21,692 research outputs found

    A phenomenological analysis of azimuthal asymmetries in unpolarized semi-inclusive deep inelastic scattering

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    We present a phenomenological analysis of the cos-phi and cos-2phi asymmetries in unpolarized semi-inclusive deep inelastic scattering, based on the recent multidimensional data released by the COMPASS and HERMES Collaborations. In the TMD framework, valid at relatively low transverse momenta, these asymmetries arise from intrinsic transverse momentum and transverse spin effects, and from their correlations. The role of the Cahn and Boer-Mulders effects in both azimuthal moments is explored up to order 1/Q. As the kinematics of the present experiments is dominated by the low-Q^2 region, higher-twist contributions turn out to be important, affecting the results of our fits.Comment: 18 pages, 5 figures, one paragraph added at the end of Section IV, one reference added. PRD versio

    Low-temperature transport through a quantum dot between two superconductor leads

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    We consider a quantum dot coupled to two BCS superconductors with same gap energies Δ\Delta. The transport properties are investigated by means of infinite-UU noncrossing approximation. In equilibrium density of states, Kondo effect shows up as two sharp peaks around the gap bounds. Application of a finite voltage bias leads these peaks to split, leaving suppressed peaks near the edges of energy gap of each lead. The clearest signatures of the Kondo effect in transport are three peaks in the nonlinear differential conductance: one around zero bias, another two at biases ±2Δ\pm 2\Delta. This result is consistent with recent experiment. We also predict that with decreasing temperature, the differential conductances at biases ±2Δ\pm 2\Delta anomalously increase, while the linear conductance descends.Comment: replaced with revised versio

    Dispersionless motion in a driven periodic potential

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    Recently, dispersionless (coherent) motion of (noninteracting) massive Brownian particles, at intermediate time scales, was reported in a sinusoidal potential with a constant tilt. The coherent motion persists for a finite length of time before the motion becomes diffusive. We show that such coherent motion can be obtained repeatedly by applying an external zero-mean square-wave drive of appropriate period and amplitude, instead of a constant tilt. Thus, the cumulative duration of coherent motion of particles is prolonged. Moreover, by taking an appropriate combination of periods of the external field, one can postpone the beginning of the coherent motion and can even have coherent motion at a lower value of position dispersion than in the constant tilt case.Comment: 4 pages, 4 figure

    Noise rectification by a superconducting loop with two weak links

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    We consider a superconducting loop with two weak links that encloses a magnetic flux. The weak links are unequal and are treated as Josephson junctions with non-sinusoidal phase dependence. We devise a model that takes into account the fluctuation of the critical currents, due to the fluctuations of the order parameter in the weak links. These fluctuations are important near the onset of superconductivity; in this regime they may significantly weaken and eventually disconnect the superconducting loop. As a consequence of these fluctuations and of the resistive noise in the junctions, the average dc voltage does not vanish. Our model can be easily extended to provide a qualitative description of a recent experiment.Comment: version accepted by PR

    Spin analog of the controlled Josephson charge current

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    We propose a controlled Josephson spin current across the junction of two non-centrosymmetric superconductors like CePt_3Si. The Josephson spin current arises due to direction dependent tunneling matrix element and different momentum dependent phases of the triplet components of the gap function. Its modulation with the angle \xi between the noncentrosymmetric axes of two superconductors is proportional to \sin \xi. This particular dependence on \xi may find application of the proposed set-up in making a Josephson spin switch.Comment: 4 pages, 1 figure; title is changed; article is rewritte

    Increasing empathic accuracy through practice and feedback in a clinical interviewing course

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    Accurate empathy, long argued to be important in psychotherapy, now is an object of social-cognitive research. Graduate-level psychology students viewed brief portions of a therapy session and inferred the thoughts and feelings of the client. Accuracy scores were the rated similarity of their inferences to the client\u27s reported thoughts and feelings. Throughout the semester course in interviewing, experimental participants practiced such judgments with feedback, while controls did not. Both groups\u27 accuracy increased from pre-to post-test on inferred feelings, in part because the post-test was easier. Nonetheless experimental participants on the post-test had greater accuracy of inferred feelings than controls. Women were more accurate than men in inferences for thoughts at post-test. Implications for training and future research are discussed

    Running-phase state in a Josephson washboard potential

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    We investigate the dynamics of the phase variable of an ideal underdamped Josephson junction in switching current experiments. These experiments have provided the first evidence for macroscopic quantum tunneling in large Josephson junctions and are currently used for state read-out of superconducting qubits. We calculate the shape of the resulting macroscopic wavepacket and find that the propagation of the wavepacket long enough after a switching event leads to an average voltage increasing linearly with time.Comment: 6 pages, 3 figure

    Statistics of voltage fluctuations in resistively shunted Josephson junctions

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    The intrinsic nonlinearity of Josephson junctions converts Gaussian current noise in the input into non-Gaussian voltage noise in the output. For a resistively shunted Josephson junction with white input noise we determine numerically exactly the properties of the few lowest cumulants of the voltage fluctuations, and we derive analytical expressions for these cumulants in several important limits. The statistics of the voltage fluctuations is found to be Gaussian at bias currents well above the Josephson critical current, but Poissonian at currents below the critical value. In the transition region close to the critical current the higher-order cumulants oscillate and the voltage noise is strongly non-Gaussian. For coloured input noise we determine the third cumulant of the voltage.Comment: 9 pages, 5 figure

    Designing arrays of Josephson junctions for specific static responses

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    We consider the inverse problem of designing an array of superconducting Josephson junctions that has a given maximum static current pattern as function of the applied magnetic field. Such devices are used for magnetometry and as Terahertz oscillators. The model is a 2D semilinear elliptic operator with Neuman boundary conditions so the direct problem is difficult to solve because of the multiplicity of solutions. For an array of small junctions in a passive region, the model can be reduced to a 1D linear partial differential equation with Dirac distribution sine nonlinearities. For small junctions and a symmetric device, the maximum current is the absolute value of a cosine Fourier series whose coefficients (resp. frequencies) are proportional to the areas (resp. the positions) of the junctions. The inverse problem is solved by inverse cosine Fourier transform after choosing the area of the central junction. We show several examples using combinations of simple three junction circuits. These new devices could then be tailored to meet specific applications.Comment: The article was submitted to Inverse Problem

    Water governance in France: institutional framework, stakeholders, arrangements and process

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    The enforcement of the European Water Framework Directive (WFD) is not such an administrative issue in France as it is in other countries, since competent authorities (water agencies) already have jurisdiction over major watersheds (districts). As far as the WFD implementation is concerned, setting and reaching objectives of water quality (good status) and implementing cost recovery policy are more challenging for France and will require necessary changes and adjustments. Water in France is not managed according to its ownership, but its uses. In this chapter, after (i) an overview of the water governance institutional framework, (ii) the water governance arrangements is tackled: the main stakeholders is described and key issues of the current process of making decision are dealt with, in the general context of implementing the WFD. The original institutional tools developed to integrate different water uses for the sake of ecosystems preservation are also considered
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