Coupling microscopic and macroscopic cellular automata

Cellular automata can model natural phenomena on many different levels of detail. Often, one specific level of detail is appropriate for the problem under investigation. But in some cases a connection between the different levels of detail is necessary. One such case is the catalytic reaction on a surface. The homogeneous crystallographic surface can reasonably well be described by mesoscopic approaches, but in the presence of defects, a microscopic simulation (where each site of the crystal lattice is individually represented) is necessary. In this paper we present a framework for coupling different types of cellular automata to achive an efficient simulation which is nevertheless detailed enough to resolve microscopic phenomena where necessary.