Physica A: Statistical Mechanics and its Applications最新文献

{"title":"Covid-19 pandemic and main comorbidities in Mexican population a complex network approach","authors":"J.J. Esquivel-Gómez,&nbsp;J.G. Barajas-Ramírez","doi":"10.1016/j.physa.2025.131015","DOIUrl":"10.1016/j.physa.2025.131015","url":null,"abstract":"<div><div>Quarantine and vaccination policies are among the most effective mechanisms used to mitigate the spread of infectious diseases. Numerous epidemic models are proposed in the literature. However, in order to produce more realistic scenarios regarding the transmission and infection processes, epidemic models should take into account the interaction among the individuals in combination with specific characteristics like age and health. In this sense, we propose a <span><math><mrow><mi>S</mi><mi>V</mi><mi>I</mi><mi>Q</mi><mi>R</mi><mi>S</mi></mrow></math></span> epidemic model that implements particular characteristics from the Mexican population, like the age distribution and the percentage of people suffering from a chronic illness like high blood pressure, obesity, and diabetes. Our model is capable of reproducing some available statistics from the last Covid-19 pandemic in México, simulating the disease spread in a complex network with degree distribution <span><math><mrow><mi>P</mi><mrow><mo>(</mo><mi>k</mi><mo>)</mo></mrow><mo>∼</mo><msup><mrow><mi>k</mi></mrow><mrow><mo>−</mo><mn>2</mn><mo>.</mo><mn>5</mn></mrow></msup></mrow></math></span>. In particular, it reproduces closely the distributions of Covid-19 infected individuals and infected individuals who also suffer from diabetes. Additionally, our model indicates through stochastic simulations that the isolation and vaccination of people suffering chronic diseases is an appropriate strategy to prevent the increase in infected individuals and avoid the overloading of health systems. Following this approach, the number of infected individuals grows slowly, preventing the overloading of health systems.</div></div>","PeriodicalId":20152,"journal":{"name":"Physica A: Statistical Mechanics and its Applications","volume":"679 ","pages":"Article 131015"},"PeriodicalIF":3.1,"publicationDate":"2025-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145222135","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Do G7 and BRICS differ in growth–emission nexus? A multifractal and wavelet approach","authors":"Zhongjie Zhang ,&nbsp;Zijian Feng ,&nbsp;Lei Shi ,&nbsp;Yi-Cheng Zhang","doi":"10.1016/j.physa.2025.131014","DOIUrl":"10.1016/j.physa.2025.131014","url":null,"abstract":"<div><div>This study examines the scale-dependent coupling between economic growth and CO<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span> emissions in the G7 and the BRICS, two major economic blocs and key emitters, by integrating multifractal detrended cross-correlation analysis (MF-DCCA) and wavelet coherence. We analyze annual per capita GDP and CO<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span> series from 1950 to 2022 to determine whether these countries exhibit distinct multiscale dependencies. MF-DCCA results show that most G7 economies exhibit nonlinear, intrinsic multifractality, while the BRICS countries display greater heterogeneity. India, China, and Brazil show clear signs of intrinsic multifractality, whereas Russia and South Africa exhibit no such evidence.Wavelet coherence further reveals that in the G7, economic growth typically leads CO<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span> emissions at business-cycle scales. Among the BRICS, Brazil, Russia, and China exhibit robust coherence at short- and mid-term scales, while India and South Africa remain weakly linked. An event–window comparison of the 1973 Oil Crisis and the 2008 Financial Crisis highlights the starkly contrasting responses of G7 and BRICS countries to these shocks. These findings enhance our understanding of multiscale growth–emission nexus and suggest that the G7 should adopt stable, long-term strategies while the BRICS require agile, scale-aware interventions to meet climate and sustainability challenges.</div></div>","PeriodicalId":20152,"journal":{"name":"Physica A: Statistical Mechanics and its Applications","volume":"679 ","pages":"Article 131014"},"PeriodicalIF":3.1,"publicationDate":"2025-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145222133","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Network transitions in the cryptocurrency market: The impact of regional conflicts","authors":"Yuanyuan Zhang ,&nbsp;Stephen Chan ,&nbsp;Nicholas Lord ,&nbsp;Jeffrey Chu ,&nbsp;Hanfang Yang ,&nbsp;Durga Chandrashekhar ,&nbsp;Xin Liao ,&nbsp;Qin Li","doi":"10.1016/j.physa.2025.131013","DOIUrl":"10.1016/j.physa.2025.131013","url":null,"abstract":"<div><div>This paper analyses the evolution of the cryptocurrency market network structure during two recent military conflicts: the first year of the 2022 Russia–Ukraine war and the first six months of the 2023 Israel–Hamas war, compared with pre-war periods. Analysing data covering the two periods of 1st January 2020 to 31st December 2022 (Russia–Ukraine), and 1st September 2022 to 29th February 2024 (Israel–Hamas), our findings reveal that before both wars officially began, the cryptocurrency network exhibited high interconnectedness, possibly due to investors anticipating conflict and shifting investments into cryptocurrencies. After the conflicts started, the network became significantly disconnected, with the Russia–Ukraine war showing a “small world” effect, where larger cryptocurrencies remained interconnected, while smaller cryptocurrencies became disconnected. In contrast, during the Israel–Hamas conflict, larger cryptocurrencies became more disconnected, driving overall network disconnectivity. Further analysis using the TVP-SV-VAR model showed that macroeconomic variables such as geopolitical risk, the U.S. Dollar Index, oil volatility and gold returns, as well as the Google Trend Index had a significant impact on the network’s structure, with varying effects across conflicts. Geopolitical risk exerted a stronger positive influence on centrality measures during the Israel–Hamas conflict, the Dollar index had a sharp negative effect on centrality following the Russia–Ukraine war, and oil volatility consistently enhanced network centrality and density in both conflicts. Gold returns shifted from having a negative to a positive effect on network connectivity, especially boosting intermediary roles during the Israel Hamas conflict, and the Google Trend Index consistently increased network centrality, highlighting the impact of rising market attention and sentiment. These results are crucial for understanding how military conflicts and economic factors impact cryptocurrency networks, providing valuable insights for academics, investors, policymakers, and legal authorities on market efficiency, risk management, and the potential use of blockchain-based assets in evading sanctions and facilitating cybercrime. As both conflicts are ongoing, future research should focus on analysing extended war periods and the influence of regulatory actions, sanctions, and cryptocurrency-specific events.</div></div>","PeriodicalId":20152,"journal":{"name":"Physica A: Statistical Mechanics and its Applications","volume":"680 ","pages":"Article 131013"},"PeriodicalIF":3.1,"publicationDate":"2025-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145271044","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Social contagion models on adaptive simplicial complexes","authors":"Ziting Luo ,&nbsp;Shuai Li ,&nbsp;Zheng Jiang ,&nbsp;Wei Chen","doi":"10.1016/j.physa.2025.131010","DOIUrl":"10.1016/j.physa.2025.131010","url":null,"abstract":"<div><div>Complex networks, composed of nodes and edges connecting them, are successful in modeling various social contagion phenomena, such as epidemic spreading or rumor diffusion in population. Recently, there is extensive interest in studying higher-order interactions which uncover the complex mechanisms of influence and reinforcement in social contagion. Yet, existing models are primarily within the framework of static networks. Here we investigate the susceptible–infected–susceptible model on adaptive simplicial complexes, in which the networks exhibiting high-order structure can change their connectivity with time depending on their dynamical state. By applying mean-field equations, we derive an implicit analytical expression of the invasion threshold in adaptive simplicial complexes, but explicit expressions of the invasion threshold in three prototypical adaptive networks. We further analyze the effects of the transmission rate, the rewiring rate and higher-order interactions on epidemic prevalence and the invasion threshold. Our model can lead to collective phenomena including first-order phase transition, bistability, and hysteresis loops. Our study paves the way to predict and control a wide variety of social contagion processes on networks.</div></div>","PeriodicalId":20152,"journal":{"name":"Physica A: Statistical Mechanics and its Applications","volume":"679 ","pages":"Article 131010"},"PeriodicalIF":3.1,"publicationDate":"2025-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145222282","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A novel memristive Hopfield neural network with grid attractor and its application in image encryption","authors":"Anna Guo,&nbsp;Chunlei Fan","doi":"10.1016/j.physa.2025.131005","DOIUrl":"10.1016/j.physa.2025.131005","url":null,"abstract":"<div><div>As a nonlinear resistor with memory characteristics, the memristor can simulate synaptic behavior in neural networks. Building upon the Hopfield neural network (HNN), this paper proposes a novel memristive HNN model by utilizing memristors to realize neuron self-synaptic connections. By adjusting the parameters of the memristor, chaotic attractors can be generated with different numbers and complex structures. The analysis of equilibrium points and stability elucidates the mechanism behind the emergence of multi-structure chaotic attractors. The dynamical characteristics are investigated through the Lyapunov exponent spectrum, bifurcation diagrams, time series, and basin of attraction. Based on the complex dynamics of the memristive HNN, we design a color image encryption scheme combining oblique diffusion and cross-channel Hilbert scanning. Oblique diffusion effectively achieves global propagation of pixel-level perturbations, while cross-channel Hilbert scanning breaks the pixel correlation within individual channels while enhancing inter-channel dependencies. Experimental results demonstrate that the algorithm exhibits extremely high key sensitivity and strong robustness, effectively resisting common attacks such as statistical analysis and differential attacks.</div></div>","PeriodicalId":20152,"journal":{"name":"Physica A: Statistical Mechanics and its Applications","volume":"679 ","pages":"Article 131005"},"PeriodicalIF":3.1,"publicationDate":"2025-09-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145222718","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Dynamic strategy update mechanisms facilitate cooperation","authors":"Bingyang Bai ,&nbsp;Yumiao Zhao ,&nbsp;Qiuhui Pan ,&nbsp;Mingfeng He","doi":"10.1016/j.physa.2025.131016","DOIUrl":"10.1016/j.physa.2025.131016","url":null,"abstract":"<div><div>In offshore aquaculture, fishermen determine their farming methods based on either their own and their neighbors' previous payoff information or their personal historical payoff data. The available farming methods include environmentally friendly practices and environmentally damaging practices. Typically, they decide which information to use for updating their farming strategies based on whether their current payoff meets a satisfactory value. This study employs a social dilemma game model to investigate this issue, where the two farming methods correspond to cooperative and defecting strategies, respectively. The utilization of payoff information reflects different strategy update mechanisms, and it is assumed that individuals decide whether to retain or switch their update mechanisms based on whether their payoff meets the satisfaction value. The results indicate that dynamic changes in strategy update mechanisms can effectively promote cooperation, favoring the adoption of environmentally friendly farming practices. Moreover, when the satisfaction value is either relatively low or high, more individuals tend to adopt such sustainable farming methods.</div></div>","PeriodicalId":20152,"journal":{"name":"Physica A: Statistical Mechanics and its Applications","volume":"679 ","pages":"Article 131016"},"PeriodicalIF":3.1,"publicationDate":"2025-09-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145222140","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Dual-Encoder Physics-Informed Variational Autoencoders for robust forward and inverse SDE solving under noisy measurements","authors":"Lin Wang,&nbsp;Min Yang","doi":"10.1016/j.physa.2025.131008","DOIUrl":"10.1016/j.physa.2025.131008","url":null,"abstract":"<div><div>Real-world measurements for stochastic differential equations (SDEs) are often corrupted by heterogeneous or high-intensity noise, which poses significant challenges for deep learning-based solvers. In this study, we propose a Dual-Encoder Physics-Informed Variational AutoEncoder (DE-PIVAE) framework that explicitly disentangles latent noise from physical variables. Unlike previous single-encoder PI-VAE approaches, our model employs one encoder to learn the underlying clean physical signal and an additional noise encoder to capture the statistical properties of measurement noise from limited sensor data. The framework incorporates physical constraints into end-to-end training and enables more accurate reconstruction of the true system states under noisy observations. We consider a broad spectrum of noisy scenarios, including different noise types, varying noise intensities, partial sensor corruption, and noise distribution misspecification. Experimental results show that DE-PIVAE achieves superior performance compared to baseline solvers, with its advantage becoming more pronounced under higher noise.</div></div>","PeriodicalId":20152,"journal":{"name":"Physica A: Statistical Mechanics and its Applications","volume":"679 ","pages":"Article 131008"},"PeriodicalIF":3.1,"publicationDate":"2025-09-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145222138","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Two types of Brownian yet non-Gaussian diffusion in the quenched disordered environment","authors":"X. Luo ,&nbsp;X.J. Dai ,&nbsp;Y.P. Li ,&nbsp;W.Y. Fan ,&nbsp;M. Hu ,&nbsp;C.Y. Wang","doi":"10.1016/j.physa.2025.131007","DOIUrl":"10.1016/j.physa.2025.131007","url":null,"abstract":"<div><div>Anomalous diffusion has been widely observed in quenched disordered environments such as living cells, and has attracted wide attention. Within the framework of the space–time correlated continuous-time random walk (CTRW), this manuscript studies two types of Brownian yet non-Gaussian diffusion. One is that when the waiting time density satisfies the weak asymptotic form <span><math><mrow><mi>ω</mi><mrow><mo>(</mo><mi>τ</mi><mo>)</mo></mrow><mo>∼</mo><msup><mrow><mi>τ</mi></mrow><mrow><mo>−</mo><mrow><mo>(</mo><mn>1</mn><mo>+</mo><mi>σ</mi><mo>)</mo></mrow></mrow></msup></mrow></math></span> with <span><math><mrow><mn>1</mn><mo>&lt;</mo><mi>σ</mi><mo>&lt;</mo><mn>2</mn></mrow></math></span>, its mean-squared displacement (MSD) exhibits a crossover phenomenon during the evolution process and eventually increases linearly with time at large timescales, while its probability density function (PDF) shows a sharp shape. The other is that when the time density follows an exponential distribution <span><math><mrow><mi>ω</mi><mrow><mo>(</mo><mi>τ</mi><mo>)</mo></mrow><mo>∼</mo><mo>exp</mo><mrow><mo>(</mo><mo>−</mo><mi>τ</mi><mo>)</mo></mrow></mrow></math></span>, its MSD always increases linearly with time, yet its PDF exhibits a generalized exponential shape and crosses over to a standard Gaussian distribution at large timescales. The diffusive behaviors are analyzed and discussed by calculating the MSD and PDF. The results reveal that the anomalous diffusion of the former is due to the weak asymptotic property of <span><math><mrow><mi>ω</mi><mrow><mo>(</mo><mi>τ</mi><mo>)</mo></mrow></mrow></math></span> while the latter is due to the nonergodicity of particles in the quenched disordered environment at the initial moment. The model explains the random motions in complex inhomogeneous environments and reproduces different observational results in biological and physical systems.</div></div>","PeriodicalId":20152,"journal":{"name":"Physica A: Statistical Mechanics and its Applications","volume":"679 ","pages":"Article 131007"},"PeriodicalIF":3.1,"publicationDate":"2025-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145222137","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Diving deep into area occupancy based continuum models for multi-class traffic: Stability of speed and density gradient formulations","authors":"Ranju Mohan ,&nbsp;Shashvat Tripathi","doi":"10.1016/j.physa.2025.130969","DOIUrl":"10.1016/j.physa.2025.130969","url":null,"abstract":"<div><div>The paper analyses and compare the stability conditions of speed and density gradient formulations of multi-class traffic flow when using area occupancy (<span><math><mrow><mi>A</mi><mi>O</mi></mrow></math></span>) as the traffic concentration measure. In a second-order continuum model of traffic flow, driver’s anticipation to traffic ahead is expressed in terms of speed and density gradient, and stability conditions are analysed based on the eigenvalues from the system of equations in both the formulations. Eigenvalues, which are characteristics speeds of traffic flow, are checked against the Banach contraction principle and the Hyers–Ulam Stability concept to check model’s oscillatory nature and to understand how well a perturbed system solution remains close to that of an unperturbed system. Anticipation terms in both formulations are overviewed to interpret stability in possible practical scenarios in traffic. Linear stability conditions are checked case by case defined based on interactions among vehicle classes. Non-linear stability conditions for the formulations are derived through wavefront expansion techniques. Further, results from numerical simulations on a hypothetical road section in various congestion scenarios show that the vehicle speeds are non-negative always in both the formulations, and characteristics speeds are real, indicating hyperbolicity of the model’s equation systems. Anisotropic behaviour of traffic is well captured in speed gradient formulation; however, characteristics speeds higher than the vehicle speeds are frequently observed in density gradient formulation. This study addresses a fundamental question: whether the classic isotropic (density gradient) or anisotropic (speed gradient) modelling approach is more physically realistic for complex, non-lane-based traffic where traditional density measure under performs. The paper is an in-depth analysis of both formulations, not only from a stability perspective, but also shares insights on the choice of <span><math><mrow><mi>A</mi><mi>O</mi></mrow></math></span> as traffic concentration measure while multi-class traffic modelling.</div></div>","PeriodicalId":20152,"journal":{"name":"Physica A: Statistical Mechanics and its Applications","volume":"679 ","pages":"Article 130969"},"PeriodicalIF":3.1,"publicationDate":"2025-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145222720","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Relaxation of a thermally bathed harmonic oscillator: A study based on the quantum group-theoretical formalism","authors":"Yan Gu ,&nbsp;Jiao Wang","doi":"10.1016/j.physa.2025.131004","DOIUrl":"10.1016/j.physa.2025.131004","url":null,"abstract":"<div><div>The quantum dynamics of a damped harmonic oscillator has been extensively studied since the 1960s of the last century. Here, with a distinct tool termed the “group-theoretical characteristic function (GCF)”, we investigate analytically how a harmonic oscillator immersed in a thermal environment would relax to its equilibrium state. We assume that the oscillator is at a pure state initially and its evolution is governed by a well-known quantum-optical master equation. Taking advantage of the GCF, the master equation can be transformed into a first-order linear partial differential equation, allowing us to write down its solution explicitly. Based on the solution, it is found that, in clear contrast with the monotonic relaxation process of its classical counterpart, the quantum oscillator may demonstrate some intriguing non-monotonic relaxation characteristics. In particular, when the initial state is a Gaussian state (i.e., a squeezed coherent state), there is a critical value of the environmental temperature below which the entropy will first increase to reach its maximum value, then turn down and converge to its equilibrium value from above. Conversely, when the temperature exceeds the critical value, the entropy converges monotonically to its equilibrium value from below. In contrast, for an initial Fock state, there are two critical temperatures instead and, in between, a new additional phase emerges, where the time curve of entropy features two extreme points. Namely, the entropy will increase to reach its maximum first, then turn down to reach its minimum, from where it begins to increase and converges to the equilibrium value eventually. Other related issues are discussed as well.</div></div>","PeriodicalId":20152,"journal":{"name":"Physica A: Statistical Mechanics and its Applications","volume":"679 ","pages":"Article 131004"},"PeriodicalIF":3.1,"publicationDate":"2025-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145222719","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}