1,181 research outputs found
Impact of presentation of research results on prescribing of medications in patients with left ventricular dysfunction
The Dirichlet Casimir effect for theory in (3+1) dimensions: A new renormalization approach
We calculate the next to the leading order Casimir effect for a real scalar
field, within theory, confined between two parallel plates in three
spatial dimensions with the Dirichlet boundary condition. In this paper we
introduce a systematic perturbation expansion in which the counterterms
automatically turn out to be consistent with the boundary conditions. This will
inevitably lead to nontrivial position dependence for physical quantities, as a
manifestation of the breaking of the translational invariance. This is in
contrast to the usual usage of the counterterms in problems with nontrivial
boundary conditions, which are either completely derived from the free cases or
at most supplemented with the addition of counterterms only at the boundaries.
Our results for the massive and massless cases are different from those
reported elsewhere. Secondly, and probably less importantly, we use a
supplementary renormalization procedure, which makes the usage of any analytic
continuation techniques unnecessary.Comment: JHEP3 format,20 pages, 2 figures, to appear in JHE
Hybrid stars with the color dielectric and the MIT bag models
We study the hadron-quark phase transition in the interior of neutron stars
(NS). For the hadronic sector, we use a microscopic equation of state (EOS)
involving nucleons and hyperons derived within the Brueckner-Bethe-Goldstone
many-body theory, with realistic two-body and three-body forces. For the
description of quark matter, we employ both the MIT bag model with a density
dependent bag constant, and the color dielectric model. We calculate the
structure of NS interiors with the EOS comprising both phases, and we find that
the NS maximum masses are never larger than 1.7 solar masses, no matter the
model chosen for describing the pure quark phase.Comment: 11 pages, 5 figures, submitted to Phys. Rev.
Screening current effects in Josephson junction arrays
The purpose of this work is to compare the dynamics of arrays of Josephson
junctions in presence of magnetic field in two different frameworks: the so
called XY frustrated model with no self inductance and an approach that takes
into account the screening currents (considering self inductances only). We
show that while for a range of parameters the simpler model is sufficiently
accurate, in a region of the parameter space solutions arise that are not
contained in the XY model equations.Comment: Figures available from the author
Stability of mode-locked kinks in the ac driven and damped sine-Gordon lattice
Kink dynamics in the underdamped and strongly discrete sine-Gordon lattice
that is driven by the oscillating force is studied. The investigation is
focused mostly on the properties of the mode-locked states in the {\it
overband} case, when the driving frequency lies above the linear band. With the
help of Floquet theory it is demonstrated that the destabilizing of the
mode-locked state happens either through the Hopf bifurcation or through the
tangential bifurcation. It is also observed that in the overband case the
standing mode-locked kink state maintains its stability for the bias amplitudes
that are by the order of magnitude larger than the amplitudes in the
low-frequency case.Comment: To appear in Springer Series on Wave Phenomena, special volume
devoted to the LENCOS'12 conference; 6 figure
Three loop anomalous dimension of the second moment of the transversity operator in the MSbar and RI' schemes
We compute the anomalous dimension of the second moment of the transversity
operator, \bar{\psi} \sigma^{\mu\nu} D^\rho \psi, at three loops in both the
MSbar and RI' schemes. As a check on the result we also determine the O(1/N_f)
critical exponent of the n-th moment of the transversity operator in
d-dimensions in the large N_f expansion and determine leading order information
on the n dependence of the anomalous dimension at three and four loops in
MSbar. In addition the RI' anomalous dimension of the non-singlet twist-2
operator, \bar{\psi} \gamma^\mu D^\nu \psi, is also determined.Comment: 18 latex pages; additional reference include
Consequences of vacuum polarization on electromagnetic waves in a Lorentz-symmetry breaking scenario
The propagation of electromagnetic waves in a Lorentz-symmetry violating
scenario where there is a region of polarized vacuum is studied. It turns out
that the photon field acquires an interesting polarization state, possibly
useful to set up upper bounds in Lorentz-violating models at laboratory scales.Comment: Latex, 4 pages. To appear in PL
A mechanism for randomness
We investigate explicit functions that can produce truly random numbers. We
use the analytical properties of the explicit functions to show that certain
class of autonomous dynamical systems can generate random dynamics. This
dynamics presents fundamental differences with the known chaotic systems. We
present realphysical systems that can produce this kind of random time-series.
We report theresults of real experiments with nonlinear circuits containing
direct evidence for this new phenomenon. In particular, we show that a
Josephson junction coupled to a chaotic circuit can generate unpredictable
dynamics. Some applications are discussed.Comment: Accepted in Physics Letters A (2002). 11 figures (.eps
Vortex dynamics and upper critical fields in ultrathin Bi films
Current-voltage (I-V) characteristics of quench condensed, superconducting,
ultrathin films in a magnetic field are reported. These I-V's show
hysteresis for all films, grown both with and without thin underlayers.
Films on Ge underlayers, close to superconductor-insulator transition (SIT),
show a peak in the critical current, indicating a structural transformation of
the vortex solid (VS). These underlayers, used to make the films more
homogeneous, are found to be more effective in pinning the vortices. The upper
critical fields (B) of these films are determined from the resistive
transitions in perpendicular magnetic field. The temperature dependence of the
upper critical field is found to differ significantly from Ginzburg-Landau
theory, after modifications for disorder.Comment: Phys Rev B, to be published Figure 6 replaced with correct figur
Quasiclassical description of transport through superconducting contacts
We present a theoretical study of transport properties through
superconducting contacts based on a new formulation of boundary conditions that
mimics interfaces for the quasiclassical theory of superconductivity. These
boundary conditions are based on a description of an interface in terms of a
simple Hamiltonian. We show how this Hamiltonian description is incorporated
into quasiclassical theory via a T-matrix equation by integrating out
irrelevant energy scales right at the onset. The resulting boundary conditions
reproduce results obtained by conventional quasiclassical boundary conditions,
or by boundary conditions based on the scattering approach. This formalism is
well suited for the analysis of magnetically active interfaces as well as for
calculating time-dependent properties such as the current-voltage
characteristics or as current fluctuations in junctions with arbitrary
transmission and bias voltage. This approach is illustrated with the
calculation of Josephson currents through a variety of superconducting
junctions ranging from conventional to d-wave superconductors, and to the
analysis of supercurrent through a ferromagnetic nanoparticle. The calculation
of the current-voltage characteristics and of noise is applied to the case of a
contact between two d-wave superconductors. In particular, we discuss the use
of shot noise for the measurement of charge transferred in a multiple Andreev
reflection in d-wave superconductors
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