Colloquium Schedule for 1999-2000 |

Riddling: Dynamics Beyond Chaos


Professor J. Alexander
Case Western Reserve University




Riddled and intermingled basins of attraction are a relatively recently noticed phenomenon in dynamical systems and differential equations.A chaotic system exhibits sensitive dependence to initial conditions; however, usually the long-term average behavior is robust, except forinitial conditions near basin boundaries. In a riddled system, the long-termaverage behavior is also infinitely sensitive to initial conditions. Thename comes from the fact that the basin of an attractor is infinitely riddled with open sets -- every point is a basin boundary. Intermingled basins arebasins for different attractors which are dense in each other. Over the pastseveral years, riddling has been observed in several scientific contexts:visually (originally), mathematically (rigorously), numerically (simulations),and experimentally (bench experiments). There are philosophical implications forreplication of phenomena, which have been discussed in the popular scientificpress under titles such as "Beyond Chaos". This talk is a survey of these developments.