559 research outputs found
Impact of lag information on network inference
Extracting useful information from data is a fundamental challenge across
disciplines as diverse as climate, neuroscience, genetics, and ecology. In the
era of ``big data'', data is ubiquitous, but appropriated methods are needed
for gaining reliable information from the data. In this work we consider a
complex system, composed by interacting units, and aim at inferring which
elements influence each other, directly from the observed data. The only
assumption about the structure of the system is that it can be modeled by a
network composed by a set of units connected with un-weighted and
un-directed links, however, the structure of the connections is not known. In
this situation the inference of the underlying network is usually done by using
interdependency measures, computed from the output signals of the units. We
show, using experimental data recorded from randomly coupled electronic
R{\"o}ssler chaotic oscillators, that the information of the lag times obtained
from bivariate cross-correlation analysis can be useful to gain information
about the real connectivity of the system
Persistence and Stochastic Periodicity in the Intensity Dynamics of a Fiber Laser During the Transition to Optical Turbulence
Many natural systems display transitions among different dynamical regimes,
which are difficult to identify when the data is noisy and high dimensional. A
technologically relevant example is a fiber laser, which can display complex
dynamical behaviors that involve nonlinear interactions of millions of cavity
modes. Here we study the laminar-turbulence transition that occurs when the
laser pump power is increased. By applying various data analysis tools to
empirical intensity time series we characterize their persistence and
demonstrate that at the transition temporal correlations can be precisely
represented by a surprisingly simple model.Comment: 10 pages, 13 figure
Anticipating the dynamics of chaotic maps
We study the regime of anticipated synchronization in unidirectionally
coupled chaotic maps such that the slave map has its own output reinjected
after a certain delay. For a class of simple maps, we give analytic conditions
for the stability of the synchronized solution, and present results of
numerical simulations of coupled 1D Bernoulli-like maps and 2D Baker maps, that
agree well with the analytic predictions.Comment: Uses the elsart.cls (v2000) style (included). 9 pages, including 4
figures. New version contains minor modifications to text and figure
Random Delays and the Synchronization of Chaotic Maps
We investigate the dynamics of an array of logistic maps coupled with random
delay times. We report that for adequate coupling strength the array is able to
synchronize, in spite of the random delays. Specifically, we find that the
synchronized state is a homogeneous steady-state, where the chaotic dynamics of
the individual maps is suppressed. This differs drastically from the
synchronization with instantaneous and fixed-delay coupling, as in those cases
the dynamics is chaotic. Also in contrast with the instantaneous and
fixed-delay cases, the synchronization does not dependent on the connection
topology, depends only on the average number of links per node. We find a
scaling law that relates the distance to synchronization with the randomness of
the delays. We also carry out a statistical linear stability analysis that
confirms the numerical results and provides a better understanding of the
nontrivial roles of random delayed interactions.Comment: 5 pages, 5 figure
Inferring long memory processes in the climate network via ordinal pattern analysis
We use ordinal patterns and symbolic analysis to construct global climate
networks and uncover long and short term memory processes. The data analyzed is
the monthly averaged surface air temperature (SAT field) and the results
suggest that the time variability of the SAT field is determined by patterns of
oscillatory behavior that repeat from time to time, with a periodicity related
to intraseasonal oscillations and to El Ni\~{n}o on seasonal-to-interannual
time scales.Comment: 10 pages, 13 figures Enlarged version, new sections and figures.
Accepted in Chao
Anticipated synchronization in coupled chaotic maps with delays
We study the synchronization of two chaotic maps with unidirectional
(master-slave) coupling. Both maps have an intrinsic delay , and coupling
acts with a delay . Depending on the sign of the difference , the
slave map can synchronize to a future or a past state of the master system. The
stability properties of the synchronized state are studied analytically, and we
find that they are independent of the coupling delay . These results are
compared with numerical simulations of a delayed map that arises from
discretization of the Ikeda delay-differential equation. We show that the
critical value of the coupling strength above which synchronization is stable
becomes independent of the delay for large delays.Comment: 10 pages, 4 figure
Characterization of the anticipated synchronization regime in the coupled FitzHugh--Nagumo model for neurons
We characterize numerically the regime of anticipated synchronization in the
coupled FitzHugh-Nagumo model for neurons. We consider two neurons, coupled
unidirectionally (in a master-slave configuration), subject to the same random
external forcing and with a recurrent inhibitory delayed connection in the
slave neuron. We show that the scheme leads to anticipated synchronization, a
regime in which the slave neuron fires the same train of pulses as the master
neuron, but earlier in time. We characterize the synchronization in the
parameter space (coupling strength, anticipation time) and introduce several
quantities to measure the degree of synchronization.Comment: 8 pages. Proceedings of the conference on "Stochastic Systems: From
Randomness to"Complexit
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