14,752 research outputs found
Equivalent hyperon-nucleon interactions in low-momentum space
Equivalent interactions in a low-momentum space for the , and interactions are calculated, using the SU quark model
potential as well as the Nijmegen OBEP model as the input bare interaction.
Because the two-body scattering data has not been accumulated sufficiently to
determine the hyperon-nucleon interactions unambiguously, the construction of
the potential even in low-energy regions has to rely on a theoretical model.
The equivalent interaction after removing high-momentum components is still
model dependent. Because this model dependence reflects the character of the
underlying potential model, it is instructive for better understanding of
baryon-baryon interactions in the strangeness sector to study the low-momentum
space interactions.Comment: 9 pages, 13 figures, accepted for publication in Phys. Rev.
He energies and radii by the coupled-cluster method with many-body average potential
The reformulated coupled-cluster method (CCM), in which average many-body
potentials are introduced, provides a useful framework to organize numerous
terms appearing in CCM equations, which enables us to clarify the structure of
the CCM theory and physical importance of various terms more easily. We
explicitly apply this framework to He, retaining one-body and two-body
correlations as the first illustrating attempt. Numerical results with using
two modern nucleon-nucleon interactions (AV18 and CD-Bonn) and their
low-momentum interactions are presented. The characters of short-range and
many-body correlations are discussed. Although not considered explicitly, the
expression of the ground-state energy in the presence of a three-nucleon force
is given.Comment: 12 pages, 11 figures, accepted for publication in PR
Three-Body-Cluster Effects on Lambda Single-Particle Energies in _{Lambda}^{17}O and_{Lambda}^{41}Ca
A method for a microscopic description of Lambda hypernuclei is formulated in
the framework of the unitary-model-operator approach. A unitarily transformed
hamiltonian is introduced and given in a cluster expansion form. The structure
of three-body-cluster terms are discussed especially on the Lambda
single-particle energy. The Lambda single-particle energies including the
three-body-cluster contributions are calculated for the 0s_{1/2}, 0p_{3/2} and
0p_{1/2} states in_{Lambda}^{17}O, and for the 0s_{1/2}, 0p_{3/2}, 0p_{1/2},
0d_{5/2}, 0d_{3/2} and 1s_{1/2} states in_{Lambda}^{41}Ca, using the Nijmegen
soft-core (NSC), NSC97a-f, the Juelich A (J A) and J B hyperon-nucleon
interactions. It is indicated that the three-body-cluster terms bring about
sizable effects in the magnitudes of the Lambda single-particle energies, but
hardly affect the Lambda spin-orbit splittings.Comment: LaTeX 19 pages including 7 figures, ptptex.sty is use
Shell structures in oxygen isotopes described with modern nucleon-nucleon interactions
Shell structures in the N\simeq Z nucleus ^{17}O and the neutron-rich oxygen
isotopes ^{23}O and ^{25}O are microscopically described by calculating
single-particle energies with modern nucleon-nucleon interactions within the
framework of the unitary-model-operator approach. It is found that the effect
of three-body cluster terms on the single-particle energy is more important in
^{23}O and ^{25}O than ^{17}O.Comment: 5 pages, 1 figure, Talk at the International Symposium on "A New Era
of Nuclear Structure Physics (NENS03)", 19-22 Nov. 2003, Niigata, Japa
Charge-dependent calculations of single-particle energies in nuclei around ^{16}O with modern nucleon-nucleon interactions
The binding energies of the ground states and several excited states related
to single-particle and -hole states in nuclei around ^{16}O are calculated
taking charge dependence into account. Effective interactions on the particle
basis are constructed from modern charge-dependent nucleon-nucleon interactions
and the Coulomb force within the framework of the unitary-model-operator
approach. Single-particle (-hole) energies are obtained from the energy
differences of the binding energies between a particle (hole) state in ^{17}O
or ^{17}F (^{15}N or ^{15}O) and the ground state of ^{16}O. The resultant
spin-orbit splittings are small for the hole state and large for the particle
state in comparison with the experimental values though the differences between
the experimental and calculated values are not very large. The charge
dependence of the calculated single-particle energies for the ground states are
in good agreement with the experimental values. Furthermore, the Thomas-Ehrman
shift due to the Coulomb force for the 1s_{1/2} states in ^{17}O and ^{17}F can
be observed.Comment: 14 pages, 12 figures, submitted to Phys. Rev.
Ground-state and single-particle energies of nuclei around ^{16}O, ^{40}Ca, and ^{56}Ni from realistic nucleon-nucleon forces
We perform ab initio calculations for nuclei around ^{16}O, ^{40}Ca, and
^{56}Ni using realistic nucleon-nucleon forces. In particular, ^{56}Ni is
computed as the heaviest nucleus in this kind of ab initio calculation.
Ground-state and single-particle energies including three-body-cluster effects
are obtained within the framework of the unitary-model-operator approach. It is
shown that the CD-Bonn nucleon-nucleon potential gives quite good results close
to the experimental values for all nuclei in the present work.Comment: 4 pages, 4 figures; accepted for publication in Physical Review
Letter
Irregular conformal blocks, with an application to the fifth and fourth Painlev\'e equations
We develop the theory of irregular conformal blocks of the Virasoro algebra.
In previous studies, expansions of irregular conformal blocks at regular
singular points were obtained as degeneration limits of regular conformal
blocks; however, such expansions at irregular singular points were not clearly
understood. This is because precise definitions of irregular vertex operators
had not been provided previously. In this paper, we present precise definitions
of irregular vertex operators of two types and we prove that one of our vertex
operators exists uniquely. Then, we define irregular conformal blocks with at
most two irregular singular points as expectation values of given irregular
vertex operators. Our definitions provide an understanding of expansions of
irregular conformal blocks and enable us to obtain expansions at irregular
singular points.
As an application, we propose conjectural formulas of series expansions of
the tau functions of the fifth and fourth Painlev\'e equations, using
expansions of irregular conformal blocks at an irregular singular point.Comment: 26 page
A generalization of determinant formulas for the solutions of Painlev\'e II and XXXIV equations
A generalization of determinant formulas for the classical solutions of
Painlev\'e XXXIV and Painlev\'e II equations are constructed using the
technique of Darboux transformation and Hirota's bilinear formalism. It is
shown that the solutions admit determinant formulas even for the transcendental
case.Comment: 20 pages, LaTeX 2.09(IOP style), submitted to J. Phys.
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