174,824 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
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
Adiabatic State Conversion and Pulse Transmission in Optomechanical Systems
Optomechanical systems with strong coupling can be a powerful medium for
quantum state engineering. Here, we show that quantum state conversion between
cavity modes with different wavelengths can be realized with high fidelity by
adiabatically varying the effective optomechanical couplings. The fidelity for
the conversion of gaussian states is derived by solving the Langevin equation
in the adiabatic limit. We also show that photon pulses can be transmitted
between input-output channels with different wavelengths via the effective
optomechanical couplings and the output pulse shape can also be manipulated.Comment: 5 pages, 2 figures. Supplementary Materials at
http://prl.aps.org/supplemental/PRL/v108/i15/e15360
Nonlocal Kirchhoff superlinear equations with indefinite nonlinearity and lack of compactness
We study the following Kirchhoff equation A
special feature of this paper is that the nonlinearity and the potential
are indefinite, hence sign-changing. Under some appropriate assumptions on
and , we prove the existence of two different solutions of the equation
via the Ekeland variational principle and Mountain Pass Theorem
Concrete: Potential material for Space Station
To build a permanent orbiting space station in the next decade is NASA's most challenging and exciting undertaking. The space station will serve as a center for a vast number of scientific products. As a potential material for the space station, reinforced concrete was studied, which has many material and structural merits for the proposed space station. Its cost-effectiveness depends on the availability of lunar materials. With such materials, only 1 percent or less of the mass of a concrete space structure would have to be transported from earth
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
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
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
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