102,276 research outputs found
Supercurrent fluctuations in short filaments
We evaluate the average and the standard deviation of the supercurrent in
superconducting nanobridges, as functions of the temperature and the phase
difference, in an equilibrium situation. We also evaluate the autocorrelation
of the supercurrent as a function of the elapsed time. The behavior of
supercurrent fluctuations is qualitatively different from from that of the
normal current: they depend on the phase difference, have a different
temperature dependence, and for appropriate range their standard deviation is
independent of the probing time. We considered two radically different
filaments and obtained very similar results for both. Fluctuations of the
supercurrent can in principle be measured
The Deuteron Spin Structure Functions in the Bethe-Salpeter Approach and the Extraction of the Neutron Structure Function
The nuclear effects in the spin-dependent structure functions and
are calculated in the relativistic approach based on the Bethe-Salpeter
equation with a realistic meson-exchange potential.
The results of calculations are compared with the non-relativistic
calculations. The problem of extraction of the neutron spin structure function,
, from the deuteron data is discussed.Comment: (Talk given at the SPIN'94 International Symposium, September 15-22,
1994, Bloomington, Indiana), 6 pages, 5 figures, Preprint Alberta Thy 29-9
Magneto-controlled nonlinear optical materials
We exploit theoretically a magneto-controlled nonlinear optical material
which contains ferromagnetic nanoparticles with a non-magnetic metallic
nonlinear shell in a host fluid. Such an optical material can have anisotropic
linear and nonlinear optical properties and a giant enhancement of
nonlinearity, as well as an attractive figure of merit.Comment: 11 pages, 2 figures. To be published in Appl. Phys. Let
Modulational instability of partially coherent signals in electrical transmission lines
We present an investigation of the modulational instability of partially
coherent signals in electrical transmission lines. Starting from the modified
Ginzburg-Landau equations and the Wigner-Moyal representation, we derive a
nonlinear dispersion relation for the modulational instability. It is found
that the effect of signal broadbandness reduces the growth rate of the
modulational instability.Comment: 5 pages, 1 figure, to appear in Physical Review
Embedded epitaxial growth of low-threshold GaInAsP/InP injection lasers
Single-growth liquid-phase embedded epitaxy in the GaInAsP/InP system is described, and a new heterostructure laser is grown using this technique. These lasers exhibit excellent current and optical confinement. Threshold currents as low as 45 mA are achieved for a laser with 4-mm-wide active region
Information filtering via Iterative Refinement
With the explosive growth of accessible information, expecially on the
Internet, evaluation-based filtering has become a crucial task. Various systems
have been devised aiming to sort through large volumes of information and
select what is likely to be more relevant. In this letter we analyse a new
ranking method, where the reputation of information providers is determined
self-consistently.Comment: 10 pages, 3 figures. Accepted for publication on Europhysics Letter
Stationary transport in mesoscopic hybrid structures with contacts to superconducting and normal wires. A Green's function approach for multiterminal setups
We generalize the representation of the real time Green's functions
introduced by Langreth and Nordlander [Phys. Rev. B 43 2541 (1991)] and Meir
and Wingreen [Phys. Rev. Lett. 68 2512 (1992)] in stationary quantum transport
in order to study problems with hybrid structures containing normal (N) and
superconducting (S) pieces. We illustrate the treatment in a S-N junction under
a stationary bias and investigate in detail the behavior of the equilibrium
currents in a normal ring threaded by a magnetic flux with attached
superconducting wires at equilibrium. We analyze the flux sensitivity of the
Andreev states and we show that their response is equivalent to the one
corresponding to the Cooper pairs with momentum q=0 in an isolated
superconducting ring.Comment: 11 pages, 3 figure
Multipole polarizability of a graded spherical particle
We have studied the multipole polarizability of a graded spherical particle
in a nonuniform electric field, in which the conductivity can vary radially
inside the particle. The main objective of this work is to access the effects
of multipole interactions at small interparticle separations, which can be
important in non-dilute suspensions of functionally graded materials. The
nonuniform electric field arises either from that applied on the particle or
from the local field of all other particles. We developed a differential
effective multipole moment approximation (DEMMA) to compute the multipole
moment of a graded spherical particle in a nonuniform external field. Moreover,
we compare the DEMMA results with the exact results of the power-law graded
profile and the agreement is excellent. The extension to anisotropic DEMMA will
be studied in an Appendix.Comment: LaTeX format, 2 eps figures, submitted for publication
A New World Average Value for the Neutron Lifetime
The analysis of the data on measurements of the neutron lifetime is
presented. A new most accurate result of the measurement of neutron lifetime
[Phys. Lett. B 605 (2005) 72] 878.5 +/- 0.8 s differs from the world average
value [Phys. Lett. B 667 (2008) 1] 885.7 +/- 0.8 s by 6.5 standard deviations.
In this connection the analysis and Monte Carlo simulation of experiments
[Phys. Lett. B 483 (2000) 15] and [Phys. Rev. Lett. 63 (1989) 593] is carried
out. Systematic errors of about -6 s are found in each of the experiments. The
summary table for the neutron lifetime measurements after corrections and
additions is given. A new world average value for the neutron lifetime 879.9
+/- 0.9 s is presented.Comment: 27 pages, 13 figures; Fig.13 update
Localization of transverse waves in randomly layered media at oblique incidence
We investigate the oblique incidence of transverse waves on a randomly
layered medium in the limit of strong disorder. An approximate method for
calculating the inverse localization length based on the assumptions of zero
energy flux and complete phase stochastization is presented. Two effects not
found at normal incidence have been studied: dependence of the localization
length on the polarization, and decrease of the localization length due to the
internal reflections from layers with small refractive indexes. The inverse
localization length (attenuation rate) for P-polarized radiation is shown to be
always smaller than that of S-waves, which is to say that long enough randomly
layered sample polarizes transmitted radiation. The localization length for
P-polarization depends non-monotonically on the angle of propagation, and under
certain conditions turns to infinity at some angle, which means that typical
(non-resonant) random realizations become transparent at this angle of
incidence (stochastic Brewster effect).Comment: 12 pages, 1 figure, accepted for publication in Physical Review
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