204 research outputs found
Emergence of the stochastic resonance in glow discharge plasma
stochastic resonance, glow discharge plasma, excitable medium, absolute mean
differenceComment: St
Selective advantage of diffusing faster
We study a stochastic spatial model of biological competition in which two
species have the same birth and death rates, but different diffusion constants.
In the absence of this difference, the model can be considered as an
off-lattice version of the Voter model and presents similar coarsening
properties. We show that even a relative difference in diffusivity on the order
of a few percent may lead to a strong bias in the coarsening process favoring
the more agile species. We theoretically quantify this selective advantage and
present analytical formulas for the average growth of the fastest species and
its fixation probability.Comment: 8 pages, 5 figures (Main Text + Supplementary Information). Accepted
versio
Avalanche statistics during coarsening dynamics
We study the coarsening dynamics of a two dimensional system via lattice
Boltzmann numerical simulations. The system under consideration is a biphasic
system consisting of domains of a dispersed phase closely packed together in a
continuous phase and separated by thin interfaces. Such system is elastic and
typically out of equilibrium. The equilibrium state is attained via the
coarsening dynamics, wherein the dispersed phase slowly diffuses through the
interfaces, causing domains to change in size and eventually rearrange
abruptly. The effect of rearrangements is propagated throughout the system via
the intrinsic elastic interactions and may cause rearrangements elsewhere,
resulting in intermittent bursts of activity and avalanche behaviour. Here we
aim at quantitatively characterizing the corresponding avalanche statistics
(i.e. size, duration, inter-avalanche time). Despite the coarsening dynamics is
triggered by an internal driving mechanism, we find quantitative indications
that such avalanche statistics displays scaling-laws very similar to those
observed in the response of disordered materials to external loads
Intermittency in Turbulence: Multiplicative random process in space and time
We present a simple stochastic algorithm for generating multiplicative
processes with multiscaling both in space and in time. With this algorithm we
are able to reproduce a synthetic signal with the same space and time
correlation as the one coming from shell models for turbulence and the one
coming from a turbulent velocity field in a quasi-Lagrangian reference frame.Comment: 23 pages, 12 figure
Earthquake statistics inferred from plastic events in soft-glassy materials
We propose a new approach for generating synthetic earthquake catalogues
based on the physics of soft glasses. The continuum approach produces
yield-stress materials based on Lattice-Boltzmann simulations. We show that, if
the material is stimulated below yield stress, plastic events occur, which have
strong similarities with seismic events. Based on a suitable definition of
displacement in the continuum, we show that the plastic events obey a
Gutenberg-Richter law with exponents similar to those for real earthquakes. We
further find that average acceleration, energy release, stress drop and
recurrence times scale with the same exponent. The approach is fully
self-consistent and all quantities can be calculated at all scales without the
need of ad hoc friction or statistical laws. We therefore suggest that our
approach may lead to new insight into understanding of the physics connecting
the micro and macro scale of earthquakes.Comment: 13 pages, 7 figure
Metastability at the Yield-Stress Transition in Soft Glasses
We study the solid-to-liquid transition in a two-dimensional fully periodic
soft-glassy model with an imposed spatially heterogeneous stress. The model we
consider consists of droplets of a dispersed phase jammed together in a
continuous phase. When the peak value of the stress gets close to the yield
stress of the material, we find that the whole system intermittently tunnels to
a metastable "fluidized" state, which relaxes back to a metastable "solid"
state by means of an elastic-wave dissipation. This macroscopic scenario is
studied through the microscopic displacement field of the droplets, whose time
statistics displays a remarkable bimodality. Metastability is rooted in the
existence, in a given stress range, of two distinct stable rheological branches
as well as long-range correlations (e.g., large dynamic heterogeneity)
developed in the system. Finally, we show that a similar behavior holds for a
pressure-driven flow, thus suggesting possible experimental tests.Comment: 13 pages, 11 figure
Polymers in Fluid Flows
The interaction of flexible polymers with fluid flows leads to a number of
intriguing phenomena observed in laboratory experiments, namely drag reduction,
elastic turbulence and heat transport modification in natural convection, and
is one of the most challenging subjects in soft matter physics. In this paper
we review our present knowledge on the subject. Our present knowledge is mostly
based on direct numerical simulations performed in the last twenty years, which
have successfully explained, at least qualitatively, most of the experimental
results. Our goal is to disentangle as much as possible the basic mechanisms
acting in the system in order to capture the basic features underlying
different theoretical approaches and explanations
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