Kazuko Sugawara-Tanabe

Particle pairs in the cranked Hartree-Fock-Bogoliubov approximation and the interacting boson model

Abstract The number projected HFB wave function is analyzed in terms of particle pairs. It is found that the S(J = 0) and D(J = 2) pairs have dominant probabilities in this wave function before the occurrence of backbending, which is clarified from the behaviour of the O(J = 12) and M(J = 10) pairs arising from the i 13 2 level. After backbending the wave function can be described mainly in terms of the O and M pairs plus the core made of S and D pairs.

Microscopic structure of collective 1+ states in deformed nuclei

Abstract A self-consistent cranked HFB plus RPA formalism is used to calculate the collective M1 mode, which is adjusted to explain the backbending curve and g -factors along the yrast line of 156 Gd. The isovector M1 mode is fragmented into several 1 + states, depending on the relative strength of the quadrupole pairing force to the quadrupole-quadrupole force.

The Thermal Linear Response Theory for the Dissipative High Spin Quantum States

The thermal linear response theory with the inclusion of the non· Markovian effect is formulated based on the thermal cranked Hartree·Fock·Bogoliubov (THFB) theory. We propose the proper strength function which is suitable to be compared with y-ray spectra from giant resonances at high spin and high temperature. A clarification is given of the relation between the stability condition of the THFB solution and the equation in the thermal random phase approximation (TRPA).

Shape coexistence at high spins in 158Er and 160Yb predicted by the self-consistent calculation☆

Abstract The self-consistent calculation based on the cranked Hartree-Fock-Bogoliubov approximation is performed to study the evolution of nuclear shapes at high spins for the nuclei 158 Er and 160 Yb. Strong quadrupole-pairing interaction reproduces the sharp backbending well without introducing the core moment-of-inertia. The coexistence of the prolate and the oblate deformations is predicted at very high spins I ⪆ 50 in both nuclei.

The structure of dipole modes in Dy isotopes from A= 160 to 164

Abstract An RPA calculation based on the self-consistent CHFB field is carried out. This calculation shows that the 1+ state around 2.5 MeV in 164Dy is due to the coherent contribution of the proton unique-parity levels ( π h 11 2 ) and the neutron unique-parity levels ( v i 13 2 ) while the 1+ state around 3 MeV has the character of a relative rotation between protons and neutrons.

g-Factors and backbending along the yrast in Er isotopes from A = 158 to 170

Abstract g-factors and energy levels are described in the framework of a self-consistent cranked HFB calculation for the Er isotopes with mass number A = 158–170. We show that the backbending behavior and the g-factor, which is a measure of spin-alignment, are sensitive to the gradual change of Fermi surface in the vi 13 2 level.

Dyson boson mapping in S-D subspace

Abstract The validity of a truncated boson space invented by Zirnbauer and Brink in the Dyson boson mapping is examined by using a one -j (= 23 2 ) model. The pairing operator is well reproduced without regard to deformation. When the deformation of a nucleus is smaller than 0.3 the quadrupole interaction is also well approximated by this method.

Thermal high spin giant dipole resonance in Er isotopes

Abstract The thermal RPA calculations based on the thermal cranked Hartree-Fock-Bogoliubov enemble are carried out for the giant dipole resonance excited on the thermal high spin states. The dynamical strength function is adopted as a quantity comparable with experimental data. According to the location of the Fermi surface the resonance components differ from those expected in the classical picture.

On the variational derivation of the thermal RPA equation

Abstract By applying the variational principle to the grand potential including residual two-body interactions, the thermal random-phase-approximation (TRPA) equation is derived without recourse to the linearization ansatz. The relation of the TRPA equation to the stability condition of the thermal Hartree-Fock-Bogoliubov (THFB) solution is elucidated.

Microscopic Structure of the Superdeformed Rotational Band in 132Ce

The self-consistent cranked Hartree-Fock-Bogoliubov calculation with the monopole- and quadrupole-pairing plus quadrupole-quadrupole interactions, predicts that the superdeformed band in 132Ce becomes yrast for spins /;;;;32. The result indicates that many dissociated nucleon pairs contribute to the rigidification of the superdeformed system, in contrast to the s-band in which the decoupling of nucleon pairs occurs only in specific high-j orbitals. 4 ) predicted the existence of the superdeformed bands and there have been a number of applications based on this model. However, no approach has been attempted from the viewpoint of fully self-consistent cranked Hartree-Fockxad Bogoliubov (CHFB) approximation. 5 )-7) Therefore, it is quite interesting to kriow whether the CHFB solution is capable of describing such states, and if so, to know to what extent we can learn from the theoretical results in comparison with the experxad imental data. In the present paper the CHFB solution is tested if it can simultaneously reproxad duce three rotational bands in 132Ce, i.e., the ground band (g. b.), the s-band (s. b.) and the superdeformed band (s. -d. b.), from the common microscopic residual interaction with rotational and time-reversal symmetries. The self-consistent CHFB approach is advantageous in (i) the spontaneous creation of deformation starting from a spherical single-particle basis, (ii) relating the collective properties directly to single-particle behavior and (iii) the self-consistent description of the evolution of intrinsic structure which is caused by the decrease of the pairing field with increasing rotational frequenxad cy. In sharp contrast to the CSM which introduces the angular frequency (J) as well as deformation parameters /3 and y, and sometimes pairing gap L1 as external variables, the CHFB scheme microscopically calculates these parameters in terms of the self-consistent solution to the CHFB equation. It has been pointed out by Hamamoto that the expectation value calculated for a given (J) may naturally deviates far from the physical value and may wander out of the physical range, so that any physical meaning cannot be attributed to when two bands cross each other.