WAVE-PROPAGATION IN HETEROGENEOUS EXCITABLE MEDIA

Heterogeneities deeply affect pulse dynamics in excitable media. In on e dimension, spatially periodic variation of the excitation threshold leads to a characteristic dependence of the propagation speed on the m odulation period d with a maximum at a certain optimal value d(opt). T he maximum speed may be larger than the pulse velocity in an effective homogeneous medium. In two dimensions, the geometry and size of heter ogeneities determine the wave dynamics. For example, an excitability d istribution made of oblique stripes with different angles of inclinati on can result in a speedup or a slowdown of the pulse. The calculation s are carried out with a modified Oregonator model for light-sensitive Belouzov-Zhabotinskii media where a heterogeneous distribution of exc itability can be achieved by inhomogeneous illumination. Nevertheless, the results do not depend on the details of the local kinetics, but a pply to the general case of excitable media.