1,109 research outputs found
Quantized Scaling of Growing Surfaces
The Kardar-Parisi-Zhang universality class of stochastic surface growth is
studied by exact field-theoretic methods. From previous numerical results, a
few qualitative assumptions are inferred. In particular, height correlations
should satisfy an operator product expansion and, unlike the correlations in a
turbulent fluid, exhibit no multiscaling. These properties impose a
quantization condition on the roughness exponent and the dynamic
exponent . Hence the exact values for two-dimensional
and for three-dimensional surfaces are derived.Comment: 4 pages, revtex, no figure
Energy Barriers for Flux Lines in 3 Dimensions
I determine the scaling behavior of the free energy barriers encountered by a
flux line in moving through a three-dimensional random potential. A combination
of numerical simulations and analytic arguments suggest that these barriers
scale with the length of the line in the same way as the fluctuation in the
free energy.Comment: 12 pages Latex, 4 postscript figures tarred, compressed, uuencoded
using `uufiles', coming with a separate fil
Intermittency of Height Fluctuations and Velocity Increment of The Kardar-Parisi-Zhang and Burgers Equations with infinitesimal surface tension and Viscosity in 1+1 Dimensions
The Kardar-Parisi-Zhang (KPZ) equation with infinitesimal surface tension,
dynamically develops sharply connected valley structures within which the
height derivative is not continuous. We discuss the intermittency issue in the
problem of stationary state forced KPZ equation in 1+1--dimensions. It is
proved that the moments of height increments behave as with for length scales . The length scale is the characteristic length of the
forcing term. We have checked the analytical results by direct numerical
simulation.Comment: 13 pages, 9 figure
Exact free energy distribution function of a randomly forced directed polymer
We study the elastic (1+1)-dimensional string subject to a random gaussian
potential on scales smaller than the correlation radius of the disorder
potential (Larkin problem). We present an exact calculation of the probability
function for the free energy of a string starting at
and ending at . The function is strongly
asymmetric, with the left tail decaying exponentially () and the right tail vanishing as . Our analysis defines a strategy for future attacks on
this class of problems.Comment: RevTeX, 4 pages, 1 figure inserte
Serologic evidence for the presence in Pteropus bats of a paramyxovirus related to equine morbillivirus.
Two outbreaks of a previously unknown disease in horses and humans occurred in Queensland in 1994. The outbreaks occurred within 1 month of each other in Brisbane and Mackay, which are approximately 1000 km apart. In the Brisbane incident, 21 horses were infected of which 14 died or were euthanized after severe clinical signs of an acute
respiratory disease. Two human cases were in patients with less well defined clinical signs; one patient died (1,2). In the Mackay incident two horses became seriously ill and died, and one person also died (3). Although it is now known that the two outbreaks occurred in August and September 1994, knowledge of the Mackay outbreak did not occur until late 1995 when the infected person died of a relapsing encephalitis. The name equine morbillivirus (EMV) has been proposed for a paramyxovirus isolated from four of the Brisbane horses and the first patient who died (2)
Anomalous Roughness in Dimer-Type Surface Growth
We point out how geometric features affect the scaling properties of
non-equilibrium dynamic processes, by a model for surface growth where
particles can deposit and evaporate only in dimer form, but dissociate on the
surface. Pinning valleys (hill tops) develop spontaneously and the surface
facets for all growth (evaporation) biases. More intriguingly, the scaling
properties of the rough one dimensional equilibrium surface are anomalous. Its
width, , diverges with system size , as
instead of the conventional universal value . This originates
from a topological non-local evenness constraint on the surface configurations.Comment: Published version in PR
A pseudo-spectral approach to inverse problems in interface dynamics
An improved scheme for computing coupling parameters of the
Kardar-Parisi-Zhang equation from a collection of successive interface
profiles, is presented. The approach hinges on a spectral representation of
this equation. An appropriate discretization based on a Fourier representation,
is discussed as a by-product of the above scheme. Our method is first tested on
profiles generated by a one-dimensional Kardar-Parisi-Zhang equation where it
is shown to reproduce the input parameters very accurately. When applied to
microscopic models of growth, it provides the values of the coupling parameters
associated with the corresponding continuum equations. This technique favorably
compares with previous methods based on real space schemes.Comment: 12 pages, 9 figures, revtex 3.0 with epsf style, to appear in Phys.
Rev.
Methods and systems for advanced spaceport information management
Advanced spaceport information management methods and systems are disclosed. In one embodiment, a method includes coupling a test system to the payload and transmitting one or more test signals that emulate an anticipated condition from the test system to the payload. One or more responsive signals are received from the payload into the test system and are analyzed to determine whether one or more of the responsive signals comprises an anomalous signal. At least one of the steps of transmitting, receiving, analyzing and determining includes transmitting at least one of the test signals and the responsive signals via a communications link from a payload processing facility to a remotely located facility. In one particular embodiment, the communications link is an Internet link from a payload processing facility to a remotely located facility (e.g. a launch facility, university, etc.)
Critical dimensions of the diffusion equation
We study the evolution of a random initial field under pure diffusion in
various space dimensions. From numerical calculations we find that the
persistence properties of the system show sharp transitions at critical
dimensions d1 ~ 26 and d2 ~ 46. We also give refined measurements of the
persistence exponents for low dimensions.Comment: 4 pages, 5 figure
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