PATTERN INTERACTION AND SPIRAL WAVES IN A 2-LAYER SYSTEM OF EXCITABLEUNITS

A system composed of two coupled lattices, hence a layered structure, is studied when the unit at each site is an active electronic circuit possessing two accessible stable steady states. In the absence of inte rlattice coupling, each lattice taken separately represents a discrete , reaction diffusion system. We show that, depending on the strength o f the diffusion coefficient, each lattice may exhibit either a wide va riety of stable steady patterns or a number of different wave patterns including rotating spirals. Moreover, for fixed reaction kinetics eac h lattice can exhibit spiral waves of both excitable and oscillatory t ype. For nonoscillating kinetics, the metastable periodiclike behavior of the unit is at the origin of the oscillatory spirals. From initial ly different global patterns or waves in each lattice, the interaction may lead to synchronization and hence a new (controlled) form and the replication of a given one. We also show how there is reentry of spir al waves between the two coupled layers associated with the ''competit ion'' of their oscillatory and excitable spiral wave properties.