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Search Results: 1 - 10 of 410175 matches for " Javier M. Buldu "
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Synchronization in semiconductor laser rings
Javier M. Buldu,M. C. Torrent,Jordi Garcia-Ojalvo
Physics , 2006, DOI: 10.1109/JLT.2007.895555
Abstract: We examine the dynamics of semiconductor lasers coupled in a ring configuration. The lasers, which have stable output intensity when isolated, behave chaotically when coupled unidirectionally in a closed chain. In this way, we show that neither feedback nor bidirectional coupling is necessary to induce chaotic dynamics at the laser output. We study the synchronization phenomena arising in this particular coupling architecture, and discuss its possible application to chaos-based communications. Next, we extend the study to bidirectional coupling and propose an appropriate technique to optical chaos encryption/decryption in closed chains of mutually coupled semiconductor lasers.
Bistable phase control via rocking in a nonlinear electronic oscillator
Javier M. Buldu,K. Staliunas,J. A. Casals,Jordi Garcia-Ojalvo
Physics , 2006, DOI: 10.1063/1.2404776
Abstract: We experimentally demonstrate the effective rocking of a nonlinear electronic circuit operating in a periodic regime. Namely, we show that driving a Chua circuit with a periodic signal, whose phase alternates (also periodically) in time, we lock the oscillation frequency of the circuit to that of the driving signal, and its phase to one of two possible values shifted by pi, and lying between the alternating phases of the input signal. In this way, we show that a rocked nonlinear oscillator displays phase bistability. We interpret the experimental results via a theoretical analysis of rocking on a simple oscillator model, based on a normal form description (complex Landau equation) of the rocked Hopf bifurcation
The cost of attack in competing networks
Boris Podobnik,Davor Horvatic,Tomislav Lipic,Matjaz Perc,Javier M. Buldu,H. Eugene Stanley
Computer Science , 2015, DOI: 10.1098/rsif.2015.0770
Abstract: Real-world attacks can be interpreted as the result of competitive interactions between networks, ranging from predator-prey networks to networks of countries under economic sanctions. Although the purpose of an attack is to damage a target network, it also curtails the ability of the attacker, which must choose the duration and magnitude of an attack to avoid negative impacts on its own functioning. Nevertheless, despite the large number of studies on interconnected networks, the consequences of initiating an attack have never been studied. Here, we address this issue by introducing a model of network competition where a resilient network is willing to partially weaken its own resilience in order to more severely damage a less resilient competitor. The attacking network can take over the competitor nodes after their long inactivity. However, due to a feedback mechanism the takeovers weaken the resilience of the attacking network. We define a conservation law that relates the feedback mechanism to the resilience dynamics for two competing networks. Within this formalism, we determine the cost and optimal duration of an attack, allowing a network to evaluate the risk of initiating hostilities.
Episodic synchronization in dynamically driven neurons
Pablo Balenzuela,Javier M. Buldu,Marcos Casanova,Jordi Garcia-Ojalvo
Quantitative Biology , 2006, DOI: 10.1103/PhysRevE.74.061910
Abstract: We examine the response of type II excitable neurons to trains of synaptic pulses, as a function of the pulse frequency and amplitude. We show that the resonant behavior characteristic of type II excitability, already described for harmonic inputs, is also present for pulsed inputs. With this in mind, we study the response of neurons to pulsed input trains whose frequency varies continuously in time, and observe that the receiving neuron synchronizes episodically to the input pulses, whenever the pulse frequency lies within the neuron's locking range. We propose this behavior as a mechanism of rate-code detection in neuronal populations. The results are obtained both in numerical simulations of the Morris-Lecar model and in an electronic implementation of the FitzHugh-Nagumo system, evidencing the robustness of the phenomenon.
Zero-lag long-range synchronization via dynamical relaying
Ingo Fischer,Raul Vicente,Javier M. Buldu,Michael Peil,Claudio R. Mirasso,M. C. Torrent,Jordi Garcia-Ojalvo
Physics , 2006, DOI: 10.1103/PhysRevLett.97.123902
Abstract: We show that simultaneous synchronization between two delay-coupled oscillators can be achieved by relaying the dynamics via a third mediating element, which surprisingly lags behind the synchronized outer elements. The zero-lag synchronization thus obtained is robust over a considerable parameter range. We substantiate our claims with experimental and numerical evidence of these synchronization solutions in a chain of three coupled semiconductor lasers with long inter-element coupling delays. The generality of the mechanism is validated in a neuronal model with the same coupling architecture. Thus, our results show that synchronized dynamical states can occur over long distances through relaying, without restriction by the amount of delay.
Generalized synchronization in relay systems with instantaneous coupling
Ricardo Gutierrez,Ricardo Sevilla-Escoboza,Pablo Piedrahita,Christian Finke,Ulrike Feudel,Javier M. Buldu,Guillermo Huerta-Cuellar,Rider Jaimes-Reategui,Yamir Moreno,Stefano Boccaletti
Physics , 2013, DOI: 10.1103/PhysRevE.88.052908
Abstract: We demonstrate the existence of generalized synchronization in systems that act as mediators between two dynamical units that, in turn, show complete synchronization with each other. These are the so-called relay systems. Specifically, we analyze the Lyapunov spectrum of the full system to elucidate when complete and generalized synchronization appear. We show that once a critical coupling strength is achieved, complete synchronization emerges between the systems to be synchronized, and at the same point, generalized synchronization with the relay system also arises. Next, we use two nonlinear measures based on the distance between phase-space neighbors to quantify the generalized synchronization in discretized time series. Finally, we experimentally show the robustness of the phenomenon and of the theoretical tools here proposed to characterize it.
Community structures and role detection in music networks
T. Teitelbaum,P. Balenzuela,P. Cano,J. M. Buldu
Physics , 2008, DOI: 10.1063/1.2988285
Abstract: We analyze the existence of community structures in two different social networks obtained from similarity and collaborative features between musical artists. Our analysis reveals some characteristic organizational patterns and provides information about the driving forces behind the growth of the networks. In the similarity network, we find a strong correlation between clusters of artists and musical genres. On the other hand, the collaboration network shows two different kinds of communities: rather small structures related to music bands and geographic zones, and much bigger communities built upon collaborative clusters with a high number of participants related through the period the artists were active. Finally, we detect the leading artists inside their corresponding communities and analyze their roles in the network by looking at a few topological properties of the nodes.
Effect of External Noise Correlation in Optical Coherence Resonance
J. M. Buldu,J. Garcia-Ojalvo,Claudio R. Mirasso,M. C. Torrent,J. M. Sancho
Physics , 2001, DOI: 10.1103/PhysRevE.64.051109
Abstract: Coherence resonance occurring in semiconductor lasers with optical feedback is studied via the Lang-Kobayashi model with external non-white noise in the pumping current. The temporal correlation and the amplitude of the noise have a highly relevant influence in the system, leading to an optimal coherent response for suitable values of both the noise amplitude and correlation time. This phenomenon is quantitatively characterized by means of several statistical measures.
Dynamics of modal power distribution in a multimode semiconductor laser with optical feedback
J. M. Buldu,J. Trull,M. C. Torrent,J. Garcia-Ojalvo,Claudio R. Mirasso
Physics , 2001, DOI: 10.1088/1464-4266/4/1/101
Abstract: The dynamics of power distribution between longitudinal modes of a multimode semiconductor laser subjected to external optical feedback is experimentally analyzed in the low-frequency fluctuation regime. Power dropouts in the total light intensity are invariably accompanied by sudden activations of several longitudinal modes. These activations are seen not to be simultaneous to the dropouts, but to occur after them. The phenomenon is statistically analysed in a systematic way, and the corresponding delay is estimated.
Synchronization interfaces and overlapping communities in complex networks
D. Li,I. Leyva,J. A. Almendral,I. Sendina-Nadal,J. M. Buldu,S. Havlin,S. Boccaletti
Physics , 2008, DOI: 10.1103/PhysRevLett.101.168701
Abstract: We show that a complex network of phase oscillators may display interfaces between domains (clusters) of synchronized oscillations. The emergence and dynamics of these interfaces are studied in the general framework of interacting phase oscillators composed of either dynamical domains (influenced by different forcing processes), or structural domains (modular networks). The obtained results allow to give a functional definition of overlapping structures in modular networks, and suggest a practical method to identify them. As a result, our algorithm could detect information on both single overlapping nodes and overlapping clusters.
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