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We study a coevolving nonlinear voter model (CNVM) on a two-layer network. Coevolution stands for coupled dynamics of the state of the nodes and of the topology of the network in each layer. The plasticity parameter p measures the relative time scale of the evolution of the states of the nodes and the evolution of the network by link rewiring. Nonlinearity of the interactions is taken into account through a parameter q that describes the nonlinear effect of local majorities being q = 1 the marginal situation of the ordinary voter model. Finally the connection between the two layers is measured by a degree of multiplexing ℓ. In terms of these three parameters, p, q and ℓ we find a rich phase diagram with different phases and transitions. When the two layers have the same plasticity p, the fragmentation transition observed in a single layer is shifted to larger values of p plasticity, so that multiplexing avoids fragmentation. Different plasticities for the two layers lead to new phases that do not exist in a CNVM in a single layer, namely an asymmetric fragmented phase for q > 1 and an active shattered phase for q 1, we can find two different transitions by increasing the plasticity parameter, a first absorbing transition with no fragmentation and a subsequent fragmentation transition. ; We acknowledge financial support from Agencia Estatal de Investigacion (AEI, Spain) and Fondo Europeo de Desarrollo Regional under Project ESoTECoS Grant No. FIS2015-63628-C2-2-R (AEI/FEDER,UE) and from Agencia Estatal de Investigacion (AEI, Spain) through the Maria de Maeztu Program for Units of Excellence in R&D (MDM-2017-0711). This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (No. 2018R1C1B5044202). ; Peer reviewed

Empirical evidence reveals that contagion processes often occur with competition of simple and complex contagion, meaning that while some agents follow simple contagion, others follow complex contagion. Simple contagion refers to spreading processes induced by a single exposure to a contagious entity while complex contagion demands multiple exposures for transmission. Inspired by this observation, we propose a model of contagion dynamics with a transmission probability that initiates a process of complex contagion. With this probability nodes subject to simple contagion get adopted and trigger a process of complex contagion. We obtain a phase diagram in the parameter space of the transmission probability and the fraction of nodes subject to complex contagion. Our contagion model exhibits a rich variety of phase transitions such as continuous, discontinuous, and hybrid phase transitions, criticality, tricriticality, and double transitions. In particular, we find a double phase transition showing a continuous transition and a following discontinuous transition in the density of adopted nodes with respect to the transmission probability. We show that the double transition occurs with an intermediate phase in which nodes following simple contagion become adopted but nodes with complex contagion remain susceptible. ; MSM and BM acknowledge financial support from the Agencia Estatal de Investigaci on (AEI, Spain) and Fondo Europeo de Desarrollo Regional under project ESOTECOS FIS2015-63628-C2-2-R (MINECO/AEI/FEDER, UE). This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (No. 2018R1C1B5044202). ; Peer reviewed

Conte, R. et al. ; The increasing integration of technology into our lives has created unprecedented volumes of data on society's everyday behaviour. Such data opens up exciting new opportunities to work towards a quantitative understanding of our complex social systems, within the realms of a new discipline known as Computational Social Science. Against a background of financial crises, riots and international epidemics, the urgent need for a greater comprehension of the complexity of our interconnected global society and an ability to apply such insights in policy decisions is clear. This manifesto outlines the objectives of this new scientific direction, considering the challenges involved in it, and the extensive impact on science, technology and society that the success of this endeavour is likely to bring about. © The Author(s) 2012. ; The publication of this work was partially supported by the European Union's Seventh Framework Programme (FP7/2007–2013) under grant agreement No. 284709, a Coordination and Support Action in the Information and Communication Technologies activity area ('FuturICT' FET Flagship Pilot Project). ; Peer Reviewed

We study correlations among different components of the spectrum of the light intensity field close to a pattern forming instability associated with the polarization of the light field. In particular we find strong correlations between opposite wave vectors of critical wave number and anticorrelations of the zero wave number and the critical one. These anticorrelations are a manifestation of nonlinear critical fluctuations of the polarization of light. ; Financial support from the European Union TMR network QSTRUCT -Project No. FMRX-CT96-0077! and from DGICYT Project No. PB94-1167 Spain is acknowleged. ; Peer Reviewed

AbstractThis article uses computer simulations as a means of assessing two different models for the competition between two languages from the interdisciplinary perspective of complex systems. These models allow for the analysis of the role of bilingual speakers and they consider two of the basic factors determining the use of each language: their relative prestige and the language loyalty of their speakers. Here we assess the effect of these parameters in different social networks, with the aim of contributing to the understanding of the role of bilingualism and social networks in processes of language contact. We first present a qualitative analysis based on a simulation tool that we have designed, in order to visualize the dynamics of the models. Secondly, we consider a qualitative analysis of the role of complex networks, identifying mechanisms for the rapid extinction of a language and for situations of language segregation. Finally, we present a quantitative analysis which shows, counter-intuitively, a transition from a final scenario of language maintenance to one of language shift as language loyalty increases. Other findings are: (i) that the scenario of language coexistence is reduced in the presence of bilingual agents; and (ii) that networks which allow for local effects reduce further the situations for which language maintenance is possible.

This article uses computer simulations as a means of assessing two different models for the competition between two languages from the interdisciplinary perspective of complex systems. These models allow for the analysis of the role of bilingual speakers and they consider two of the basic factors determining the use of each language: their relative prestige and the language loyalty of their speakers. Here we assess the effect of these parameters in different social networks, with the aim of contributing to the understanding of the role of bilingualism and social networks in processes of language contact. We first present a qualitative analysis based on a simulation tool that we have designed, in order to visualize the dynamics of the models. Secondly, we consider a qualitative analysis of the role of complex networks, identifying mechanisms for the rapid extinction of a language and for situations of language segregation. Finally, we present a quantitative analysis which shows, counter-intuitively, a transition from a final scenario of language maintenance to one of language shift as language loyalty increases. Other findings are: (i) that the scenario of language coexistence is reduced in the presence of bilingual agents; and (ii) that networks which allow for local effects reduce further the situations for which language maintenance is possible. ; In addition, for generous financial support, Xavier Castelló and Maxi San Miguel thank the Spanish Ministry for Science and Innovation and the European Regional Development Fund (grant FIS2007-60327, FISICOS), and Lucía Loureiro-Porto thanks the Autonomous Government of Galicia (INCITE grant 08PXIB204016PR) and the Spanish Ministry for Science and Innovation and the European Regional Development Fund (grants HUM2007–60706 and FFI2011-26693-C02-02). ; Peer reviewed

ArXiv Number: 1102.3118.- PACS numbers: 89.75.-k, 05.10.-a, 87.23.G ; We introduce a general methodology of update rules accounting for arbitrary interevent time distributions in simulations of interacting agents. In particular we consider 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 scale free networks with an update probability inversely proportional to the persistence, that is, the time since the last event. We find that in the thermodynamic limit, at variance with standard updates, the system orders slowly. The approach to the absorbing state is characterized by a power law decay of the density of interfaces, observing that the mean time to reach the absorbing state might be not well defined. ; We acknowledge nancial support from MICINN(Spain) through project FISICOS (FIS2007- 60327). J.F.-G. aknowledges a predoctoral fellowship form the Government of the Balearic Islands. ; Peer reviewed

C. R. Mirasso et al.- ArXiv Number physics/9906027 ; We report detailed measurements of the pump-current dependency of the self-pulsating frequency of semiconductor CD lasers. A distinct kink in this dependence is found and explained using rate-equation model. The kink denotes a transition between a region where the self-pulsations are weakly sustained relaxation oscillations and a region where Q-switching takes place. Simulations show that spontaneous emission noise plays a crucial role for the cross-over. ; This work was supported by the European Union through the Project HCM CHRXCT94-0594. ; Peer reviewed

We describe the dynamical behavior found in numerical solutions of the Vector Complex Ginzburg-Landau equation in parameter values where plane waves are stable. Topological defects in the system are responsible for a rich behavior. At low coupling between the vector components, a frozen phase is found, whereas a gas-like phase appears at higher coupling. The transition is a consequence of a defect unbinding phenomena. Entropy functions display a characteristic behavior around the transition. ; Financial support from DGES (Spain) Project PB94-1167 and from the European Union TMR network QSTRUCT (Project FMRX-CT96-0077)is acknowledged. ; Peer Reviewed

The degenerate parametric oscillator above threshold is studied with phenomenological stochastic colored (nonwhite) pump noise for arbitrary pump to subharmonic relaxation rate. The current experimental limits of large intracavity threshold photon numbers (very small quantum noise) are considered, allowing for a semi-classical treatment of the system dynamics. A comparison between the effects of isotropic and squeezed pump noise on the internal transient and steady-state fluctuations is presented by simulation of the nonlinear semi-classical stochastic Langevin equations in the Wigner quadrature representation. It is found that the transient squeezing for the system starting in the unstable steady state (the vacuum) is not degraded by stochastic pump noise. A damped oscillatory behavior of the noise levels (periodic exchange of fluctuations between the squeezed quadrature of the signal and the pump) is observed for large damping of the signal in the turn on of pump depletion. Finally, it is shown that the limited squeezing above threshold in the steady state (50%) due to pump depletion can be enhanced if squeezed stochastic noise with sufficient significant spectral components (broadband squeezing) is fed to the pump. The above-threshold steady-state squeezing has been calculated analytically from the linearized stochastic equations and the effects of the time scale associated to the relaxation of the pump noise (the noise correlation time) compared to the dissipative time scale of the system and the pump to subharmonic loss ratio are presented. ; This work has been supported by the European Union under Contract No. ERB4050PL931060. ; Peer Reviewed

Synchronization of spatiotemporally chaotic extended systems is considered in the context of coupled one-dimensional complex Ginzburg-Landau equations (CGLE). A regime of coupled spatiotemporal intermittency (STI) is identified and described in terms of the space-time synchronized chaotic motion of localized structures. A quantitative measure of synchronization as a function of coupling parameter is given through distribution functions and information measures. The coupled STI regime is shown to disappear into regular dynamics for situations of strong coupling when localized structures become unstable, hence a description in terms of a single CGLE is not appropriate. ; Financial support from DGICYT Project PB94-1167 (Spain) and European Union QSTRUCT (FMRX-CT96- 0077) are acknowledged. R.M. acknowledges support from PEDECIBA and CONICYT (Uruguay). ; Peer Reviewed

The original publication is available at Springer website: http://www.springer.com/computer/mathematics/book/978-4-431-73150-4. ; 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 analyse also a small world social structure, in order to capture the effect of long range social interactions. In both cases, a final scenario of dominance of one language and extinction of the other is obtained, but with smaller times for extinction in the latter case. In addition, we compare our results to our previous work on the agent based version of Abrams-Strogatz model. ; We acknowledge financial support from the MEC (Spain) through project CONOCE2 (FIS2004-00953). X. C. also acknowledges financial support from a Ph.D. fellowship of the Govern de les Illes Balears (Spain). L. L-P. also acknowledges financial support from the Autonomous Government of Galicia (PGIDIT05PXIC20401PN), and the MEC (Spain) and the ERDF (HUM2004-00940). ; http://dx.doi.org/10.1007/978-4-431-73167-2

Switching between linearly polarized states of slightly different optical frequencies with the same transversemode pattern is found, as the injection current is increased. Switchings found here for semiconductor rate-equation models incorporating a vector electric field, birefringence, and the α factor are similar to previously reported experimental results. © 1996 Optical Society of America. ; This study was partially supported by CICYT (Spain) projects TIC95/0563 and PB94/1167 and European Union HCM grant CHRX-CT-93-0114. ; Peer Reviewed

Studies of cultural differentiation have shown that social mechanisms that normally lead to cultural convergence—homophily and influence—can also explain how distinct cultural groups can form. However, this emergent cultural diversity has proven to be unstable in the face of cultural drift—small errors or innovations that allow cultures to change from within. The authors develop a model of cultural differentiation that combines the traditional mechanisms of homophily and influence with a third mechanism of network homophily, in which network structure co-evolves with cultural interaction. Results show that in certain regions of the parameter space, these co-evolutionary dynamics can lead to patterns of cultural diversity that are stable in the presence of cultural drift. The authors address the implications of these findings for understanding the stability of cultural diversity in the face of increasing technological trends toward globalization.