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Lag synchronization is a basic phenomenon in mismatched coupled systems, delay coupled systems and time-delayed systems. It is characterized by a lag configuration that establishes a unique time shift between all the state variables of the coupled systems. In this report, an attempt is made how to induce multiple lag configurations in coupled systems when different pairs of state variables attain different time shift. A design of coupling is presented to realize this multiple lag synchronization. Numerical illustration is given using examples of the R\"ossler system and the slow-fast Hindmarsh-Rose neuron model. The multiple lag scenario is physically realized in an electronic circuit of two Sprott systems., Comment: 10 pages, 5 figures

Using the damped harmonic oscillator equations as a mathematical template, several novel chaotic oscillators are developed with an emphasis on mathematical simplicity and ease of electronic circuit implementation. These chaotic systems offer an intuitive introduction to chaos theory, enabling comparison of mathematical and computational analyses with experimental results.

Synchronization of chaotic oscillators in a generalized sense leads to richer behavior than identical chaotic oscillations in coupled systems. It may imply a more complicated connection between the synchronized trajectories in the state spaces of coupled systems. We suggest a method here that can be used to detect and study generalized synchronization in drive-response systems. This technique, the auxiliary system method, utilizes a second, identical response system to monitor the synchronized motions. The method can be implemented both numerically and experimentally and in some cases it leads to analytical results for generalized synchronization.

The influence of parameter mismatches on multirhythmic patterns in chains of coupled Rossler circuits are explored experimentally. The parameter mismatches in coupled chaotic oscillators are found to help form a kind of multirhythmic pattern as reported in chains of biological coupled oscillators [Phys. Rev. Lett. 92 228102]. Moreover, a new type of multirhythmic pattern based on the envelope of time series is observed.

We construct a new RC phase shift network based Chua's circuit, which exhibits a period-doubling bifurcation route to chaos. Using coupled versions of such a phase-shift network based Chua's oscillators, we describe a new method for achieving complete synchronization (CS), approximate lag synchronization (LS) and approximate anticipating synchronization (AS) without delay or parameter mismatch. Employing the Pecora and Carroll approach, chaos synchronization is achieved in coupled chaotic oscillators, where the drive system variables control the response system. As a result, AS or LS or CS is demonstrated without using a variable delay line both experimentally and numerically., Accepted for publication in CHAOS

Synchronous behavior in networks of coupled oscillators is a commonly observed phenomenon attracting a growing interest in physics, biology, communication, and other fields of science and technology. Besides global synchronization, one can also observe splitting of the full network into several clusters of mutually synchronized oscillators. In this paper, we study the conditions for such cluster partitioning into ensembles for the case of identical chaotic systems. We focus mainly on the existence and the stability of unique unconditional clusters whose rise does not depend on the origin of the other clusters. Also, conditional clusters in arrays of globally nonsymmetrically coupled identical chaotic oscillators are investigated. The design problem of organizing clusters into a given configuration is discussed.

A new method is introduced for automatic simulation of three kinds of chaotic oscillators: Chua's circuit, generalized Chua's circuit and chaotic oscillator implemented with saturated functions. The former generates the double-scroll, and the others 1D n-scroll attractors. The third chaotic oscillator is modified to generate 2D n-scrolls attractors. The oscillators are modelled by applying state variables and piecewise-linear approximation. Basically, the method computes the eigenvalues of the oscillators to begin time simulation and to make control of step-size automatically.

Phase synchronization(PS) and generalized synchronization(GS) of a chaotic oscillator driven by two chaotic signals is investigated. Anti-biased PS and biased GS in the presence of biased coupling are found, i.e., the response oscillator can be phase synchronized (generally synchronized) by the drive with a weaker (stronger) coupling rather than the stronger (weaker) driver. The mechanism for these behaviors are explored.

We study global stability of synchronization in asymmetrically connected networks of limit-cycle or chaotic oscillators. We extend the connection graph stability method to directed graphs with node balance, the property that all nodes in the network have equal input and output weight sums. We obtain the same upper bound for synchronization in asymmetrically connected networks as in the network with a symmetrized matrix, provided that the condition of node balance is satisfied. In terms of graphs, the symmetrization operation amounts to replacing each directed edge by an undirected edge of half the coupling strength. It should be stressed that without node balance this property in general does not hold.

Two integrated continuous-time chaotic oscillators based on cross-coupled -g m oscillators are presented and their application to random bit generation is described. Numerical and experimental results show that the generated binary streams pass standard randomness statistical tests. Simulation using Cadence verifies possible circuit operation in the RF range

The shift Δt between unstable periodic orbits of coupled oscillators occurring in the chaotic synchronization regime has been studied. It is shown that this time shift is the same for all equiphase orbits with various topological parameters and depends on the coupling parameter e. This dependence obeys the universal power law Δt ∼ en with an exponent of n = −1.

Two coupled dynamical systems which both behave chaotically without coupling are studied. The coupling is linear. We show that the coupled system can behave regularly.

Synchronization of multiple chaotic oscillators in Hamiltonian form is numerically studied and is achieved by appealing to complex systems theory [1–5]. The topology that we consider is the irregular coupled network. Two cases are considered: i) chaotic synchronization without master oscillator (where the final collective behaviour is a new chaotic state) and ii) chaotic synchronization with master oscillator (where the final collective behaviour is imposed by the dynamics of the master oscillator to multiple slave oscillators). The Hysteretic and Rössler chaotic oscillators in Hamiltonian form will be used as examples.

We demonstrate the existence of phase synchronization of two chaotic rotators. Contrary to phase synchronization of chaotic oscillators, here the Lyapunov exponents corresponding to both phases remain positive even in the synchronous regime. Such frequency locked dynamics with different ratios of frequencies are studied for driven continuous-time rotators and for discrete circle maps. We show that this transition to phase synchronization occurs via a crisis transition to a band-structured attractor.

We study two-layer networks of identical phase oscillators. Each individual layer is a ring network for which a non-local intra-layer coupling leads to the formation of a chimera state. The number of oscillators and their natural frequencies is in general different across the layers. We couple the phases of individual oscillators in one layer to the phase of the mean field of the other layer. This coupling from the mean field to individual oscillators is done in both directions. For a sufficient strength of this interlayer coupling, the phases of the mean fields lock across the two layers. In contrast, both layers continue to exhibit chimera states with no locking between the phases of individual oscillators across layers, and the two mean field amplitudes remain uncorrelated. Hence, the networks’ mean fields show phase synchronization which is analogous to the one between low-dimensional chaotic oscillators. The required coupling strength to achieve this mean field phase synchronization increases with the mismatches in the network sizes and the oscillators’ natural frequencies. We acknowledge funding from the Spanish Ministry of Economy and Competitiveness, Grant FIS2014-54177-R (R.G.A and G.R.), the CERCA Programme of the Generalitat de Catalunya (R.G.A), the European Unions Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 642563 (R.G.A and I.M.) and by the DFG in the framework of SFB 910 (E.S., A.Z. and G.R.).

International audience; The relationship between network structure and dynamics is one of the most extensively investigated problems in the theory of complex systems of recent years. Understanding this relationship is of relevance to a range of disciplines—from neuroscience to geomorphology. A major strategy of investigating this relationship is the quantitative comparison of a representation of network architecture (structural connectivity, SC) with a (network) representation of the dynamics (functional connectivity, FC). Here, we show that one can distinguish two classes of functional connectivity—one based on simultaneous activity (co-activity) of nodes, the other based on sequential activity of nodes. We delineate these two classes in different categories of dynamical processes—excitations, regular and chaotic oscillators—and provide examples for SC/FC correlations of both classes in each of these models. We expand the theoretical view of the SC/FC relationships, with conceptual instances of the SC and the two classes of FC for various application scenarios in geomorphology, ecology, systems biology, neuroscience and socio-ecological systems. Seeing the organisation of dynamical processes in a network either as governed by co-activity or by sequential activity allows us to bring some order in the myriad of observations relating structure and function of complex networks.

The experimental study of a secure chaotic synchronized communication system is presented. The synchronization between two digital chaotic oscillators, serving as a transmitter-receiver scheme, is studied. The oscillators exhibit rich chaotic behavior and are unidirectionally coupled, forming a master-slave topology. Both the input information signal and the transmitted chaotic signal are digital ones.

The transition from the phase-unlocking state to the phase-locking state is found at the desynchronization of synchronous chaos of coupled oscillators. In the phase-locking case, the motions of all oscillators are chaotic and desynchronized, however spatial ordering is identified in their phase distribution.