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Reputation and reciprocity : review
Chengyi Xia, Juan Wang, Matjaž Perc, Zhen Wang, 2023, review article

Abstract: Reputation and reciprocity are key mechanisms for cooperation in human societies, often going hand in hand to favor prosocial behavior over selfish actions. Here we review recent researches at the interface of physics and evolutionary game theory that explored these two mechanisms. We focus on image scoring as the bearer of reputation, as well as on various types of reciprocity, including direct, indirect, and network reciprocity. We review different definitions of reputation and reciprocity dynamics, and we show how these affect the evolution of cooperation in social dilemmas. We consider first-order, second-order, as well as higherorder models in well-mixed and structured populations, and we review experimental works that support and inform the results of mathematical modeling and simulations. We also provide a synthesis of the reviewed researches along with an outlook in terms of six directions that seem particularly promising to explore in the future.
Keywords: pattern formation, Monte Carlo method, complex network, evolutionary game theory, cooperation, social physics
Published in DKUM: 20.06.2024; Views: 27; Downloads: 0
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Complex evolutionary interactions in multiple populations
Kaipeng Hu, Pengyue Wang, Junzhou He, Matjaž Perc, Lei Shi, 2023, original scientific article

Abstract: In competitive settings that entail several populations, individuals often engage in intra- and interpopulation interactions that determine their fitness and evolutionary success. With this simple motivation, we here study a multipopulation model where individuals engage in group interactions within their own population and in pairwise interactions with individuals from different populations. We use the evolutionary public goods game and the prisoner’s dilemma game to describe these group and pairwise interactions, respectively. We also take into account asymmetry in the extent to which group and pairwise interactions determine the fitness of individuals. We find that interactions across multiple populations reveal new mechanisms through which the evolution of cooperation can be promoted, but this depends on the level of interaction asymmetry. If inter- and intrapopulation interactions are symmetric, the sole presence of multiple populations promotes the evolution of cooperation. Asymmetry in the interactions can further promote cooperation at the expense of the coexistence of the competing strategies. An in-depth analysis of the spatiotemporal dynamics reveals loop-dominated structures and pattern formation that can explain the various evolutionary outcomes. Thus, complex evolutionary interactions in multiple populations reveal an intricate interplay between cooperation and coexistence, and they also open up the path toward further explorations of multipopulation games and biodiversity.
Keywords: social physics, evolutionary dynamics, coupled populations, phase transition
Published in DKUM: 17.06.2024; Views: 30; Downloads: 0
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Turing patterns in simplicial complexes
Shupeng Gao, Lili Chang, Matjaž Perc, Zhen Wang, 2023, original scientific article

Abstract: The spontaneous emergence of patterns in nature, such as stripes and spots, can be mathematically explained by reaction-diffusion systems. These patterns are often referred as Turing patterns to honor the seminal work of Alan Turing in the early 1950s. With the coming of age of network science, and with its related departure from diffusive nearest-neighbor interactions to long-range links between nodes, additional layers of complexity behind pattern formation have been discovered, including irregular spatiotemporal patterns. Here we investigate the formation of Turing patterns in simplicial complexes, where links no longer connect just pairs of nodes but can connect three or more nodes. Such higher-order interactions are emerging as a new frontier in network science, in particular describing group interaction in various sociological and biological systems, so understanding pattern formation under these conditions is of the utmost importance. We show that a canonical reaction-diffusion system defined over a simplicial complex yields Turing patterns that fundamentally differ from patterns observed in traditional networks. For example, we observe a stable distribution of Turing patterns where the fraction of nodes with reactant concentrations above the equilibrium point is exponentially related to the average degree of 2-simplexes, and we uncover parameter regions where Turing patterns will emerge only under higher-order interactions, but not under pairwise interactions.
Keywords: Turing pattern, higher-order network, nonlinear dynamics, pattern formation
Published in DKUM: 31.05.2024; Views: 93; Downloads: 0
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Social mobility and network reciprocity shape cooperation in collaborative networks
Wen-Jing Li, Zhi Chen, Jun Wang, Luo-Luo Jiang, Matjaž Perc, 2023, original scientific article

Abstract: Relationships in social networks change over time due to various factors, including mobility, preferences for moral behavior, and the consequent making and breaking of social ties. We therefore study how these factors affect cooperation in actual collaborative networks, where individuals adaptively move with a certain probability. We find that individuals preferentially move towards the sites with a high degree, which yields networks with a higher average degree, but at the same time is conducive to cooperation because positions at the hubs are most beneficial in that way. On the one hand, social mobility thus enhances network reciprocity by generating much more cooperation seeds than the original network, but on the other, it also washes out the network structure and creates well-mixed like conditions if too frequent. Thus, only with limited mobility is network reciprocity optimally enhanced and can yield best conditions for robust cooperation in social networks. And we expect optimal conditions for other forms of moral behavior to require the same patterns of moderate social mobility.
Keywords: cooperation, network reciprocity, social mobility
Published in DKUM: 30.05.2024; Views: 71; Downloads: 0
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Digitalisation and decarbonisation challenges of inland waterways freight logistics transport and their integration into regional supply chains : a case study
Gbako Shekwoyemi, Dimitrios Paraskevadakis, Jun Ren, Jin Wang, 2023, original scientific article

Abstract: An era of increased sustainable transport, the European inland navigation industry has received significant attention to attain sustainable transport. Tremendous opportunities to substantially move freight on waterways are present in the UK; however, several challenges have been appropriately addressed, including infrastructural gaps and various institutional support programs. The paper addresses the UK's current situation of inland navigation and the key challenges affecting the sectors as a viable alternative transport solution. The article explores and summarises the geographic opportunities, commercial feasibility, and the current condition of the UK'S inland navigation sector. From the practical scenario of the UK's experience, an attempt was made by the authors to find the critical challenges and issues faced by the industry. The emerging themes from the analysis of this paper indicated governance and leadership issues, cooperation, and coordination mechanism between establishments with various functions and responsibilities, merged with infrastructural investment, are strategic elements for expansion in the UK. Conclusively, the authors presented recommendations for improvement and sustainable development.
Keywords: inland waterway transport, decarbonisation, digitalisation, challenges, sustainable development, intermodal transport, modal shift, waterway infrastructure, investments
Published in DKUM: 06.03.2024; Views: 275; Downloads: 8
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Multifractality in quasienergy space of coherent states as a signature of quantum chaos
Qian Wang, Marko Robnik, 2021, original scientific article

Abstract: We present the multifractal analysis of coherent states in kicked top model by expanding them in the basis of Floquet operator eigenstates. We demonstrate the manifestation of phase space structures in the multifractal properties of coherent states. In the classical limit, the classical dynamical map can be constructed, allowing us to explore the corresponding phase space portraits and to calculate the Lyapunov exponent. By tuning the kicking strength, the system undergoes a transition from regularity to chaos. We show that the variation of multifractal dimensions of coherent states with kicking strength is able to capture the structural changes of the phase space. The onset of chaos is clearly identified by the phase-space-averaged multifractal dimensions, which are well described by random matrix theory in a strongly chaotic regime. We further investigate the probability distribution of expansion coefficients, and show that the deviation between the numerical results and the prediction of random matrix theory behaves as a reliable detector of quantum chaos.
Keywords: quantum chaos, multifractal analysis, kicked top, coherent states
Published in DKUM: 13.10.2023; Views: 386; Downloads: 16
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Quantum chaos in the extended Dicke model
Qian Wang, 2022, original scientific article

Abstract: We systematically study the chaotic signatures in a quantum many-body system consisting of an ensemble of interacting two-level atoms coupled to a single-mode bosonic field, the so-called extended Dicke model. The presence of the atom–atom interaction also leads us to explore how the atomic interaction affects the chaotic characters of the model. By analyzing the energy spectral statistics and the structure of eigenstates, we reveal the quantum signatures of chaos in the model and discuss the effect of the atomic interaction. We also investigate the dependence of the boundary of chaos extracted from both eigenvalue-based and eigenstate-based indicators on the atomic interaction. We show that the impact of the atomic interaction on the spectral statistics is stronger than on the structure of eigenstates. Qualitatively, the integrablity-to-chaos transition found in the Dicke model is amplified when the interatomic interaction in the extended Dicke model is switched on.
Keywords: quantum chaos, extended Dicke model, spectral statistics, eigenstate structure
Published in DKUM: 13.10.2023; Views: 288; Downloads: 17
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A geostress measurement method based on an integrated drilling and optical microscopic imaging system
Jinchao Wang, Chunying Wang, Zengqiang Han, Yiteng Wang, Xinjian Tang, 2018, original scientific article

Abstract: Conventional geostress measurement methods are limited by deficiencies including the measurable depth, the complexity, and the long duration of operation. To address these problems and achieve the measurement of geostress in deep wells under conditions of complex high pressures and high temperatures, we propose a new measurement method for geostress based on an integrated drilling and optical microscopy system. Its innovative integrated structure eliminates the problems associated with complex procedures and depth limits, and avoids rock creep caused by long delays, significantly improving the accuracy and range of the measurements. It works by using microscopic imaging and direct contact probes to capture the changes of a borehole’s cross-sectional outlines before and after stress relief. The resulting images are analyzed with search circles to obtain the positions of probe apices, which can be fitted into ellipses that describe the outlines, and calculate the state of the stress. The validity and accuracy of the method was verified by in-door tests and field applications in the ZK1 borehole. The results show that: (1) the integrated system can be used to measure micrometer-grade deformations; (2) the searchcircle approach can accurately obtain the positions of probe apices; and (3) the stress measurement method based on the system is accurate and feasible.
Keywords: geostress, probe, optical microscopy, measurement while drilling, search circle
Published in DKUM: 11.10.2018; Views: 1516; Downloads: 568
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A fundamental study of the performance of X-section cast-in-place concrete single piles
Yu Wang, Yaru Lv, Dongdong Zhang, Jieying Zhou, 2016, original scientific article

Abstract: X-section cast-in-place concrete (XCC) piles are used because they have a higher bearing capacity than circularsection cast-in-place concrete (CCC) piles of the same cross-sectional area. Although the bearing capacity of XCC piles has been studied, the performance of XCC single piles, especially for the stress-transfer mechanism dependent on the geometrical effects, is still not fully understood. This paper reports two comparative field static load tests on an XCC and a CCC single pile of the same cross-sectional area. In addition, corresponding threedimensional numerical back-analyses are performed to provide a fundamental understanding. The measured and computed results reveal that the XCC single pile has an approximately 25% higher ultimate bearing capacity than the CCC single pile. This is because the XCC single pile has an approximately 20% larger total side resistance, which is caused by a 60% larger pile perimeter and a slightly smaller unit side resistance. Lateral soil arching effects are developed, causing a non-uniform effective normal stress and a shear stress across the circumference of the XCC single pile. It is suggested that XCC single piles have a higher efficiency in terms of material saving compared with CCC single piles.
Keywords: X-section cast-in-place concrete pile, field static load test, three-dimensional numerical back-analysis, stresstransfer mechanism, side resistance, soil arching
Published in DKUM: 15.06.2018; Views: 1391; Downloads: 177
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