54 research outputs found
Evolution of particle-scale dynamics in an aging clay suspension
Multispeckle x-ray photon correlation spectroscopy was employed to
characterize the slow dynamics of a colloidal suspension formed by
highly-charged, nanometer-sized disks. At scattering wave vectors
corresponding to interparticle length scales, the dynamic structure factor
follows a form ], where
1.5. The characteristic relaxation time increases with the sample age
approximately as and decreases with
approximately as . Such a compressed exponential decay with
relaxation time that varies inversely with is consistent with recent models
that describe the dynamics in disordered elastic media in terms of strain from
random, local structural rearrangements. The amplitude of the measured decay in
varies with in a manner that implies caged particle motion at
short times. The decrease in the range of this motion and an increase in
suspension conductivity with increasing indicate a growth in the
interparticle repulsion as the mechanism for internal stress development
implied by the models.Comment: 4 pages, includes 4 postscript figures; accepted for publication in
Phys Rev Let
Fracture Strength of Disordered Media: Universality, Interactions, and Tail Asymptotics
We study the asymptotic properties of fracture strength distributions of disordered elastic media by a combination of renormalization group, extreme value theory, and numerical simulation. We investigate the validity of the “weakest-link hypothesis” in the presence of realistic long-ranged interactions in the random fuse model. Numerical simulations indicate that the fracture strength is well-described by the Duxbury-Leath-Beale (DLB) distribution which is shown to flow asymptotically to the Gumbel distribution. We explore the relation between the extreme value distributions and the DLB-type asymptotic distributions and show that the universal extreme value forms may not be appropriate to describe the nonuniversal low-strength tail.Peer reviewe
A study of flux lines lattice order and critical current with time of flight small angle neutron scattering
Small angle neutron scattering (SANS) is an historical technique to study the
flux lines lattice (FLL) in a superconductor. Structural characteristics of the
FLL can be revealed, providing fundamental information for the physics of
vortex lattice.
However, the spatial resolution is limited and all the correlation lengths of
order are difficult to extract with precision.
We show here that a time of flight technique reveals the Bragg peak of the
FLL, and also its translational order with a better resolution.
We discuss the implication of these results for pinning mechanisms in a
Niobium sample.Comment: accepted in PR
The jamming transition as probed by quasistatic shear flow
We study the rheology of amorphous packings of soft, frictionless particles
close to jamming. Implementing a quasistatic simulation method we generate a
well defined ensemble of states that directly samples the system at its
yield-stress. A continuous jamming transition from a freely-flowing state to a
yield stress situation takes place at a well defined packing fraction, where
the scaling laws characteristic of isostatic solids are observed. We propose
that long-range correlations observed below the transition are dominated by
this isostatic point, while those that are observed above the transition are
characteristic of dense, disordered elastic media.Comment: 4 pages, 6 figures, revised versio
Acoustic attenuation in glasses and its relation with the boson peak
A theory for the vibrational dynamics in disordered solids [W. Schirmacher,
Europhys. Lett. {\bf 73}, 892 (2006)], based on the random spatial variation of
the shear modulus, has been applied to determine the wavevector ()
dependence of the Brillouin peak position ( and width (),
as well as the density of vibrational states (), in disordered
systems. As a result, we give a firm theoretical ground to the ubiquitous
dependence of observed in glasses. Moreover, we derive a
quantitative relation between the excess of the density of states (the boson
peak) and , two quantities that were not considered related before.
The successful comparison of this relation with the outcome of experiments and
numerical simulations gives further support to the theory.Comment: To appear on PR
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