25,852 research outputs found
Simulations of Noise in Disordered Systems
We use particle dynamics simulations to probe the correlations between noise
and dynamics in a variety of disordered systems, including superconducting
vortices, 2D electron liquid crystals, colloids, domain walls, and granular
media. The noise measurements offer an experimentally accessible link to the
microscopic dynamics, such as plastic versus elastic flow during transport, and
can provide a signature of dynamical reordering transitions in the system. We
consider broad and narrow band noise in transport systems, as well as the
fluctuations of dislocation density in a system near the melting transition.Comment: 12 pages, 9 postscript figures, requires spie.cls. SPIE Conference on
Fluctuations and Noise 2003, invited contributio
Disordering Transitions and Peak Effect in Polydisperse Particle Systems
We show numerically that in a binary system of Yukawa particles, a dispersity
driven disordering transition occurs. In the presence of quenched disorder this
disordering transition coincides with a marked increase in the depinning
threshold, known as a peak effect. We find that the addition of poorly pinned
particles can increase the overall pinning in the sample by increasing the
amount of topological disorder present. If the quenched disorder is strong
enough to create a significant amount of topological disorder in the
monodisperse system, addition of a poorly pinned species generates further
disorder but does not produce a peak in the depinning force. Our results
indicate that for binary mixtures, optimal pinning occurs for topological
defect fraction densities of 0.2 to 0.25. For defect densities below this
range, the system retains orientational order. We determine the effect of the
pinning density, strength, and radius on the depinning peak and find that the
peak effect is more pronounced in weakly pinning systems.Comment: 8 pages, 8 postscript figures. Version to appear in PR
- …