1,885 research outputs found
Lowest eigenvalue of the nuclear shell model Hamiltonian
In this paper we investigate regular patterns of matrix elements of the
nuclear shell model Hamiltonian , by sorting the diagonal matrix elements
from the smaller to larger values. By using simple plots of non-zero matrix
elements and lowest eigenvalues of artificially constructed "sub-matrices"
of , we propose a new and simple formula which predicts the lowest
eigenvalue with remarkable precisions.Comment: six pages, four figures, Physical Review C, in pres
SU(3) realization of the rigid asymmetric rotor within the IBM
It is shown that the spectrum of the asymmetric rotor can be realized quantum
mechanically in terms of a system of interacting bosons. This is achieved in
the SU(3) limit of the interacting boson model by considering higher-order
interactions between the bosons. The spectrum corresponds to that of a rigid
asymmetric rotor in the limit of infinite boson number.Comment: 9 pages, 2 figures, LaTeX, epsfi
Ground state magnetic dipole moment of 35K
The ground state magnetic moment of 35K has been measured using the technique
of nuclear magnetic resonance on beta-emitting nuclei. The short-lived 35K
nuclei were produced following the reaction of a 36Ar primary beam of energy
150 MeV/nucleon incident on a Be target. The spin polarization of the 35K
nuclei produced at 2 degrees relative to the normal primary beam axis was
confirmed. Together with the mirror nucleus 35S, the measurement represents the
heaviest T = 3/2 mirror pair for which the spin expectation value has been
obtained. A linear behavior of gp vs. gn has been demonstrated for the T = 3/2
known mirror moments and the slope and intercept are consistent with the
previous analysis of T = 1/2 mirror pairs.Comment: 14 pages, 5 figure
Coherent Pair State of Pion in Constituent Quark Model
A coherent state of pions is introduced to the nonrelativistic quark model.
The coherent pair approximation is employed for the pion field in order to
maintain the spin-isospin symmetry. In this approximation the pion is localized
in the momentum space, and the vertex form factor in the pion-quark interaction
is derived from this localization. The nucleon masses and wave functions are
calculated using this model, and our results are compared to those of the quark
model with the one pion exchange potential. Similar result is obtained for the
mass spectrum, but there exists a clear difference in the internal structure of
nucleon resonances.Comment: 17 pages, 2 figures, revtex, submitted to Phys. Rev.
Alternative Interpretation of Sharply Rising E0 Strengths in Transitional Regions
It is shown that strong 0+2 -> 0+1 E0 transitions provide a clear signature
of phase transitional behavior in finite nuclei. Calculations using the IBA
show that these transition strengths exhibit a dramatic and robust increase in
spherical-deformed shape transition regions, that this rise matches well the
existing data, that the predictions of these E0 transitions remain large in
deformed nuclei, and that these properties are intrinsic to the way that
collectivity and deformation develop through the phase transitional region in
the model, arising from the specific d-boson coherence in the wave functions,
and that they do not necessarily require the explicit mixing of normal and
intruder configurations from different IBA spaces.Comment: 6 pages, 3 figure
Theory of magnetoelectric resonance in two-dimensional antiferromagnet via spin-dependent metal-ligand hybridization mechanism
We investigate magnetic excitations in an Heisenberg model
representing two-dimensional antiferromagnet . In
terahertz absorption experiment of the compound, Goldstone mode as well as
novel magnetic excitations, conventional magnetic resonance at 2 meV and both
electric- and magnetic-active excitation at 4 meV, have been observed. By
introducing a hard uniaxial anisotropy term , three modes can
be explained naturally. We also indicate that, via the spin-dependent
metal-ligand hybridization mechanism, the 4 meV excitation is an
electric-active mode through the coupling between spin and electric-dipole.
Moreover, at 4 meV excitation, an interference between magnetic and electric
responses emerges as a cross correlated effect. Such cross correlation effects
explain the non-reciprocal linear directional dichroism observed in .Comment: 5 pages, 3 figure
Quadrupole Collective States in a Large Single-J Shell
We discuss the ability of the generator coordinate method (GCM) to select
collective states in microscopic calculations. The model studied is a
single- shell with hamiltonian containing the quadrupole-quadrupole
interaction. Quadrupole collective excitations are constructed by means of the
quadrupole single-particle operator. Lowest collective bands for =31/2 and
particle numbers =4,6,8,10,12, and are found. For lower values of ,
exact solutions are obtained and compared with the GCM results.Comment: submitted for publication in Phys. Rev. C, revtex, 28 pages, 15
PostScript figures available on request from [email protected], preprint
No. IFT/17/9
Static response of Fermi liquids with tensor interactions
We use Landau's theory of a normal Fermi liquid to derive expressions for the
static response of a system with a general tensor interaction that conserves
the total spin and the total angular momentum of the quasiparticle-quasihole
pair. The magnetic susceptibility is calculated in detail, with the inclusion
of the center of mass tensor and cross vector terms in addition to the exchange
tensor one. We also introduce a new parametrization of the tensor Landau
parameters which significantly reduces the importance of high angular harmonic
contributions. For nuclear matter and neutron matter we find that the two most
important effects of the tensor interaction are to give a contribution from
multipair states and to renormalize the magnetic moments. Response to a weak
probe may be calculated using similar methods, replacing the magnetic moments
with the matrix elements of the weak charges
Microscopic description of Gamow-Teller transitions in middle pf--shell nuclei by a realistic shell model calculation
GT transitions in nuclei are studied in terms of a large-scale
realistic shell-model calculation, by using Towner's microscopic parameters.
values to low-lying final states are reproduced with a reasonable
accuracy. Several gross properties with respect to the GT transitions are
investigated with this set of the wavefunctions and the operator. While the
calculated total GT strengths show no apparent disagreement with the
measured ones, the calculated total GT strengths are somewhat larger than
those obtained from charge-exchange experiments. Concerning the Ikeda sum-rule,
the proportionality of to persists to an excellent
approximation, with a quenching factor of 0.68. For the relative GT
strengths among possible isospin components, the lowest isospin component
gathers greater fraction than expected by the squared CG coefficients of the
isospin coupling. It turns out that these relative strengths are insensitive to
the size of model space. Systematics of the summed values are
discussed for each isospin component.Comment: IOP-LaTeX 23 pages, to appear in J. Phys. G., 5 Postscript figures
available upon reques
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