Self-organized criticality in the Olami-Feder-Christensen model

A system is in a self-organized critical state if the distribution of some measured events obeys a power law. The finite-size scaling of this distribu tion with the lattice size is usually enough to assume that the system disp lays self-organized criticality This approach, however, can be misleading. In this paper we analyze the behavior of the branching rate sigma of the ev ents to establish whether a system is in a critical state. We apply this me thod to the Olami-Feder-Christensen model to obtain evidence that, in contr ast to previous results, the model is critical in the conservative regime o nly.