SELF-ORGANIZED CRITICAL SCALING AT SURFACES

At dissipative boundaries, models of self-organized criticality show p eculiar scalings, different from the bulk ones, in the distributions c haracterizing avalanches. For Abelian models with Dirichlet boundary c onditions, evidence of this is obtained by a mean field approach to se mi-infinite sandpiles, and by numerical simulations in two and three d imensions. On the other hand, within the mean field description, close d Neumann conditions restore bulk scaling exponents also at the border . Numerical results are consistent with this property also at finite d .