Physics Colloquium
Friday, November 21, 2003

Dr. Michael F. Shlesinger

Chief Scientist for Nonlinear Science
Office of Naval Research

Stretched Times and Divergent Times Scales in Glassy Materials

The manner in which a rapidly cooled liquid transforms into a glassy material is still an open scientific question. While it is obvious that viscosity of the liquid increases as the temperature is lowered, it is not as obvious how dielectric relaxation and conductivity change with cooling. We present a model based on the anomalously slow "fractal time" random movement of mobile defects in a glass and calculate how this induces relaxation. We find the relaxation to be governed by stretched exponential kinetics with the time scale dependent on mobile defect concentration. We examine how this time scale diverges under decreasing temperature and increasing pressure. Our results modify the traditional Vogel-Fulcher law and also generalize it to include high pressure effects. Our predictions agree well with conductivity experiments on ion-doped polymers.

Refreshments 3:30 P.M. Room E200 Math/Science Center