PHYSICAL MATHEMATICS SEMINAR TITLE: STRESS PROPAGATION IN FRACTIONAL GRANULAR MATTER AUTHOR: RAVA DA SILVEIRA Department of Physics Harvard University ABSTRACT: This talk presents a continuum theory of stress in granular media, and compares simple predictions of the theory with experimental results. Starting from the elastic deformation of individual grains we construct systematically a coarse-grained description of the medium. This description involves fabric tensors that encode the geometry of the granular packing and relate strains to stresses. Another ingredient of the description that emerges naturally is a reorientation tensor: in contrast to usual continuum media, here grains are free to reorient in order to relieve stress. After establishing the general properties of the continuum description, we calculate stress propagation in a two dimensional granular medium in response to an applied point force -- paralleling a common experimental setup. A wealth of outcomes, depending on the texture of the granular assembly, affords an interpretative framework for experiments. Finally, we discuss interesting singular solutions that may arise in limiting cases. TUESDAY, APRIL 1, 2003 2:30 pm Building 2, Room 338 Refreshments will be served at 3:30 PM in Room 2-349 Massachusetts Institute of Technology Department of Mathematics Cambridge, MA 02139