24,705 research outputs found
On the nonlocal viscosity kernel of mixtures
In this report we investigate the multiscale hydrodynamical response of a
liquid as a function of mixture composition. This is done via a series of
molecular dynamics simulations where the wave vector dependent viscosity kernel
is computed for three mixtures each with 7-15 different compositions. We
observe that the nonlocal viscosity kernel is dependent on composition for
simple atomic mixtures for all the wave vectors studied here, however, for a
model polymer melt mixture the kernel is independent of composition for large
wave vectors. The deviation from ideal mixing is also studied. Here it is shown
that a Lennard-Jones mixture follows the ideal mixing rule surprisingly well
for a large range of wave vectors, whereas for both the Kob-Andersen mixture
and the polymer melt large deviations are found. Furthermore, for the polymer
melt the deviation is wave vector dependent such that there exists a critical
length scale at which the ideal mixing goes from under-estimating to
over-estimating the viscosity
Tolerance and Sensitivity in the Fuse Network
We show that depending on the disorder, a small noise added to the threshold
distribution of the fuse network may or may not completely change the
subsequent breakdown process. When the threshold distribution has a lower
cutoff at a finite value and a power law dependence towards large thresholds
with an exponent which is less than , the network is not sensitive
to the added noise, otherwise it is. The transition between sensitivity or not
appears to be second order, and is related to a localization-delocalization
transition earlier observed in such systems.Comment: 12 pages, 3 figures available upon request, plain Te
P02.69. Self administered acupuncture for treatment of chemotherapy associated nausea: a pilot study
SU(3) sextet model with Wilson fermions
We investigate the spectrum and IR properties of the SU(3) "sextet" model
with two Dirac fermions in the two-index symmetric representation via lattice
simulations. This model is a prime candidate for a realization of Walking
Technicolor, which features a minimal matter content and it is expected to be
inside or very close to the lower boundary of the conformal window. We use the
Wilson discretization for the fermions and map the phase structure of the
lattice model. We study several spectral and gradient flow observables both in
the bulk and the weak coupling phases. While in the bulk phase we find clear
signs of chiral symmetry breaking, in the weak coupling phase there is no clear
indication for it, and instead the chiral limit of the model seems compatible
with an IR-conformal behavior.Comment: 32 pages, many figure
Self-diffusion of Rod-like Viruses Through Smectic Layer
We report the direct visualization at the scale of single particles of mass
transport between smectic layers, also called permeation, in a suspension of
rod-like viruses. Self-diffusion takes place preferentially in the direction
normal to the smectic layers, and occurs by quasi-quantized steps of one rod
length. The diffusion rate corresponds with the rate calculated from the
diffusion in the nematic state with a lamellar periodic ordering potential that
is obtained experimentally.Comment: latex, 4 pages, 4 figures, accepted in Phys. Rev. Let
Scaling behavior in the dynamics of a supercooled Lennard-Jones mixture
We present the results of a large scale molecular dynamics computer
simulation of a binary, supercooled Lennard-Jones fluid. At low temperatures
and intermediate times the time dependence of the intermediate scattering
function is well described by a von Schweidler law. The von Schweidler exponent
is independent of temperature and depends only weakly on the type of
correlator. For long times the correlation functions show a Kohlrausch behavior
with an exponent that is independent of temperature. This dynamical
behavior is in accordance with the mode-coupling theory of supercooled liquids.Comment: 6 pages, RevTex, three postscript figures available on request,
MZ-Physics-10
Random phase approximation and its extension for the quantum O(2) anharmonic oscillator
We apply the random phase approximation (RPA) and its extension called
renormalized RPA to the quantum anharmonic oscillator with an O(2) symmetry. We
first obtain the equation for the RPA frequencies in the standard and in the
renormalized RPA approximations using the equation of motion method. In the
case where the ground state has a broken symmetry, we check the existence of a
zero frequency in the standard and in the renormalized RPA approximations. Then
we use a time-dependent approach where the standard RPA frequencies are
obtained as small oscillations around the static solution in the time-dependent
Hartree-Bogoliubov equation. We draw a parallel between the two approaches.Comment: 26 pages, Latex file, no figur
XY Spin Fluid in an External Magnetic Field
A method of integral equations is developed to study inhomogeneous fluids
with planar spins in an external field. As a result, the calculations for these
systems appear to be no more difficult than those for ordinary homogeneous
liquids. The approach proposed is applied to the ferromagnetic XY spin fluid in
a magnetic field using a soft mean spherical closure and the Born-Green-Yvon
equation. This provides an accurate reproduction of the complicated phase
diagram behavior obtained by cumbersome Gibbs ensemble simulation and multiple
histogram reweighting techniques.Comment: 4 pages, 3 figures, submitted to Phys. Rev. Let
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