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Is Seismicity Operating at a Critical Point?

Physical Review Letters 2021年第12期126卷 128501-128501页

作者： Shyam Nandan Sumit Kumar Ram Guy Ouillon Didier Sornette Swiss Seismological Service ETH Zürich Sonneggstrasse 5 8092 Zürich Switzerland Department of Management Technology and Economics ETH Zürich Scheuchzerstrasse 7 8092 Zürich Switzerland Lithophyse 4 rue de l’Ancien Sénat 06300 Nice France Institute of Risk Analysis Prediction and Management (Risks-X) Academy for Advanced Interdisciplinary Studies Southern University of Science and Technology (SUSTech) 518055 Shenzhen China

Seismicity and faulting within the Earth’s crust are characterized by many scaling laws that are usually interpreted as qualifying the existence of underlying physical mechanisms associated with some kind of criticality in the sense of phase transitions. Using an augmented epidemic-type aftershock sequence (ETAS) model that accounts for the spatial variability of the background rates μ(x,y), we present a direct quantitative test of criticality. We calibrate the model to the ANSS catalog of the entire globe, the region around California, and the Geonet catalog for the region around New Zealand using an extended expectation-maximization (EM) algorithm including the determination of μ(x,y). We demonstrate that the criticality reported in previous studies is spurious and can be attributed to a systematic upward bias in the calibration of the branching ratio of the ETAS model, when not accounting correctly for spatial variability. We validate the version of the ETAS model that possesses a space varying background rate μ(x,y) by performing pseudoprospective forecasting tests. The noncriticality of seismicity has major implications for the prediction of large events.

关键词： complex systems Critical exponents Critical phenomena Earthquake statistics & scaling patterns in complex systems Scaling laws of complex systems Self-organized systems

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Systematic assessment of the quality of fit of the stochastic block model for empirical networks

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Physical Review E 2022年第5期105卷 054311-054311页

作者： Felipe Vaca-Ramírez Tiago P. Peixoto Department of Network and Data Science Central European University 1100 Vienna Austria

We perform a systematic analysis of the quality of fit of the stochastic block model (SBM) for 275 empirical networks spanning a wide range of domains and orders of size magnitude. We employ posterior predictive model checking as a criterion to assess the quality of fit, which involves comparing networks generated by the inferred model with the empirical network, according to a set of network descriptors. We observe that the SBM is capable of providing an accurate description for the majority of networks considered, but falls short of saturating all modeling requirements. In particular, networks possessing a large diameter and slow-mixing random walks tend to be badly described by the SBM. However, contrary to what is often assumed, networks with a high abundance of triangles can be well described by the SBM in many cases. We demonstrate that simple network descriptors can be used to evaluate whether or not the SBM can provide a sufficiently accurate representation, potentially pointing to possible model extensions that can systematically improve the expressiveness of this class of models.

关键词： Community structure Network formation & growth patterns in complex systems Block models

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Relationship between the size of a camphor-driven rotor and its angular velocity

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Physical Review E 2017年第1期96卷 012609-012609页

作者： Yuki Koyano Marian Gryciuk Paulina Skrobanska Maciej Malecki Yutaka Sumino Hiroyuki Kitahata Jerzy Gorecki Department of Physics Chiba University Chiba 263-8522 Japan Institute of Physical Chemistry Polish Academy of Sciences Warsaw 01-224 Poland Department of Applied Physics Faculty of Science Tokyo University of Science Tokyo 125-8585 Japan

We consider a rotor made of two camphor disks glued below the ends of a plastic stripe. The disks are floating on a water surface and the plastic stripe does not touch the surface. The system can rotate around a vertical axis located at the center of the stripe. The disks dissipate camphor molecules. The driving momentum comes from the nonuniformity of surface tension resulting from inhomogeneous surface concentration of camphor molecules around the disks. We investigate the stationary angular velocity as a function of rotor radius ℓ. For large ℓ the angular velocity decreases for increasing ℓ. At a specific value of ℓ the angular velocity reaches its maximum and, for short ℓ it rapidly decreases. Such behavior is confirmed by a simple numerical model. The model also predicts that there is a critical rotor size below which it does not rotate. Within the introduced model we analyze the type of this bifurcation.

关键词： Bifurcations Chemical Physics & Physical Chemistry patterns in complex systems Self-organized systems Active brownian particles Active matter Dynamical systems Self-propelled particles Bifurcation analysis Chaos & nonlinear dynamics

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Self-Organized Target Wave Chimeras in Reaction-Diffusion Media

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Physical Review Letters 2024年第20期133卷 207203-207203页

作者： Bing-Wei Li Jie Xiao Teng-Chao Li Alexander V. Panfilov Hans Dierckx School of Physics Hangzhou Normal University Hangzhou 311121 China Ural Federal University Computational Biomedicine Laboratory 620002 Ekaterinburg Russia Department of Physics and Astronomy Ghent University B-9000 Ghent Belgium World-Class Research Center “Digital biodesign and personalized healthcare ” I. M. Sechenov First Moscow State Medical University 119991 Moscow Russia Department of Mathematics KU Leuven Campus Kortrijk (KULAK) Kortrijk 8500 Belgium iSi Health Institute of Physics-based Modeling for In Silico Health KU Leuven Leuven 3000 Belgium

An important development in nonlinear dynamics is the discovery of chimera states that represent the coexistence of synchronized and desynchronized activity in populations of identically coupled oscillators. Identification and characterization of chimera states is currently an active area of theoretical and applied research. Here, we unveil a novel chimera state called “self-organized target wave chimera” in reaction-diffusion media where synchronized target waves spontaneously emerge from a pacemaker composed of asynchronous oscillators. This regime contrasts with a widely accepted perspective that synchronized target waves can be generated only by the individuals, which comprise the pacemaker, behaving in a synchronized manner. We characterize the features of self-organized target wave chimeras and present a phase diagram of existence of such a regime. The underlying phenomenological mechanism for the emergence of target wave chimeras is further analyzed. Our studies offer an affirmative answer to the existence of target wave chimeras in reaction-diffusion media and advance the general understanding of the onset of chimera states.

关键词： Chimera states Collective dynamics Coupled oscillators patterns in complex systems Synchronization

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Confinement-Induced Transition between Wavelike Collective Cell Migration Modes

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Physical Review Letters 2019年第16期122卷 168101-168101页

作者： Vanni Petrolli Magali Le Goff Monika Tadrous Kirsten Martens Cédric Allier Ondrej Mandula Lionel Hervé Silke Henkes Rastko Sknepnek Thomas Boudou Giovanni Cappello Martial Balland Université Grenoble Alpes Laboratoire Interdisciplinaire de Physique CNRS F-38000 Grenoble France CEA LETI MINATEC 17 rue des Martyrs 38054 Grenoble cedex 9 France Department of Mathematics University of Bristol Bristol BS81TW United Kingdom School of Science and Engineering University of Dundee Dundee DD1 4HN United Kingdom School of Life Sciences University of Dundee Dundee DD1 5EH United Kingdom

The structural and functional organization of biological tissues relies on the intricate interplay between chemical and mechanical signaling. Whereas the role of constant and transient mechanical perturbations is generally accepted, several studies recently highlighted the existence of long-range mechanical excitations (i.e., waves) at the supracellular level. Here, we confine epithelial cell monolayers to quasi-one-dimensional geometries, to force the establishment of tissue-level waves of well-defined wavelength and period. Numerical simulations based on a self-propelled Voronoi model reproduce the observed waves and exhibit a phase transition between a global and a multinodal wave, controlled by the confinement size. We confirm experimentally the existence of such a phase transition, and show that wavelength and period are independent of the confinement length. Together, these results demonstrate the intrinsic origin of tissue oscillations, which could provide cells with a mechanism to accurately measure distances at the supracellular level.

关键词： Cell locomotion Cell mechanics Cell migration Emergence of patterns patterns in complex systems Self-organization Cell membrane

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Extended Weyl-Wigner phase-space framework for nonlinear systems: Typical and modified prey-predator-like dynamics

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Physical Review E 2024年第3期110卷 034218页

作者： A. E. Bernardini O. Bertolami Departamento de Física Departamento de Física e Astronomia Faculdade de Ciências da

The extension of the phase-space Weyl-Wigner quantum mechanics to the subset of Hamiltonians in the form of H(q,p)=K(p)+V(q) [with K(p) replacing single p2 contributions] is revisited. Deviations from classical and stationary profiles are identified in terms of Wigner functions and Wigner currents for Gaussian and gamma/Laplacian distribution ensembles. The procedure is successful in accounting for the exact pattern of quantum fluctuations when compared with the classical phase-space pattern. General results are then specialized to some specific Hamiltonians revealing nonlinear dynamics, and suggest a novel algorithm to treat quantum modifications mapped by Wigner currents. Our analysis shows that the framework encompasses, for instance, the quantized prey-predator-like scenarios subjected to statistical constraints.

关键词： Mathematical physics patterns in complex systems Hamiltonian systems Population dynamics Phase space methods Semiclassical methods

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Nonequilibrium thermodynamics of glycolytic traveling wave: Benjamin-Feir instability

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Physical Review E 2021年第1期104卷 014221-014221页

作者： Premashis Kumar Gautam Gangopadhyay S. N. Bose National Centre For Basic Sciences Block-JD Sector-III Salt Lake Kolkata 700 106 India

Evolution of the nonequilibrium thermodynamic entities corresponding to dynamics of the Hopf instabilities and traveling waves at a nonequilibrium steady state of a spatially extended glycolysis model is assessed here by implementing an analytically tractable scheme incorporating a complex Ginzburg-Landau equation (CGLE). In the presence of self and cross diffusion, a more general amplitude equation exploiting the multiscale Krylov-Bogoliubov averaging method serves as an essential tool to reveal the various dynamical instability criteria, especially Benjamin-Feir (BF) instability, to estimate the corresponding nonlinear dispersion relation of the traveling wave pattern. The critical control parameter, wave-number selection criteria, and magnitude of the complex amplitude for traveling waves are modified by self- and cross-diffusion coefficients within the oscillatory regime, and their variabilities are exhibited against the amplitude equation. Unlike the traveling waves, a low-amplitude broad region appears for the Hopf instability in the concentration dynamics as the system phase passes through minima during its variation with the control parameter. The total entropy production rate of the uniform Hopf oscillation and glycolysis wave not only qualitatively reflects the global dynamics of concentrations of intermediate species but almost quantitatively. Despite the crucial role of diffusion in generating and shaping the traveling waves, the diffusive part of the entropy production rate has a negligible contribution to the system's total entropy production rate. The Hopf instability shows a more complex and colossal change in the energy profile of the open nonlinear system than in the traveling waves. A detailed analysis of BF instability shows a contrary nature of the semigrand Gibbs free energy with discrete and continuous wave numbers for the traveling wave. We hope the Hopf and traveling wave pattern around the BF instability in terms of energetics and dissipati

关键词： Bifurcations Nonequilibrium & irreversible thermodynamics patterns in complex systems Multiple time scale dynamics Reaction diffusion systems Traveling waves Chaos & nonlinear dynamics Chemical waves Pattern formation

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Boundaries Control Collective Dynamics of Inertial Self-Propelled Robots

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Physical Review Letters 2018年第18期120卷 188002-188002页

作者： A. Deblais T. Barois T. Guerin P. H. Delville R. Vaudaine J. S. Lintuvuori J. F. Boudet J. C. Baret H. Kellay Univ. Bordeaux CNRS LOMA UMR 5798 F-33405 Talence France CNRS Univ. Bordeaux CRPP UPR 8641 115 Avenue Schweitzer 33600 Pessac France

Simple ingredients, such as well-defined interactions and couplings for the velocity and orientation of self-propelled objects, are sufficient to produce complex collective behavior in assemblies of such entities. Here, we use assemblies of rodlike robots made motile through self-vibration. When confined in circular arenas, dilute assemblies of these rods act as a gas. Increasing the surface fraction leads to a collective behavior near the boundaries: polar clusters emerge while, in the bulk, gaslike behavior is retained. The coexistence between a gas and surface clusters is a direct consequence of inertial effects as shown by our simulations. A theoretical model, based on surface mediated transport accounts for this coexistence and illustrates the exact role of the boundaries. Our study paves the way towards the control of collective behavior: By using deformable but free to move arenas, we demonstrate that the surface induced clusters can lead to directed motion, while the topology of the surface states can be controlled by biasing the motility of the particles.

关键词： Aggregation Clustering Collective behavior Emergence of patterns Flocking Granular materials patterns in complex systems Phase separation Swarming

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Model of polar auxin transport coupled to mechanical forces retrieves robust morphogenesis along the Arabidopsis root

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Physical Review E 2017年第3期95卷 032410-032410页

作者： J. Roberto Romero-Arias Valeria Hernández-Hernández Mariana Benítez Elena R. Alvarez-Buylla Rafael A. Barrio Instituto de Física Universidad Nacional Autónoma de México Apartado Postal 20-364 01000 México Distrito Federal Mexico Instituto de Matemáticas Universidad Nacional Autónoma de México Campus Juriquilla Boulevard Juriquilla 3001 Juriquilla Querétaro 76230 Mexico Instituto de Ecología Universidad Nacional Autónoma de México Apartado Postal 70-275 04510 México Distrito Federal Mexico Laboratoire Reproduction et Développement des Plantes University of Lyon ENS de Lyon UCB Lyon 1 CNRS INRA 46 Allée d'Italie 69364 Lyon Cedex 07 France Centro de Ciencias de la Complejidad Universidad Nacional Autónoma de México Ciudad Universitaria 04510 México Distrito Federal Mexico

Stem cells are identical in many scales, they share the same molecular composition, DNA, genes, and genetic networks, yet they should acquire different properties to form a functional tissue. Therefore, they must interact and get some external information from their environment, either spatial (dynamical fields) or temporal (lineage). In this paper we test to what extent coupled chemical and physical fields can underlie the cell's positional information during development. We choose the root apical meristem of Arabidopsis thaliana to model the emergence of cellular patterns. We built a model to study the dynamics and interactions between the cell divisions, the local auxin concentration, and physical elastic fields. Our model recovers important aspects of the self-organized and resilient behavior of the observed cellular patterns in the Arabidopsis root, in particular, the reverse fountain pattern observed in the auxin transport, the PIN-FORMED (protein family of auxin transporters) polarization pattern and the accumulation of auxin near the region of maximum curvature in a bent root. Our model may be extended to predict altered cellular patterns that are expected under various applied auxin treatments or modified physical growth conditions.

关键词： Cell growth Cell polarity Cell signaling Diffusion Morphogenesis patterns in complex systems

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Pattern recognition with neuronal avalanche dynamics

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Physical Review E 2019年第1期99卷 010302(R)-010302(R)页

作者： L. Michiels van Kessenich D. Berger L. de Arcangelis H. J. Herrmann Computational Physics for Engineering Materials IfB ETH Zürich 8093 Zürich Switzerland and Departamento de Fisica Universidade Federal do Ceará 60451-970 Fortaleza Ceará Brazil

Pattern recognition is a fundamental neuronal process which enables a cortical system to interpret visual stimuli. How the brain learns to recognize patterns is, however, an unsolved problem. The frequently employed method of back propagation excels at this task but has been found to be unbiological in many aspects. In this Rapid Communication we achieve pattern recognition tasks in a biologically, fully consistent framework. We consider a neuronal network exhibiting avalanche dynamics, as observed experimentally, and implement negative feedback signals. These are chemical signals, such as dopamine, which mediate synaptic plasticity and sculpt the network to achieve certain tasks. The system is able to distinguish horizontal and vertical lines with high accuracy, as well as to perform well at the more complicated task of handwritten digit recognition. Resulting from the learning mechanism, spatially separate activity regions emerge, as observed in the primary visual cortex using functional magnetic resonance imaging techniques. The results therefore suggest that negative feedback signals offer an explanation for the emergence of distinct activity areas in the visual cortex.

关键词： Clustering Degree distributions Learning Memory Neuroplasticity patterns in complex systems Scaling laws of complex systems Self-organized criticality Brain network Scaling methods

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