Pairing fluctuations and gauge symmetry restoration in rotating superfluid nuclei

Rapidly rotating nuclei provide us good testing grounds to study the pairing correlations; in fact, the transition from the superfluid to the normal phase is realized at high-spin states. The role played by the pairing correlations is quite different in these two phases: The static (BCS like mean-field) contribution is dominant in the superfluid phase, while the dynamic fluctuations beyond the mean-field approximation are important in the normal phase. The influence of the pairing fluctuations on the high-spin rotational spectra and moments of inertia is discussed.Comment: 14 pages, 5 figures, a contribution to the book "50 Years of Nuclear BCS", edited by R.A.Broglia and V.Zelevinsk

Heuristic quantization of the cranking model

We propose a simple and systematic method to quantize the cranking model and to calculate the matrix elements of intrinsic operators entering the generalized intensity relations. An example of the application is given to show the Coriolis coupling effects for B(E3) values of the 3- octupole states in Gd isotopes.Comment: 2 pages, Latex, using epsf.sty, 1 postscript figure Talk given at the International School of Nuclear Physics, 18th. Course: "4pi High-Resolution Gamma Ray Spectroscopy and Nuclear Structure", Erice, Italy, Sep. 16-24, 199

Magnetic Properties of Precession Modes Built on High-K Multi-quasiparticle States in ^{178}W

We present an example that shows that the random phase approximation performed on high-K multi-quasiparticle configurations leads to a rotor picture by calculating excitation energies and magnetic properties of ^{178}W. Then we deduce the effective g_R of the high-K rotors and compare it with that of the low-K one.Comment: 6 pages, 3 figures, Prog. Theor. Phys., accepte

Theoretical study of the decay-out spin of superdeformed bands in the Dy and Hg regions

Decay of the superdeformed bands have been studied mainly concentrating upon the decay-out spin, which is sensitive to the tunneling probability between the super- and normal-deformed wells. Although the basic features are well understood by the calculations, it is difficult to precisely reproduce the decay-out spins in some cases. Comparison of the systematic calculations with experimental data reveals that values of the calculated decay-out spins scatter more broadly around the average value in both the $A \approx$ 150 and 190 regions, which reflects the variety of calculated tunneling probability in each band.Comment: 6 pages 4 figures (30 PS files). To appear in Proc. of NS2000 (Nuclear Structure 2000) conf., at MSU, 15-19 Aug., 200

Microscopic Description of Nuclear Wobbling Motion -- Rotation of traxially deformed nuclei --

The nuclear wobbling motion in the Lu region is studied by the microscopic cranked mean-field plus RPA method. The Woods-Saxon potential is used as a mean-field with a new parameterization which gives reliable description of rapidly rotating nuclei. The prescription of symmetry-preserving residual interaction makes the calculation of the RPA step parameter-free, and we find the wobbling-like RPA solution if the triaxial deformation of the mean-field is suitably chosen. It is shown that the calculated out-of-band $B(E2)$ of the wobbling-like solution depends on the triaxial deformation in the same way as in the macroscopic rotor model, and can be used to probe the triaxiality of the nuclear mean-field.Comment: 10 pages, 8 figures, talk at International Conference on Nuclear Structure Physics, Shanghai, June 200

High-K Precession modes: Axially symmetric limit of wobbling motion

The rotational band built on the high-K multi-quasiparticle state can be interpreted as a multi-phonon band of the precession mode, which represents the precessional rotation about the axis perpendicular to the direction of the intrinsic angular momentum. By using the axially symmetric limit of the random-phase-approximation (RPA) formalism developed for the nuclear wobbling motion, we study the properties of the precession modes in $^{178}$W; the excitation energies, B(E2) and B(M1) values. We show that the excitations of such a specific type of rotation can be well described by the RPA formalism, which gives a new insight to understand the wobbling motion in the triaxial superdeformed nuclei from a microscopic view point.Comment: 14 pages, 8 figures (Spelling of the authors name was wrong at the first upload, so it is corrected

Efficient Method for Quantum Number Projection and Its Application to Tetrahedral Nuclear States

We have developed an efficient method for quantum number projection from most general HFB type mean-field states, where all the symmetries like axial symmetry, number conservation, parity and time-reversal invariance are broken. Applying the method, we have microscopically calculated, for the first time, the energy spectra based on the exotic tetrahedral deformation in $^{108,110}$Zr. The nice low-lying rotational spectra, which have all characteristic features of the molecular tetrahedral rotor, are obtained for large tetrahedral deformation, \alpha_{32} \gtsim 0.25, while the spectra are of transitional nature between vibrational and rotational with rather high excitation energies for $\alpha_{32}\approx 0.1-0.2$Comment: Trivial mistakes are correcte