We investigate, using mean-field theory and simulation, the effect of asymmetry on the critical behavior and probability density of Bak–Sneppen models. Two kinds of anisotropy are investigated: (i) different numbers of sites to the left and right of the central (minimum) site are updated and...

By mapping the optimization problems to physical systems, the paper presents a general-purpose stochastic optimization method with extremal dynamics. It is built up with the traveling salesman problem (TSP) being a typical NP-complete problem. As self-organized critical processes of extremal...

Extremal dynamics is the mechanism that drives the Bak-Sneppen model into a (self-organized) critical state, marked by a singular stationary probability density p(x). With the aim of understanding this phenomenon, we study the BS model and several variants via mean-field theory and simulation....

The spin market model [S. Bornholdt, Int. J. Mod. Phys. C 12 (2001) 667] is generalized by employing co-evolutionary principles, where strategies of the interacting and competitive traders are represented by local and global couplings between the nodes of dynamic directed stochastic network. The...

We present a simplified model for the exploitation of resources by interacting agents, in an economy with small-world properties. It is shown that Gaussian distributions of wealth, with some cutoff at a poverty line are present for all values of the parameters, while the frequency of maxima and...

We present a simplified model for the exploitation of resources by interacting agents, where each agent receives a random fraction of the available resources. An extremal dynamics ensures that the poorest agent has a chance to change its economic welfare. After a long transient; the system...

In this paper we define some stochastic perturbations of the BTW model which make it into Manna model. These models have a continuous parameter p, where p=0 and 1 correspond to the BTW and Manna models respectively. We have investigated the properties of the statistical observables of the waves...

Self-organized criticality (SOC) has been claimed to play an important role in many natural and social systems. In the present work we empirically investigate the relevance of this theory to stock-market dynamics. Avalanches in stock-market indices are identified using a multi-scale...

Recently, Peters et al. (Phys. Rev. Lett. 88 (2002) 018701)) have found power-law behaviour in the distribution of rain events. Here it is shown that the observed self-similar features in both the reservoir level and the distribution of rain events, can quantitatively be reproduced from an...

We report an experiment on a granular packing: a box filled with glass beads is tilted very slowly up to the maximum angle of stability where a big avalanche is produced. During the build-up period many rearrangements occur on the free surface of the packing. Digital imaging was used to study...