Scale-free dynamics in physical and biological systems can arise from a variety of causes. Here, we explore a branching process which leads to such dynamics. We find conditions for the appearance of power laws and study quantitatively what happens to these power laws when such conditions are violated. From a branching process model, we predict the behavior of two systems which seem to exhibit n...

Friction in a dense two-dimensional granular material is studied by molecular dynamics simulations. Initially the particles are ordered in a triangular lattice where the top layer feels a constant vertical pressure and horizontal velocity field. The dynamics of the material at low velocities is found to be characterized by avalanche-type motion during short time intervals followed by long stati...

Magneto-optical methods allow us to observe the dynamics of domain wall motion, but this is intrinsically a very noisy process. We discuss a new method allowing us to reduce the measurement noise, taking advantage of the acquisition of a whole temporal sequence of images. The resulting avalanche distributions give interesting hints as to the magnetization dynamics, but are strongly dependent on...

Based on the synergetic approach, the theory of a single avalanche formation is presented for the simplest sandpile model. The stationary values of sand velocity, slope and avalanche intensity are derived as functions of control parameter (externally driven sandpile tilt). The statistical ensemble of avalanche intensities is considered to investigate diffusion in ultrametric space of hierarchic...

Snow avalanche paths are major geomorphic features in the Rocky Mountains of Glacier National Park, Montana. They are the most common and geographically widespread form of mass-wasting in the central portion of the park. Field work and aerialphoto studies identified over 800 such paths in the study area. Other mass-wasting phenomena are also common. Snow avalanche path directions in the study a...