We introduce an efficient cellular automaton for the coagulation-fission process with diffusion 2A->3A, 2A->A in arbitrary dimensions. As the well-known Domany-Kinzel model, it is defined on a tilted hypercubic lattice and evolves by parallel updates. The model exhibits a non-equilibrium phase transition from an active into an absorbing phase and its critical properties are expected to be of the same type as in the pair contact process with diffusion. High-precision simulations on a parallel computer suggest that various quantities of interest do not show the expected power-law scaling, calling for new approaches to understand this unusual type of critical behavior.

Comment: 11 pages, 6 eps figures