1. Collective dynamics of stock market effciencyLuiz G. A. Alves, Higor Y. D. Sigaki, Matjaž Perc, Haroldo V. Ribeiro, 2020, izvirni znanstveni članek Opis: Summarized by the efcient market hypothesis, the idea that stock prices fully refect all available information is always confronted with the behavior of real-world markets. While there is plenty of evidence indicating and quantifying the efciency of stock markets, most studies assume this efciency to be constant over time so that its dynamical and collective aspects remain poorly understood. Here we defne the time-varying efciency of stock markets by calculating the permutation entropy within sliding time-windows of log-returns of stock market indices. We show that major world stock markets can be hierarchically classifed into several groups that display similar long-term efciency profles. However, we also show that efciency ranks and clusters of markets with similar trends are only stable for a few months at a time. We thus propose a network representation of stock markets that aggregates their short-term efciency patterns into a global and coherent picture. We fnd this fnancial network to be strongly entangled while also having a modular structure that consists of two distinct groups of stock markets. Our results suggest that stock market efciency is a collective phenomenon that can drive its operation at a high level of informational efciency, but also places the entire system under risk of failure.
Ključne besede: collective dynamics, social physics, econophysics, stock market
Objavljeno v DKUM: 14.01.2025; Ogledov: 0; Prenosov: 4
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2. Diverse strategic identities induce dynamical states in evolutionary gamesIrene Sendiña-Nadal, Inmaculada Leyva, Matjaž Perc, David Papo, Marko Jusup, Zhen Wang, Juan A. Almendral, Pouya Manshour, Stefano Boccaletti, 2020, izvirni znanstveni članek Opis: Evolutionary games provide the theoretical backbone for many aspects of our social life: from cooperation to crime, from climate inaction to imperfect vaccination and epidemic spreading, from antibiotics overuse to biodiversity preservation. An important, and so far overlooked, aspect of reality is the diverse strategic identities of individuals. While applying the same strategy to all interaction partners may be an acceptable assumption for simpler forms of life, this fails to account for the behavior of more complex living beings. For instance, we humans act differently around different people. Here we show that allowing individuals to adopt different strategies with different partners yields a very rich evolutionary dynamics, including time-dependent coexistence of cooperation and defection, systemwide shifts in the dominant strategy, and maturation in individual choices. Our results are robust to variations in network type and size, and strategy updating rules. Accounting for diverse strategic identities thus has far-reaching implications in the mathematical modeling of social games.
Ključne besede: cooperation, evolutionary game theory, social physics, collective dynamics, complex system
Objavljeno v DKUM: 20.11.2024; Ogledov: 0; Prenosov: 6
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3. Strategically positioning cooperators can facilitate the contagion of cooperationGuoli Yang, Matteo Cavaliere, Cheng Zhu, Matjaž Perc, 2021, izvirni znanstveni članek Opis: The spreading of cooperation in structured population is a challenging problem which can be observed at diferent scales of social and biological organization. Generally, the problem is studied by evaluating the chances that few initial invading cooperators, randomly appearing in a network, can lead to the spreading of cooperation. In this paper we demonstrate that in many scenarios some cooperators are more infuential than others and their initial positions can facilitate the spreading of cooperation. We investigate six diferent ways to add initial cooperators in a network of cheaters, based on diferent network-based measurements. Our research reveals that strategically positioning the initial cooperators in a population of cheaters allows to decrease the number of initial cooperators necessary to successfully seed cooperation. The strategic positioning of initial cooperators can also help to shorten the time necessary for the restoration of cooperation. The optimal ways in which the initial cooperators should be placed is, however, non-trivial in that it depends on the degree of competition, the underlying game, and the network structure. Overall, our results show that, in structured populations, few cooperators, well positioned in strategically chosen places, can spread cooperation faster and easier than a large number of cooperators that are placed badly.
Ključne besede: cooperation, evolutionary game theory, social physics, collective dynamics, complex system
Objavljeno v DKUM: 22.10.2024; Ogledov: 0; Prenosov: 3
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4. Eco-evolutionary dynamics of multigames with mutationsSourav Roy, Sayantan Nag Chowdhury, Prakash Chandra Mali, Matjaž Perc, Dibakar Ghosh, 2022, izvirni znanstveni članek Opis: Most environments favor defection over cooperation due to natural selection. Nonetheless, the emergence of cooperation is omnipresent in many biological, social, and economic systems, quite contrary to the well-celebrated Darwinian theory of evolution. Much research has been devoted to better understanding how and why cooperation persists among selfinterested individuals despite their competition for limited resources. Here we go beyond a single social dilemma since individuals usually encounter various social challenges. In particular, we propose and study a mathematical model incorporating both the prisoner’s dilemma and the snowdrift game. We further extend this model by considering ecological signatures like mutation and selfless one-sided contribution of altruist free space. The nonlinear evolutionary dynamics that results from these upgrades offer a broader range of equilibrium outcomes, and it also often favors cooperation over defection. With the help of analytical and numerical calculations, our theoretical model sheds light on the mechanisms that maintain biodiversity, and it helps to explain the evolution of social order in human societies.
Ključne besede: public goods, cooperation, mutation, social physics, evolutionary dynamics
Objavljeno v DKUM: 15.07.2024; Ogledov: 137; Prenosov: 9
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5. Complex evolutionary interactions in multiple populationsKaipeng Hu, Pengyue Wang, Junzhou He, Matjaž Perc, Lei Shi, 2023, izvirni znanstveni članek Opis: 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.
Ključne besede: social physics, evolutionary dynamics, coupled populations, phase transition
Objavljeno v DKUM: 17.06.2024; Ogledov: 129; Prenosov: 21
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6. Time delays shape the eco‑evolutionary dynamics of cooperationSourav Roy, Sayantan Nag Chowdhury, Srilena Kundu, Gourab Kumar Sar, Jeet Banerjee, Biswambhar Rakshit, Prakash Chandra Mali, Matjaž Perc, Dibakar Ghosh, 2023, izvirni znanstveni članek Opis: We study the intricate interplay between ecological and evolutionary processes through the lens of the prisoner’s dilemma game. But while previous studies on cooperation amongst selfsh individuals often assume instantaneous interactions, we take into consideration delays to investigate how these might afect the causes underlying prosocial behavior. Through analytical calculations and numerical simulations, we demonstrate that delays can lead to oscillations, and by incorporating also the ecological variable of altruistic free space and the evolutionary strategy of punishment, we explore how these factors impact population and community dynamics. Depending on the parameter values and the initial fraction of each strategy, the studied eco-evolutionary model can mimic a cyclic dominance system and even exhibit chaotic behavior, thereby highlighting the importance of complex dynamics for the efective management and conservation of ecological communities. Our research thus contributes to the broader understanding of group decision-making and the emergence of moral behavior in multidimensional social systems.
Ključne besede: cooperation, time delay, evolutionary dynamics, social dilemma, social physics
Objavljeno v DKUM: 04.04.2024; Ogledov: 191; Prenosov: 19
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8. Probabilistic sharing solves the problem of costly punishmentXiaojie Chen, Attila Szolnoki, Matjaž Perc, 2014, izvirni znanstveni članek Opis: Cooperators that refuse to participate in sanctioning defectors create the secondorder free-rider problem. Such cooperators will not be punished because they contribute to the public good, but they also eschew the costs associated with punishing defectors. Altruistic punishers - those that cooperate and punish - are at a disadvantage, and it is puzzling how such behaviour has evolved. We show that sharing the responsibility to sanction defectors rather than relying on certain individuals to do so permanently can solve the problem of costly punishment. Inspired by the fact that humans have strong but also emotional tendencies for fair play, we consider probabilistic sanctioning as the simplest way of distributing the duty. In well-mixed populations the public goods game is transformed into a coordination game with full cooperation and defection as the two stable equilibria, while in structured populations pattern formation supports additional counterintuitive solutions that are reminiscent of Parrondoʼs paradox.
Ključne besede: social dynamics, networks, punishment, public goods, econophysics
Objavljeno v DKUM: 03.07.2017; Ogledov: 1274; Prenosov: 424
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9. Costly hide and seek pays : unexpected consequences of deceit in a social dilemmaAttila Szolnoki, Matjaž Perc, 2014, izvirni znanstveni članek Opis: Deliberate deceptiveness intended to gain an advantage is commonplace in human and animal societies. In a social dilemma, an individual may only pretend to be a cooperator to elicit cooperation from others, while in reality he is a defector. With this as motivation, we study a simple variant of the evolutionary prisonerʼs dilemma game entailing deceitful defectors and conditional cooperators that lifts the veil on the impact of such two-faced behavior. Defectors are able to hide their true intentions at a personal cost, while conditional cooperators are probabilistically successful at identifying defectors and act accordingly. By focusing on the evolutionary outcomes in structured populations, we observe a number of unexpected and counterintuitive phenomena. We show that deceitful behavior may fare better if it is costly, and that a higher success rate of identifying defectors does not necessarily favor cooperative behavior. These results are rooted in the spontaneous emergence of cycling dominance and spatial patterns that give rise to fascinating phase transitions, which in turn reveal the hidden complexity behind the evolution of deception.
Ključne besede: social dynamics, deceit, evolutionary games, public goods, econophysics, cooperation
Objavljeno v DKUM: 30.06.2017; Ogledov: 1198; Prenosov: 188
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10. A methodology for improving strategic decisions in social systems with a lack of informationCarlos A. Legna Verna, Andrej Škraba, 2010, izvirni znanstveni članek Opis: The design of strategies for social systems requires the use of qualitative information owing to the fact that quantitative information can be insufficient to solve the problems involved. The information that the specialists and the decision makers obtain is often incomplete and unreliable. Nevertheless, leaders have to make strategic decisions despite these deficiencies which should be based on the formal models (Kljajić et al. 2000; Škraba et al, 2003; Škraba et al 2007).
This paper describes a methodology elaborated to design the strategy of the city of Santa Cruz (on the Canary Islands). It has two main sections: the elaboration of a qualitative model and the use of System Dynamics. We combine them in a way that allows mixing qualitative and quantitative information to achieve a better understanding of the structure of the region, to know the tendencies of the present scenario and to estimate of the effects of alternative strategic decisions. We have obtained these results working with scarce quantitative information. This methodology may be applied to any social systems with similar characteristics.
Ključne besede: qualitative models, system dynamics, social strategies
Objavljeno v DKUM: 10.07.2015; Ogledov: 1031; Prenosov: 332
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