Self-organised criticality in dilute lattice
  The variation of z in BTW model in presence of holes (dissipative sites) has been studied. The value of z decreases as the fraction of number of holes increases. Interstingly, it is observed that the variation of the rate of change of z with the fraction of number of holes is different for the two different types of distribution of holes over the lattice. When the holes are randomly distributed over the lattice then the dissipation is more compared to that of the case when the holes are present in the form of a single compact cluster with same fraction. The value of z is less in the first case than that observed in the second case. 
Ajanta Bhowal Acharyya (Lady Brabourne College, Calcutta, India)
cond-mat.stat-mech