1,824 research outputs found
Introduction: Localized Structures in Dissipative Media: From Optics to Plant Ecology
Localised structures in dissipative appears in various fields of natural
science such as biology, chemistry, plant ecology, optics and laser physics.
The proposed theme issue is to gather specialists from various fields of
non-linear science toward a cross-fertilisation among active areas of research.
This is a cross-disciplinary area of research dominated by the nonlinear optics
due to potential applications for all-optical control of light, optical
storage, and information processing. This theme issue contains contributions
from 18 active groups involved in localized structures field and have all made
significant contributions in recent years.Comment: 14 pages, 0 figure, submitted to Phi. Trasaction Royal Societ
On localized vegetation patterns, fairy circles and localized patches in arid landscapes
We investigate the formation of localized structures with a varying width in
one and two-dimensional systems. The mechanism of stabilization is attributed
to strong nonlocal coupling mediated by a Lorentzian type of Kernel. We show
that, in addition to stable dips found recently [see, e.g., C. Fernandez-Oto,
M. G. Clerc, D. Escaff, and M. Tlidi, Phys. Rev. Lett. {\bf{110}}, 174101
(2013)], exist stable localized peaks which appear as a result of strong
nonlocal coupling, i.e. mediated by a coupling that decays with the distance
slower than an exponential. We applied this mechanism to arid ecosystems by
considering a prototype model of a Nagumo type. In one-dimension, we study the
front that connects the stable uniformly vegetated state with the bare one
under the effect of strong nonlocal coupling. We show that strong nonlocal
coupling stabilizes both---dip and peak---localized structures. We show
analytically and numerically that the width of localized dip, which we
interpret as fairy circle, increases strongly with the aridity parameter. This
prediction is in agreement with filed observations. In addition, we predict
that the width of localized patch decreases with the degree of aridity.
Numerical results are in close agreement with analytical predictions
Bouncing localized structures in a liquid-crystal light-valve experiment
Experimental evidence of bouncing localized structures in a nonlinear optical
system is reported.Comment: 4 page
Extreme events prediction from nonlocal partial information in a spatiotemporally chaotic microcavity laser
The forecasting of high-dimensional, spatiotemporal nonlinear systems has
made tremendous progress with the advent of model-free machine learning
techniques. However, in real systems it is not always possible to have all the
information needed; only partial information is available for learning and
forecasting. This can be due to insufficient temporal or spatial samplings, to
inaccessible variables or to noisy training data. Here, we show that it is
nevertheless possible to forecast extreme events occurrence in incomplete
experimental recordings from a spatiotemporally chaotic microcavity laser using
reservoir computing. Selecting regions of maximum transfer entropy, we show
that it is possible to get higher forecasting accuracy using nonlocal data vs
local data thus allowing greater warning times, at least twice the time horizon
predicted from the nonlinear local Lyapunov exponent
Dielectric resonances of lattice animals and other fractal structures
Electrical and optical properties of binary inhomogeneous media are currently
modelled by a random network of metallic bonds (conductance ,
concentration ) and dielectric bonds (conductance , concentration
). The macroscopic conductivity of this model is analytic in the complex
plane of the dimensionless ratio of the conductances of
both phases, cut along the negative real axis. This cut originates in the
accumulation of the resonances of clusters with any size and shape. We
demonstrate that the dielectric response of an isolated cluster, or a finite
set of clusters, is characterised by a finite spectrum of resonances, occurring
at well-defined negative real values of , and we define the cross-section
which gives a measure of the strength of each resonance. These resonances show
up as narrow peaks with Lorentzian line shapes, e.g. in the weak-dissipation
regime of the model. The resonance frequencies and the corresponding
cross-sections only depend on the underlying lattice, on the geometry of the
clusters, and on their relative positions. Our approach allows an exact
determination of these characteristics. It is applied to several examples of
clusters drawn on the square lattice. Scaling laws are derived analytically,
and checked numerically, for the resonance spectra of linear clusters, of
lattice animals, and of several examples of self-similar fractals.Comment: 25 pages, plain TeX. Figures (hard copies) available upon request, to
appear in the Journal of Physics
Long-term effects of rotational wetland mowing on breeding birds: evidence from a 30-year experiment
Wetlands are amongst the richest, yet most threatened types of habitats on Earth.
One major threat is the modification of water regime for human activities, which disrupts
normal ecosystem equilibrium. In lacustrine wetlands, reduced flooding allows shrubs to
take over, ultimately leading to a shift towards woody communities. To counter this,
wetland managers have initiated a variety of measures, including mowing, burning, and
pasturing. Because of the short time frames of previous studies on the subject, little is
known on their potential negative side effects on the ecosystem. Here, we evaluate the
long-term effect of mowing on breeding populations of the five most abundant species in
our central European study area (the reed warbler Acrocephalus scirpaceus, the common
reed bunting Emberiza schoeniclus, Savi’s warbler Locustella luscinioides, the water rail
Rallus aquaticus, and the bearded reedling Panurus biarmicus). This study, of an
unprecedented time scale (30 years), shows that rotational mowing has no long-term
detrimental effects on birds. However, optimal mowing regime for the birds might often be
less frequent than what is usually applied. We recommend that mowing be spaced every
3 years at least, and ideally every 6 years or more. We discuss additional measures that
could be implemented to complement mowing. Because of the widespread distribution of
the target habitat and species, our study provides readily applicable information for wetland
managers in Europe and worldwide
- …