The universality class of absorbing phase transitions with a conserved   field
  We investigate the critical behavior of systems exhibiting a continuous absorbing phase transition in the presence of a conserved field coupled to the order parameter. The results obtained point out the existence of a new universality class of nonequilibrium phase transitions that characterizes a vast set of systems including conserved threshold transfer processes and stochastic sandpile models. 
Michela Rossi, Romualdo Pastor-Satorras, Alessandro Vespignani