1,721,016 research outputs found
Advanced Topics on Cellular Self-Organizing Nets and Chaotic Nonlinear Dynamics to Model and Control Complex Systems
No full textTopologically-induced suppression of explosive synchronization
No full textNowadays, explosive synchronization is a well documented phenomenon occurring in networks when the node frequency and its degree are correlated. This first-order transition, which may coexists with classical synchronization, has been recently causally linked to some pathological brain states like epilepsy and fibromyalgia. It is then intriguing how most of neuronal systems can operate in normal conditions avoiding explosive synchronization. Here, we have discovered that synchronization in networks where the oscillators are coupled via degree-biased Laplacian operators, naturally controls the transition from explosive to standard synchronization in neuronal-like systems. We prove analytically that explosive synchronization emerges when using this theoretical setting in star-like (neuronal) networks. As soon as this star-like network is topologically converted to a network containing cycles, e.g., via synaptic connections to other neurons, the explosive synchronization gives rise to classical synchronization. This allows us to hypothesize that such topological control of explosive synchronization could be a mechanism for the brain to naturally work in normal, non-pathological, conditions.M.M. thanks financial support PRE2020-092875 by MCIN/AEI /10.13039/501100011033 and by FSE invierte en
tu futuro. E.E. thanks Grant PID2019-107603GB-I00 by MCIN/ AEI /10.13039/501100011033.Peer reviewe
Effect of individual behavior on epidemic spreading in activity-driven networks
No full textIn this work we study the effect of behavioral changes of individuals on the propagation of epidemic diseases. Specifically, we consider a susceptible-infected-susceptible model over a network of contacts that evolves in a time scale that is comparable to the individual disease dynamics. The phenomenon is modeled in the context of activity-driven networks, in which contacts occur on the basis of activity potentials. To offer insight into behavioral strategies targeting both susceptible and infected individuals, we consider two separate behaviors that may emerge in respiratory syndromes and sexually transmitted infections. The first is related to a reduction in the activity of infected individuals due to quarantine or illness. The second is instead associated with a selfish self-protective behavior of susceptible individuals, who tend to reduce contact with the rest of the population on the basis of a risk perception. Numerical and theoretical results suggest that behavioral changes could have a beneficial effect on the disease spreading, by increasing the epidemic threshold and decreasing the steady-state fraction of infected individuals
Spatial pinning control of Vicsek's Agents
No full textIn this work we study a system of mobile agents that
move in an anisotropic space and interact according to
the Vicsek model. In particular, the space is divided
in two regions: in the first one, agents obey to the traditional
Vicsek model, while in the second one, called
control region, a motion control law is added. The control
law forces the pinned agents, that are the agents
moving in the control region, to follow a criterion mediating
between the tendency to adopt the average direction
of neighboring agents, and that to follow an imposed
preferential direction. We show that, for low and
medium levels of noise in the system, the control law is
effective to drive the system towards a global ordered
state, while, for high levels of noise, a strong control
action leads to a configuration, for some aspects paradoxical,
where all the agents tend to avoid the control
region and occupy for most of the time the remaining
part of the space
Apparent remote synchronization of amplitudes: A demodulation and interference effect
No full textA form of "remote synchronization" was recently described, wherein amplitude fluctuations across a ring of non-identical, non-linear electronic oscillators become entrained into spatially-structured patterns. According to linear models and mutual information, synchronization and causality dip at a certain distance, then recover before eventually fading. Here, the underlying mechanism is finally elucidated through novel experiments and simulations. The system non-linearity is found to have a dual role: it supports chaotic dynamics, and it enables the energy exchange between the lower and higher sidebands of a predominant frequency. This frequency acts as carrier signal in an arrangement resembling standard amplitude modulation, wherein the lower sideband and the demodulated baseband signals spectrally overlap. Due to a spatially-dependent phase relationship, at a certain distance near-complete destructive interference occurs between them, causing the observed dip. Methods suitable for detecting non-trivial entrainment, such as transfer entropy and the auxiliary system approach, nevertheless, reveal that synchronization and causality actually decrease with distance monotonically. Remoteness is, therefore, arguably only apparent, as also reflected in the propagation of external perturbations. These results demonstrate a complex mechanism of dynamical interdependence, and exemplify how it can lead to incorrectly inferring synchronization and causality
Topologically induced suppression of explosive synchronization
No full text13 pages, 11 figures.Nowadays, explosive synchronization is a well-documented phenomenon consisting in a first-order transition that may coexist with classical synchronization. Typically, explosive synchronization occurs when the network structure is represented by the classical graph Laplacian, and the node frequency and its degree are correlated. Here, we answer the question on whether this phenomenon can be observed in networks when the oscillators are coupled via degree-biased Laplacian operators. We not only observe that this is the case but also that this new representation naturally controls the transition from explosive to standard synchronization in a network. We prove analytically that explosive synchronization emerges when using this theoretical setting in star-like networks. As soon as this star-like network is topologically converted into a network containing cycles, the explosive synchronization gives rise to classical synchronization. Finally, we hypothesize that this mechanism may play a role in switching from normal to explosive states in the brain, where explosive synchronization has been proposed to be related to some pathologies like epilepsy and fibromyalgia.M.M. acknowledges financial support (No. PRE2020-092875) by MCIN/AEI /10.13039/501100011033 and by FSE invierte en tu futuro. E.E. acknowledges Grant No. PID2019-107603GB-I00 by MCIN/ AEI /10.13039/501100011033. M.M. and E.E. acknowledge funding from the Spanish Ministerio de Ciencia e Innovación, Agencia Estatal de Investigación Program for Units of Excellences María de Maeztu (No. CEX2021-001164-M /10.13039/501100011033).With funding from the Spanish government through the "Severo Ochoa Centre of Excellence" accreditation (CEX2021-001164-M).Peer reviewe
Effects of Long-Range Connections in Distributed Control of Collective Motion
No full textThe introduction of long-range connections in locally connected networks leads to the so-called small-world effect: when few long-range connections are added to the original topology, the characteristic path length decreases, whereas a high clustering coefficient is preserved. In this paper, it is shown that long-range connections introduced in a network model describing the interactions of a group of mobile robots increase the tendency to form a coordinated group of robots which travel in the same direction. The leadership of informed individuals in the group is also increased
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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