Publications (163)219.37 Total impact
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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 noninteracting 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.Physica A: Statistical Mechanics and its Applications 04/2014; 399:24. · 1.68 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: Motivated by the idea that some characteristics are specific to the relations between individuals and not to the individuals themselves, we study a prototype model for the dynamics of the states of the links in a fixed network of interacting units. Each link in the network can be in one of two equivalent states. A majority linkdynamics rule is implemented, so that in each dynamical step the state of a randomly chosen link is updated to the state of the majority of neighboring links. Nodes can be characterized by a link heterogeneity index, giving a measure of the likelihood of a node to have a link in one of the two states. We consider this linkdynamics model in fully connected networks, square lattices, and ErdösRenyi random networks. In each case we find and characterize a number of nontrivial asymptotic configurations, as well as some of the mechanisms leading to them and the time evolution of the link heterogeneity index distribution. For a fully connected network and random networks there is a broad distribution of possible asymptotic configurations. Most asymptotic configurations that result from link dynamics have no counterpart under traditional node dynamics in the same topologies.Physical Review E 12/2012; 86(6):066113. · 2.31 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: During the last decade, much attention has been paid to language competition in the complex systems community, that is, how the fractions of speakers of several competing languages evolve in time. In this paper, we review recent advances in this direction and focus on three aspects. First, we consider the shift from twostate models to threestate models that include the possibility of bilingual individuals. The understanding of the role played by bilingualism is essential in sociolinguistics. In particular, the question addressed is whether bilingualism facilitates the coexistence of languages. Second, we will analyze the effect of social interaction networks and physical barriers. Finally, we will show how to analyze the issue of bilingualism from a game theoretical perspective.Advances in Complex Systems 01/2012; 15:1250048. · 0.65 Impact Factor 
Article: Cooperation in an Adaptive Network
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ABSTRACT: We study the dynamics of a set of agents distributed in the nodes of an adaptive network. Each agent plays with all its neighbors a weak prisoner's dilemma collecting a total payoff. We study the case where the network adapts locally depending on the total payoff of the agents. In the parameter regime considered, a steady state is always reached (strategies and network configuration remain stationary), where cooperation is highly enhanced. However, when the adaptability of the network and the incentive for defection are high enough, we show that a slight perturbation of the steady state induces large oscillations (with cascades) in behavior between the nearly alldefectors state and the allcooperators outcome.Advances in Complex Systems 11/2011; 03(01n04). · 0.65 Impact Factor 
Article: Update rules and interevent time distributions: slow ordering versus no ordering in the voter model.
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ABSTRACT: We introduce a general methodology of update rules accounting for arbitrary interevent time (IET) distributions in simulations of interacting agents. We consider in particular update rules that depend on the state of the agent, so that the update becomes part of the dynamical model. As an illustration we consider the voter model in fully connected, random, and scalefree networks with an activation probability inversely proportional to the time since the last action, where an action can be an update attempt (an exogenous update) or a change of state (an endogenous update). We find that in the thermodynamic limit, at variance with standard updates and the exogenous update, the system orders slowly for the endogenous update. The approach to the absorbing state is characterized by a powerlaw decay of the density of interfaces, observing that the mean time to reach the absorbing state might be not well defined. The IET distributions resulting from both update schemes show powerlaw tails.Physical Review E 07/2011; 84(1 Pt 2):015103. · 2.31 Impact Factor 
Article: Agent Based Models of Language Competition: Macroscopic descriptions and OrderDisorder transitions
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ABSTRACT: We investigate the dynamics of two agent based models of language competition. In the first model, each individual can be in one of two possible states, either using language X or language Y, while the second model incorporates a third state XY, representing individuals that use both languages (bilinguals). We analyze the models on complex networks and twodimensional square lattices by analytical and numerical methods, and show that they exhibit a transition from onelanguage dominance to language coexistence. We find that the coexistence of languages is more difficult to maintain in the bilinguals model, where the presence of bilinguals facilitates the ultimate dominance of one of the two languages. A stability analysis reveals that the coexistence is more unlikely to happen in poorly connected than in fully connected networks, and that the dominance of just one language is enhanced as the connectivity decreases. This dominance effect is even stronger in a twodimensional space, where domain coarsening tends to drive the system towards language consensus.Journal of Statistical Mechanics Theory and Experiment 04/2010; 2010(04):P04007. · 1.87 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: We study the collective behavior of nonequilibrium systems subjected to an external field with a dynamics characterized by the existence of noninteracting states. Aiming at exploring the generality of the results, we consider two types of model according to the nature of their state variables: (i) a vector model, where interactions are proportional to the overlap between the states, and (ii) a scalar model, where interactions depend on the distance between states. The phase space is numerically characterized for each model in a fully connected network and in random and scalefree networks. For both models, the system displays three phases: two ordered phases, one parallel to the field and another orthogonal to the field, and one disordered phase. By placing the particles on a smallworld network, we show that an ordered phase in a state different from the one imposed by the field is possible because of the longrange interactions that exist in fully connected, random and scalefree networks. This phase does not exist in a regular lattice and emerges when longrange interactions are included in a smallworld network.New Journal of Physics 01/2010; 12(1):013010. · 4.06 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: We search for conditions under which a characteristic time scale for ordering dynamics toward either of two absorbing states in a finite complex network of interactions does not exist. With this aim, we study random networks and networks with mesoscale community structure built up from randomly connected cliques. We find that large heterogeneity at the mesoscale level of the network appears to be a sufficient mechanism for the absence of a characteristic time for the dynamics. Such heterogeneity results in dynamical metastable states that survive at any time scale.Physical Review E 02/2009; 79(1 Pt 2):016109. · 2.31 Impact Factor 
Article: Gradual learning and the evolution of cooperation in the spatial Continuous Prisoner’s Dilemma
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ABSTRACT: The usual mechanism for modeling learning in spatially structured evolutionary games has to date been imitation of some successful neighbor. However, it seems natural that individuals hesitate to imitate their neighbor’s acts, specially if they can imply high costs. Here we study the effect of incorporating resistance to imitation on these models. Our framework is the spatial Continuous Prisoner’s Dilemma. For this evolutionary game, it has been reported that occasional errors in the imitation process can explain the emergence of cooperation from a noncooperative initial state. In this work, we show that this only occurs for particular regimes of low costs of cooperation. Furthermore, we display how resistance gets greater the range of scenarios where cooperative individuals can invade selfish populations. In this context, where resistance to imitation can be interpreted as a general rule of gradual learning, our results show that the less that is learnt in a single step from a successful neighbors, the larger the degree of global cooperation finally attained. In general, the effect of stepbystep learning can be more efficient for the evolution of cooperation than a full blast one.Physics of Condensed Matter 01/2009; 71(2):273280. · 1.28 Impact Factor 
Conference Paper: Modelling language competition: bilingualism and complex social networks
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ABSTRACT: In the general context of dynamics of social consensus, we study an agent based model for the competition between two socially equivalent languages, addressing the role of bilingualism and social structure. In a regular network, we study the formation of linguistic domains and their interaction across the boundaries. We also analyse the dynamics on a small world network and on a network with community structure. In all cases, a final scenario of dominance of one language and extinction of the other is obtained (dominanceextinction state). In comparison with the regular network, smaller times for extinction are found in the small world network. In the network with communities instead, the average time for extinction does not give a characteristic time for the dynamics, and metastable states are observed at all time scales.7th International Conference on Language evolution EVOLANG7, Barcelon, Spain; 05/2008  [Show abstract] [Hide abstract]
ABSTRACT: We study a coevolution voter model on a network that evolves according to the state of the nodes. In a single update, a link between oppositestate nodes is rewired with probability $p$, while with probability $1p$ one of the nodes takes its neighbor's state. A meanfield approximation reveals an absorbing transition from an active to a frozen phase at a critical value $p_c=\frac{\mu2}{\mu1}$ that only depends on the average degree $\mu$ of the network. The approach to the final state is characterized by a time scale that diverges at the critical point as $\tau \sim p_cp^{1}$. We find that the active and frozen phases correspond to a connected and a fragmented network respectively. We show that the transition in finitesize systems can be seen as the sudden change in the trajectory of an equivalent random walk at the critical rewiring rate $p_c$, highlighting the fact that the mechanism behind the transition is a competition between the rates at which the network and the state of the nodes evolve.11/2007;  [Show abstract] [Hide abstract]
ABSTRACT: We address the role of community structure of an interaction network in ordering dynamics, as well as associated forms of metastability. We consider the voter and AB model dynamics in a network model which mimics social interactions. The AB model includes an intermediate state between the two excluding options of the voter model. For the voter model we find dynamical metastable disordered states with a characteristic mean lifetime. However, for the AB dynamics we find a power law distribution of the lifetime of metastable states, so that the mean lifetime is not representative of the dynamics. These trapped metastable states, which can order at all time scales, originate in the mesoscopic network structure.EPL (Europhysics Letters) 01/2007; 79:66006. · 2.26 Impact Factor 
Conference Paper: Information feedback and cultural dynamics.
Proceedings of the IV Conference of the European Social Simulation Association, Edited by F. Amblard, IRIT Editions, 467 (2007).; 01/2007  [Show abstract] [Hide abstract]
ABSTRACT: There exists a broad experimental evidence of transient pattern formation in the Fréedericksz transition for nematics. This is a problem of interest in the general context of pattern selection mechanisms. We present a dynamical theoretical analysis of pattern structuration appropriate to the twist geometry. Our scheme is based on stochastic nematodynamics equations which incorporate fluctuations. By monitoring the time evolution of the wavenumber corresponding to the maximum of the structure factor we are able to predict the time of appearance and the stage of formation of the pattern. This dynamics is studied both in a linear and nonlinear regimes. Finally the case of a periodically modulated Fréedericksz transition is also presented.Physica Scripta 11/2006; 38(3):418. · 1.03 Impact Factor 
Conference Paper: Group formation and Mass Media effects in Cultural Dynamics: The power of being subtle
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ABSTRACT: A system of agents interacting in a network with a globalizationpolaritation transition is studied in the context of a cultural dissemination model. We consider different types of fields interpreted as forms of mass media acting on the system. Both for autonomous and external fields, polarization grows in the system when the probability of the agents to interact with the external field is increased. There exists a threshold value of this probability beyond which the system remains always polarized. The domain of parameters of the global regime is larger for nonuniform local mass media than for uniform mass media or external fields. However, the zero field limit is discontinuous. For vanishingly small probability of interaction with the external field, autonomous or external fields are able to order a system that would fall in a polarized phase under local interactions of the agents alone. We also consider the formation of groups when the agents are allowed to choose partners taking into account their degree of similarity. We find that in the globalized phase a large cluster is formed with all agents sharing the same cultural traits. In the polarized phase, several cultural groups coexist due to the formation of cultural barrierComputing in Economics and Finance 2006, Limassol, Cyprus; 06/2006 
Article: Local versus global interactions in nonequilibrium transitions: A model of social dynamics.
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ABSTRACT: A nonequilibrium system of locally interacting elements in a lattice with an absorbing orderdisorder phase transition is studied under the effect of additional interacting fields. These fields are shown to produce interesting effects in the collective behavior of this system. Both for autonomous and external fields, disorder grows in the system when the probability of the elements to interact with the field is increased. There exists a threshold value of this probability beyond which the system is always disordered. The domain of parameters of the ordered regime is larger for nonuniform local fields than for spatially uniform fields. However, the zero field limit is discontinous. In the limit of vanishingly small probability of interaction with the field, autonomous or external fields are able to order a system that would fall in a disordered phase under local interactions of the elements alone. We consider different types of fields which are interpreted as forms of mass media acting on a social system in the context of Axelrod's model for cultural dissemination.Physical Review E 05/2006; 73(4 Pt 2):046119. · 2.31 Impact Factor  01/2006: pages 2943;
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ABSTRACT: Without Abstract01/2006: pages 368371;  [Show abstract] [Hide abstract]
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Article: Use of nonlinear properties of intracavity type II second harmonic generation for image processing
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ABSTRACT: We discuss the use of intracavity typeII second harmonic generation for alloptical processing of images. Injecting an image in a pump beam linearly polarized and a homogeneous field in the orthogonally polarized pump, it is possible to magnify the contrast and to recognize the contour of any part of the image whose intensity is above a tunable reference level. This can be done using ideal planar cavities where all the fields are resonant as well as in the more realistic situation where only the fundamental fields are resonant and using cavities with spherical mirrors.Applied Physics B 11/2005; 81(7):955962. · 1.78 Impact Factor
Publication Stats
2k  Citations  
219.37  Total Impact Points  
Top Journals
Institutions

2007–2014

Institute for CrossDisciplinary Physics and Complex Systems
Palma, Balearic Islands, Spain


1989–2011

University of the Balearic Islands
 • Institute for CrossDisciplinary Physics and Complex Systems (IFISC)
 • Department of Physics
Palma, Balearic Islands, Spain


1997–2006

Mediterranean Institute for Advanced Studies (IMEDEA)
Esporles, Balearic Islands, Spain


1970–2006

University of Barcelona
 • Department of Structure and Constituents of Matter
 • Departament de Química Física
 • Facultad de Física
Barcino, Catalonia, Spain


2003

Free University of Brussels
 Applied Physics and Photonics (TONA)
Brussels, BRU, Belgium


2001

Polytechnic University of Catalonia
 Department of Physics and Nuclear Engineering (FEN)
Barcelona, Catalonia, Spain


1999

Université Libre de Bruxelles
Bruxelles, Brussels Capital Region, Belgium


1996

The University of Arizona
Tucson, Arizona, United States


1993

Universidad de Cantabria
Santander, Cantabria, Spain


1991

Bryn Mawr College
 Department of Physics
Bryn Mawr, Pennsylvania, United States


1980–1981

Temple University
 Department of Physics
Philadelphia, PA, United States
