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Jamming
and Glassy Behavior in Granular and Soft Matter Systems
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Thursday, 16. Jan. 2014 |
Audio-only-Recording as MP3-File
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15:15 – 16:10 |
Abstract:
Granular
and soft-matter systems, such as foams, colloids and emulsions, undergo a
"jamming transition"
from a
liquid-like state to a rigid but disordered solid state as one varies system
parameters. In athermal
systems
at low densities, jamming may occur via compression as one increases the
packing fraction of
the
particles. At higher densities, jamming may occur when the applied shear stress
decreases below a
critical
yield stress. At finite temperatures, jamming may occur as one lowers the
temperature and freezes
into a
glassy state. A "jamming phase diagram" has been proposed as a means
to unify these three different
routes to
jamming. Using numerical simulations of a simple model system of frictionless
disks in two dimensions,
we review
the jamming behavior with respect to compression, shearing, and varying
temperature.
We find
that while compression can give a range of jamming packing fractions depending
on the initial state,
shear
driven jamming defines a unique packing fraction where the yield stress
vanishes; critical scaling applies
at this
shear driven jamming transition. Adding finite temperature to our model we use
dimensional analysis
and
numerical simulations to argue that, contrary to the jamming phase diagram
conjecture, athermal jamming
and the
equilibrium glass transition appear to be distinctly different physical
phenomena.
Work done in collaboration with Peter Olsson and Daniel Vagberg of