703,405 research outputs found
Glass transition in granular media
In the framework of schematic hard spheres lattice models for granular media
we investigate the phenomenon of the ``jamming transition''. In particular,
using Edwards' approach, by analytical calculations at a mean field level, we
derive the system phase diagram and show that ``jamming'' corresponds to a
phase transition from a ``fluid'' to a ``glassy'' phase, observed when
crystallization is avoided. Interestingly, the nature of such a ``glassy''
phase turns out to be the same found in mean field models for glass formers.Comment: 7 pages, 4 figure
Vortex Glass and Vortex Liquid in Oscillatory Media
We study the disordered, multi-spiral solutions of two-dimensional
homogeneous oscillatory media for parameter values at which the single
spiral/vortex solution is fully stable. In the framework of the complex
Ginzburg-Landau (CGLE) equation, we show that these states, heretofore believed
to be static, actually evolve on ultra-slow timescales. This is achieved via a
reduction of the CGLE to the evolution of the sole vortex position and phase
coordinates. This true defect-mediated turbulence occurs in two distinct
phases, a vortex liquid characterized by normal diffusion of individual
spirals, and a slowly relaxing, intermittent, ``vortex glass''.Comment: 4 pages, 2 figures, submitted to Physical Review Letter
Development of a theory of the spectral reflectance of minerals, part 2
Theory of diffuse reflectance of particulate media including garnet, glass, corundum powders, and mixture
Raising Women's Pay: An Agenda For Equity
An agenda and series of recommendations that offer concrete solutions to the problems of unequal pay, occupational segregation, glass ceiling discrimination, and low-wage and temporary work.More reports like this one are available on WE's website under Media Center > Publications > Making Workplaces Fairer
Jamming transition in granular media: A mean field approximation and numerical simulations
In order to study analytically the nature of the jamming transition in
granular material, we have considered a cavity method mean field theory, in the
framework of a statistical mechanics approach, based on Edwards' original idea.
For simplicity we have applied the theory to a lattice model and a transition
with exactly the same nature of the glass transition in mean field models for
usual glass formers is found. The model is also simulated in three dimensions
under tap dynamics and a jamming transition with glassy features is observed.
In particular two step decays appear in the relaxation functions and dynamic
heterogeneities resembling ones usually observed in glassy systems. These
results confirm early speculations about the connection between the jamming
transition in granular media and the glass transition in usual glass formers,
giving moreover a precise interpretation of its nature.Comment: 11 pages, 12 figure
Glassy dynamics and dynamical heterogeneity in colloids
Concentrated colloidal suspensions are a well-tested model system which has a
glass transition. Colloids are suspensions of small solid particles in a
liquid, and exhibit glassy behavior when the particle concentration is high;
the particles are roughly analogous to individual molecules in a traditional
glass. Because the particle size can be large (100 nm - 1000 nm), these samples
can be studied with a variety of optical techniques including microscopy and
dynamic light scattering. Here we review the phenomena associated with the
colloidal glass transition, and in particular discuss observations of spatial
and temporally heterogeneous dynamics within colloidal samples near the glass
transition. Although this Chapter focuses primarily on results from
hard-sphere-like colloidal particles, we also discuss other colloidal systems
with attractive or soft repulsive interactions.Comment: Chapter of "Dynamical heterogeneities in glasses, colloids, and
granular media", Eds.: L. Berthier, G. Biroli, J-P Bouchaud, L. Cipelletti
and W. van Saarloos (Oxford University Press, to appear), more info at
http://w3.lcvn.univ-montp2.fr/~lucacip/DH_book.ht
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