7,791 research outputs found
An MO theory of the cubic field splitting of 3d5 6S ions in II-IV compounds of Td symmetry
Molecular orbital techniques used to find cubic field splitting 3a of certain ions in periodic group II-VI compounds of T sub d symmetr
Dynamical Susceptibility in KDP-type Crysals above and below Tc II
The path probability method (PPM) in the tetrahedron-cactus approximation is
applied to the Slater-Takagi model with dipole-dipole interaction for
KH2PO4-type hydrogen-bonded ferroelectric crystals in order to derive a small
dip structure in the real part of dynamical susceptibility observed at the
transition temperature Tc. The dip structure can be ascribed to finite
relaxation times of electric dipole moments responsible for the first order
transition with contrast to the critical slowing down in the second order
transition. The light scattering intensity which is related to the imaginary
part of dynamical susceptibility is also calculated above and below the
transition temperature and the obtained central peak structure is consistent
with polarization fluctuation modes in Raman scattering experiments.Comment: 8 pages, 11 figure
Cluster variation - Pade` approximants method for the simple cubic Ising model
The cluster variation - Pade` approximant method is a recently proposed tool,
based on the extrapolation of low/high temperature results obtained with the
cluster variation method, for the determination of critical parameters in
Ising-like models. Here the method is applied to the three-dimensional simple
cubic Ising model, and new results, obtained with an 18-site basic cluster, are
reported. Other techniques for extracting non-classical critical exponents are
also applied and their results compared with those by the cluster variation -
Pade` approximant method.Comment: 8 RevTeX pages, 3 PostScript figure
Continuum Electromechanical Modeling of Protein-Membrane Interaction
A continuum electromechanical model is proposed to describe the membrane
curvature induced by electrostatic interactions in a solvated protein-membrane
system. The model couples the macroscopic strain energy of membrane and the
electrostatic solvation energy of the system, and equilibrium membrane
deformation is obtained by minimizing the electro-elastic energy functional
with respect to the dielectric interface. The model is illustrated with the
systems with increasing geometry complexity and captures the sensitivity of
membrane curvature to the permanent and mobile charge distributions.Comment: 5 pages, 12 figure
Rotating string in doubled geometry with generalized isometries
In this paper, we first construct a globally well-defined non-geometric
background which contains several branes in type II string theory compactified
on a 7-torus. One of these branes is called 5^2_2, which is a codimension-2
object and has a non-trivial monodromy given by a T-duality transformation. The
geometry near the 5^2_2-brane is shown to approach the non-geometric background
constructed in arXiv:1004.2521. We then construct the solution of a fundamental
string rotating along a non-trivial cycle in the 5^2_2 background. Although the
background is not axisymmetric in the usual sense, we show that it is actually
axisymmetric as a doubled geometry by explicitly finding a generalized Killing
vector. We perform a generalized coordinate transformation into a system where
the generalized isometry is manifest, and show that the winding and momentum
charges of the string solution is explicitly conserved in that system.Comment: 32 pages, 5 figures; v2: typos corrected, to appear in Physical
Review D; v3 minor errors fixed, improvements and a reference added to
section 4.
Application of exchange Monte Carlo method to ordering dynamics
We apply the exchange Monte Carlo method to the ordering dynamics of the
three-state Potts model with the conserved order parameter. Even for the deeply
quenched case to low temperatures, we have observed a rapid domain growth; we
have proved the efficiency of the exchange Monte Carlo method for the ordering
process. The late-stage growth law has been found to be for
the case of conserved order parameter of three-component system.Comment: 7 pages including 5 eps figures, to appear in New J. Phys.
http://www.njp.or
Dynamical Susceptibility in KH2PO4-type Crystals above and below Tc
The time dependent cluster approximation called the path probability method
(PPM) is applied to a pseudo-spin Ising Hamiltonian of the Slater-Takagi model
for KH2PO4-type hydrogen-bonded ferroelectrics in order to calculate the
homogeneous dynamical susceptibility above and below the ferroelectric
transition temperature. Above the transition temperature all the calculations
are carried out analytically in the cactus approximation of the PPM. Below the
transition temperature the dynamical susceptibility is also calculated
accurately since the analytical solution of spontaneous polarization in the
ferroelectric phase can be utilized. When the temperature is approached from
both sides of the transition temperature, only one of relaxation times shows a
critical slowing down and makes a main contribution to the dynamical
susceptibility. The discrepancy from Slater model (ice-rule limit) is discussed
in comparison with some experimental data.Comment: 8 pages, 10 figure
NMR characterization of spin-1/2 alternating antiferromagnetic chains in the high-pressure phase of (VO)2P2O7
Local-susceptibility measurements via the NMR shifts of P and V
nuclei in the high-pressure phase of (VO)PO confirmed the
existence of a unique alternating antiferromagnetic chain with a zero-field
spin gap of 34 K. The P nuclear spin-lattice relaxation rate scales with
the uniform spin susceptibility below about 15 K which shows that the
temperature dependence of both the static and dynamical spin susceptibilities
becomes identical at temperatures not far below the spin-gap energy.Comment: 6 pages, 5 figures; To be published in J. Phys. Condens. Matte
Colloids in active fluids: Anomalous micro-rheology and negative drag
We simulate an experiment in which a colloidal probe is pulled through an
active nematic fluid. We find that the drag on the particle is non-Stokesian
(not proportional to its radius). Strikingly, a large enough particle in
contractile fluid (such as an actomyosin gel) can show negative viscous drag in
steady state: the particle moves in the opposite direction to the externally
applied force. We explain this, and the qualitative trends seen in our
simulations, in terms of the disruption of orientational order around the probe
particle and the resulting modifications to the active stress.Comment: 5 pages, 3 figure
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