10,408 research outputs found

    Macroscopic Quantum Tunneling and the "cosmic" Josephson effect

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    We discuss the possible influence of a cosmic magnetic field on the macroscopic quantum tunneling process associated, in a cosmological context, to the decay of the "false vacuum." We find a close analogy with the effects of an external magnetic field applied to a Josephson junction in the context of low-temperature/high-temperature superconducting devices.Comment: 4 pages, 1 pdf figure. Added references and an inset in Fig. 1, results unchanged. To appear in Phys. Rev. D (Brief Report

    Double Transverse-Spin Asymmetries in Drell-Yan Processes with Antiprotons

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    We present next-to-leading order predictions for double transverse-spin asymmetries in Drell--Yan dilepton production initiated by proton--antiproton scattering. The kinematic region of the proposed PAX experiment at GSI: 30\lesssim{s}\lesssim200\GeV^2 and 2\lesssim{M}\lesssim7\GeV is examined. The Drell--Yan asymmetries turn out to be large, in the range 20--40%. Measuring these asymmetries would provide the cleanest determination of the quark transversity distributions.Comment: 11 pages, 7 figures, uses elsart and feynmp (included); one new reference adde

    The One Dimensional Damped Forced Harmonic Oscillator Revisited

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    In this paper we give a general solution to the problem of the damped harmonic oscillator under the influence of an arbitrary time-dependent external force. We employ simple methods accessible for beginners and useful for undergraduate students and professors in an introductory course of mechanics.Comment: 4 Latex page

    Charged currents, color dipoles and xF_3 at small x

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    We develop the light-cone color dipole description of highly asymmetric diffractive interactions of left-handed and right-handed electroweak bosons. We identify the origin and estimate the strength of the left-right asymmetry effect in terms of the light-cone wave functions. We report an evaluation of the small-x neutrino-nucleon DIS structure functions xF_3 and 2xF_1 and present comparison with experimental data.Comment: 11 pages, 3 figures, misprints correcte

    Diagnostics for specific PAHs in the far-IR: searching neutral naphthalene and anthracene in the Red Rectangle

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    Context. In the framework of the interstellar polycyclic aromatic hydrocarbons (PAHs) hypothesis, far-IR skeletal bands are expected to be a fingerprint of single species in this class. Aims. We address the question of detectability of low energy PAH vibrational bands, with respect to spectral contrast and intensity ratio with ``classical'' Aromatic Infrared Bands (AIBs). Methods. We extend our extablished Monte-Carlo model of the photophysics of specific PAHs in astronomical environments, to include rotational and anharmonic band structure. The required molecular parameters were calculated in the framework of the Density Functional Theory. Results. We calculate the detailed spectral profiles of three low-energy vibrational bands of neutral naphthalene, and four low-energy vibrational bands of neutral anthracene. They are used to establish detectability constraints based on intensity ratios with ``classical'' AIBs. A general procedure is suggested to select promising diagnostics, and tested on available Infrared Space Observatory data for the Red Rectangle nebula. Conclusions. The search for single, specific PAHs in the far-IR is a challenging, but promising task, especially in view of the forthcoming launch of the Herschel Space Observatory.Comment: 13 pages, 13 figures, accepted for publication in A&

    Observation of a New Fluxon Resonant Mechanism in Annular Josephson Tunnel Structures

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    A novel dynamical state has been observed in the dynamics of a perdurbed sine-Gordon system. This resonant state, has been experimentally observed as a singularity in the dc current voltage characteristic of an annular Josephson tunnel junction, excited in the presence of a magnetic field. With this respect, it can be assimilated to self-resonances known as Fiske steps. Differently from these, however, we demonstrate, on the basis of numerical simulations, that its detailed dynamics involves rotating fluxon pairs, a mechanism associated, so far, to self-resonances known as zero-field steps.Comment: 4 pages, 2 figures, submitted to Physical Review Letter