Pacemakers versus synchronization in excitable chemical systems

The Belousov-Zhabotinsky (BZ) chemical reaction is the prototype excitable chemical reaction, a relaxation oscillator consisting of a fast activator (HBrO₂) and an inhibitor (Br^-) whose production is determined by slow catalytic oxidation of brominated malonic acid. The unstirred BZ reaction in "2D" systems shows a variety of patterns: target patterns generated by oscillatory pacemakers, oscillatory pacemakers in an oscillatory medium, bulk oscillations (synchronized or phase waves), depending upon the catalyst (ferroin, manganese, cerium, mixtures). We describe an experimental and theoretical study of this phenomenon. The type of pattern can be explained, at least in part, by a combination of the redox potential of the catalyst, and the relative time scales of HBrO₂ and Br^- production. Transitions between dynamical states may help understand "dynamical disease" (see L. Glass, Chaos, 2015) in biological systems.