The best way of finding a hidden target is a general question which concerns many fields of natural and social sciences. It is of vital importance for foraging animals. It has been observed that many species adopt an intermittent behaviour, alternating phases of intensive search and slow...

We consider a simple model of annihilation reaction, when particles are located on a regular lattice, one of them presenting a fluctuating activity. Time-correlated fluctuations are addressed. The reaction probability and the reaction function are determined exactly. It is shown that the usual,...

We study the dynamics of a tracer particle, which performs a totally directed random walk in an adsorbed monolayer composed of mobile hard-core particles undergoing continuous exchanges with a vapour phase. In terms of a mean-field-type approach, based on the decoupling of the...

We study the kinetics of diffusion-controlled A+B→B reactions, in which both species are moving randomly on a d-dimensional lattice and react upon encounters, provided that both species are in reactive states. Particles’ reactivity fluctuates randomly between active and passive forms. We...

We focus on two models of nearest-neighbour random walks on d-dimensional regular hyper-cubic lattices that are usually assumed to be identical—the discrete-time Polya walk, in which the walker steps at each integer moment of time, and the Montroll–Weiss continuous-time random walk in which...

We study the distribution P(ω) of the random variable ω=x1/(x1+x2), where x1 and x2 are the wealths of two individuals selected at random from the same tempered Paretian ensemble characterized by the distribution Ψ(x)∼ϕ(x)/x1+α, where α0 is the Pareto index and ϕ(x) is the cut-off...

A stochastic model is proposed to take into account the effect of a weak external field associated to diffusion, a discrete Master Equation is written down for the spatial distribution of particles. Approximate solutions are found for the first two cumulants, and applied to an example of...

A cellular automation model is used to describe the dynamics of the catalytic oxidation of CO on a Pt(1 0 0) surface. The cellular automation rules account for the structural phase transformations of the Pt substrate, the reaction kinetics of the adsorbed phase and diffusion of adsorbed species....

The application of the Onsager-Machlup principle to non-linear fluctuations of a thermodynamic variable is discussed. The Onsager law of proportionality of fluxes and forces is obtained by an integral method. Approximate calculation of the transition probabilities and of the most probable...

The form of the reaction rates in the birth-and-death formalism of a chemical reaction is obtained by applying the principle of stationarity of the thermodynamic equilibrium distribution.