628 research outputs found
Extended Optical Model Analyses of Elastic Scattering and Fusion Cross Section Data for the C+Pb System at Near-Coulomb-Barrier Energies by using a Folding Potential
Simultaneous analyses are performed for elastic scattering and
fusion cross section data for the C+Pb system at
near-Coulomb-barrier energies by using the extended optical model approach in
which the polarization potential is decomposed into direct reaction (DR) and
fusion parts. Use is made of the double folding potential as a bare potential.
It is found that the experimental elastic scattering and fusion data are well
reproduced without introducing any normalization factor for the double folding
potential and also that both DR and fusion parts of the polarization potential
determined from the analyses satisfy separately the dispersion
relation. Furthermore, it is shown that the imaginary parts of both DR and
fusion potentials at the strong absorption radius change very rapidly, which
results in a typical threshold anomaly in the total imaginary potential as
observed with tightly bound projectiles such as -particle and O.Comment: 26 pages, 7 figures, submitted to Physical Review
Semi-classical Characters and Optical Model Description of Heavy Ion Scattering, Direct Reactions, and Fusion at Near-barrier Energies
An approach is proposed to calculate the direct reaction (DR) and fusion
probabilities for heavy ion collisions at near-Coulomb-barrier energies as
functions of the distance of closest approach D within the framework of the
optical model that introduces two types of imaginary potentials, DR and fusion.
The probabilities are calculated by using partial DR and fusion cross sections,
together with the classical relations associated with the Coulomb trajectory.
Such an approach makes it possible to analyze the data for angular
distributions of the inclusive DR cross section, facilitating the determination
of the radius parameters of the imaginary DR potential in a less ambiguous
manner. Simultaneous -analyses are performed of relevant data for the
O+Pb system near the Coulomb-barrier energy
Thermal conductivity of quantum magnetic monopoles in the frustrated pyrochlore Yb2Ti2O7
We report low-temperature thermal conductivity of pyrochlore
YbTiO, which contains frustrated spin-ice correlations with
significant quantum fluctuations. In the disordered spin-liquid regime,
exhibits a nonmonotonic magnetic field dependence, which is well
explained by the strong spin-phonon scattering and quantum monopole
excitations. We show that the excitation energy of quantum monopoles is
strongly suppressed from that of dispersionless classical monopoles. Moreover,
in stark contrast to the diffusive classical monopoles, the quantum monopoles
have a very long mean free path. We infer that the quantum monopole is a novel
heavy particle, presumably boson, which is highly mobile in a three-dimensional
spin liquid.Comment: 8 pages, 9 figure
Cluster dynamical mean-field study of the Hubbard model on a 3D frustrated hyperkagome lattice
We study the Hubbard model on a geometrically-frustrated hyperkagome lattice
by a cluster extension of the dynamical mean field theory. We calculate the
temperature () dependences of the specific heat () and the spin-lattice
relaxation time () in correlated metallic region. shows a peak at
and rapidly decreases as . On the other hand, has a
peak at a higher temperature than , and largely decreases
below , followed by the Korringa law as . Both
peak temperatures are suppressed and the peaks become sharper as electron
correlation is increased. These behaviors originate from strong renormalization
of the energy scales in the peculiar electronic structure in this frustrated
system; a pseudo-gap like feature, the van-Hove singularity, and the flat band.
The results are discussed in comparison with the experimental data in the
hyperkagome material, NaIrO.Comment: 4 pages, 4 figures, Conference proceedings for Highly Frustrated
Magnetism 200
Extended Optical Model Analyses of Elastic Scattering and Fusion Cross Section Data for the 7Li+208Pb System at Near-Coulomb-Barrier Energies using the Folding Potential
Simultaneous analyses previously made for elastic scattering and
fusion cross section data for the Li+Pb system is extended to the
Li+Pb system at near-Coulomb-barrier energies based on the
extended optical model approach, in which the polarization potential is
decomposed into direct reaction (DR) and fusion parts. Use is made of the
double folding potential as a bare potential. It is found that the experimental
elastic scattering and fusion data are well reproduced without introducing any
normalization factor for the double folding potential and that both the DR and
fusion parts of the polarization potential determined from the
analyses satisfy separately the dispersion relation. Further, we find that the
real part of the fusion portion of the polarization potential is attractive
while that of the DR part is repulsive except at energies far below the Coulomb
barrier energy. A comparison is made of the present results with those obtained
from the Continuum Discretized Coupled Channel (CDCC) calculations and a
previous study based on the conventional optical model with a double folding
potential. We also compare the present results for the Li+Pb system
with the analysis previously made for the Li+Pb system.Comment: 7 figures, submitted to PR
A Novel Method for the Solution of the Schroedinger Eq. in the Presence of Exchange Terms
In the Hartree-Fock approximation the Pauli exclusion principle leads to a
Schroedinger Eq. of an integro-differential form. We describe a new spectral
noniterative method (S-IEM), previously developed for solving the
Lippman-Schwinger integral equation with local potentials, which has now been
extended so as to include the exchange nonlocality. We apply it to the
restricted case of electron-Hydrogen scattering in which the bound electron
remains in the ground state and the incident electron has zero angular
momentum, and we compare the acuracy and economy of the new method to three
other methods. One is a non-iterative solution (NIEM) of the integral equation
as described by Sams and Kouri in 1969. Another is an iterative method
introduced by Kim and Udagawa in 1990 for nuclear physics applications, which
makes an expansion of the solution into an especially favorable basis obtained
by a method of moments. The third one is based on the Singular Value
Decomposition of the exchange term followed by iterations over the remainder.
The S-IEM method turns out to be more accurate by many orders of magnitude than
any of the other three methods described above for the same number of mesh
points.Comment: 29 pages, 4 figures, submitted to Phys. Rev.
Extended Optical Model Analyses of Elastic Scattering and Fusion Cross Sections for 6Li + 208Pb System at Near-Coulomb-Barrier Energies by using Folding Potential
Based on the extended optical model approach in which the polarization
potential is decomposed into direct reaction (DR) and fusion parts,
simultaneous analyses are performed for elastic scattering and
fusion cross section data for the Li+Pb system at
near-Coulomb-barrier energies. A folding potential is used as the bare
potential. It is found that the real part of the resultant DR part of the
polarization potential is repulsive, which is consistent with the results from
the Continuum Discretized Coupled Channel (CDCC) calculations and the
normalization factors needed for the folding potentials. Further, it is found
that both DR and fusion parts of the polarization potential satisfy separately
the dispersion relation.Comment: 6 figure
Lattice dynamics and electron-phonon coupling in Sr2RuO4
The lattice dynamics in SrRuO has been studied by inelastic neutron
scattering combined with shell-model calculations. The in-plane bond-stretching
modes in SrRuO exhibit a normal dispersion in contrast to all
electronically doped perovskites studied so far. Evidence for strong electron
phonon coupling is found for c-polarized phonons suggesting a close connection
with the anomalous c-axis charge transport in SrRuO.Comment: 11 pages, 8 figures 2 table
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