20,320 research outputs found
Boundary integral equation methods for the elastic and thermoelastic waves in three dimensions
In this paper, we consider the boundary integral equation (BIE) method for
solving the exterior Neumann boundary value problems of elastic and
thermoelastic waves in three dimensions based on the Fredholm integral
equations of the first kind. The innovative contribution of this work lies in
the proposal of the new regularized formulations for the hyper-singular
boundary integral operators (BIO) associated with the time-harmonic elastic and
thermoelastic wave equations. With the help of the new regularized
formulations, we only need to compute the integrals with weak singularities at
most in the corresponding variational forms of the boundary integral equations.
The accuracy of the regularized formulations is demonstrated through numerical
examples using the Galerkin boundary element method (BEM).Comment: 24 pages, 6 figure
Cooperative order and excitation spectra in the bicomponent spin networks
A ferrimagnetic spin model composed of spin-dimers and
spin-chains is studied by combining the bond-operator representation (for
spin-dimers) and Holstein-Primakoff transformation (for spins).
A finite interaction between the spin-dimer and the spin chain
makes the spin chains ordered antiferromagnetically and the spin dimers
polarized. The effective interaction between the spin chains, mediated by the
spin dimers, is calculated up to the third order. The staggered magnetization
in the spin dimer is shown proportional to . It presents an
effective staggered field reacting on the spin chains. The degeneracy of the
triplons is lifted due to the chain magnetization and a mode with longitudinal
polarization is identified. Due to the triplon-magnon interaction, the
hybridized triplon-like excitations show different behaviors near the vanishing
. On the other hand, the hybridized magnon-like excitations open a
gap . These results consist well with the experiments
on CuFeGeO.Comment: 7 pages, 5 figure
Relationship between the symmetry energy and the single-nucleon potential in isospin-asymmetric nucleonic matter
In this contribution, we review the most important physics presented
originally in our recent publications. Some new analyses, insights and
perspectives are also provided. We showed recently that the symmetry energy
and its density slope at an arbitrary density
can be expressed analytically in terms of the magnitude and momentum dependence
of the single-nucleon potentials using the Hugenholtz-Van Hove (HVH) theorem.
These relationships provide new insights about the fundamental physics
governing the density dependence of nuclear symmetry energy. Using the isospin
and momentum (k) dependent MDI interaction as an example, the contribution of
different terms in the single-nucleon potential to the and
are analyzed in detail at different densities. It is shown that the
behavior of is mainly determined by the first-order symmetry
potential of the single-nucleon potential. The density
slope depends not only on the first-order symmetry potential
but also the second-order one . Both the
and at normal density are
constrained by the isospin and momentum dependent nucleon optical potential
extracted from the available nucleon-nucleus scattering data. The
especially at high density and momentum affects
significantly the , but it is theoretically poorly understood and
currently there is almost no experimental constraints known.Comment: 9 pages, 6 figures, Review paper, Contribution to the "Topical Issue"
on "Nuclear Symmetry Energy" in European Physical Journal
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