW solution is not in conflict with the current understanding of SN physics. In contrast, the vacuum oscillation and the LOW solutions to the solar neutrino problem can be excluded at the 4σ4\sigma level for most of the SN parameter ranges found in simulations. Only a marginal region with low values of \Ee, and \Eb is left over, in which these oscillation solutions can be reconciled with the neutrino signal of SN 1987A.Comment: 23 pages, 20 figures, v2: brief comments adde

    Planck-scale effects on WIMP dark matter

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    There exists a widely known conjecture that gravitational effects violate global symmetries. We study the effect of global-symmetry violating higher-dimension operators induced by Planck-scale physics on the properties of WIMP dark matter. Using an effective description, we show that the lifetime of the WIMP dark matter candidate can satisfy cosmological bounds under reasonable assumptions regarding the strength of the dimension-five operators. On the other hand, the indirect WIMP dark matter detection signal is significantly enhanced due to new decay channels.Comment: 12 pages, 4 figures. Version accepted for publication in Frontier

    Non-Gaussian Geostatistical Modeling using (skew) t Processes

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    We propose a new model for regression and dependence analysis when addressing spatial data with possibly heavy tails and an asymmetric marginal distribution. We first propose a stationary process with tt marginals obtained through scale mixing of a Gaussian process with an inverse square root process with Gamma marginals. We then generalize this construction by considering a skew-Gaussian process, thus obtaining a process with skew-t marginal distributions. For the proposed (skew) tt process we study the second-order and geometrical properties and in the tt case, we provide analytic expressions for the bivariate distribution. In an extensive simulation study, we investigate the use of the weighted pairwise likelihood as a method of estimation for the tt process. Moreover we compare the performance of the optimal linear predictor of the tt process versus the optimal Gaussian predictor. Finally, the effectiveness of our methodology is illustrated by analyzing a georeferenced dataset on maximum temperatures in Australi

    Superconducting/magnetic three state nanodevice for memory and reading applications

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    We present a simple nanodevice that can operate in two modes: i) three-state memory and ii) reading device. The nanodevice is fabricated with an array of ordered triangular-shaped nanomagnets embedded in a superconducting thin film. The input signal is ac current and the output signal is dc voltage. Vortex ratchet effect in combination with out of plane magnetic anisotropy of the nanomagnets is the background physics which governs the nanodevice performance.Comment: 10 pages, 4 figure

    The Timing Counter of the MEG experiment: calibration and performance

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    The MEG detector is designed to test Lepton Flavor Violation in the μ+→e+γ\mu^+\rightarrow e^+\gamma decay down to a Branching Ratio of a few 10−1310^{-13}. The decay topology consists in the coincident emission of a monochromatic photon in direction opposite to a monochromatic positron. A precise measurement of the relative time te+γt_{e^+\gamma} is crucial to suppress the background. The Timing Counter (TC) is designed to precisely measure the time of arrival of the e+e^+ and to provide information to the trigger system. It consists of two sectors up and down stream the decay target, each consisting of two layers. The outer one made of scintillating bars and the inner one of scintillating fibers. Their design criteria and performances are described.Comment: Presented at the 12th Topical Seminar on Innovative Particle and Radiation Detectors (IPRD10) 7 - 10 June 2010, Siena. Accepted by Nuclear Physics B (Proceedings Supplements) (2011)tal

    Scanning laser techniques for characterisation of different surface breaking defect geometries

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    Measurements using a laser scanning system consisting of a pulsed Nd:YAG laser to generate surface ultrasonic waves and an interferometer to detect the surface displacement, are presented for different samples and defect geometries. We show, rstly, details of the interaction of Rayleigh waves in thick samples with machined slots inclined at an angle to the surface normal, or with simple branched geometries, scanning the generation source over the defect (SLLS) or scanning the detection point over the defect (SLD). Secondly, we discuss effects of Lamb waves interacting with V-shaped defects in thin samples. The results from these measurements have shown that the signal enhancement found in the near-eld in both cases can be used to position the defect and gain an idea of its geometry, and have shown this to be a suitable ngerprint of the presence of the defect
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