Beckman Fellow 2001-02

Karin A Dahmen


Avalanches, Disorder, and what Magnets, Earthquakes, and Bacterial Colonies may have in common

Candy wrappers, magnets, earthquake faults, and many other systems respond to slowly changing external conditions with crackling noise, that is, with discrete, impulsive events that span a huge range of sizes (Barkhausen noise or avalanches in the case of magnets, earthquakes in the case of the earth). Because the behavior of these systems is regular over a very broad range of sizes, one might expect that it does not depend on the microscopic details of the system. Indeed, observations show that entire classes of systems exhibit the same behavior on long length and time scales, which can be predicted from rather simple models. During her Center appointment, Professor Dahmen and her group plan to model Barkhausen noise in disordered magnets as a representative of these systems and to compute predictions for the universal aspects of the behavior on long length scales as a function of disorder, field-sweep rate, and temperature. They will use ideas and tools from disordered systems theory and the theory of phase transitions. The study is intended to lead to a better understanding of magnetic materials and also provide analysis methods that would be applicable to a much broader set of systems with crackling noise, ranging from superconductors to earthquakes.