Chaos

Nonlinear systems can have very complicated nontransient behaviour in addition to the static and periodic solutions familiar to everyone. Mathematicians have known for years about the existence of chaotic solutions (persisting modes of dynamic behaviour that have no simple recurrence properties, even though they are not stochastic), but it is only recently that much progress has been made in analysing them. The paper introduces some of the main features of the study of chaotic solutions and tries to relate them to more familiar topics such as feedback and spectra. The authors believe that chaos is more prevalent than is realised and they hope that readers will be alerted to the possibility that some effects which have been blamed on noise are actually instances of chaotic behaviour of a completely deterministic nature.