3,585 research outputs found
Universal interface width distributions at the depinning threshold
We compute the probability distribution of the interface width at the
depinning threshold, using recent powerful algorithms. It confirms the
universality classes found previously. In all cases, the distribution is
surprisingly well approximated by a generalized Gaussian theory of independant
modes which decay with a characteristic propagator G(q)=1/q^(d+2 zeta); zeta,
the roughness exponent, is computed independently. A functional renormalization
analysis explains this result and allows to compute the small deviations, i.e.
a universal kurtosis ratio, in agreement with numerics. We stress the
importance of the Gaussian theory to interpret numerical data and experiments.Comment: 4 pages revtex4. See also the following article cond-mat/030146
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
Dynamics below the depinning threshold
We study the steady-state low-temperature dynamics of an elastic line in a
disordered medium below the depinning threshold. Analogously to the equilibrium
dynamics, in the limit T->0, the steady state is dominated by a single
configuration which is occupied with probability one. We develop an exact
algorithm to target this dominant configuration and to analyze its geometrical
properties as a function of the driving force. The roughness exponent of the
line at large scales is identical to the one at depinning. No length scale
diverges in the steady state regime as the depinning threshold is approached
from below. We do find, a divergent length, but it is associated only with the
transient relaxation between metastable states.Comment: 4 pages, 3 figure
Thermal Effects in the dynamics of disordered elastic systems
Many seemingly different macroscopic systems (magnets, ferroelectrics, CDW,
vortices,..) can be described as generic disordered elastic systems.
Understanding their static and dynamics thus poses challenging problems both
from the point of view of fundamental physics and of practical applications.
Despite important progress many questions remain open. In particular the
temperature has drastic effects on the way these systems respond to an external
force. We address here the important question of the thermal effect close to
depinning, and whether these effects can be understood in the analogy with
standard critical phenomena, analogy so useful to understand the zero
temperature case. We show that close to the depinning force temperature leads
to a rounding of the depinning transition and compute the corresponding
exponent. In addition, using a novel algorithm it is possible to study
precisely the behavior close to depinning, and to show that the commonly
accepted analogy of the depinning with a critical phenomenon does not fully
hold, since no divergent lengthscale exists in the steady state properties of
the line below the depinning threshold.Comment: Proceedings of the International Workshop on Electronic Crystals,
Cargese(2008
Grothendieck rings of towers of generalized Weyl algebras in the finite orbit case
Previously we showed that the tensor product of a weight module over a
generalized Weyl algebra (GWA) with a weight module over another GWA is a
weight module over a third GWA. In this paper we compute tensor products of
simple and indecomposable weight modules over generalized Weyl algebras
supported on a finite orbit. This allows us to give a complete presentation by
generators and relations of the Grothendieck ring of the categories of weight
modules over a tower of generalized Weyl algebras in this setting. We also
obtain partial results about the split Grothendieck ring. We described the case
of infinite orbits in previous work.Comment: Some sections have been reorganized, 32 pages, 4 figure
Creep dynamics of elastic manifolds via exact transition pathways
We study the steady state of driven elastic strings in disordered media below
the depinning threshold. In the low-temperature limit, for a fixed sample, the
steady state is dominated by a single configuration, which we determine exactly
from the transition pathways between metastable states. We obtain the dynamical
phase diagram in this limit. At variance with a thermodynamic phase transition,
the depinning transition is not associated with a divergent length scale of the
steady state below threshold, but only of the transient dynamics. We discuss
the distribution of barrier heights, and check the validity of the dynamic
phase diagram at small but finite temperatures using Langevin simulations. The
phase diagram continues to hold for broken statistical tilt symmetry. We point
out the relevance of our results for experiments of creep motion in elastic
interfaces.Comment: 14 pages, 18 figure
Imunidade de pinhão-manso a Heterodera glycines.
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Previous issue date: 2011-01-20201
Width distribution of contact lines on a disordered substrate
We have studied the roughness of a contact line of a liquid meniscus on a
disordered substrate by measuring its width distribution. The comparison
between the measured width distribution and the width distribution calculated
in previous works, extended here to the case of open boundary conditions,
confirms that the Joanny-de Gennes model is not sufficient to describe the
dynamics of contact lines at the depinning threshold. This conclusion is in
agreement with recent measurements which determine the roughness exponent by
extrapolation to large system sizes.Comment: 4 pages, 3 figure
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