224,996 research outputs found
Universal Statistics of the Critical Depinning Force of Elastic Systems in Random Media
We study the rescaled probability distribution of the critical depinning
force of an elastic system in a random medium. We put in evidence the
underlying connection between the critical properties of the depinning
transition and the extreme value statistics of correlated variables. The
distribution is Gaussian for all periodic systems, while in the case of random
manifolds there exists a family of universal functions ranging from the
Gaussian to the Gumbel distribution. Both of these scenarios are a priori
experimentally accessible in finite, macroscopic, disordered elastic systems.Comment: 4 pages, 4 figure
Towards a Definition of Role-related Concepts for Business Modeling
Abstract—While several role-related concepts play an\ud
important role in business modeling, their definitions,\ud
relations, and use differ greatly between languages, papers,\ud
and reports. Due to this, the knowledge captured by models is\ud
not transferred correctly, and models are incomparable. In this\ud
paper, we provide a meta-model and definitions for several\ud
role-related concepts based on the practice of existing modeling\ud
languages and ontological analysis. This forms a basis for\ud
creating comparable, formal business models, which enable\ud
further enterprise engineering, in a repeatable wa
Depinning of a domain wall in the 2d random-field Ising model
We report studies of the behaviour of a single driven domain wall in the
2-dimensional non-equilibrium zero temperature random-field Ising model,
closely above the depinning threshold. It is found that even for very weak
disorder, the domain wall moves through the system in percolative fashion. At
depinning, the fraction of spins that are flipped by the proceeding avalanche
vanishes with the same exponent beta=5/36 as the infinite percolation cluster
in percolation theory. With decreasing disorder strength, however, the size of
the critical region decreases. Our numerical simulation data appear to reflect
a crossover behaviour to an exponent beta'=0 at zero disorder strength. The
conclusions of this paper strongly rely on analytical arguments. A scaling
theory in terms of the disorder strength and the magnetic field is presented
that gives the values of all critical exponent except for one, the value of
which is estimated from scaling arguments.Comment: 13 pages Revtex, 13 eps figure
UD Annotatrix: An Annotation Tool For Universal Dependencies
In this paper we introduce the UD Annotatrix annotation tool for manual annotation of Universal Dependencies. This tool has been designed with the aim that it should be tailored to the needs of the Universal Dependencies (UD) community, including that it should operate in fully-offline mode, and is freely-available under the GNU GPL licence. In this paper, we provide some background to the tool, an overview of its development, and background on how it works. We compare it with some other widely-used tools which are used for Universal Dependencies annotation, describe some features unique to UD Annotatrix, and finally outline some avenues for future work and provide a few concluding remarks
Short time relaxation of a driven elastic string in a random medium
We study numerically the relaxation of a driven elastic string in a two
dimensional pinning landscape. The relaxation of the string, initially flat, is
governed by a growing length separating the short steady-state
equilibrated lengthscales, from the large lengthscales that keep memory of the
initial condition. We find a macroscopic short time regime where relaxation is
universal, both above and below the depinning threshold, different from the one
expected for standard critical phenomena. Below the threshold, the zero
temperature relaxation towards the first pinned configuration provides a novel,
experimentally convenient way to access all the critical exponents of the
depinning transition independently.Comment: 4.2 pages, 3 figure
Non-steady relaxation and critical exponents at the depinning transition
We study the non-steady relaxation of a driven one-dimensional elastic
interface at the depinning transition by extensive numerical simulations
concurrently implemented on graphics processing units (GPUs). We compute the
time-dependent velocity and roughness as the interface relaxes from a flat
initial configuration at the thermodynamic random-manifold critical force.
Above a first, non-universal microscopic time-regime, we find a non-trivial
long crossover towards the non-steady macroscopic critical regime. This
"mesoscopic" time-regime is robust under changes of the microscopic disorder
including its random-bond or random-field character, and can be fairly
described as power-law corrections to the asymptotic scaling forms yielding the
true critical exponents. In order to avoid fitting effective exponents with a
systematic bias we implement a practical criterion of consistency and perform
large-scale (L~2^{25}) simulations for the non-steady dynamics of the continuum
displacement quenched Edwards Wilkinson equation, getting accurate and
consistent depinning exponents for this class: \beta = 0.245 \pm 0.006, z =
1.433 \pm 0.007, \zeta=1.250 \pm 0.005 and \nu=1.333 \pm 0.007. Our study may
explain numerical discrepancies (as large as 30% for the velocity exponent
\beta) found in the literature. It might also be relevant for the analysis of
experimental protocols with driven interfaces keeping a long-term memory of the
initial condition.Comment: Published version (including erratum). Codes and Supplemental
Material available at https://bitbucket.org/ezeferrero/qe
Non-universal equilibrium crystal shape results from sticky steps
The anisotropic surface free energy, Andreev surface free energy, and
equilibrium crystal shape (ECS) z=z(x,y) are calculated numerically using a
transfer matrix approach with the density matrix renormalization group (DMRG)
method. The adopted surface model is a restricted solid-on-solid (RSOS) model
with "sticky" steps, i.e., steps with a point-contact type attraction between
them (p-RSOS model). By analyzing the results, we obtain a first-order shape
transition on the ECS profile around the (111) facet; and on the curved surface
near the (001) facet edge, we obtain shape exponents having values different
from those of the universal Gruber-Mullins-Pokrovsky-Talapov (GMPT) class. In
order to elucidate the origin of the non-universal shape exponents, we
calculate the slope dependence of the mean step height of "step droplets"
(bound states of steps) using the Monte Carlo method, where p=(dz/dx,
dz/dy)$, and represents the thermal averag |p| dependence of , we
derive a |p|-expanded expression for the non-universal surface free energy
f_{eff}(p), which contains quadratic terms with respect to |p|. The first-order
shape transition and the non-universal shape exponents obtained by the DMRG
calculations are reproduced thermodynamically from the non-universal surface
free energy f_{eff}(p).Comment: 31 pages, 21 figure
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