Complex, fractal structures are widespread in ecological systems and in some characteristic features of evolutionary processes. The origin of such patterns in terms of their dynamics is a challenging problem. A theory for these phenomena might have important implications in issues like the...

A number of authors have in recent years proposed that the processes of macroevolution may give rise to self-organized critical phenomena which could have a significant effect on the dynamics of ecosystems. In particular, it has been suggested that mass extinction may arise through a purely...

Certain systems with slow driving and avalanche-like dissipation events are naturally close to a critical point when the ratio of two energy scales is large. The first energy scale is the threshold above which an avalanche is triggered, the second scale is the threshold above which a site is...

We study the Ising model with pair and alternate triplet interactions subjected to an external magnetic field on a family of infinitely ramified fractal lattices with a triangular topology. The three-dimensional phase diagram and correlation length critical exponents are calculated within an...

The dynamics of a tree-like evolution is investigated as a function of the range k of the interactions between competing entities which are located at the extremities of the branches. Speciation (branching) events are supposed to be driven by extremal dynamics. Extinction events are allowed and...

We apply the renormalization group approach to the sandpile on the triangular lattice. The only attractive fixed point is found. The obtained fixed point height probabilities are compared with numerical simulations. The value of critical exponent of avalanche size distribution is found to be τ...

This paper presents an overview of an approach to address complexity issues and real-life engineering problems in large, urban transportation systems. In this context we discuss the fundamental problem of designing a metropolitan transportation system which is both efficient and controlable.

We introduce a new class of models in which a large number of "agents" organize under the influence of an externally imposed coherent noise. The model shows reorganization events whose size distribution closely follows a power-law over many decades, even in the case where the agents do not...