Sandpile models with dynamically varying critical slopes.

Sandpile models with randomized updating rules are studied. The randomness is not quenched, but set dynamically by the dissipation events (avalanches) in the system. Relaxation from fixed updating rules is here a consequence of medium anisotropy and motivated by the behavior of various driven physical systems. A one-dimensional sandpile model in which the critical slope at a site varies as the process proceeds displays self-organized criticality. The model allows one to build in an internal relaxation mechanism separated from the external driving Aux and underlying the noise of the process.