THURSDAY, Oct. 11, 12 p.m. 11th floor Gamow Tower
John A. Scales
Colorado School of Mines
Experimental studies of wave propagation in random media
For the past few years I've been engaged in a variety of laboratory experiments involving wave propagation in random media. On the one hand, it is natural to ask how we can understand (and even exploit) disorder in naturally occurring systems. On the other, waves in random media provide an ideal system for studying some interesting fundamental physics questions such as quantum chaos, localization, metal-insulator transitions, the breakdown of macroscopic diffusion models, and other issues. Waves that are multiply scattered (or reverberating in closed systems) are very sensitive to changes. This allows us to see very small changes by making long measurements. Another late-time feature in strong scattering systems is that they may achieve (by multiple scattering) an isotropic radiation field analogous to thermal equilibrium, in which the system response function can be retrieved by cross-correlating noise. The examples we will discuss will include laser ultrasound and electromagnetic waves in the millimeter band; both are non-contacting, phase-sensitive techniques.