15,512 research outputs found
Cauchy problem for the Boltzmann-BGK model near a global Maxwellian
In this paper, we are interested in the Cauchy problem for the Boltzmann-BGK
model for a general class of collision frequencies. We prove that the
Boltzmann-BGK model linearized around a global Maxwellian admits a unique
global smooth solution if the initial perturbation is sufficiently small in a
high order energy norm. We also establish an asymptotic decay estimate and
uniform -stability for nonlinear perturbations.Comment: 26 page
Detecting the degree of macroscopic quantumness using an overlap measurement
We investigate how to experimentally detect a recently proposed measure to
quantify macroscopic quantum superpositions [Phys. Rev. Lett. 106, 220401
(2011)], namely, "macroscopic quantumness" . Schemes based on
overlap measurements for harmonic oscillator states and for qubit states are
extensively investigated. Effects of detection inefficiency and coarse-graining
are analyzed in order to assess feasibility of the schemes.Comment: 12 pages, 8 figures, to be published in J. Opt. Soc. Am.
String Cosmology of the D-brane Universe
We analyze homogeneous anisotropic cosmology driven by the dilaton and the
self-interacting ``massive'' antisymmetric tensor field which are indispensable
bosonic degrees with the graviton in the NS-NS sector of string theories with
D-branes. We found the attractor solutions for this system, which show the
overall features of general solutions, and confirmed it through numerical
analysis. The dilaton possesses the potential due to the presence of the
D-brane and the curvature of extra dimensions. In the presence of the
non-vanishing antisymmetric tensor field, the homogeneous universe expands
anisotropically while the D-brane term dominates. The isotropy is recovered as
the dilaton rolls down and the curvature term dominates. With the stabilizing
potential for the dilaton, the isotropy can also be recovered.Comment: 23 pages, 8 figures. Final version, to appear in Phys. Rev.
Exosuit-induced improvements in walking after stroke: comprehensive analysis on gait energetics and biomechanics
Outstanding Poster Presentation Finalis
Stability of Transonic Characteristic Discontinuities in Two-Dimensional Steady Compressible Euler Flows
For a two-dimensional steady supersonic Euler flow past a convex cornered
wall with right angle, a characteristic discontinuity (vortex sheet and/or
entropy wave) is generated, which separates the supersonic flow from the gas at
rest (hence subsonic). We proved that such a transonic characteristic
discontinuity is structurally stable under small perturbations of the upstream
supersonic flow in . The existence of a weak entropy solution and Lipschitz
continuous free boundary (i.e. characteristic discontinuity) is established. To
achieve this, the problem is formulated as a free boundary problem for a
nonstrictly hyperbolic system of conservation laws; and the free boundary
problem is then solved by analyzing nonlinear wave interactions and employing
the front tracking method.Comment: 26 pages, 3 figure
Extending the Real-Time Maude Semantics of Ptolemy to Hierarchical DE Models
This paper extends our Real-Time Maude formalization of the semantics of flat
Ptolemy II discrete-event (DE) models to hierarchical models, including modal
models. This is a challenging task that requires combining synchronous
fixed-point computations with hierarchical structure. The synthesis of a
Real-Time Maude verification model from a Ptolemy II DE model, and the formal
verification of the synthesized model in Real-Time Maude, have been integrated
into Ptolemy II, enabling a model-engineering process that combines the
convenience of Ptolemy II DE modeling and simulation with formal verification
in Real-Time Maude.Comment: In Proceedings RTRTS 2010, arXiv:1009.398
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