42,270 research outputs found
Comparison of Canonical and Grand Canonical Models for selected multifragmentation data
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
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
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
In a class of SUSY SO(10) with
intermediate gauge symmetry, we observe that the
prediction on the unification mass is unaffected by
Planck-scale-induced gravitational and intermediate-scale-threshold effects,
although the intermediate scale 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
GeV and GeV are
permitted in the minimal models. Possibilities of low-mass right-handed gauge
bosons corresponding to 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
Realistic caloric curves are obtained for 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 6 to 6.5 MeV.Comment: Revtex, 10 pages, 4 postscipt figures, To appear in Phys. Rev. C
(Rapid Communications
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