Condensed Matter seminar: "Avalanche statistics and the effect of inertia, or polymer welding, crazing and strain hardening and the connection to entanglements"

Wed, 02/20/2013 - 16:00 - 17:00
Mark Robbins, Johns Hopkins University

Many systems evolve through a series of rapid avalanches that have a power
law distribution of sizes. Examples include magnetic domain walls, fluid
interfaces, deforming ice crystals and earthquakes. A common explanation for
this power law behavior is that driving systems slowly places them near a
critical point. Theoretical studies indicate that inertia should drive
systems away from criticality, yet the underdamped dynamics of the earth's
crust produce some of the best documented power law scaling behavior - the
Gutenberg-Richter law for earthquakes. To test the role of inertia we have
performed extensive simulations of sheared amorphous solids in two and three
dimensions. Finite-size scaling of simulations with thousands to millions of
particles was used to analyze the distributions of event sizes as a function
of the degree of damping. The results show that inertia leads to a new
underdamped universality class rather than destroying criticality. A
critical damping rate is identified that separates overdamped and
underdamped scaling. The nature of spatial correlations in avalanches was
also studied. They exhibit striking anisotropic properties with a scaling
exponent that varies continuously with angle.