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The analysis of some species-rich, well-defined food webs shows that they display the so-called small world behavior shared by a number of disparate complex systems. The three systems analysed (Ythan estuary web, Silwood web and the Little Rock lake web) have different levels of taxonomic resolution, but all of them involve high clustering and short path(More)
In a recent study, Ohira and Sawatari presented a simple model of computer network traac dynamics. These authors showed that a phase transition point is present separating the low-traac phase with no congestion from the congestion phase as the packet creation rate increases. We further investigated this model by relaxing the network topology using a random(More)
A new model ecosystem of many interacting species is introduced in which the species are connected through a random matrix with a given connectivity. The model is studied both analytically and by numerical simulations. A probability distribution derived from the model is in good agreement with simulations and ÿeld data. It is also shown that the(More)
Many natural systems, as social insects, perform complex computations collectively. In these groups, large numbers of individuals communicate in a local way and send information to its nearest neighbors. Interestingly, a general observation of these societies reveals that the computational capabilities of individuals are fairly limited, suggesting that the(More)
A new order parameter approximation to Random Boolean Networks (RBN) is introduced, based on the concept of Boolean derivative. A statistical argument involving an annealed approximation is used, allowing to measure the order parameter in terms of the statistical properties of a random matrix. Using the same formalism, a Lyapunov exponent is calculated,(More)
We describe a method to discriminate between ordered and turbulent behavior in a general class of collective systems known as Globally Coupled Maps (GCM). Our method is able to discover an unknown small ordered region inside the turbulent phase of GCM parameter space. The computational nature of the method is the main novelty of our approach; it is another(More)
We suggest that the interaction of a Globally Coupled Map (GCM) with an individual element inside the system is, from a computational point of view, indistinguishable of a (,)-dependent noise in the turbulent region of the phase space. Therefore, we can use the framework of Computational Mechanics to give a measure that clearly separates the ordered from(More)
In recent studies, new measures of complexity for nonlinear systems have been proposed based on probabilistic grounds, as the LMC measure (Phys. Lett. A 209 (1995) 321). All these measures share an intuitive consideration: complexity seems to emerge in nature close to instability points, as for example the phase transition points characteristic of critical(More)