174,152 research outputs found
Green's function for the Relativistic Coulomb System via Sum Over Perturbation Series
We evaluate the Green's function of the D-dimensional relativistic Coulomb
system via sum over perturbation series which is obtained by expanding the
exponential containing the potential term in the path integral
into a power series. The energy spectra and wave functions are extracted from
the resulting amplitude.Comment: 13 pages, ReVTeX, no figure
Similarity Solutions of a Class of Perturbative Fokker-Planck Equation
In a previous work, a perturbative approach to a class of Fokker-Planck
equations, which have constant diffusion coefficients and small time-dependent
drift coefficients, was developed by exploiting the close connection between
the Fokker-Planck equations and the Schrodinger equations. In this work, we
further explore the possibility of similarity solutions of such a class of
Fokker-Planck equations. These solutions possess definite scaling behaviors,
and are obtained by means of the so-called similarity method
Net profitability of airline alliances, an empirical study
This study examines the net return for airlines before and after joining an
alliance. The research database was compiled from ICAOData, and comprised 15
international airlines as subjects and their net financial results for a period of 11 years as
primary research variables. Two variables, the averages of five and three years net
performance before joining an alliance, were tested against another variable, the average
net performance five years after joining the alliance. Results show a deterioration of net
profits after joining an alliance, although this trend was only significant when comparing
performance over the short-term. However, the performance of American airlines
accounted for most of this trend, which may have being partly affected by the consequences
of September 11 2001
Hyperspherical Close-Coupling Calculation of D-wave Positronium Formation and Excitation Cross Sections in Positron-Hydrogen Scattering
Hyperspherical close-coupling method is used to calculate the elastic,
positronium formation and excitation cross sections for positron collisions
with atomic hydrogen at energies below the H(n=4) threshold for the J=2 partial
wave. The resonances below each inelastic threshold are also analyzed. The
adiabatic hyperspherical potential curves are used to identify the nature of
these resonances.Comment: 12 pages(in a TeX file) +8 Postscript figure
Thermalization and temperature distribution in a driven ion chain
We study thermalization and non-equilibrium dynamics in a dissipative quantum
many-body system -- a chain of ions with two points of the chain driven by
thermal bath under different temperature. Instead of a simple linear
temperature gradient as one expects from the classical heat diffusion process,
the temperature distribution in the ion chain shows surprisingly rich patterns,
which depend on the ion coupling rate to the bath, the location of the driven
ions, and the dissipation rates of the other ions in the chain. Through
simulation of the temperature evolution, we show that these unusual temperature
distribution patterns in the ion chain can be quantitatively tested in
experiments within a realistic time scale.Comment: 5 pages, 5 figure
Statistical properties of the method of regularization with periodic Gaussian reproducing kernel
The method of regularization with the Gaussian reproducing kernel is popular
in the machine learning literature and successful in many practical
applications.
In this paper we consider the periodic version of the Gaussian kernel
regularization.
We show in the white noise model setting, that in function spaces of very
smooth functions, such as the infinite-order Sobolev space and the space of
analytic functions, the method under consideration is asymptotically minimax;
in finite-order Sobolev spaces, the method is rate optimal, and the efficiency
in terms of constant when compared with the minimax estimator is reasonably
high. The smoothing parameters in the periodic Gaussian regularization can be
chosen adaptively without loss of asymptotic efficiency. The results derived in
this paper give a partial explanation of the success of the
Gaussian reproducing kernel in practice. Simulations are carried out to study
the finite sample properties of the periodic Gaussian regularization.Comment: Published by the Institute of Mathematical Statistics
(http://www.imstat.org) in the Annals of Statistics
(http://www.imstat.org/aos/) at http://dx.doi.org/10.1214/00905360400000045
Far-infrared spectroelectrochemistry: a study of linear molybdenum/iron/sulfur clusters
The far-infrared spectroelectrochemistry of linear M/Fe/S (M=Mo, W) complexes was investigated in methylene chloride and dichloroethane. With CsI as spectral windows, bands above 200 cm−1 can be observed in methylene chloride, except for a weak methylene chloride band at 450 cm−1. Substitution of dichloroethane for methylene chloride, solvents of nearly identical electrochemical properties, allows one to observe solute bands in the 450-cm−1 region. The far-infrared spectroelectrochemistry of [MoFe2S4Cl4]2− and its tungsten analogue was investigated. The disappearance of the oxidation bands and the appearance of bands due to the reduced product could be clearly observed. The origin of the vibrational bands could be clearly identified using 34S-substituted complexes. In addition to the far-infrared bands, the resonance Raman spectroelectrochemistry of the oxidized and reduced complex, along with the 34S-substituted complexes was obtained. Far-infrared and resonance Raman spectroelectrochemistry can be combined to understand the electrochemical mechanism of transition metal complexes.
The far-infrared spectroelectrochemistry of [MoFe2S4Cl4]2− and its tungsten analogue was investigated. The disappearance of the initial bands and the appearance of bands due to the reduced product could be clearly observed. Resonance Raman spectroscopy and the use of 34S-substituted complexes were used for characterization of the reactant and products
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