335 research outputs found
Nonlocality-induced front interaction enhancement
We demonstrate that nonlocal coupling strongly influences the dynamics of
fronts connecting two equivalent states. In two prototype models we observe a
large amplification in the interaction strength between two opposite fronts
increasing front velocities several orders of magnitude. By analyzing the
spatial dynamics we prove that way beyond quantitative effects, nonlocal terms
can also change the overall qualitative picture by inducing oscillations in the
front profile. This leads to a mechanism for the formation of localized
structures not present for local interactions. Finally, nonlocal coupling can
induce a steep broadening of localized structures, eventually annihilating
them.Comment: 4 pages, 6 figure
A compartmental model for Xylella fastidiosa diseases with explicit vector seasonal dynamics
The bacterium Xylella fastidiosa (Xf) is mainly transmitted by the
spittlebug, Philaenus spumarius, in Europe, where it has caused significant
economic damage to olive and almond trees. Understanding the factors that
determine disease dynamics in pathosystems that share similarities can help
design control strategies focused on minimizing transmission chains. Here we
introduce a compartmental model for Xf-caused diseases in Europe that accounts
for the main relevant epidemiological processes, including the seasonal
dynamics of P. spumarius. The model was confronted with epidemiological data
from the two major outbreaks of Xf in Europe, the olive quick disease syndrome
(OQDS) in Apulia, Italy, caused by the subspecies pauca, and the almond leaf
scorch disease (ALSD) in Majorca, Spain, caused by subspecies multiplex and
fastidiosa. Using a Bayesian inference framework, we show how the model
successfully reproduces the general field data in both diseases. In a global
sensitivity analysis, the vector-plant and plant-vector transmission rates,
together with the vector removal rate, were the most influential parameters in
determining the time of the infected host population peak, the incidence peak
and the final number of dead hosts. We also used our model to check different
vector-based control strategies, showing that a joint strategy focused on
increasing the rate of vector removal while lowering the number of annual
newborn vectors is optimal for disease control.Comment: 18 pages, 8 figure
Spatial effects in parasite-induced marine diseases of immobile hosts
Emerging marine infectious diseases pose a substantial threat to marine ecosystems and the conservation of their biodiversity. Compartmental models of epidemic transmission in marine sessile organisms, available only recently, are based on non-spatial descriptions in which space is homogenized and parasite mobility is not explicitly accounted for. However, in realistic scenarios epidemic transmission is conditioned by the spatial distribution of hosts and the parasites' mobility patterns, calling for an explicit description of space. In this work, we develop a spatially explicit individual-based model to study disease transmission by waterborne parasites in sessile marine populations. We investigate the impact of spatial disease transmission through extensive numerical simulations and theoretical analysis. Specifically, the effects of parasite mobility into the epidemic threshold and the temporal progression of the epidemic are assessed. We show that larger values of pathogen mobility imply more severe epidemics, as the number of infections increases, and shorter timescales to extinction. An analytical expression for the basic reproduction number of the spatial model, R~0, is derived as a function of the non-spatial counterpart, R 0, which characterizes a transition between a disease-free and a propagation phase, in which the disease propagates over a large fraction of the system.Fil: Giménez Romero, Àlex. Consejo Superior de Investigaciones CientÃficas. Instituto de FÃsica Interdisciplinar y Sistemas Complejos; EspañaFil: Vazquez, Federico. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Calculo. - Consejo Nacional de Investigaciones CientÃficas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Calculo; Argentina. Consejo Superior de Investigaciones CientÃficas. Instituto de FÃsica Interdisciplinar y Sistemas Complejos; EspañaFil: López, Cristóbal. Consejo Superior de Investigaciones CientÃficas. Instituto de FÃsica Interdisciplinar y Sistemas Complejos; EspañaFil: MatÃas, Manuel A.. Consejo Superior de Investigaciones CientÃficas. Instituto de FÃsica Interdisciplinar y Sistemas Complejos; Españ
Dynamics of localized and patterned structures in the Lugiato-Lefever equation determine the stability and shape of optical frequency combs
It has been recently uncovered that coherent structures in microresonators such as cavity solitons and patterns are intimately related to Kerr frequency combs. In this work, we present a general analysis of the regions of existence and stability of cavity solitons and patterns in the Lugiato-Lefever equation, a mean-field model that finds applications in many different nonlinear optical cavities. We demonstrate that the rich dynamics and coexistence of multiple solutions in the Lugiato-Lefever equation are of key importance to understanding frequency comb generation. A detailed map of how and where to target stable Kerr frequency combs in the parameter space defined by the frequency detuning and the pump power is provided. Moreover, the work presented also includes the organization of various dynamical regimes in terms of bifurcation points of higher codimension in regions of parameter space that were previously unexplored in the Lugiato-Lefever equation. We discuss different dynamical instabilities such as oscillations and chaotic regimes.This research was supported by the Research Foundation-Flanders (FWO), by the Spanish MINECO, and FEDER under Grants FISICOS (Grant No. FIS2007-60327) and INTENSE@COSYP (Grant No. FIS2012-30634), by Comunitat Autonoma de les Illes Balears, by the Research Council of the Vrije Universiteit Brussel (VUB), and by the Belgian Science Policy Office (BelSPO) under Grant No. IAP 7-35. S. Coen also acknowledges the support of the Marsden Fund of the Royal Society of New Zealand.Peer reviewe
Effects of a localized beam on the dynamics of excitable cavity solitons
We study the dynamical behavior of dissipative solitons in an optical cavity
filled with a Kerr medium when a localized beam is applied on top of the
homogeneous pumping. In particular, we report on the excitability regime that
cavity solitons exhibits which is emergent property since the system is not
locally excitable. The resulting scenario differs in an important way from the
case of a purely homogeneous pump and now two different excitable regimes, both
Class I, are shown. The whole scenario is presented and discussed, showing that
it is organized by three codimension-2 points. Moreover, the localized beam can
be used to control important features, such as the excitable threshold,
improving the possibilities for the experimental observation of this
phenomenon.Comment: 9 Pages, 12 figure
Rare Events and Scale--Invariant Dynamics of Perturbations in Delayed Dynamical Systems
We study the dynamics of perturbations in time delayed dynamical systems.
Using a suitable space-time coordinate transformation, we find that the time
evolution of the linearized perturbations (Lyapunov vector) can be mapped to
the linear Zhang surface growth model [Y.-C. Zhang, J. Phys. France {\bf 51},
2129 (1990)], which is known to describe surface roughening driven by power-law
distributed noise. As a consequence, Lyapunov vector dynamics is dominated by
rare random events that lead to non-Gaussian fluctuations and multiscaling
properties.Comment: Final version to appear in Phys. Rev. Lett., 4 pages, 3 eps fig
Phase-space structure of two-dimensional excitable localized structures
In this work we characterize in detail the bifurcation leading to an
excitable regime mediated by localized structures in a dissipative nonlinear
Kerr cavity with a homogeneous pump. Here we show how the route can be
understood through a planar dynamical system in which a limit cycle becomes the
homoclinic orbit of a saddle point (saddle-loop bifurcation). The whole picture
is unveiled, and the mechanism by which this reduction occurs from the full
infinite-dimensional dynamical system is studied. Finally, it is shown that the
bifurcation leads to an excitability regime, under the application of suitable
perturbations. Excitability is an emergent property for this system, as it
emerges from the spatial dependence since the system does not exhibit any
excitable behavior locally.Comment: 10 pages, 9 figure
Dynamics on Complex Networks and Applications
At the eight-year anniversary of Watts & Strogatz's work on the collective
dynamics of small-world networks and seven years after Barabasi & Albert's
discovery of scale-free networks, the area of dynamical processes on complex
networks is at the forefront of the current research on nonlinear dynamics and
complex systems. This volume brings together a selection of original
contributions in complementary topics of statistical physics, nonlinear
dynamics and biological sciences, and is expected to provide the reader with a
comprehensive up-to-date representation of this rapidly developing area.Comment: Preface article of the Physica D Special Issue "Dynamics on Complex
Networks and Applications" (4 pages). Full issue available at
http://www.sciencedirect.com/science/journal/0167278
Formation of stellar inner discs and rings in spiral galaxies through minor mergers
Recent observations show that inner disks and rings (IDs and IRs) are not preferentially found in barred galaxies, pointing to the relevance of formation mechanisms different to the traditional bar-origin scenario. Nevertheless, the role of minor mergers in the formation of these inner components (ICs), while often invoked, is still poorly understood. We have investigated the capability of minor mergers to trigger the formation of IDs and IRs in spiral galaxies through collisionless N-body simulations. Our models prove that minor mergers are an efficient mechanism to form rotationally-supported stellar ICs in spirals, neither requiring strong dissipation nor noticeable bars, and suggest that their role in the formation of ICs must have been much more complex than just bar triggering
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