10,625 research outputs found
Scaling Invariance in a Time-Dependent Elliptical Billiard
We study some dynamical properties of a classical time-dependent elliptical
billiard. We consider periodically moving boundary and collisions between the
particle and the boundary are assumed to be elastic. Our results confirm that
although the static elliptical billiard is an integrable system, after to
introduce time-dependent perturbation on the boundary the unlimited energy
growth is observed. The behaviour of the average velocity is described using
scaling arguments
AN ANALYSIS OF U.S. DAIRY POLICY DEREGULATION USING AN IMPERFECT COMPETITION MODEL
An imperfect competition model of the U.S. milk market is developed for analyzing the impacts of dairy policy deregulation. Estimated degree-of-competition parameters indicate that the U.S. milk market has become more competitive over time. The usefulness of the model is demonstrated by showing the relative differences of dynamic simulation results of the imperfect competition model with the results of a conventional exogenous fluid differential model.Agricultural and Food Policy,
GENERIC ADVERTISING WEAROUT: THE CASE OF THE NEW YORK CITY FLUID MILK CAMPAIGN
This article examines two major generic fluid milk advertising campaigns in New York City during the 1986-92 period. Estimates from a time-varying parameter model show that the evolution of the impact of generic advertising on fluid milk sales over each campaign followed a bell-shaped pattern. Results also show that the first campaign was effective for twice as long as the second campaign and that it has a higher peak and higher average advertising elasticity. These findings may reflect long-term generic milk advertising wearout in the New York City market.Marketing,
Hidden Breit-Wigner distribution and other properties of random matrices with preferential basis
We study statistical properties of a class of band random matrices which
naturally appears in systems of interacting particles. The local spectral
density is shown to follow the Breit-Wigner distribution in both localized and
delocalized regimes with width independent on the band/system size. We analyse
the implications of this distribution to the inverse participation ratio, level
spacing statistics and the problem of two interacting particles in a random
potential.Comment: 4 pages, 4 postscript figures appended, new version with minor
change
QCD near the Light Cone
Starting from the QCD Lagrangian, we present the QCD Hamiltonian for near
light cone coordinates. We study the dynamics of the gluonic zero modes of this
Hamiltonian. The strong coupling solutions serve as a basis for the complete
problem. We discuss the importance of zero modes for the confinement mechanism.Comment: 32 pages, ReVTeX, 2 Encapsulated PostScript figure
Trapping of Projectiles in Fixed Scatterer Calculations
We study multiple scattering off nuclei in the closure approximation. Instead
of reducing the dynamics to one particle potential scattering, the scattering
amplitude for fixed target configurations is averaged over the target
groundstate density via stochastic integration. At low energies a strong
coupling limit is found which can not be obtained in a first order optical
potential approximation. As its physical explanation, we propose it to be
caused by trapping of the projectile. We analyse this phenomenon in mean field
and random potential approximations.
(PACS: 24.10.-i)Comment: 15 page
Nasal carriage of Staphylococcus aureus treated with topical mupirocin (pseudomonic acid) in a children's hospital
2% mupirocin ointment applied intra-nasally for 5 days was assessed for elimination of nasal carriage of Staphylococcus aureus in 31 staff members in a children's hospital. Three volunteers failed to complete the trial because of side effects, i.e. buccal reddening and swelling, and unpleasant taste. During treatment staphylococcal nasal carriage was not found in any case; of the 24 post-treatment nasal swabs taken 4 days after treatment 22 were still negative. Re-colonization with S. aureus of different phage types occurred in the remaining two cases
Local Spectral Density for a Periodically Driven System of Coupled Quantum States with Strong Imperfection in Unperturbed Energies
A random matrix theory approach is applied in order to analyze the
localization properties of local spectral density for a generic system of
coupled quantum states with strong static imperfection in the unperturbed
energy levels. The system is excited by an external periodic field, the
temporal profile of which is close to monochromatic one. The shape of local
spectral density is shown to be well described by the contour obtained from a
relevant model of periodically driven two-states system with irreversible
losses to an external thermal bath. The shape width and the inverse
participation ratio are determined as functions both of the Rabi frequency and
of parameters specifying the localization effect for our system in the absence
of external field.Comment: 6 pages, 5 figures, submitted to Optics and Spectroscop
Aperiodic order and pure point diffraction
We give a leisurely introduction into mathematical diffraction theory with a
focus on pure point diffraction. In particular, we discuss various
characterisations of pure point diffraction and common models arising from cut
and project schemes. We finish with a list of open problems.Comment: 14 page
Gauge-invariant and infrared-improved variational analysis of the Yang-Mills vacuum wave functional
We study a gauge-invariant variational framework for the Yang-Mills vacuum
wave functional. Our approach is built on gauge-averaged Gaussian trial
functionals which substantially extend previously used trial bases in the
infrared by implementing a general low-momentum expansion for the vacuum-field
dispersion (which is taken to be analytic at zero momentum). When completed by
the perturbative Yang-Mills dispersion at high momenta, this results in a
significantly enlarged trial functional space which incorporates both dynamical
mass generation and asymptotic freedom. After casting the dynamics associated
with these wave functionals into an effective action for collections of soft
vacuum-field orbits, the leading infrared improvements manifest themselves as
four-gradient interactions. Those turn out to significantly lower the minimal
vacuum energy density, thus indicating a clear overall improvement of the
vacuum description. The dimensional transmutation mechanism and the dynamically
generated mass scale remain almost quantitatively robust, however, which
ensures that our prediction for the gluon condensate is consistent with
standard values. Further results include a finite group velocity for the soft
gluonic modes due to the higher-gradient corrections and indications for a
negative differential color resistance of the Yang-Mills vacuum.Comment: 47 pages, 5 figures (vs2 contains a few minor stylistic adjustments
to match the published version
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