15,034 research outputs found
Physics of planetary atmospheres III - The time-dependent coupled Hartree-Fock approximation
Coupled Hartree-Fock approximation for calculating frequency-dependent refractive index of helium ga
Drawn to the Sea: Charles Bradford Hudson (1865-1939), Artist, Author, Army Officer, with Special Notice of His Work for the United States Fish Commission and Bureau of Fisheries
The biography of Charles Bradford Hudson that follows this preface had its seeds about 1965 when I (VGS) was casually examining the extensive files of original illustrations of fishes stored in the Division of Fishes, National Museum of Natural History, Smithsonian Institution. I happened upon the unpublished illustration of a rainbow trout by Hudson and was greatly impressed with its quality. The thought occurred to me then that the artist must have gone on to do more than just illustrate fishes. During the next 20 years I occasionally pawed through those files, which contained the work of numerous artists, who had worked from 1838 to
the present. In 1985, I happened to discuss the files with my supervisor, who urged me to produce a museum exhibit of original fish illustrations. This I did, selecting 200 of the illustrations representing 21 artists, including, of course, Hudson. As part of the text for the exhibit, Drawn from the Sea, Art in the Service of Ichthyology, I prepared short biographies of each of the artists. The exhibit, with an available poster, was shown in the Museum for six months,
and a reduced version was exhibited in U.S. and Canadian museums during the next 3 years
Cohomology of Conformal Algebras
Conformal algebra is an axiomatic description of the operator product
expansion of chiral fields in conformal field theory. On the other hand, it is
an adequate tool for the study of infinite-dimensional Lie algebras satisfying
the locality property. The main examples of such Lie algebras are those
``based'' on the punctured complex plane, like the Virasoro algebra and loop
algebras. In the present paper we develop a cohomology theory of conformal
algebras with coefficients in an arbitrary module. It possesses standard
properties of cohomology theories; for example, it describes extensions and
deformations. We offer explicit computations for most of the important
examples.Comment: 46 pp., AMSLaTeX, uses epsfig, amssymb, amsc
Anderson localization of solitons in optical lattices with random frequency modulation
We report on phenomenon of Anderson-type localization of walking solitons in
optical lattices with random frequency modulation, manifested as dramatic
enhancement of soliton trapping probability on lattice inhomogeneities with
growth of the frequency fluctuation level. The localization process is strongly
sensitive to the lattice depth since in shallow lattices walking solitons
experience random refraction and/or multiple scattering in contrast to
relatively deep lattices, where solitons are typically immobilized in the
vicinity of local minimums on modulation frequency.Comment: 13 pages, 4 figures, to appear in Physical Review
Fast simulation of the leaky bucket algorithm
We use fast simulation methods, based on importance sampling, to efficiently estimate cell loss probability in queueing models of the Leaky Bucket algorithm. One of these models was introduced by Berger (1991), in which the rare event of a cell loss is related to the rare event of an empty finite buffer in an "overloaded" queue. In particular, we propose a heuristic change of measure for importance sampling to efficiently estimate the probability of the rare empty-buffer event in an asymptotically unstable GI/GI/1/k queue. This change of measure is, in a way, "dual" to that proposed by Parekh and Walrand (1989) to estimate the probability of a rare buffer overflow event. We present empirical results to demonstrate the effectiveness of our fast simulation method. Since we have not yet obtained a mathematical proof, we can only conjecture that our heuristic is asymptotically optimal, as k/spl rarr//spl infin/
Vortices and quasiparticles near the "superconductor-insulator" transition in thin films
We study the low temperature behavior of an amorphous superconducting film
driven normal by a perpendicular magnetic field (B). For this purpose we
introduce a new two-fluid formulation consisting of fermionized field induced
vortices and electrically neutralized Bogoliubov quasiparticles (spinons)
interacting via a long-ranged statistical interaction. This approach allows us
to access a novel non-Fermi liquid phase which naturally interpolates between
the low B superconductor and the high B normal metal. We discuss the transport,
thermodynamic, and tunneling properties of the resulting "vortex metal" phase.Comment: 4 pages, 1 figure, references adde
Analog-digital simulation of transient-induced logic errors and upset susceptibility of an advanced control system
A simulation study is described which predicts the susceptibility of an advanced control system to electrical transients resulting in logic errors, latched errors, error propagation, and digital upset. The system is based on a custom-designed microprocessor and it incorporates fault-tolerant techniques. The system under test and the method to perform the transient injection experiment are described. Results for 2100 transient injections are analyzed and classified according to charge level, type of error, and location of injection
Color Bosonization, Chiral Parametrization of Gluonic Field and QCD Effective Action
We develop a color bosonization approach to treatment of QCD gauge field
(''gluons'') at low energies in order to derive an effective color action of
QCD taking into account the quark chiral anomaly in the case of SU(2) color..
We have found that there exists such a region in the chiral sector of color
space, where a gauge field coincides with of chirally rotated vector field,
while an induced axial vector field disappears. In this region, the unit color
vector of chiral field plays a defining role, and a gauge field is parametrized
in terms of chiral parameters, so that no additional degrees of freedom are
introduced by the chiral field. A QCD gauge field decomposition in color
bosonization is a sum of a chirally rotated gauge field and an induced
axial-vector field expressed in terms of gluonic variables. An induced
axial-vector field defines the chiral color anomaly and an effective color
action of QCD. This action admits existence of a gauge invariant d=2 condensate
of induced axial-vector field and mass.Comment: 13 pages, LaTe
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