We show that a network-organized metapopulation of cooperators, defectors and destructors playing the public goods game with mutations, can collectively reach global synchronization or chimera states. Global synchronization is accompanied by a collective periodic burst of cooperation, whereas chimera states reflect the tendency of the networked metapopulation to be fragmented in clusters of synchronous and incoherent bursts of cooperation. Numerical simulations have shown that the system's dynamics alternates between these two steady states through a first order transition. Depending on the parameters determining the dynamical and topological properties, chimera states with different numbers of (in)coherent clusters are observed. Our results present the first example of chimera states in the context of evolutionary game theory. This provides a valuable insight into the details of their occurrence, extending the relevance of such states to natural and social systems.

We are looking for candidates with experience in the description of complex systems in terms of complex networks.   We offer a postdoc position for 1 year (can be extended to 18 months) to work on the project "Study of dynamic transitions in complex networks: a functional multilayer approach, models and validation” in collaboration with Albert Diaz-Guilera, Matteo Palassini and Conrad J. Pérez-Vicente at the Universitat de Barcelona Institute of Complex Systems   Analytical and computational skills are highly appreciated.   Salary is expected to be that of a young postdoc in the Spanish system, equivalent to a Juan de la Cierva grant, 1.800€/month gross. Salary and duration have some flexibility.   Candidates should send by email a detailed CV and the name of two scientists that could provide references to   albert.diaz@ub.edu   Applications will be accepted until October 31st. A final decision is expected at the end of November and the position should be preferibly filled at the beginning of January 2017.  

Gemma Rosell joins the CLabB as a FPU grant holder from the Spanish Ministry of Education

Abstract: Experiments with networks of discrete reactive bistable electrochemical elements organized in regular and nonregular tree networks are presented to confirm an alternative to the Turing mechanism for the formation of self-organized stationary patterns. The results show that the pattern formation can be described by the identification of domains that can be activated individually or in combinations. The method also enabled the localization of chemical reactions to network substructures and the identification of critical sites whose activation results in complete activation of the system. Although the experiments were performed with a specific nickel electrodissolution system, they reproduced all the salient dynamic behavior of a general network model with a single nonlinearity parameter. Thus, the considered pattern-formation mechanism is very robust, and similar behavior can be expected in other natural or engineered networked systems that exhibit, at least locally, a treelike structure.

The paper by Ruben Requejo and Albert Diaz-Guilera on replicator dynamics with diffusion on multiplex networks has appeared in Phys Rev E

Pol Colomer, Kolja Kleineberg, and Oleguer Sagarra defended their respective PhDs in the last month. Our congratulations to the new doctors and the best luck in their professional careers.

Active and reactive behaviour in human mobility: the influence of attraction points on pedestrians

Human mobility is becoming an accessible field of study, thanks to the progress and availability of tracking technologies as a common feature of smart phones. We describe an example of a scalable experiment exploiting these circumstances at a public, outdoor fair in Barcelona (Spain). Participants were tracked while wandering through an open space with activity stands attracting their attention. We develop a general modelling framework based on Langevin dynamics, which allows us to test the influence of two distinct types of ingredients on mobility: reactive or context-dependent factors, modelled by means of a force field generated by attraction points in a given spatial configuration and active or inherent factors, modelled from intrinsic movement patterns of the subjects. The additive and constructive framework model accounts for some observed features. Starting with the simplest model (purely random walkers) as a reference, we progressively introduce different ingredients such as persistence, memory and perceptual landscape, aiming to untangle active and reactive contributions and quantify their respective relevance. The proposed approach may help in anticipating the spatial distribution of citizens in alternative scenarios and in improving the design of 2 public events based on a facts-based approach. 

Our paper "Hidden geometric correlations in real multiplex networks" was published in Nature Physics

Abstract: Real networks often form interacting parts of larger and more complex systems. Examples can be found in different domains, ranging from the Internet to structural and functional brain networks. Here, we show that these multiplex systems are not random combinations of single network layers. Instead, they are organized in specific ways dictated by hidden geometric correlations between the layers. We find that these correlations are significant in different real multiplexes, and form a key framework for answering many important questions. Specifically, we show that these geometric correlations facilitate the definition and detection of multidimensional communities, which are sets of nodes that are simultaneously similar in multiple layers. They also enable accurate trans-layer link prediction, meaning that connections in one layer can be predicted by observing the hidden geometric space of another layer. And they allow efficient targeted navigation in the multilayer system using only local knowledge, outperforming navigation in the single layers only if the geometric correlations are sufficiently strong.

Read the paper: 
rdcu.be/i9iO
or
http://dx.doi.org/doi:10.1038/nphys3812

ClabB is part of the new Universitat de Barcelona Institute of Complex Systems

Ebrahim is collaborating in the project "Xarxes UB"