41,245 research outputs found
Many-body dynamics of a Bose system with attractive interactions on a ring
We investigate the many-body dynamics of an effectively attractive
one-dimensional Bose system confined in a toroidal trap. The mean-field theory
predicts that a bright-soliton state will be formed when increasing the
interparticle interaction over a critical point. The study of quantum many-body
dynamics in this paper reveals that there is a modulation instability in a
finite Bose system correspondingly. We show that Shannon entropy becomes
irregular near and above the critical point due to quantum correlations. We
also study the dynamical behavior of the instability by exploring the momentum
distribution and the fringe visibility, which can be verified experimentally by
releasing the trapComment: 6 pages,5 figure
Planet formation in highly inclined binaries
We explore planet formation in binary systems around the central star where
the protoplanetary disk plane is highly inclined with respect to the companion
star orbit. This might be the most frequent scenario for binary separations
larger than 40 AU, according to Hale (1994). We focus on planetesimal accretion
and compute average impact velocities in the habitable region and up to 6 AU
from the primary.Comment: Accepted for publication on A&
Exploring the origins of the Dzyalloshinski-Moria interaction in MnSi
By using magnetization and small-angle neutron scattering (SANS)
measurements, we have investigated the magnetic behavior of Mn_{1-x}Ir_{x}Si
system to explore the effect of increased carrier density and spin-orbit
interaction on the magnetic properties of MnSi. We determine estimates of the
spin wave stiffness and the Dzyalloshinski-Moria, DM, interaction strength and
compare with Mn_{1-x}Co_{x}Si and Mn_{1-x}Fe_{x}Si. Despite the large
differences in atomic mass and size of the substituted elements,
Mn_{1-x}Co_{x}Si and Mn_{1-x}Ir_{x}Si show nearly identical variations in their
magnetic properties with substitution. We find a systematic dependence of the
transition temperature, the ordered moment, the helix period and the DM
interaction strength with electron count for Mn{1-x}Ir{x}Si, Mn_{1-x}Co_{x}Si,
and Mn_{1-x}Fe_{x}Si indicating that the magnetic behavior is primarily
dependent upon the additional carrier density rather than on the mass or size
of the substituting species. This indicates that the variation in magnetic
properties, including the DM interaction strength, are primarily controlled by
the electronic structure as Co and Ir are isovalent. Our work suggests that
although the rigid band model of electronic structure along with Moira's model
of weak itinerant magnetism describe this system surprisingly well,
phenomenological models for the DM interaction strength are not adequate to
describe this system.Comment: 17 pages, 7 Figure
Algebraic-matrix calculation of vibrational levels of triatomic molecules
We introduce an accurate and efficient algebraic technique for the
computation of the vibrational spectra of triatomic molecules, of both linear
and bent equilibrium geometry. The full three-dimensional potential energy
surface (PES), which can be based on entirely {\it ab initio} data, is
parameterized as a product Morse-cosine expansion, expressed in bond-angle
internal coordinates, and includes explicit interactions among the local modes.
We describe the stretching degrees of freedom in the framework of a Morse-type
expansion on a suitable algebraic basis, which provides exact analytical
expressions for the elements of a sparse Hamiltonian matrix. Likewise, we use a
cosine power expansion on a spherical harmonics basis for the bending degree of
freedom. The resulting matrix representation in the product space is very
sparse and vibrational levels and eigenfunctions can be obtained by efficient
diagonalization techniques. We apply this method to carbonyl sulfide OCS,
hydrogen cyanide HCN, water HO, and nitrogen dioxide NO. When we base
our calculations on high-quality PESs tuned to the experimental data, the
computed spectra are in very good agreement with the observed band origins.Comment: 11 pages, 2 figures, containg additional supporting information in
epaps.ps (results in tables, which are useful but not too important for the
paper
Scalable Parallel Numerical CSP Solver
We present a parallel solver for numerical constraint satisfaction problems
(NCSPs) that can scale on a number of cores. Our proposed method runs worker
solvers on the available cores and simultaneously the workers cooperate for the
search space distribution and balancing. In the experiments, we attained up to
119-fold speedup using 256 cores of a parallel computer.Comment: The final publication is available at Springe
Higher-order conservative interpolation between control-volume meshes: Application to advection and multiphase flow problems with dynamic mesh adaptivity
© 2016 .A general, higher-order, conservative and bounded interpolation for the dynamic and adaptive meshing of control-volume fields dual to continuous and discontinuous finite element representations is presented. Existing techniques such as node-wise interpolation are not conservative and do not readily generalise to discontinuous fields, whilst conservative methods such as Grandy interpolation are often too diffusive. The new method uses control-volume Galerkin projection to interpolate between control-volume fields. Bounded solutions are ensured by using a post-interpolation diffusive correction. Example applications of the method to interface capturing during advection and also to the modelling of multiphase porous media flow are presented to demonstrate the generality and robustness of the approach
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