17,730 research outputs found
Comment on "Effects of Point Defects on the Phase Diagram of Vortex States in High-Tc Superconductors in the B || c Axis"
We comment on a recent work by Nonomura and Hu who simulated the 3D XY model
for a type-II superconductor in an applied magnetic field, in the presence of
uncorrelated point randomness. We clarify the nature of the "vortex slush"
state that they found, and argue that this state is unstable in the
thermodynamic limit.Comment: 2 pages, 2 figure
Glassiness, Rigidity and Jamming of Frictionless Soft Core Disks
The jamming of bi-disperse soft core disks is considered, using a variety of
different protocols to produce the jammed state. In agreement with other works,
we find that cooling and compression can lead to a broad range of jamming
packing fractions , depending on cooling rate and initial
configuration; the larger the degree of big particle clustering in the initial
configuration, the larger will be the value of . In contrast, we find
that shearing disrupts particle clustering, leading to a much narrower range of
as the shear strain rate varies. In the limit of vanishingly small
shear strain rate, we find a unique non-trivial value for the jamming density
that is independent of the initial system configuration. We conclude that shear
driven jamming is a unique and well defined critical point in the space of
shear driven steady states. We clarify the relation between glassy behavior,
rigidity and jamming in such systems and relate our results to recent
experiments.Comment: 10 pages, 11 figures, significantly expanded version as accepted for
publication in PR
Dissipation and Rheology of Sheared Soft-Core Frictionless Disks
We use numerical simulations to investigate the effect of different
dissipative models on the shearing rheology of massive soft-core frictionless
disks in two dimensions. We show that the presence of Newtonian (overdamped) vs
Bagnoldian (inertial) rheology is related to the formation of large connected
clusters of disks, and that sharp transitions may exist between the two as
system parameters vary. In the limit of strongly inelastic collisions, we find
that rheological curves collapse to a well-defined limit when plotted against
an appropriate dimensionless strain rate.Comment: 6 pages, 5 figures, revised to published versio
Critical Scaling of Bagnold Rheology at the Jamming Transition of Frictionless Two Dimensional Disks
We carry out constant volume simulations of steady-state, shear driven,
rheology in a simple model of bidisperse, soft-core, frictionless disks in two
dimensions, using a dissipation law that gives rise to Bagnoldian rheology. We
carry out a detailed critical scaling analysis of our resulting data for
pressure and shear stress , in order to determine the critical
exponent that describes the algebraic divergence of the Bagnold
transport coefficients, as the jamming transition is approached from below. We
show that it is necessary, for the strain rates considered in this work, to
consider the leading correction-to-scaling term in order to achieve a
self-consistent analysis of our data. Our resulting value is clearly larger than the theoretical prediction by Otsuki and Hayakawa,
and is consistent with earlier numerical results by Peyneau and Roux, and
recent theoretical predictions by DeGiuli et al. We have also considered the
macroscopic friction and similarly find results consistent
with Peyneau and Roux, and with DeGiuli et al. Our results confirm that the
shear driven jamming transition in Bagnoldian systems is well described by a
critical scaling theory (as was found previously for Newtonian systems), and we
relate this scaling theory to the phenomenological constituent laws for
dilatancy and friction.Comment: 20 pages, 21 figures; revised manuscript according to published
versio
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