4,727 research outputs found
Quark-Model Baryon-Baryon Interaction and its Applications to Hypernuclei
The quark-model baryon-baryon interaction fss2, proposed by the Kyoto-Niigata
group, is a unified model for the complete baryon octet (B_8=N, Lambda, Sigma
and Xi), which is formulated in a framework of the (3q)-(3q) resonating-group
method (RGM) using the spin-flavor SU_6 quark-model wave functions and
effective meson-exchange potentials at the quark level. Model parameters are
determined to reproduce properties of the nucleon-nucleon system and the
low-energy cross section data for the hyperon-nucleon scattering. Due to the
several improvements including the introduction of vector-meson exchange
potentials, fss2 has achieved very accurate description of the NN and YN
interactions, comparable to various one-boson exchange potentials. We review
the essential features of fss2 and our previous model FSS, and their
predictions to few-body systems in confrontation with the available
experimental data. Some characteristic features of the B_8 B_8 interactions
with the higher strangeness, S=-2, -3, -4, predicted by fss2 are discussed.
These quark-model interactions are now applied to realistic calculations of
few-body systems in a new three-cluster Faddeev formalism which uses
two-cluster RGM kernels. As for the few-body systems, we discuss the
three-nucleon bound states, the Lambda NN-Sigma NN system for the hypertriton,
the alpha alpha Lambda system for 9Be Lambda, and the Lambda Lambda alpha
system for 6He Lambda Lambda.Comment: 20 pages, 12 figures, 18th Nishinomiya Yukawa Memorial Symposium on
Strangeness in Nuclear Matter, 4 - 5 December 2003, Nishinomiya, Japan. (to
be published in Prog. Theor. Phys. Suppl.
Addendum: Triton and hypertriton binding energies calculated from SU_6 quark-model baryon-baryon interactions
Previously we calculated the binding energies of the triton and hypertriton,
using an SU_6 quark-model interaction derived from a resonating-group method of
two baryon clusters. In contrast to the previous calculations employing the
energy-dependent interaction kernel, we present new results using a
renormalized interaction, which is now energy independent and reserves all the
two-baryon data. The new binding energies are slightly smaller than the
previous values. In particular the triton binding energy turns out to be 8.14
MeV with a charge-dependence correction of the two-nucleon force, 190 keV,
being included. This indicates that about 350 keV is left for the energy which
is to be accounted for by three-body forces.Comment: 4 pages, 1 figur
Three-Cluster Equation Using Two-Cluster RGM Kernel
We propose a new type of three-cluster equation which uses two-cluster
resonating-group-method (RGM) kernels. In this equation, the orthogonality of
the total wave-function to two-cluster Pauli-forbidden states is essential to
eliminate redundant components admixed in the three-cluster systems. The
explicit energy-dependence inherent in the exchange RGM kernel is
self-consistently determined. For bound-state problems, this equation is
straightforwardly transformed to the Faddeev equation which uses a modified
singularity-free T-matrix constructed from the two-cluster RGM kernel. The
approximation of the present three-cluster formalism can be examined with more
complete calculation using the three-cluster RGM. As a simple example, we
discuss three di-neutron (3d') and 3 alpha systems in the harmonic-oscillator
variational calculation. The result of the Faddeev calculation is also
presented for the 3' system.Comment: 12 pages, no figur
Estimation of Precautionary Demand by Financial Anxieties
Pioneering work of modelling financial anxieties was given by Kimura et al (1999) as psychological change of people due to financial shocks. Since they regressed financial position (easy or tight) by nonstationary interest rate, their results exhibit high peaks not only in financial crisis period of 1997 and 1998, but also in the bubble economy period of 1987 to 1989, which seems to be a spurious regression. Furthermore, defining financial anxieties as the conditional variance in TARCH model, one of estimated coefficients did not satisfy sign condition. We got rid of these difficulties by introducing a growth rate model, where a change of financial position (toward ''tight'') under a change of interest rate (toward ''fall'') is regarded as financial anxieties. Such anxieties are quantified by conditional variance of EGARCH model and shown to be stationary. Precautionary demand caused by financial anxieties is estimated in VEC model and it is shown that money adjusted by precautionary demand satisfies a long-run equilibrium relationship in the system (adjusted money, real GDP, interest rate) even in the interval 1980q1 to 2003q2.financial anxieties, precautionary demand, cointegration, EGARCH
The Juelich hyperon-nucleon model revisited
A one-boson-exchange model for the hyperon-nucleon (\Lambda N, \Sigma N)
interaction is presented. The model incorporates the standard one boson
exchanges of the lowest pseudoscalar and vector meson multiplets with coupling
constants fixed by SU(6) flavor symmetry relations. As the main new feature of
the model, the contributions in the scalar--isoscalar (\sigma) and
vector--isovector (\rho) exchange channels are now constrained by a microscopic
model of correlated \pi\pi and K \bar K exchange. Additional short-ranged
ingredients of the model in the scalar--isovector (a_0) and scalar--isospin-1/2
(\kappa) channels are likewise viewed as arising from meson-meson correlations
but are treated phenomenologically. With this model a satisfactory reproduction
of the available hyperon-nucleon data can be achieved.Comment: 24 pages, 13 figures, some modifications to text, several references
added, some figures corrected, to appear in Phys. Rev.
FE analysis on tube hydroforming of small diametr ZM21 magnesium alloy tube
Tube hydroforming (THF) is one of the plasticity processing methods. Tubular parts, for instance automotive components are expanded by forces such as internal pressure and axial compression in order to deform an objective shape. THF has less restriction on shape and size of workpieces owing to adopting the liquid tool. The demand of a small diameter magnesium alloy tubular parts have been increased for applying small medical and electronic devices. In this study, it was investigated that influence of process conditions such as processing temperature, internal pressure and axial feeding amount on formability of small diameter ZM21 magnesium alloy tube with outer diameter of 2.0mm and thickness of 0.20mm. Furthermore, the processing conditions for improving the formability of material in THF were examined. For prior evaluation of deformation characteristics in the warm THF of small diameter ZM21 magnesium alloy tube, a finite element (FE) simulation was conducted. The FE method (FEM) code was used LS-DYNA 3D for analysis of the FE model of the tube and the dies. The material characteristics were obtained by tensile test and fracture test. From FE analysis results, it was elucidated that effect of the processing temperature, the variable internal pressure and the axial feeding amount on deformation behavior. The formability of ZM21 magnesium alloy tube was improved by processing at 250 C. The difference of deformation characteristic between FE results and experimental results was compared. As the results, the processing condition which could improve the formability of ZM21 tube was clarified using this FE model. The effect of adding the straightening stage in the loading path after the preform on formability was investigated. The thinning of the wall thickness of the tube was inhibited by calibration after the axial feeding
Field-induced staggered magnetic moment in the quasi-two-dimensional organic Mott insulator -(BEDT-TTF)Cu[N(CN)]Cl
We investigated the magnetism under a magnetic field in the
quasi-two-dimensional organic Mott insulator
-(BEDT-TTF)Cu[N(CN)]Cl through magnetization and
C-NMR measurements. We found that in the nominally paramagnetic phase
(i.e., above N\'eel temperature) the field-induced local moments have a
staggered component perpendicular to the applied field. As a result, the
antiferromagnetic transition well defined at a zero field becomes crossover
under a finite field. This unconventional behavior is qualitatively reproduced
by the molecular-field calculation for Hamiltonian including the exchange,
Dzyaloshinsky-Moriya (DM), and Zeeman interactions. This calculation also
explains other unconventional magnetic features in
-(BEDT-TTF)Cu[N(CN)]Cl reported in the literature. The
present results highlight the importance of the DM interaction in field-induced
magnetism in a nominally paramagnetic phase, especially in low-dimensional spin
systems.Comment: 11 pages, 12 figures, selected for Editors' Suggestion
Emergence of inhomogeneous moments from spin liquid in the triangular-lattice Mott insulator -(ET)Cu(CN)
The static and dynamic local spin susceptibility of the organic Mott
insulator -(ET)Cu(CN), a model material of the spin- 1/2
triangular lattice, is studied by C NMR spectroscopy from room
temperature down to 20 mK. We observe an anomalous field-dependent spectral
broadening with the continuous and bipolar shift distribution, appearing
without the critical spin fluctuations. It is attributable to spatially
nonuniform magnetizations induced in the spin liquid under magnetic fields. The
amplitude of the magnetization levels off below 1 K, while the low-lying spin
fluctuations survive toward the ground state, as indicated by the temperature
profile of the relaxation rates.Comment: 4 pages, 4 figure
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