M. San Miguel

Institute for Cross-Disciplinary Physics and Complex Systems, Palma, Balearic Islands, Spain

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Publications (285)455.5 Total impact

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    ABSTRACT: Social structures emerge as a result of individuals managing a variety of different of social relationships. Societies can be represented as highly structured dynamic multiplex networks. Here we study the dynamical origins of the specific community structures of a large-scale social multiplex network of a human society that interacts in a virtual world of a massive multiplayer online game. There we find substantial differences in the community structures of different social actions, represented by the various network layers in the multiplex. Community size distributions are either similar to a power-law or appear to be centered around a size of 50 individuals. To understand these observations we propose a voter model that is built around the principle of triadic closure. It explicitly models the co-evolution of node- and link-dynamics across different layers of the multiplex. Depending on link- and node fluctuation rates, the model exhibits an anomalous shattered fragmentation transition, where one layer fragments from one large component into many small components. The observed community size distributions are in good agreement with the predicted fragmentation in the model. We show that the empirical pairwise similarities of network layers, in terms of link overlap and degree correlations, practically coincide with the model. This suggests that several detailed features of the fragmentation in societies can be traced back to the triadic closure processes.
    Full-text · Article · Jan 2016
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    Full-text · Article · Dec 2015 · Royal Society Open Science
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    Marina Diakonova · Victor M Eguiluz · Maxi San Miguel
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    ABSTRACT: Coupling dynamics of the states of the nodes of a network to the dynamics of the network topology leads to generic absorbing and fragmentation transitions. The coevolving voter model is a typical system that exhibits such transitions at some critical rewiring. We study the robustness of these transitions under two distinct ways of introducing noise. Noise affecting all the nodes destroys the absorbing-fragmentation transition, giving rise in finite-size systems to two regimes: bimodal magnetization and dynamic fragmentation. Noise targeting a fraction of nodes preserves the transitions but introduces shattered fragmentation with its characteristic fraction of isolated nodes and one or two giant components. Both the lack of absorbing state for homogeneous noise and the shift in the absorbing transition to higher rewiring for targeted noise are supported by analytical approximations.
    Full-text · Article · Sep 2015 · Physical Review E
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    Marina Diakonova · Vincenzo Nicosia · Vito Latora · Maxi San Miguel
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    ABSTRACT: We address the issue of the reducibility of the dynamics on a multilayer network to an equivalent process on an aggregated single-layer network. As a typical example of models for opinion formation in social networks, we implement the voter model on a two-layer multiplex network, and we study its dynamics as a function of two control parameters, namely the fraction of edges simultaneously existing in both layers of the network (edge overlap), and the fraction of nodes participating in both layers (interlayer connectivity or degree of multiplexity). We compute the asymptotic value of the number of active links (interface density) in the thermodynamic limit, and the time to reach an absorbing state for finite systems, and we compare the numerical results with the analytical predictions on equivalent single-layer networks obtained through various possible aggregation procedures. We find a large region of parameters where the interface density of large multiplexes gives systematic deviations from that of the aggregates. We show that neither of the standard aggregation procedures is able to capture the highly nonlinear increase in the lifetime of a finite size multiplex at small interlayer connectivity. These results indicate that multiplexity should be appropriately taken into account when studying voter model dynamics, and that, in general, single-layer approximations might be not accurate enough to properly understand processes occurring on multiplex networks, since they might flatten out relevant dynamical details.
    Full-text · Article · Jul 2015 · New Journal of Physics
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    Full-text · Article · Jul 2015 · Scientific Reports
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    Adrián Carro · Raúl Toral · Maxi San Miguel
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    ABSTRACT: We focus on the influence of external sources of information upon financial markets. In particular, we develop a stochastic agent-based market model characterized by a certain herding behavior as well as allowing traders to be influenced by an external dynamic signal of information. This signal can be interpreted as a time-varying advertising, public perception or rumor, in favor or against one of two possible trading behaviors, thus breaking the symmetry of the system and acting as a continuously varying exogenous shock. As an illustration, we use a well-known German Indicator of Economic Sentiment as information input and compare our results with Germany's leading stock market index, the DAX, in order to calibrate some of the model parameters. We study the conditions for the ensemble of agents to more accurately follow the information input signal. The response of the system to the external information is maximal for an intermediate range of values of a market parameter, suggesting the existence of three different market regimes: amplification, precise assimilation and undervaluation of incoming information.
    Full-text · Article · Jun 2015 · PLoS ONE
  • M.S. Miguel · M. Diakonova · V. Eguiluz
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    ABSTRACT: We introduce a co evolution voter model in a multilayer, by coupling a fraction of nodes across two network layers and where each layer evolves according to its own temporal scale. For the symmetric case the dynamics preserve the absorbing-fragmentation transition observed in a monolayer network at a critical timescale that depends on interlayer connectivity. The time evolution equations obtained by pair approximation can be mapped to a co evolution voter model in a single layer with an effective average degree. In asymmetric settings, the fragmentation shows an anomalous transition with two large components in opposite states and the breakdown in many isolated nodes. We identify the growth of the number of components as a precursor of the shattered transitions.
    No preview · Article · Apr 2015
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    ABSTRACT: The advent of geolocated ICT technologies opens the possibility of exploring how people use space in cities, bringing an important new tool for urban scientists and planners, especially for regions where data is scarce or not available. Here we apply a functional network approach to determine land use patterns from mobile phone records. The versatility of the method allows us to run a systematic comparison between Spanish cities of various sizes. The method detects four major land use types that correspond to different temporal patterns. The proportion of these types, their spatial organization and scaling show a strong similarity between all cities that breaks down at a very local scale, where land use mixing is specific to each urban area. Finally, we introduce a model inspired by Schelling's segregation, able to explain and reproduce these results with simple interaction rules between different land uses.
    Full-text · Article · Mar 2015
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    Haydee Lugo · Maxi San Miguel
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    ABSTRACT: We introduce a two layer network model for social coordination incorporating two relevant ingredients: a) different networks of interaction to learn and to obtain a payoff , and b) decision making processes based both on social and strategic motivations. Two populations of agents are distributed in two layers with intralayer learning processes and playing interlayer a coordination game. We find that the skepticism about the wisdom of crowd and the local connectivity are the driving forces to accomplish full coordination of the two populations, while polarized coordinated layers are only possible for all-to-all interactions. Local interactions also allow for full coordination in the socially efficient Pareto-dominant strategy in spite of being the riskier one.
    Preview · Article · Jan 2015 · Scientific Reports
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    ABSTRACT: Human mobility has been traditionally studied using surveys that deliver snapshots of population displacement patterns. The growing accessibility to ICT information obtained from portable digital media has recently opened the possibility of going beyond such fixed pictures, exploring human behavior at high spatio-temporal resolutions. Mobile phone records, geolocated tweets, check-ins from Foursquare or geotagged photos, have contributed to this purpose at different scales from cities to countries and in different areas of the world. Many of these previous works have lacked, however, details on the attributes of the individuals. In this work, we analyze credit-card transaction records as mobility proxies and assess the influence of sociodemographic characteristics on the way people move and spend their money in cities. In particular, we focus on Barcelona and Madrid, the two most populated cities of Spain, and by examining the geolocated credit-card transactions of individuals living in the two provinces, we find that consumption habits and mobility patterns vary according to gender, age and occupation. Differences in distance traveled and travel purpose are observed between younger and older people, but, curiously, either between males and females of similar age. While mobility displays some generic features, here we show that sociodemographic characteristics play a relevant role and must be taken into account for human mobility modelization.
    Full-text · Article · Nov 2014 · Scientific Reports

  • No preview · Article · Aug 2014 · Physical Review Letters
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    Marina Diakonova · Maxi San Miguel · Víctor M. Eguíluz
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    ABSTRACT: We introduce a coevolution voter model in a multilayer by coupling a fraction of nodes across two network layers (the degree of multiplexing) and allowing each layer to evolve according to its own topological temporal scale. When these time scales are the same, the time evolution equations can be mapped to a coevolution voter model in a single layer with an effective average degree. Thus the dynamics preserve the absorbing-fragmentation transition at a critical value that increases with the degree of multiplexing. When the two layers have different topological time scales, we find an anomalous transition, named shattered fragmentation, in which the network in one layer splits into two large components in opposite states and a multiplicity of isolated nodes. We identify the growth of the number of components as a signature of this anomalous transition. We also find the critical level of interlayer coupling needed to prevent the fragmentation in a layer connected to a layer that does not fragment.
    Preview · Article · Jun 2014 · Physical Review E
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    Daniele Vilone · Jose J. Ramasco · Angel Sánchez · Maxi San Miguel
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    ABSTRACT: The interplay of social and strategic motivations in human interactions is a largely unexplored question in collective social phenomena. Whether individuals' decisions are taken in a pure strategic basis or due to social pressure without a rational background crucially influences the model outcome. Here we study a networked Prisoner's Dilemma in which decisions are made either based on the replication of the most successful neighbor's strategy (unconditional imitation) or by pure social imitation following an update rule inspired by the voter model. The main effects of the voter dynamics are an enhancement of the final consensus, i.e., asymptotic states are generally uniform, and a promotion of cooperation in certain regions of the parameter space as compared to the outcome of purely strategic updates. Thus, voter dynamics acts as an interface noise and has a similar effect to a pure random noise; furthermore, its influence is mostly independent of the network heterogeneity. When strategic decisions are made following other update rules such as the replicator or Moran processes, the dynamic mixed state found under unconditional imitation for some parameters disappears, but an increase of cooperation in certain parameter regions is still observed. Comparing our results with recent experiments on the Prisoner's Dilemma, we conclude that such a mixed dynamics may explain moody conditional cooperation among the agents.
    Full-text · Article · May 2014 · Physical Review E
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    J.C. González-Avella · M.G. Cosenza · M. San Miguel
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    ABSTRACT: We investigate the emergence of localized coherent behavior in systems consisting of two populations of social agents possessing a condition for non-interacting states, mutually coupled through global interaction fields. We employ two examples of such dynamics: (i) Axelrod’s model for social influence, and (ii) a discrete version of a bounded confidence model for opinion formation. In each case, the global interac- tion fields correspond to the statistical mode of the states of the agents in each population. In both systems we find localized coherent states for some values of parameters, consisting of one population in a homogeneous state and the other in a disordered state. This situation can be considered as a social analogue to a chimera state arising in two interacting populations of oscillators. In addition, other asymp- totic collective behaviors appear in both systems depending on parameter values: a common homogeneous state, where both populations reach the same state; different homogeneous states, where both population reach homogeneous states different from each other; and a disordered state, where both populations reach inhomogeneous states.
    Full-text · Article · Apr 2014 · Physica A: Statistical Mechanics and its Applications
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    ABSTRACT: The voter model has been studied extensively as a paradigmatic opinion dynamics model. However, its ability to model real opinion dynamics has not been addressed. We introduce a noisy voter model (accounting for social influence) with recurrent mobility of agents (as a proxy for social context), where the spatial and population diversity are taken as inputs to the model. We show that the dynamics can be described as a noisy diffusive process that contains the proper anisotropic coupling topology given by population and mobility heterogeneity. The model captures statistical features of U.S. presidential elections as the stationary vote-share fluctuations across counties and the long-range spatial correlations that decay logarithmically with the distance. Furthermore, it recovers the behavior of these properties when the geographical space is coarse grained at different scales—from the county level through congressional districts, and up to states. Finally, we analyze the role of the mobility range and the randomness in decision making, which are consistent with the empirical observations.
    Full-text · Article · Apr 2014 · Physical Review Letters
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    Adrián Carro · Federico Vazquez · Raúl Toral · Maxi San Miguel
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    ABSTRACT: We study a network model that couples the dynamics of link states with the evolution of the network topology. The state of each link, either A or B, is updated according to the majority rule or zero-temperature Glauber dynamics, in which links adopt the state of the majority of their neighboring links in the network. Additionally, a link that is in a local minority is rewired to a randomly chosen node. While large systems evolving under the majority rule alone always fall into disordered topological traps composed by frustrated links, any amount of rewiring is able to drive the network to complete order, by relinking frustrated links and so releasing the system from traps. However, depending on the relative rate of the majority rule and the rewiring processes, the system evolves towards different ordered absorbing configurations: either a one-component network with all links in the same state or a network fragmented in two components with opposite states. For low rewiring rates and finite size networks there is a domain of bistability between fragmented and non-fragmented final states. Finite size scaling indicates that fragmentation is the only possible scenario for large systems and any nonzero rate of rewiring.
    Full-text · Article · Mar 2014 · Physical Review E
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    Full-text · Article · Sep 2013
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    Full-text · Dataset · Jul 2013
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    Adrián Carro · Raúl Toral · Maxi San Miguel
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    ABSTRACT: A thoroughly revised and updated version of this work has been published as "Markets, Herding and Response to External Information" in PLOS ONE 10(7), June 2015, with DOI: 10.1371/journal.pone.0133287.
    Preview · Article · Feb 2013
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    ABSTRACT: Information-communication technology promotes collaborative environments like Wikipedia where, however, controversy and conflicts can appear. To describe the rise, persistence, and resolution of such conflicts, we devise an extended opinion dynamics model where agents with different opinions perform a single task to make a consensual product. As a function of the convergence parameter describing the influence of the product on the agents, the model shows spontaneous symmetry breaking of the final consensus opinion represented by the medium. In the case when agents are replaced with new ones at a certain rate, a transition from mainly consensus to a perpetual conflict occurs, which is in qualitative agreement with the scenarios observed in Wikipedia.
    Full-text · Article · Feb 2013 · Physical Review Letters

Publication Stats

6k Citations
455.50 Total Impact Points

Institutions

  • 2007-2015
    • Institute for Cross-Disciplinary Physics and Complex Systems
      Palma, Balearic Islands, Spain
  • 1989-2015
    • University of the Balearic Islands
      • • Institute for Cross-Disciplinary Physics and Complex Systems (IFISC)
      • • Department of Physics
      Palma, Balearic Islands, Spain
  • 2009
    • Aalto University
      • Department of Biomedical Engineering and Computational Science
      Helsinki, Uusimaa, Finland
  • 1997-2007
    • Mediterranean Institute for Advanced Studies (IMEDEA)
      Esporles, Balearic Islands, Spain
  • 1970-2006
    • University of Barcelona
      • • Department of Structure and Constituents of Matter
      • • Facultad de Física
      Barcino, Catalonia, Spain
  • 2003
    • Free University of Brussels
      • Applied Physics and Photonics (TONA)
      Brussels, BRU, Belgium
  • 1999
    • Spanish National Research Council
      Madrid, Madrid, Spain
  • 1984
    • Università degli Studi di Roma "La Sapienza"
      • Department of Physics
      Roma, Latium, Italy
  • 1981
    • Temple University
      • Department of Physics
      Philadelphia, PA, United States