Author(s): Jinhyuk Yun (윤진혁), Sang Hoon Lee (이상훈), and Hawoong Jeong (정하웅)
A study of the entire editing history of English Wikipedia shows that the articles cluster into four categories based on how frequently and how aggressively they are edited.
[Phys. Rev. E 93, 012307] Published Fri Jan 22, 2016
We consider a mean-field model of coupled phase oscillators with quenched disorder in the coupling strengths and natural frequencies. When these two kinds of disorder are uncorrelated (and when the positive and negative couplings are equal in number and strength), it is known that phase coherence cannot occur and synchronization is absent. Here we explore the effects of correlating the disorder. Specifically, we assume that any given oscillator either attracts or repels all the others, and that the sign of the interaction is deterministically correlated with the given oscillator's natural frequency. For symmetrically correlated disorder with zero mean, we find that the system spontaneously synchronizes, once the width of the frequency distribution falls below a critical value. For asymmetrically correlated disorder, the model displays coherent traveling waves: the complex order parameter becomes nonzero and rotates with constant frequency different from the system's mean natural frequency. Thus, in both cases, correlated disorder can trigger phase coherence.
Transient dynamics are of large interest in many areas of science. Here, a generalization of basin stability (BS) is presented: constrained basin stability (CBS) that is sensitive to various different types of transients arising from finite size perturbations. CBS is applied to the paradigmatic Lorenz system for uncovering nonlinear precursory phenomena of a boundary crisis bifurcation. Further, CBS is used in a model of the Earth's carbon cycle as a return time-dependent stability measure of the system's global attractor. Both case studies illustrate how CBS's sensitivity to transients complements BS in its function as an early warning signal and as a stability measure. CBS is broadly applicable in systems where transients matter, from physics and engineering to sustainability science. Thus, CBS complements stability analysis with BS as well as classical linear stability analysis and will be a useful tool for many applications.
Author(s): Mark J. Panaggio, Daniel M. Abrams, Peter Ashwin, and Carlo R. Laing
Chimera states are dynamical patterns in networks of coupled oscillators in which regions of synchronous and asynchronous oscillation coexist. Although these states are typically observed in large ensembles of oscillators and analyzed in the continuum limit, chimeras may also occur in systems with f…[Phys. Rev. E] Published Thu Jan 07, 2016
Author(s): C. L. N. Oliveira, A. P. Vieira, D. Helbing, J. S. Andrade, Jr., and H. J. Herrmann
Ensuring efficient pedestrian streams through transit corridors such as subway hallways is a problem of significant relevance to many cities. By modeling self-driven particles, scientists show that modulating the shape of a hallway’s walls might help to separate opposite pedestrian flows.
[Phys. Rev. X 6, 011003] Published Thu Jan 07, 2016
Pantheon 1.0, a manually verified dataset of globally famous biographies
Scientific Data, Published online: 5 January 2016; doi:10.1038/sdata.2015.75
Problem solving (e.g., drug design, traffic engineering, software development) by task forces represents a substantial portion of the economy of developed countries. Here we use an agent-based model of cooperative problem solving systems to study the influence of diversity on the performance of a task force. We assume that agents cooperate by exchanging information on their partial success and use that information to imitate the more successful agent in the system -- the model. The agents differ only in their propensities to copy the model. We find that, for easy tasks, the optimal organization is a homogeneous system composed of agents with the highest possible copy propensities. For difficult tasks, we find that diversity can prevent the system from being trapped in sub-optimal solutions. However, when the system size is adjusted to maximize performance the homogeneous systems outperform the heterogeneous systems, i.e., for optimal performance, sameness should be preferred to diversity.
Author(s): Sangeeta Rani Ujjwal, Nirmal Punetha, and Ramakrishna Ramaswamy
We study the dynamics of nonlocally coupled phase oscillators in a modular network. The interactions include a phase lag, a. Depending upon the various parameters the system exhibits a number of different dynamical states. In addition to global synchrony (GS) there can also be modular synchrony (MS)…[Phys. Rev. E] Published Wed Dec 23, 2015
Author(s): Jinhyuk Yun, Sang Hoon Lee, and Hawoong Jeong
Wikipedia is a free Internet encyclopedia with enormous amount of contents. This encyclopedia is written by volunteers with various backgrounds in a collective fashion; anyone can access and edit most of the articles. This open editing nature may give us prejudice that Wikipedia is unstable and unre…[Phys. Rev. E] Published Wed Dec 30, 2015
Author(s): Dong Zhou, Avi Gozolchiani, Yosef Ashkenazy, and Shlomo Havlin
A new method allows researchers to extract climate connections between remote regions from global temperature datasets.
[Phys. Rev. Lett. 115, 268501] Published Wed Dec 30, 2015
The dynamics of two symmetrically coupled populations of rotators is studied for different values of the inertia. The system is characterized by different types of solutions, which all coexist with the fully synchronized state. At small inertia, the system is no more chaotic and one observes mainly quasi-periodic chimeras, while the usual (stationary) chimera state is not anymore observable. At large inertia, one observes two different kind of chaotic solutions with broken symmetry: the intermittent chaotic chimera, characterized by a synchronized population and a population displaying a turbulent behaviour, and a second state where the two populations are both chaotic but whose dynamics adhere to two different macroscopic attractors. The intermittent chaotic chimeras are characterized by a finite life-time, whose duration increases as a power-law with the system size and the inertia value. Moreover, the chaotic population exhibits clear intermittent behavior, displaying a laminar phase where the two populations tend to synchronize, and a turbulent phase where the macroscopic motion of one population is definitely erratic. In the thermodynamic limit, these states survive for infinite time and the laminar regimes tends to disappear, thus giving rise to stationary chaotic solutions with broken symmetry contrary to what observed for chaotic chimeras on a ring geometry.
In this paper, we study dynamical systems in which a large number N of identical Landau-Stuart oscillators are globally coupled via a mean-field. Previously, it has been observed that this type of system can exhibit a variety of different dynamical behaviors. These behaviors include time periodic cluster states in which each oscillator is in one of a small number of groups for which all oscillators in each group have the same state which is different from group to group, as well as a behavior in which all oscillators have different states and the macroscopic dynamics of the mean field is chaotic. We argue that this second type of behavior is “extensive” in the sense that the chaotic attractor in the full phase space of the system has a fractal dimension that scales linearly with N and that the number of positive Lyapunov exponents of the attractor also scales linearly with N. An important focus of this paper is the transition between cluster states and extensive chaos as the system is subjected to slow adiabatic parameter change. We observe discontinuous transitions between the cluster states (which correspond to low dimensional dynamics) and the extensively chaotic states. Furthermore, examining the cluster state, as the system approaches the discontinuous transition to extensive chaos, we find that the oscillator population distribution between the clusters continually evolves so that the cluster state is always marginally stable. This behavior is used to reveal the mechanism of the discontinuous transition. We also apply the Kaplan-Yorke formula to study the fractal structure of the extensively chaotic attractors.
We study collective dynamics in rotator ensembles and focus on the multistability of synchronous regimes in a chain of coupled rotators. We provide a detailed analysis of the number of coexisting regimes and estimate in particular, the synchronization boundary for different types of individual frequency distribution. The number of wave-based regimes coexisting for the same parameters and its dependence on the chain length are estimated. We give an analytical estimation for the synchronization frequency of the in-phase regime for a uniform individual frequency distribution.
Author(s): Jakob Runge
Measures of information transfer have become a popular approach to analyze interactions in complex systems such as the Earth or the human brain from measured time series. Recent work has focused on causal definitions of information transfer aimed at decompositions of predictive information about a t…
[Phys. Rev. E 92, 062829] Published Mon Dec 28, 2015
Author(s): Sun-Ting Tsai, Chin-De Chang, Ching-Hao Chang, Meng-Xue Tsai, Nan-Jung Hsu, and Tzay-Ming Hong
The ubiquity of power-law relations in empirical data displays physicists' love of simple laws and uncovering common causes among seemingly unrelated phenomena. However, many reported power laws lack statistical support and mechanistic backings, not to mention discrepancies with real data are often …
[Phys. Rev. E 92, 062925] Published Mon Dec 28, 2015
Author(s): V. M. Bastidas, I. Omelchenko, A. Zakharova, E. Schöll, and T. Brandes
Chimera states are complex spatiotemporal patterns in networks of identical oscillators, characterized by the coexistence of synchronized and desynchronized dynamics. Here we propose to extend the phenomenon of chimera states to the quantum regime, and uncover intriguing quantum signatures of these …
[Phys. Rev. E 92, 062924] Published Mon Dec 28, 2015
We analyze star-type networks of phase oscillators by virtue of two methods. For identical oscillators we adopt the Watanabe-Strogatz approach, which gives full analytical description of states, rotating with constant frequency. For nonidentical oscillators, such states can be obtained by virtue of the self-consistent approach in a parametric form. In this case stability analysis cannot be performed, however with the help of direct numerical simulations we show which solutions are stable and which not. We consider this system as a model for a drum orchestra, where we assume that the drummers follow the signal of the leader without listening to each other and the coupling parameters are determined by a geometrical organization of the orchestra.
Author(s): Juan Ignacio Perotti, Claudio Juan Tessone, and Guido Caldarelli
The quest for a quantitative characterization of community and modular structure of complex networks produced a variety of methods and algorithms to classify different networks. However, it is not clear if such methods provide consistent, robust, and meaningful results when considering hierarchies a…
[Phys. Rev. E 92, 062825] Published Tue Dec 22, 2015
Author(s): Arindam Mishra, Chittaranjan Hens, Mridul Bose, Prodyot K. Roy, and Syamal K. Dana
We report chimeralike states in an ensemble of oscillators using a type of global coupling consisting of two components: attractive and repulsive mean-field feedback. We identify the existence of two types of chimeralike states in a bistable Liénard system; in one type, both the coherent and the inc…
[Phys. Rev. E 92, 062920] Published Tue Dec 22, 2015
We consider the existence of non-synchronized fixed points to the Kuramoto model defined on sparse networks: specifically, networks where each vertex has degree exactly three. We show that "most" such networks support multiple attracting phase-locked solutions that are not synchronized, and study the depth and width of the basins of attraction of these phase-locked solutions. We also show that it is common in "large enough" graphs to find phase-locked solutions where one or more of the links has angle difference greater than $\pi/2$.
Author(s): Roberto Murcio, A. Paolo Masucci, Elsa Arcaute, and Michael Batty
An analysis of London’s street network shows how the network has evolved over time from a heterogeneous to homogeneous fractal pattern.
[Phys. Rev. E 92, 062130] Published Thu Dec 17, 2015
Author(s): Xiukai Sui, Bin Wu, and Long Wang
The likelihood that a mutant fixates in the wild population, i.e., fixation probability, has been intensively studied in evolutionary game theory, where individuals' fitness is frequency dependent. However, it is of limited interest when it takes long to take over. Thus the speed of evolution become…
[Phys. Rev. E 92, 062124] Published Mon Dec 14, 2015
Author(s): A. Navas, J. A. Villacorta-Atienza, I. Leyva, J. A. Almendral, I. Sendiña-Nadal, and S. Boccaletti
Synchronization of networked oscillators is known to depend fundamentally on the interplay between the dynamics of the graph's units and the microscopic arrangement of the network's structure. We here propose an effective network whose topological properties reflect the interplay between the topolog…
[Phys. Rev. E 92, 062820] Published Tue Dec 15, 2015
Author(s): Rinku Jacob, K. P. Harikrishnan, R. Misra, and G. Ambika
We propose a general method for the construction and analysis of unweighted e - recurrence networks from chaotic time series. The selection of the critical threshold ec in our scheme is done empirically and we show that its value is closely linked to the embedding dimension M. In fact, we are able t…[Phys. Rev. E] Published Fri Dec 11, 2015
Article
The percolation transition has been regarded as model-independent, namely determined by the geometry of a system but otherwise identical for bond or site percolation models. Here, the authors show the violation of this assumption both analytically and numerically for networks with null percolation thresholds.
Nature Communications doi: 10.1038/ncomms10196
Authors: Filippo Radicchi, Claudio Castellano
A new measure to characterize stability of complex dynamical systems against large perturbation is suggested, the stability threshold (ST). It quantifies the magnitude of the weakest perturbation capable to disrupt the system and switch it to an undesired dynamical regime. In the phase space, the stability threshold corresponds to the "thinnest site" of the attraction basin and therefore indicates the most "dangerous" direction of perturbations. We introduce a computational algorithm for quantification of the stability threshold and demonstrate that the suggested approach is effective and provides important insights. The generality of the obtained results defines their vast potential for application in such fields as engineering, neuroscience, power grids, Earth science and many others where robustness of complex systems is studied.
In this paper, we analyze the limiting spectral distribution of the adjacency matrix of a random graph ensemble, proposed by Chung and Lu, in which a given expected degree sequence $\overline{w}_n^{^{T}} = (w^{(n)}_1,\ldots,w^{(n)}_n)$ is prescribed on the ensemble. Let $\mathbf{a}_{i,j} =1$ if there is an edge between the nodes $\{i,j\}$ and zero otherwise, and consider the normalized random adjacency matrix of the graph ensemble: $\mathbf{A}_n$ $=$ $ [\mathbf{a}_{i,j}/\sqrt{n}]_{i,j=1}^{n}$. The empirical spectral distribution of $\mathbf{A}_n$ denoted by $\mathbf{F}_n(\mathord{\cdot})$ is the empirical measure putting a mass $1/n$ at each of the $n$ real eigenvalues of the symmetric matrix $\mathbf{A}_n$. Under some technical conditions on the expected degree sequence, we show that with probability one, $\mathbf{F}_n(\mathord{\cdot})$ converges weakly to a deterministic distribution $F(\mathord{\cdot})$. Furthermore, we fully characterize this distribution by providing explicit expressions for the moments of $F(\mathord{\cdot})$. We apply our results to well-known degree distributions, such as power-law and exponential. The asymptotic expressions of the spectral moments in each case provide significant insights about the bulk behavior of the eigenvalue spectrum.
The description and analysis of spatio-temporal dynamics is a crucial task in many scientific disciplines. In this work, we propose a method which uses the mapogram as a similarity measure between spatially distributed data instances at different time points. The resulting similarity values of the pairwise comparison are used to construct a recurrence plot in order to benefit from established tools of recurrence quantification analysis and recurrence network analysis. In contrast to other recurrence tools for this purpose, the mapogram approach allows the specific focus on different spatial scales that can be used in a multi-scale analysis of spatio-temporal dynamics. We illustrate this approach by application on mixed dynamics, such as traveling parallel wave fronts with additive noise, as well as more complicate examples, pseudo-random numbers and coupled map lattices with a semi-logistic mapping rule. Especially the complicate examples show the usefulness of the multi-scale consideration in order to take spatial pattern of different scales and with different rhythms into account. So, this mapogram approach promises new insights in problems of climatology, ecology, or medicine.