INVERSE AVALANCHES IN THE ABELIAN SANDPILE MODEL

We define and study the inverse of particle addition process in the Ab elian sandpile model. We show how to obtain the unique recurrent confi guration corresponding to a single particle deletion by a sequence of operations called inverse avalanches. We study the probability distrib ution of s1, the number of ''untopplings'' in the first inverse avalan che. For a square lattice, we determine Prob(s1) exactly for s1 = 0, 1 , 2, and 3. For large s1, we show that Prob(s1) varies as s1(-11/8). I n the direct avalanches, this is related to the probability distributi on of the number of sites which topple as often as the site where the particle was added. These results are verified by numerical simulation s.