17,859 research outputs found
A semiclassical theory of quantum noise in open chaotic systems
We consider the quantum evolution of classically chaotic systems in contact
with surroundings. Based on -scaling of an equation for time evolution
of the Wigner's quasi-probability distribution function in presence of
dissipation and thermal diffusion we derive a semiclassical equation for
quantum fluctuations. This identifies an early regime of evolution dominated by
fluctuations in the curvature of the potential due to classical chaos and
dissipation. A stochastic treatment of this classical fluctuations leads us to
a Fokker-Planck equation which is reminiscent of Kramers' equation for
thermally activated processes. This reveals an interplay of three aspects of
evolution of quantum noise in weakly dissipative open systems; the reversible
Liouville flow, the irreversible chaotic diffusion which is characteristic of
the system itself, and irreversible dissipation induced by the external
reservoir. It has been demonstrated that in the dissipation-free case a
competition between Liouville flow in the contracting direction of phase space
and chaotic diffusion sets a critical width in the Wigner function for quantum
fluctuations. We also show how the initial quantum noise gets amplified by
classical chaos and ultimately equilibrated under the influence of dissipation.
We establish that there exists a critical limit to the expansion of phase
space. The limit is determined by chaotic diffusion and dissipation. Making use
of appropriate quantum-classical correspondence we verify the semiclassical
analysis by the fully quantum simulation in a chaotic quartic oscillator.Comment: Plain Latex, 27 pages, 6 ps figure, To appear in Physica
Spacelab baseline ECS trace contaminant removal test program
An estimate of the Spacelab Baseline Environmental Control System's contaminated removal capability was required to allow determination of the need for a supplemental trace contaminant removal system. Results from a test program to determine this removal capability are presented
Radial deformation of the earth by oceanic tidal loading
A high-degree spherical harmonic series is used to compute the radial deformation of the Earth by oceanic tidal loading. By exploiting fast numerical transforms, this approach is found to be much more efficient, but no less accurate, than the traditional Green's function approach. The method is used to derive an atlas of load tide maps for 10 constitutents of the NSWC ocean tide model
Low-Mass Dileptons at the CERN-SpS: Evidence for Chiral Restoration?
Using a rather complete description of the in-medium spectral function
- being constrained by various independent experimental information - we
calculate pertinent dilepton production rates from hot and dense hadronic
matter. The strong broadening of the resonance entails a reminiscence to
perturbative annihilation rates in the vicinity of the phase
boundary. The application to dilepton observables in Pb(158AGeV)+Au collisions
- incorporating recent information on the hadro-chemical composition at
CERN-SpS energies - essentially supports the broadening scenario. Possible
implications for the nature of chiral symmetry restoration are outlined.Comment: 6 pages ReVTeX including 5 eps-figure
Tests of Ocean-Tide Models by Analysis of Satellite-To-Satellite Range Measurements: An Update
Seven years of GRACE intersatellite range-rate measurements are used to test the new ocean tide model FES2014 and to compare against similar results obtained with earlier models. These qualitative assessments show that FES2014 represents a marked improvement in accuracy over its earlier incarnation, FES2012, with especially notable improvements in the Arctic Ocean for constituents K(sub 1) and S(sub 2). Degradation appears to have occurred in two anomalous regions: the Ross Sea for the O(sub 1) constituent and the Weddell Sea for M(sub 2)
Advanced passive communication satellite systems comparison studies. Volume 1 - Summary Final report
Passive communication satellites feasibility for Comsat system - Vol.
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