Physics (Internal)

Aggregation, packing, and response of soft matter

This event is part of the Biophysics/Condensed Matter Seminar Series.

Abstract: We will consider two problems in condensed matter physics which highlight the role of geometry and their non-equilibrium nature in organizing structure and dynamics. We will first consider the familiar example of spherical grains deposited randomly inside a container in a gravitational field, and discuss conditions under which a fully ordered face centered cubic crystal can be grown using a template. The growth of disorder observed in experiments will be compared with minimal models of defect growth and propagation from layer to layer. Then, we will examine the response of a disordered packing to applied shear, and discuss the nucleation of various ordered phases, their shapes and orientation. The growth of order will be compared with those observed in thermal hard sphere models. Next, we will examine the buckling instabilities of thin elastic sheets subjected to twist which lead to wrinkling, stress focusing and energy condensation in creased structures. This system shows the geometric nonlinearity, competition between bending and stretching energies, and development of singularities inherent in the response of soft thin materials to loading.