FROM SELF-ORGANIZED CRITICALITY TO 1ST-ORDER-LIKE BEHAVIOR - A NEW-TYPE OF PERCOLATIVE TRANSITION

A modification of one of the standard models of avalanches in a sandpi le is proposed. We allow two different values of the critical slope: a sliding never starts with a slope below the upper value and stops onl y when the local slope falls below the lower one. As a result we find that the only avalanches present involve the whole system, in sharp co ntrast with what is expected from self-organized critical models. This behavior resembles more a first-order transition than a second-order one. We present a method to study the gradual change from one behavior to the other. A possible link with percolative transitions is discuss ed.