Avalanches in three and four dimensions

Nonuniversality and scaling breakdown in a nonconservative earthquake model

We use extensive numerical simulations to test recent claims of universality in the nonconservative regime of the Olami-Feder-Christensen model. By studying larger systems and a wider range of dissipation levels than previously considered we conclude that there is no evidence of universality in the model with only limited regions of the event size distributions displaying power-law behavior. We further analyze the dimension of the largest events in the model, D(max), using a multiscaling method. This reveals that although D(max) initially increases with system size, for larger systems the dimension ultimately decreases with system size casting further doubt on the criticality of the model.

Physics of the Granular State

Granular materials display a variety of behaviors that are in many ways different from those of other substances. They cannot be easily classified as either solids or liquids. This has prompted the generation of analogies between the physics found in a simple sandpile and that found in complicated microscopic systems, such as flux motion in superconductors or spin glasses. Recently, the unusual behavior of granular systems has led to a number of new theories and to a new era of experimentation on granular systems.