42,270 research outputs found

    Comparison of Canonical and Grand Canonical Models for selected multifragmentation data

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    Calculations for a set of nuclear multifragmentation data are made using a Canonical and a Grand Canonical Model. The physics assumptions are identical but the Canonical Model has an exact number of particles, whereas, the Grand Canonical Model has a varying number of particles, hence, is less exact. Interesting differences are found.Comment: 12 pages, Revtex, and 3 postscript figure

    Novel superconductivity: from bulk to nano systems

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    We begin with an introduction of superconductivity by giving a brief history of the phenomenon. The phenomenological Ginzburg–Landau theory and the microscopic theory of Bardeen, Cooper and Schrieffer are outlined. In view of recently available multi-band superconductors, relevant theories of both types are discussed. Unlike the traditional GL theory an extended GL theory is developed relevant to temperatures below the critical temperature. Superconductivity in a nanosystem is the highlight of the remaining part of the paper. Theories and experiments are discussed to give an interested reader an updated account and overview of what is new in this active area of research

    Universal pulse sequence to minimize spin dephasing in the central spin decoherence problem

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    We present a remarkable finding that a recently discovered [G. S. Uhrig, Phys. Rev. Lett. 98, 100504 (2007)] series of pulse sequences, designed to optimally restore coherence to a qubit in the spin-boson model of decoherence, is in fact completely model-independent and generically valid for arbitrary dephasing Hamiltonians given sufficiently short delay times between pulses. The series maximizes qubit fidelity versus number of applied pulses for sufficiently short delay times because the series, with each additional pulse, cancels successive orders of a time expansion for the fidelity decay. The "magical" universality of this property, which was not appreciated earlier, requires that a linearly growing set of "unknowns" (the delay times) must simultaneously satisfy an exponentially growing set of nonlinear equations that involve arbitrary dephasing Hamiltonian operators.Comment: Published in PRL, revise

    Precision and uncertainties in mass scale predictions in SUSY SO(10) with SU(2)_L x SU(2)_R x U(1)_{B-L} x SU(3)_C intermediate breaking

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    In a class of SUSY SO(10) with SU(2)LxSU(2)RxU(1)B−LxSU(3)CSU(2)_L x SU(2)_R x U(1)_{B-L} x SU(3)_C (g2L≠g2R)(g_{2L}\neq g_{2R}) intermediate gauge symmetry, we observe that the prediction on the unification mass (MU)(M_U) is unaffected by Planck-scale-induced gravitational and intermediate-scale-threshold effects, although the intermediate scale (MI)(M_I) itself is subject to such corrections. In particular, without invoking the presence of additional lighter scalar degrees of freedom but including plausible and reasonable threshold effects, we find that interesting solutions for neutrino physics corresponding to MI≃1010−1013M_I\simeq 10^{10}-10^{13} GeV and MU≃(5−6)x1017M_U\simeq (5-6) x 10^{17} GeV are permitted in the minimal models. Possibilities of low-mass right-handed gauge bosons corresponding to MI≃1−10M_I\simeq 1-10 TeV consistent with the CERN-LEP data are pointed out in a number of models when threshold effects are included using effective mass parameters.Comment: 12 pages including 7 tables (Typos corrected as per the published version

    Caloric curve in Au + Au collisions

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    Realistic caloric curves are obtained for 197Au+197Au^{197}Au + ^{197}Au reaction with incident energy ranging from 35 to 130 MeV/nucleon in the dynamic statistical multifragmentation model. It is shown that for excitation energy 3 to 8 MeV/nucleon, the temperature remains constant in the range 5 to 6 MeV, which is close to experiment. The mechanism of energy deposition through the tripartition of colliding system envisaged in this model together with inter-fragment nuclear interaction are found to play important role. A possible signature of liquid-gas phase transition is seen in the specific heat distribution calculated from these caloric curves, and the critical temperature is found to be ∼\sim 6 to 6.5 MeV.Comment: Revtex, 10 pages, 4 postscipt figures, To appear in Phys. Rev. C (Rapid Communications
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