332 research outputs found
New effective nuclear forces with a finite-range three-body term and their application to AMD+GCM calculations
We propose new effective inter-nucleon forces with a finite-range three-body
operator. The proposed forces are suitable for describing the nuclear structure
properties over a wide mass number region, including the saturation point of
nuclear matter. The forces are applied to microscopic calculations of
() nuclei and O isotopes with a method of antisymmetrized molecular
dynamics. We present the characteristics of the forces and discuss the
importance of the finite-range three-body term.Comment: 15 pages, 11 figures, submitted to Phys.Rev.
Structure of Excited States of 10Be studied with Antisymmetrized Molecular Dynamics
We study structure of excited states of 10Be with the method of variation
after spin parity projection in the framework of antisymmetrized molecular
dynamics. Present calculations describe many excited states and reproduce the
experimental data of E2 and E1 transitions and the new data of the
transition strength successfully. We make systematic discussions on the
molecule-like structures of light unstable nuclei and the important role of the
valence neutrons based on the results obtained with the framework which is free
from such model assumptions as the existence of inert cores and clusters.Comment: 15 pages, RevTex, seven postscript figures (using epsf.sty
Deformations in N=14 isotones
Systematic analysis of deformations in neutron-rich N=14 isotones was done
based on the method of antisymmetrized molecular dynamics. The property of the
shape coexistence in Si, which is known to have the oblate ground state
and the prolate excited states, was successfully described. The results suggest
that the shape coexistence may occur also in neutron-rich N=14 nuclei as well
as Si. It was found that the oblate neutron shapes are favored because
of the spin-orbit force in most of N=14 isotones. moments and
transition strengths in the neutron-rich nuclei were discussed in relation to
the intrinsic deformations, and a possible difference between the proton and
neutron deformations in Ne was proposed.Comment: 13 pages, 7 figures, sumitted to Phys.Rev.
Structure of excited states of Be-11 studied with Antisymmetrized Molecular Dynamics
The structures of the ground and excited states of Be-11 were studied with a
microscopic method of antisymmetrized molecular dynamics. The theoretical
results reproduce the abnormal parity of the ground state and predict various
kinds of excited states. We suggest a new negative-parity band with a
well-developed clustering structure which reaches high-spin states. Focusing on
a clustering structure, we investigated structure of the ground and
excited states. We point out that molecular orbits play important roles for the
intruder ground state and the low-lying states. The features of
the breaking of clusters were also studied with the help of data for
Gamow-Teller transitions.Comment: 24 pages, 7 figures, to be submitted to Phys.Rev.
Cluster structures in Oxygen isotopes
Cluster structure of 16O,18O and 20O is investigated by the antisymmettrized
molecular dynamics (AMD) plus generator coordinate method (GCM). We have found
the K^{\pi}=0 and 0 rotational bands of 18O that have the prominent
14C+\alpha cluster structure. Clustering systematics becomes richer in 20O. We
suggest the K^{\pi}=0 band that is the mixture of the 12C+\alpha+4n and
14C+6He cluster structures, and the K^{\pi}=0 band that has the 14C+6He
cluster structure. The K^{\pi}=0 and 0 bands that have the
prominent 16C+\alpha cluster structure are also found.Comment: 9pages, 9figure
Hadron-hadron interaction from SU(2) lattice QCD
We evaluate interhadron interactions in two-color lattice QCD from
Bethe-Salpeter amplitudes on the Euclidean lattice. The simulations are
performed in quenched SU(2) QCD with the plaquette gauge action at and the Wilson quark action. We concentrate on S-wave scattering states
of two scalar diquarks. Evaluating different flavor combinations with various
quark masses, we try to find out the ingredients in hadronic interactions.
Between two scalar diquarks (, the lightest baryon in SU(2)
system), we observe repulsion in short-range region, even though present quark
masses are not very light. We define and evaluate the "quark-exchange part" in
the interaction, which is induced by adding quark-exchange diagrams, or
equivalently, by introducing Pauli blocking among some of quarks. The repulsive
force in short-distance region arises only from the "quark-exchange part", and
disappears when quark-exchange diagrams are omitted. We find that the strength
of repulsion grows in light quark-mass regime and its quark-mass dependence is
similar to or slightly stronger than that of the color-magnetic interaction by
one-gluon-exchange (OGE) processes. It is qualitatively consistent with the
constituent-quark model picture that a color-magnetic interaction among quarks
is the origin of repulsion. We also find a universal long-range attractive
force, which enters in any flavor channels of two scalar diquarks and whose
interaction range and strength are quark-mass independent. The weak quark-mass
dependence of interaction ranges in each component implies that meson-exchange
contributions are small and subdominant, and the other contributions, {\it ex.}
flavor exchange processes, color-Coulomb or color-magnetic interactions, are
considered to be predominant, in the quark-mass range we evaluated.Comment: 14 pages, 20 figure
cluster structure in B
The cluster structures of the excited states in B are studied by
analyzing the isoscalar monopole and quadrupole strengths in the
B(,) reaction at MeV. The excitation strengths are
compared with the predictions by the shell-model and antisymmetrized
molecular-dynamics (AMD) calculations. It is found that the large monopole
strength for the state at MeV is well described by the AMD
calculation and is an evidence for a developed cluster structure.Comment: Revised according to the referees' comment
Important role of the spin-orbit interaction in forming the 1/2^+ orbital structure in Be isotopes
The structure of the second 0^+ state of ^{10}Be is investigated using a
microscopic model based on the molecular-orbit (MO) model.
The second 0^+ state, which has dominantly the (1/2^+)^2 configuration, is
shown to have a particularly enlarged structure. The kinetic
energy of the two valence neutrons occupying along the axis is
reduced remarkably due to the strong clustering and, simultaneously,
the spin-orbit interaction unexpectedly plays important role to make the energy
of this state much lower. The mixing of states with different spin structure is
shown to be important in negative-parity states. The experimentally observed
small-level spacing between 1^- and 2^- (~ 300 keV) is found to be an evidence
of this spin-mixing effect. ^{12}{Be} is also investigated using
model, in which four valence neutrons are considered to
occupy the (3/2^-)^2(1/2^+)^2 configuration. The energy surface of ^{12}Be is
shown to exhibit similar characteristics, that the remarkable
clustering and the contribution of the spin-orbit interaction make the binding
of the state with (3/2^-)^2(1/2^+)^2 configuration properly stronger in
comparison with the closed p-shell (3/2^-)^2(1/2^-)^2 configuration.Comment: 14 pages, 4 figure
Triaxial deformation in 10Be
The triaxial deformation in Be is investigated using a microscopic
model. The states of two valence neutrons are classified
based on the molecular-orbit (MO) model, and the -orbit is introduced
about the axis connecting the two -clusters for the description of the
rotational bands. There appear two rotational bands comprised mainly of and , respectively, at low excitation energy, where the two
valence neutrons occupy or orbits. The
triaxiality and the -mixing are discussed in connection to the molecular
structure, particularly, to the spin-orbit splitting. The extent of the
triaxial deformation is evaluated in terms of the electro-magnetic transition
matrix elements (Davydov-Filippov model, Q-invariant model), and density
distribution in the intrinsic frame. The obtained values turned out to be
.Comment: 15 pages, latex, 3 figure
Existence of a phase transition under finite magnetic field in the long-range RKKY Ising spin glass DyYRuSi
A phase transition of a model compound of the long-range Ising spin glass
(SG) DyYRuSi, where spins interact via the RKKY
interaction, has been investigated. The static and the dynamic scaling analyses
reveal that the SG phase transition in the model magnet belongs to the
mean-field universality class. Moreover, the characteristic relaxation time in
finite magnetic fields exhibits a critical divergent behavior as well as in
zero field, indicating a stability of the SG phase in finite fields. The
presence of the SG phase transition in field in the model magnet strongly
syggests that the replica symmetry is broken in the long-range Ising SG.Comment: 4 pages, 4 figures, to be published in JPSJ (2010
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