Wave propagation in spatially extended media and far from equilibrium has been the subject of a wide study in the last years (for a review see Cross M.C., Hohenberg P.C., Rev. Mod. Phys. 65, 851 (1993)). In particular, wave propagation in excitable chemical media is being studied extensively, because it constitutes a good example for excitation waves in other contexts just like the biological one with waves of excitation in neural or cardiac tissue. The term excitable medium refers to a system as an ensemble of coupled excitable elements, where each of one exhibits the dynamics of a stable fixed point when it is perturbed up to a threshold. The closed trajectory in the phase space is translated to a travelling wave in the real time-space.
Normally, it is easier to consider homogeneous media. However, real biological media are often inhomogeneous. In this respect, wave front propagation in nonhomogeneous media has been studied from different points of view, such as the interaction of waves and inert obstacles (which is considered to be responsible for reentries to anchor or planar fronts broken), and the effect of modulations or fluctuations on the local excitability of the medium.
In our laboratory, it is being carried out an experimental study in the framework of the light-sensitive Belousov- Zhabotinsky (BZ) reaction about the dynamics of wave fronts under the effect of different spatio-temporal distributions of the light intensity (which is our control parameter). Till now, the different studied cases concerning both deterministic and stochastic forcing are:
Deterministic forcing
Excitability spatially modulated
Periodically modulated excitability in subexcitable media
Stochastic forcing
Disordered excitability
Non excitable random clusters
Spatio-temporal fluctuations correlated in time