8,589 research outputs found
Nuclear G-Matrix Elements from Nonlocal Potentials
We study effects of nonlocality in the nuclear force on the G-matrix elements
for finite nuclei. Nuclear G-matrix elements for \O16 are calculated in the
harmonic oscillator basis from a nonlocal potential which models quark exchange
effects between two nucleons. We employ a simple form of potential that gives
the same phase shifts as a realistic local nucleon potential. The G-matrix
elements calculated from the nonlocal potential show moderate increase in
repulsion from those derived from the local potential.Comment: 11 page, LaTeX, 2 PS figures, uses epsf.st
Negative Parity Baryons in the QCD Sum Rule
Masses and couplings of the negative parity excited baryons are studied in
the QCD sum rule. Separation of the negative-parity spectrum is proposed and is
applied to the flavor octet and singlet baryons. We find that the quark
condensate is responsible for the mass splitting of the ground and the
negative-parity excited states. This is expected from the chiral symmetry and
supports the idea that the negative-parity baryon forms a parity doublet with
the ground state. The meson-baryon coupling constants are also computed for the
excited states in the QCD sum rule. It is found that the \pi NN^* coupling
vanishes in the chiral limit.Comment: 13pp, LaTeX, 1 EPS figure, uses epsf.sty, Talk given by M.O. at
CEBAF/INT workshop "N* physics", Seattle, September (1996), to appear in the
proceeding
Determination of the axial coupling constant in the linear representations of chiral symmetry
If a baryon field belongs to a certain linear representation of chiral
symmetry of , the axial coupling constant can be
determined algebraically from the commutation relations derived from the
superconvergence property of pion-nucleon scattering amplitudes. This
establishes an algebraic explanation for the values of of such as the
non-relativistic quark model, large- limit and the mirror assignment for
two chiral partner nucleons. For the mirror assignment, the axial charges of
the positive and negative parity nucleons have opposite signs. Experiments of
eta and pion productions are proposed in which the sign difference of the axial
charges can be observed.Comment: 7 pages, proceedings for EMI int. conf. at RCNP, Dec. 200
Chiral symmetry aspects of positive and negative parity baryons
Chiral symmetry aspects for baryon properties are studied. After a brief
discussion on general framework, we introduce two distinctive chiral group
representations for baryons: the naive and mirror assignments. Using linear
sigma models, nucleon properties are studied in both representations. Finally,
we propose an experiment to distinguish the two assignments in the reactions of
pion and eta productions.Comment: PTPTeX 12 pages, Proceedings for the YITP-RCNP workshop Chiral
Restoration in Nuclear Medium, Kyoto, October 200
A Large-scale CO Imaging of the Galactic Center. II. Dynamical Properties of Molecular Clouds
The data from the Nobeyama Radio Observatory 45 m telescope Galactic Center
CO survey have been analyzed to generate a compilation of molecular clouds with
intense CO emission in this region. Clouds are identified in an automated
manner throughout the main part of the survey data for all CO emission peaks
exceeding 10 K (). Correlations between the size, velocity dispersion,
virial mass, and the CO luminosity, for the molecular clouds in the Galactic
center were shown. We diagnosed gravitational stabilities of identified clouds
assuming that the disk clouds are nearly at the onset of gravitational
instability. Most of the clouds and cloud complexes in the Galactic center are
gravitationally stable, while some clouds with intense CO emission are
gravitationally unstable.Comment: 4 pages, 4 figures, to appear in the Proceedings of the 32nd COSPAR
Scientific Assembl
Relation between the separable and one-boson-exchange potential for the covariant Bethe-Salpeter equation
We investigate the relation between the rank I separable potential for the
covariant Bethe-Salpeter equation and the one-boson-exchange potential. After
several trials of the parameter choices, it turns out that it is not always
possible to reproduce the phase-shifts calculated from a single term of the
one-boson-exchange potential especially of the -exchange term,
separately by the rank I separable potential. Instead, it is shown that the
separable potential is useful to parameterize the total nucleon-nucleon
interaction.Comment: 10 pages, 8 figures, to appear in J.Phys.
Interfaces of correlated electron systems: Proposed mechanism for colossal electroresistance
Mott's metal-insulator transition at an interface due to band bending is
studied by the density matrix renormalization group (DMRG). We show that the
result can be recovered by a simple modification of the conventional Poisson's
equation approach used in semi-conductor heterojunctions. A novel mechanism of
colossal electroresistance is proposed, which incorporates the hysteretic
behavior of the transition in higher dimensions.Comment: 5 pages, 3 figures, title change
Quantum description for a chiral condensate disoriented in a certain direction in isospace
We derive a quantum state of the disoriented chiral condensate dynamically,
considering small quantum fluctuations around a classical chiral condensate
disoriented in a certain direction in isospace. The obtained
nonisosinglet quantum state has the characteristic features; (i) it has the
form of the squeezed state, (ii) the state contains not only the component of
pion quanta in the direction but also the component in the
perpendicular direction to and (iii) the low momentum pions in the
state violate the isospin symmetry. With the quantum state, we calculate the
probability of the neutral fraction depending on the time and the pion's
momentum, and find that the probability has an unfamiliar form. For the low
momentum pions, the parametric resonance mechanism works with the result that
the probability of the neutral fraction becomes the well known form
approximately and that the charge fluctuation is small.Comment: 19 page
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