Physics Colloquium - Friday, April 28st, 2006, 4:00 P.M.

E300 Math/Science Center; Refreshments at 3:30 P.M. in Room E200

Narayanan Menon

University of Massachusetts, Amherst Squeezing some new facts out of glasses

Molecules in a glass are relatively immobile even though they are arranged in much the same way as in a freely-flowing liquid. There are two broad classes of explanations for this state of dynamical arrest: one set of ideas explains it in terms of the density of these systems. When a liquid contracts on cooling, molecules that were already hindered in their motion by the dense packing in a liquid now find no room at all to rearrange themselves. Another explanation is that lowered temperature renders molecules too inactive to explore an increasingly mountainous free energy landscape. I will discuss experiments in which we separate unambiguously the effects of volume restrictions and lowered temperature in a common glass-forming system.