共查询到20条相似文献,搜索用时 15 毫秒
1.
W. L. Lu F. M. Atay J. Jost 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,63(3):399-406
Complexity of dynamical networks can arise not only from
the complexity of the topological structure but also from the time
evolution of the topology. In this paper, we study the synchronous
motion of coupled maps in time-varying complex networks both
analytically and numerically. The temporal variation is rather
general and formalized as being driven by a metric dynamical system.
Four network models are discussed in detail in which the
interconnections between vertices vary through time randomly. These
models are: 1) i.i.d. sequences of random graphs with fixed wiring
probability, 2) groups of graphs with random switches between the
individual graphs, 3) graphs with temporary random failures of
nodes, and 4) the meet-for-dinner model where the vertices are
randomly grouped. We show that the temporal variation and randomness
of the connection topology can enhance synchronizability in many
cases; however, there are also instances where they reduce
synchronizability. In analytical terms, the Hajnal diameter of the
coupling matrix sequence is presented as a measure for the
synchronizability of the graph topology. In topological terms, the
decisive criterion for synchronization of coupled chaotic maps is
that the union of the time-varying graphs contains a spanning tree. 相似文献
2.
N. Kouvaris A. Provata 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,66(1):97-106
An ecosystem containing three interacting species is studied using both Mean Field approach and Kinetic Monte Carlo
simulations on a lattice substrate. The so called 3rd order LLV model involves birth, death and reaction
processes with 3rd order nonlinearities and feedbacks. At the mean field level this system exhibits conservative
oscillations; the analytic form of the constant of motion is presented. The stochastic simulations show that the
density oscillations disappear for sufficiently large lattices, while they are present locally, on small lattice
windows. Introduction of mixing via long range migration in the two reacting species changes this picture. For small
migration rates p, the behavior remains as with p = 0 and the system is divided into local asynchronous oscillators.
As p increases the system passes through a phase transition and exhibits a weak disorder limit cycle through a supercritical
Hopf-like bifurcation. The amplitude of the limit cycle depends on the rate p, on the range of migration
r and on the system kinetic rates k1, k2 and k3. 相似文献
3.
N. Fujiwara J. Kurths 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,69(1):45-49
We employ a spectral decomposition method to
analyze synchronization of a non-identical oscillator network.
We study the case that a small parameter mismatch
of oscillators is characterized by one parameter
and phase synchronization is observed.
We derive a linearized equation for each eigenmode of the coupling matrix.
The parameter mismatch
is reflected on inhomogeneous term in the linearized equation.
We find that the
oscillation of each mode is essentially characterized only by
the eigenvalue of the coupling matrix with a suitable normalization.
We refer to this property as spectral universality,
because it is observed irrespective of network topology.
Numerical results in various network topologies
show good agreement with those based on linearized equation.
This universality is also observed in a system
driven by additive independent Gaussian noise. 相似文献
4.
M. Ponce C. C. Masoller Arturo C. Martí 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,67(1):83-93
We study a network of coupled logistic maps whose interactions occur with a certain distribution of delay times. The local
dynamics is chaotic in the absence of coupling and thus the network is a paradigm of a complex system. There are two regimes
of synchronization, depending on the distribution of delays: when the delays are sufficiently heterogeneous the network synchronizes
on a steady-state (that is unstable for the uncoupled maps); when the delays are homogeneous, it synchronizes in a time-dependent
state (that is either periodic or chaotic). Using two global indicators we quantify the synchronizability on the two regimes,
focusing on the roles of the network connectivity and the topology. The connectivity is measured in terms of the average number
of links per node, and we consider various topologies (scale-free, small-world, star, and nearest-neighbor with and without
a central hub). With weak connectivity and weak coupling strength, the network displays an irregular oscillatory dynamics
that is largely independent of the topology and of the delay distribution. With heterogeneous delays, we find a threshold
connectivity level below which the network does not synchronize, regardless of the network size. This minimum average number
of neighbors seems to be independent of the delay distribution. We also analyze the effect of self-feedback loops and find
that they have an impact on the synchronizability of small networks with large coupling strengths. The influence of feedback,
enhancing or degrading synchronization, depends on the topology and on the distribution of delays. 相似文献
5.
S. Risau-Gusman G. Abramson 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,60(4):515-520
We analyze general two-species stochastic models, of the
kind generally used for the study of population dynamics. Although
usually defined a priori, the deterministic version of these
models can be obtained as the infinite volume limit of many
stochastic models (which are necessarily defined by more parameters
than the deterministic one). It is known that damped oscillations in
a deterministic model usually correspond to oscillatory-like
fluctuations in their deterministic counterparts. The quality of
these “oscillations" depends on details of each stochastic model.
We show, however, that the parameters of the deterministic system
are generally enough to obtain very good bounds for the quality of
“oscillations" in any of its stochastic counterparts. These
bounds are shown to depend on only one dimensionless parameter. 相似文献
6.
M.?Morillo J.?Gómez-Ordó?ez J. M.?Casado J.?Casado-Pascual D.?Cubero 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,69(1):59-64
In this article, we investigate the stochastic resonance
(SR) effect in a finite array of noisy bistable systems with
nearest-neighbor coupling driven by a weak time-periodic driving
force. The array is characterized by a collective variable. By means
of numerical simulations, the signal-to-noise ratio (SNR) and the
gain are estimated as functions of the noise and the interaction
coupling strength. A strong enhancement of the SR phenomenon for
this collective variable in comparison with SR in single unit
bistable systems is observed. Gains larger than unity are obtained
for some parameter values and multi-frequency driving forces,
indicating that the system is operating in a non-linear regime
albeit the smallness of the driving amplitude. The large SNR values
observed are basically due to the fact that the output fluctuations
are small and short lived, in comparison with their typical values
in a linear regime. A non-monotonic behavior of the SNR with the
coupling strength is also obtained. 相似文献
7.
A. D. Chepelianskii A. S. Pikovsky D. L. Shepelyansky 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,60(2):225-229
We show, in a framework of a classical nonequilibrium model,
that rotational angles of electrons moving in two dimensions (2D)
in a perpendicular magnetic field can be synchronized
by an external microwave field whose frequency
is close to the Larmor frequency. The synchronization eliminates
collisions between electrons and thus creates
a regime with zero diffusion corresponding to the zero-resistance states
observed in experiments with high mobility 2D electron gas (2DEG).
For long range Coulomb interactions electrons form a rotating
hexagonal Wigner crystal.
Possible relevance of this effect of
synchronization-induced self-assembly
for planetary rings is discussed. 相似文献
8.
S. Zhu J. Fang X. Luo 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,18(1):123-128
A linear array of three lasers that are coupled mutually in space is investigated. It is shown that the phase of the laser
fields is locked with intermediate coupling while the laser intensities are totally chaotic and chaotically synchronized.
When the intensities of lasers reenter the regime of chaotic synchronization at smaller coupling constant, the laser fields
show low degree of phase locking. The phase differences in the fields between three lasers show rich patterns when the coupling
is changed.
Received 3 August 2001 and Received in final form 27 September 2001 相似文献
9.
10.
C. J. Tessone D. H. Zanette R. Toral 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,62(3):319-326
We study the influence of repulsive interactions on an
ensemble of coupled excitable rotators. We find that a moderate
fraction of repulsive interactions can trigger global firing of the
ensemble. The regime of global firing, however, is suppressed in
sufficiently large systems if the network of repulsive interactions
is fully random, due to self-averaging in its degree distribution.
We thus introduce a model of partially random networks with a broad
degree distribution, where self-averaging due to size growth is
absent. In this case, the regime of global firing persists for large
sizes. Our results extend previous work on the constructive effects
of diversity in the collective dynamics of complex systems. 相似文献
11.
P. S.?Burada G.?Schmid D.?Reguera J. M.?Rubi P.?H?nggi 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,69(1):11-18
We demonstrate the existence of stochastic resonance (SR)
in confined systems arising from entropy variations associated to
the presence of irregular boundaries. When the motion of a Brownian
particle is constrained to a region with uneven boundaries, the
presence of a periodic input may give rise to a peak in the spectral
amplification factor and therefore to the appearance of the SR
phenomenon. We have proved that the amplification factor depends on
the shape of the region through which the particle moves and that by
adjusting its characteristic geometric parameters one may optimize
the response of the system. The situation in which the appearance of
such entropic stochastic resonance (ESR) occurs is common for
small-scale systems in which confinement and noise play an prominent
role. The novel mechanism found could thus constitute an important
tool for the characterization of these systems and can put to use
for controlling their basic properties. 相似文献
12.
Cells of Voronoi diagrams in two dimensions are usually considered as having edges of zero width. However, this is not the case in several experimental situations in which the thickness of the edges of the cells is relatively large. In this paper, the concept of a thick Voronoi tessellation, that is with edges of non-zero width, is introduced and the statistics of cell areas, as thickness changes, are analyzed. 相似文献
13.
R. Donner 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,63(3):349-361
Networks of interacting components are a class of complex systems that has attracted considerable interest over the last decades.
In particular, if the dynamics of the autonomous components is characterised by an oscillatory behaviour, different types
of synchronisation can be observed in dependence on the type and strength of interactions. In this contribution, we study
the transition from non-synchronised to synchronised phase dynamics in complex networks. The most common approach to quantify
the degree of phase synchronisation in such systems is the consideration of measures of phase coherence which are averaged
over all pairs of interacting components. However, this approach implicitly assumes a spatially homogeneous synchronisation process,
which is typically not present in complex networks. As a potential alternative, two novel methods of multivariate phase synchronisation analysis are considered: synchronisation cluster analysis (SCA) and the linear variance decay (LVD)
dimension method. The strengths and weaknesses of the traditional as well as both new approaches are briefly illustrated for
a Kuramoto model with long-range coupling. As a practical application, we study how spatial heterogeneity influences the transition
to phase synchronisation in traffic networks where intersecting material flows are subjected to a self-organised decentralised
control. We find that the network performance and the degree of phase synchronisation are closely related to each other and
decrease significantly in the case of structural heterogeneities. The influences of the different parameters of our control
approach on the synchronisation process are systematically studied, yielding a sequence of Arnold tongues which correspond
to different locking modes. 相似文献
14.
D. A. Kenwright A. Bahraminasab A. Stefanovska P. V. E. McClintock 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,65(3):425-433
We show that the transitions which occur between close orders of synchronization in the cardiorespiratory system are mainly
due to modulation of the cardiac and respiratory processes by low-frequency components. The experimental evidence is derived
from recordings on healthy subjects at rest and during exercise. Exercise acts as a perturbation of the system that alters
the mean cardiac and respiratory frequencies and changes the amount of their modulation by low-frequency oscillations. The
conclusion is supported by numerical evidence based on a model of phase-coupled oscillators, with white noise and lowfrequency
noise. Both the experimental and numerical approaches confirm that low-frequency oscillations play a significant role in the
transitional behavior between close orders of synchronization. 相似文献
15.
J. Boissonade 《The European physical journal. E, Soft matter》2009,28(3):337-346
We develop a general model and the associated numerical algorithm to compute the swelling dynamics of chemo-responsive polyelectrolyte
gels immersed in a reactive ionic solution kept at a non-equilibrium stationary state by a permanent feed of fresh reactants.
Using an autocatalytic bistable but nonoscillatory reaction, namely, the bromate-sulfite reaction, we predict that a piece
of hydrogel that swells/shrinks as a function of p H can exhibit spontaneous mechanical and chemical oscillations. This constitutes the extension to realistic and experimentally
feasible conditions of results previously obtained on a toy model with artificial swelling conditions. 相似文献
16.
M. N. Kuperman D. H. Zanette 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,70(2):243-248
Inspired by Axelrod’s model of culture dissemination, we
introduce and analyze a model for a population of coupled
oscillators where different levels of synchronization can be
assimilated to different degrees of cultural organization. The
state of each oscillator is represented by a set of phases, and
the interaction – which occurs between homologous phases – is
weighted by a decreasing function of the distance between
individual states. Both ordered arrays and random networks are
considered. We find that the transition between synchronization
and incoherent behaviour is mediated by a clustering regime with
rich organizational structure, where any two oscillators can be
synchronized in some of their phases, while their remain
unsynchronized in the others. 相似文献
17.
A. Shabunin A. Efimov 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,65(3):387-393
A spatio-temporal process in the Lattice Lotka Volterra (LLV) model, when realized on low dimensional support, is studied.
It is shown that the introduction of a long-range mixing causes a drastic change in the system’s behavior, which transits
from small random-like fluctuations to global oscillations when the mixing rate transcends above a critical point. The amplitude
of the induced oscillations is well defined by the mixing rate and is insensitive to the initial conditions and the lattice
size variations. The observed behavior essentially differs from that predicted by the Mean-Field model which is conservative.
The oscillations are of limit-cycle type and appear as a stochastic analog of a Hopf bifurcation. 相似文献
18.
Z.-Z. Zhang S.-G. Zhou T. Zou 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,56(3):259-271
In this paper, firstly, we study analytically the topological
features of a family of hierarchical lattices (HLs) from the view
point of complex networks. We derive some basic properties of HLs
controlled by a parameter q: scale-free degree distribution with
exponent γ=2+ln 2/(ln q), null clustering
coefficient, power-law behavior of grid coefficient, exponential
growth of average path length (non-small-world), fractal scaling
with dimension dB=ln (2q)/(ln 2), and disassortativity.
Our results show that scale-free networks are not always
small-world, and support the conjecture that self-similar scale-free
networks are not assortative. Secondly, we define a deterministic
family of graphs called small-world hierarchical lattices (SWHLs).
Our construction preserves the structure of hierarchical lattices,
including its degree distribution, fractal architecture, clustering
coefficient, while the small-world phenomenon arises. Finally, the
dynamical processes of intentional attacks and collective
synchronization are studied and the comparisons between HLs and
Barabási-Albert (BA) networks as well as SWHLs are shown. We
find that the self-similar property of HLs and SWHLs significantly
increases the robustness of such networks against targeted damage on
hubs, as compared to the very vulnerable non fractal BA networks,
and that HLs have poorer synchronizability than their counterparts
SWHLs and BA networks. We show that degree distribution of
scale-free networks does not suffice to characterize their
synchronizability, and that networks with smaller average path
length are not always easier to synchronize. 相似文献
19.
A. Pluchino A. Rapisarda V. Latora 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,65(3):395-402
We have recently introduced [Phys. Rev. E 75, 045102(R) (2007); AIP Conference Proceedings 965, 2007, p. 323] an efficient method for the detection and identification of modules in complex networks, based on the de-synchronization
properties (dynamical clustering) of phase oscillators. In this paper we apply the dynamical clustering tecnique to the identification
of communities of marine organisms living in the Chesapeake Bay food web. We show that our algorithm is able to perform a
very reliable classification of the real communities existing in this ecosystem by using different kinds of dynamical oscillators.
We compare also our results with those of other methods for the detection of community structures in complex networks. 相似文献
20.
E. Heinsalu M. Patriarca F. Marchesoni 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,69(1):19-22
We study the effects of the confining conditions on the
occurrence of stochastic resonance (SR) in continuous bistable
systems. We model such systems by means of double-well potentials
that diverge like |x|q for |x|↦∞. For super-harmonic
(hard) potentials with q > 2 the SR peak sharpens with increasing q, whereas for sub-harmonic (soft) potentials, q < 2, it
gets
suppressed. 相似文献