Physical Society Colloquium

Jamming

Andrea Liu

University of Pennsylvania

All around us things seem to get jammed. Before breakfast, coffee grounds and cereal jam as they refuse to flow into our filters and bowls. On the way to work, we are caught in traffic jams. In factories, powders jam as they clog in the conduits that were designed to have them flow smoothly from one side of the factory floor to the other. Our recourse in all these situations is to pound on our containers, dashboards and conduits until the jam miraculously disappears. We are usually so irritated by the jam that we do not notice that the approach to jamming and the jammed state, in all of these situations, have common properties and similar behaviors that are quite different from those in systems near the liquid-solid transition. I will discuss recent progress in understanding these phenomena from a more unified point of view.