Fixed-Energy Sandpiles Belong Generically to Directed Percolation
  Fixed-energy sandpiles with stochastic update rules are known to exhibit a nonequilibrium phase transition from an active phase into infinitely many absorbing states. Examples include the conserved Manna model, the conserved lattice gas, and the conserved threshold transfer process. It is believed that the transitions in these models belong to an autonomous universality class of nonequilibrium phase transitions, the so-called Manna class. Contrarily, the present numerical study of selected (1+1)-dimensional models in this class suggests that their critical behavior converges to directed percolation after very long time, questioning the existence of an independent Manna class. 
Mahashweta Basu, Urna Basu, Sourish Bondyopadhyay, P. K. Mohanty, and   Haye Hinrichsen
cond-mat.stat-mech