PHYSICAL MATHEMATICS SEMINAR TITLE: SEMIFLEXIBLE POLYMER NETWORKS SPEAKER: ALEX LEVINE Department of Physics University of Massachusetts, Amherst ABSTRACT: Networks of filamentous proteins play a crucial role in cell mechanics. These cytoskeletal networks, together with various cross-linking and other associated proteins largely determine the (visco-)elastic response of cells. In this talk I discuss a model system of cross-linked, stiff filaments in order to explore the connection between the microstructure under strain and the macroscopic response of cytoskeletal networks. We find two distinct regimes as a function of cross-link density and filament rigidity: one characterized by affine deformation and one by non-affine deformation. We characterize the crossover between these two. Finally, I will also discuss the complete breakdown of long-range elasticity in progressively more dilute actin networks - the rigidity percolation transition. TUESDAY, APRIL 15, 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