We briefly review a Statistical Mechanics approach for the description of granular materials following the original ideas developed by Edwards. We show that Edwards’ assumptions works very well for a class of lattice models and we discuss some recent analytic results obtained in such a...

We present different bit-string models of haploid asexual populations in which individuals may exchange part of their genome with other individuals (parasex) according to a given probability. We study the advantages of this parasex concerning population sizes, genetic fitness and diversity. We...

Clusters of parallel spins in the square-lattice Ising model are defined as groups of traders acting together on the Cont-Bouchaud stock market model. As in the random percolation case, we see a crossover from a power-law behaviour to a more Gaussian distribution for the market fluctuations.

A percolation model is presented, with computer simulations for illustrations, to show how the sales of a new product may penetrate the consumer market. We review the traditional approach in the marketing literature, which is based on differential or difference equations similar to the logistic...

We modify twice the Penna model for biological ageing. First, we introduce back (good) mutations and a memory for them into the model. It allows us to observe an improvement of the species fitness over long-time scales as well as punctuated equilibrium. Second, we adopt a food/space competition...

A Monte Carlo computer simulation model is presented to study the evolution of stock price and the distribution of price fluctuation. The resistance is described by an elastic energy Ee=e·x2 resulting from the price deviation x from an initial value and the momentum trading by the potential...

A computer simulation model is used to study the density profile and flow of a miscible gaseous fluid mixture consisting of differing constituent masses (mA=mB/3) through an open matrix. The density profile is found to decay with the height ∝exp(−mA(B)h), consistent with the barometric...

For the percolation model of strain in a deforming metal proposed earlier, we develop sum rule and mean field approximations which predict a critical point. The numerical work is restricted to the simpler of two cases proposed in the earlier work, in which the cell walls are “strong”, and...

Recent progress with Sornette, Dhar and Kirsch is reviewed on the old question of how diffusing particles in a fixed external field travel through a random medium (biased ants in a labyrinth). Simulations show log-periodic oscillations in time for strong bias and suggest a phase transition...