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Zhi-Xi Wu

Publications and source records attributed to Zhi-Xi Wu.

At least 19 recordsLinked to original sources

Frequency Locking to Environmental Forcing Suppresses Oscillatory Extinction in Phage-Bacteria Interactions

Bacteriophage-bacteria interactions are central to microbial ecology, influencing evolution, biogeochemical cycles, and pathogen behavior. Most theoretical models assume static environments and passive bacterial hosts, neglecting the joint effects of bacterial traits and environmental fluctuations on coexistence dynamics. This limitation hinders the prediction of microbial persistence in dynamic ecosystems such as soils and oceans. Using a minimal ordinary differential equation framework, we demonstrate that environmental fluctuations can suppress destructive oscillations through resonance, promoting coexistence where static models otherwise predict collapse. Counterintuitively, we find that lower bacterial growth rates are helpful in enhancing survival under high infection pressure, elucidating the observed post-infection growth reduction. Our studies highlight bacterial hosts as active builders of ecological dynamics and environmental variation as a potential stabilizing force. Our findings thus bridge a theory-experiment gap and provide a framework for predicting microbial responses to environmental stress, which might have potential implications for phage therapy, microbiome management, and climate-impacted community resilience as well.

physics.bio-ph

Three-state coevolutionary game dynamics with environmental feedback

Environmental feedback mechanisms are ubiquitous in real-world complex systems. In this study, we incorporate a homogeneous environment into the evolutionary dynamics of a three-state system comprising cooperators, defectors, and empty nodes. Both coherence resonance and equilibrium states, resulting from the tightly clustering of cooperator agglomerates, enhance population survival and environmental quality. The resonance phenomenon arises at the transition between cooperative and defective payoff parameters in the prisoner's dilemma game.

nlin.AO

Higher-order evolutionary dynamics with game transitions

Higher-order interactions are prevalent in real-world complex systems and exert unique influences on system evolution that cannot be captured by pairwise interactions. We incorporate game transitions into the higher-order prisoner's dilemma game model, where these transitions consistently promote cooperation. Moreover, in systems with game transitions, the proportion of higher-order interactions has a dual impact, either enhancing the emergence and persistence of cooperation or facilitating invasions that promote defection within an otherwise cooperative system. Correspondingly, bistable states, consisting of mutual defection and either mutual cooperation or coexistence, are consistently identified in both theoretical analyses and simulation results.

nlin.AO

Unified signal response for stochastic resonance in bistable systems

The phenomenon of stochastic resonance, wherein the stimulus-response of a system can be maximized by an intermediate level of noise, has been extensively investigated through linear response theory. As yet a unified response-noise or response-frequency formula embracing diverse factors, such as noise color, damping coefficients, and coupling, is still lacking. In the present work, we theoretically investigate the benefit roles of Gaussian white noise and Ornstein- Uhlenbeck noise on the signal amplification of systems ranging from a single overdamped bistable particle to the mean-field coupled underdamped Duffing oscillators and severally deduce their signal response expressions. We find that the formulas of signal response in these different cases can be reduced to a uniform Lorentz function form. Furthermore, based on the general expression, we explain explicitly the role of driving frequency, coupling and the noise color on stochastic resonance. Our results contribute to a deep theoretical understanding of stochastic resonance in bistable systems.

nlin.AO

Optimizing and reducing stochastic resonance by noise color in globally coupled bistable systems

We investigate the collective signal response of two typical nonlinear dynamical models, the mean-field coupled overdamped bistable oscillators and the underdamped Duffing oscillators, with respect to both the additive Ornstein-Uhlenbeck noise and the weak periodical stimulus. Based on the linear response theory, we theoretically derive the dependences of the ensemble signal response on the noise intensity and driving frequency of both systems. Furthermore, we theoretically demonstrate that the noise color monotonically weakens the strength of stochastic resonance in the overdamped situation, but nonmonotonically strengthens it in the underdamped counterpart. Such a result goes against the conventional wisdom that the color of the additive noise impairs the magnitude of stochastic resonance. Finally, we perform the numerical integration to verify our theoretical results and discuss potential connections with the functional significance of 1/f noise.

physics.bio-ph

Coevolutionary game dynamics with localized environmental resource feedback

Dynamic environments shape diverse dynamics in evolutionary game systems. We introduce spatial heterogeneity of resources into the prisoner's dilemma game model to explore coevolutionary game dynamics with environmental feedback. The availability of resources significantly affects the survival competitiveness of surrounding individuals. Feedback between individuals' strategies and the resources they can use leads to the oscillating dynamic known as the "oscillatory tragedy of the commons". Our findings indicate that when the influence of individuals' strategies on the update rate of resources is significantly high in systems characterized by environmental heterogeneity, they can attain an equilibrium state that avoids the oscillatory tragedy. In contrast to the numerical results obtained in well-mixed structures, self-organized clustered patterns emerge in simulations utilizing square lattices, further enhancing the stability of the system. We discuss critical phenomena in detail, demonstrating that the aforementioned transition is robust across various system parameters, including the strength of cooperators in restoring the environment, initial distributions of cooperators, system size and structures, and noise.

q-bio.PE

Intercellular competitive growth dynamics with microenvironmental feedback

Normal life activities between cells rely crucially on the homeostasis of the cellular microenvironment, but aging and cancer will upset this balance. In this paper, we introduce the microenvironmental feedback mechanism to the growth dynamics of multicellular organisms, which changes the cellular competitive ability, and thereby regulates the growth of multicellular organisms. We show that the presence of microenvironmental feedback can effectively delay aging, but cancer cells may grow uncontrollably due to the emergence of the tumor microenvironment (TME). We study the effect of the fraction of cancer cells relative to that of senescent cells on the feedback rate of the microenvironment on the lifespan of multicellular organisms, and find that the average lifespan shortened is close to the data for non-Hodgkin lymphoma in Canada from 1980 to 2015. We also investigate how the competitive ability of cancer cells affects the lifespan of multicellular organisms, and reveal that there is an optimal value of the competitive ability of cancer cells allowing the organism to survive longest. Interestingly, the proposed microenvironmental feedback mechanism can give rise to the phenomenon of Parrondo's paradox: when the competitive ability of cancer cells switches between a too high and a too low value, multicellular organisms are able to live longer than in each case individually. Our results may provide helpful clues targeted therapies aimed at TME.

nlin.AO

Resonance induced by higher-order coupling diversity

The studies of collective oscillations induced by higher-order interactions point out the necessity of group effect in coupling modelization. As yet the related advances are mainly concentrated on nonlinear coupling patterns and cannot be straightforwardly extended to the linear ones. In present work, we introduce the standard deviation of dynamic behavior for the interacting group to complement the higher-order effect that beyond pairwise in diffusive coupling. By doing so, the higher-order effect can be flexibly extended to the linearly coupled system. We leverage this modelization to embrace the influence of heterogeneous higher-order coupling, including promoting and inhibiting effects, on the signal response for two conventional models, the globally coupled overdamped bistable oscillators and excitable FitzHugh-Nagumo neurons. Particularly, we numerically and analytically reveal that the optimal signal response can be obtained by an intermediate degree of higher-order coupling diversity for both systems. This resonant signal response stems from the competition between dispersion and aggregation induced by heterogeneous higher-order and positive pairwise couplings, respectively. Our results contribute to a better understanding of the signal propagation in linearly coupled systems.

nlin.AO

Anomalous diffusion of self-align active particle in flow background

Active particles (i.e., self-propelled particles or called microswimmers), different from passive Brownian particles, possess more complicated translational and angular dynamics, which can generate a series of anomalous transport phenomena. In this letter, we study the two-dimensional dynamics of a self-propelled pointlike particle with self-aligning property moving in Poiseuille flow. The results show the effective anomalous diffusion coefficient changes sharply with the change of temperature and speed of background Poiseuille flow. The relaxation property of moving speed and the position probability distribution function of particles is also obtained. The observation of several types of anomalous diffusion and normal diffusion regime indicates the self-aligning property may be universal and can be used as a reference for future experiments analysis and modeling.

cond-mat.soft

Game-environment feedback dynamics for voluntary prisoner's dilemma games

Recently, the eco-evolutionary game theory which describes the coupled dynamics of strategies and environment have attracted great attention. At the same time, most of the current work is focused on the classic two-player two-strategy game. In this work, we study multi-strategy eco-evolutionary game theory which is an extension of the framework. For simplicity, we'll focus on the voluntary participation Prisoner's dilemma game. For the general class of payoff-dependent feedback dynamics, we show the conditions for the existence and stability of internal equilibrium by using the replicator dynamics, respectively. Where internal equilibrium points, such as, two-strategy coexistence states, three-strategy coexistence states, persistent oscillation states and interior saddle points. These states are determined by the relative feedback strength and payoff matrix, and are independent of the relative feedback speed and initial state. In particular, the three-strategy coexistence provides a new mechanism for maintaining biodiversity in biology, ecology, and sociology. Besides, we find that this three-strategy model return to the persistent oscillation state of the two-strategy model when there is no defective strategy at the initial moment.

physics.soc-ph

Multistage onset of epidemics in heterogeneous networks

We develop a theory for the susceptible-infected-susceptible (SIS) epidemic model on networks that incorporate both network structure and dynamic correlations. This theory can account for the multistage onset of the epidemic phase in scale-free networks. This phenomenon is characterized by multiple peaks in the susceptibility as a function of the infection rate. It can be explained by that, even under the global epidemic threshold, a hub can sustain the epidemics for an extended period. Moreover, our approach improves theoretical calculations of prevalence close to the threshold in heterogeneous networks and also can predict the average risk of infection for neighbors of nodes with different degree and state on uncorrelated static networks.

physics.soc-ph

Cooperator-driven and defector-driven punishments: How do they influence cooperation?

Economic studies have shown that there are two types of regulation schemes which can be considered as a vital part of today's global economy: self-regulation enforced by self-regulation organizations to govern industry practices, and government regulation which is considered as another scheme to sustain corporate adherence. An outstanding problem of particular interest is to understand quantitatively the role of these regulation schemes in evolutionary dynamics. Typically, punishment usually occurs for enforcement of regulations. Taking into account both types of punishments to curve the regulations, we develop a game model where six evolutionary situations with corresponding combinations of strategies are considered. Furthermore, a semi-analytical method is developed to allow us to give an accurate estimations of the boundaries between the phases of full defection and nondefection. We find that, associated with the evolutionary dynamics, for infinite well-mixed population, the mix of both punishments performs better than one punishment alone in promoting public cooperation, but for networked population the cooperator-driven punishment turns out to be a better choice. We also uncover monotonous facilitating effects of synergy effect, punishment fine and feedback sensitivity on the public cooperation for infinite well-mixed population. Conversely, for networked population an optimal intermediate range of feedback sensitivity is needed to best promote punishers' populations. Overall, networked structure is overall more favorable for punishers and further for public cooperation, because of both network reciprocity and mutualism between punishers and cooperators who do not punish defectors.

physics.soc-ph

Kuramoto dilemma alleviated by optimizing connectivity and rationality

Recently, Antonioni and Cardillo proposed a coevolutionary model based on the intertwining of oscillator synchronization and evolutionary game theory [Phys. Rev. Lett. \textbf{118}, 238301 (2017)], in which each Kuramoto oscillator can decide whether to interact-or not-with its neighbors, and all oscillators can receive some benefits from the local synchronization but those who choose to interact must pay a cost. Oscillators are allowed to update their strategies according to payoff difference, wherein the strategy of an oscillator who has obtained higher payoff is more likely to be followed. Utilizing this coevolutionary model, we find that the global synchronization level reaches the highest level when the average degree of the underlying interaction network is moderate. We also study how synchronization is affected by the individual rationality in choosing strategy.

physics.soc-ph

Enhancement of cooperation by giving high-degree neighbors more help

In this paper, we study the effect of preferential assistance on cooperation in the donation game. Cooperators provide benefits to their neighbors at some costs. Defectors pay no cost and do not distribute any benefits. The total contribution of a cooperator is fixed and he/she distributes his/her contribution unevenly to his/her neighbors. Each individual is assigned a weight that is the power of its degree, where the exponent $α$ is an adjustable parameter. The amount that cooperator $i$ contributes to a neighbor $j$ is proportional to $j$'s weight. Interestingly, we find that there exists an optimal value of $α$ (which is positive), leading to the highest cooperation level. This phenomenon indicates that, to enhance cooperation, individuals could give high-degree neighbors more help, but only to a certain extent.

physics.soc-ph

Small world yields optimal public goods in presence of both altruistic and selfish cooperators

Empirical studies have shown that individuals' behaviors are largely influenced by social conformity, including punishment. However, a coevolutionary theoretical framework that takes into account effects of conformity on individuals' punishment behaviors has not been put forward yet. Herein we propose a coevolutionary game model to extend the theory of cooperation with conformity in spatial public goods game by considering pool punishment, as well as two converse feedback modes of conformity that strongly affect cooperators' punishment behaviors. We focus on how different parameters and spatial structures govern evolutionary dynamics on three different kinds of networks by employing mean-field analysis based on replicator dynamics and Monte Carlo simulations. On regular lattices, defectors are overall extincted since cooperators, especially selfish cooperators, have great evolutionary advantages due to strong network reciprocity, and at the same time the number of altruistic cooperators decays. Conversely, abundant shortcuts in regular random networks lead to the prevalence of altruistic cooperators, but cooperators suffer from free-riding behaviors of defectors. Of particular interest, we find that small-world topology can simultaneously help cooperators successfully outperform defectors by means of strong network reciprocity, and enable rich contacting opportunities with defectors to facilitate the expansion of altruistic cooperators. Therefore, we clarify that small world is the optimal topology subject to the dominance of altruistic cooperators.

physics.soc-ph

Solving the Dynamic Correlation Problem of the Susceptible-Infected-Susceptible Model on Networks

The Susceptible-Infected-Susceptible model is a canonical model for emerging disease outbreaks. Such outbreaks are naturally modeled as taking place on networks. A theoretical challenge in network epidemiology is the dynamic correlations coming from that if one node is occupied, or infected (for disease spreading models), then its neighbors are likely to be occupied. By combining two theoretical approaches---the heterogeneous mean-field theory and the effective degree method---we are able to include these correlations in an analytical solution of the SIS model. We derive accurate expressions for the average prevalence (fraction of infected) and epidemic threshold. We also discuss how to generalize the approach to a larger class of stochastic population models.

physics.soc-ph

Controlling herding in minority game systems

Resource allocation takes place in various types of real-world complex systems such as urban traf- fic, social services institutions, economical and ecosystems. Mathematically, the dynamical process of complex resource allocation can be modeled as minority games in which the number of resources is limited and agents tend to choose the less used resource based on available information. Spontaneous evolution of the resource allocation dynamics, however, often leads to a harmful herding behavior accompanied by strong fluctuations in which a large majority of agents crowd temporarily for a few resources, leaving many others unused. Developing effective control strategies to suppress and elim- inate herding is an important but open problem. Here we develop a pinning control method. That the fluctuations of the system consist of intrinsic and systematic components allows us to design a control scheme with separated control variables. A striking finding is the universal existence of an optimal pinning fraction to minimize the variance of the system, regardless of the pinning patterns and the network topology. We carry out a detailed theoretical analysis to understand the emergence of optimal pinning and to predict the dependence of the optimal pinning fraction on the network topol- ogy. Our theory is generally applicable to systems with heterogeneous resource capacities as well as varying control and network topological parameters such as the average degree and the degree dis- tribution exponent. Our work represents a general framework to deal with the broader problem of controlling collective dynamics in complex systems with potential applications in social, economical and political systems.

physics.soc-ph

Peer pressure: enhancement of cooperation through mutual punishment

An open problem in evolutionary game dynamics is to understand the effect of peer pressure on cooperation in a quantitative manner. Peer pressure can be modeled by punishment, which has been proved to be an effective mechanism to sustain cooperation among selfish individuals. We investigate a symmetric punishment strategy, in which an individual will punish each neighbor if their strategies are different, and vice versa. Because of the symmetry in imposing the punishment, one might expect intuitively the strategy to have little effect on cooperation. Utilizing the prisoner's dilemma game as a prototypical model of interactions at the individual level, we find, through simulation and theoretical analysis, that proper punishment, when even symmetrically imposed on individuals, can enhance cooperation. Besides, we find that the initial density of cooperators plays an important role in the evolution of cooperation driven by mutual punishment.

physics.soc-ph