arXiv subjects

Koichi Sato

Publications and source records attributed to Koichi Sato.

23 records · Page 2Linked to original sources

arXiv2011

Shape fluctuations in the ground and excited 0+ states of 30Mg and 32Mg

Large-amplitude collective dynamics of shape phase transition in the low-lying states of 30-36Mg is investigated by solving the five-dimensional (5D) quadrupole collective Schroedinger equation. The collective masses and potentials of the 5D collective Hamiltonian are microscopically derived with use of the constrained Hartree-Fock-Bogoliubov plus local quasiparticle RPA method. Good agreement with the recent experimental data is obtained for the excited 0+ states as well as the ground bands. For 30Mg, the shape coexistence picture that the deformed excited 0+ state coexists with the spherical ground state approximately holds. On the other hand, large-amplitude quadrupole-shape fluctuations dominate in both the ground and the excited 0+ states in 32Mg, so that the interpretation of 'coexisting spherical excited 0+ state' based on the naive inversion picture of the spherical and deformed configurations does not hold.

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arXiv2011

Microscopic description of large-amplitude shape-mixing dynamics with local QRPA inertial functions

We introduce a microscopic approach to derive all the inertial functions in the five-dimensional quadrupole collective Hamiltonian. Local normal modes are evaluated on the constrained mean field in the quasiparticle random-phase approximation in order to derive the inertial functions. The collective Hamiltonians for neutron-rich Mg isotopes are determined with use of this approach, and the shape coexistence/mixing around the N = 20 region is analyzed.

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arXiv2011

Microscopic description of large-amplitude shape-mixing dynamics with inertial functions derived in local quasiparticle random-phase approximation

On the basis of the adiabatic self-consistent collective coordinate method, we develop an efficient microscopic method of deriving the five-dimensional quadrupole collective Hamiltonian and illustrate its usefulness by applying it to the oblate-prolate shape coexistence/mixing phenomena in proton-rich 68,70,72Se. In this method, the vibrational and rotational collective masses (inertial functions) are determined by local normal modes built on constrained Hartree-Fock-Bogoliubov states. Numerical calculations are carried out using the pairing-plus-quadrupole Hamiltonian including the quadrupole-pairing interaction. It is shown that the time-odd components of the moving mean-field significantly increase the vibrational and rotational collective masses in comparison with the Inglis-Belyaev cranking masses. Solving the collective Schroedinger equation, we evaluate excitation spectra, quadrupole transitions and moments. Results of the numerical calculation are in excellent agreement with recent experimental data and indicate that the low-lying states of these nuclei are characterized as an intermediate situation between the oblate-prolate shape coexistence and the so-called gamma unstable situation where large-amplitude triaxial-shape fluctuations play a dominant role.

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arXiv2010

Shape mixing dynamics in the low-lying states of proton-rich Kr isotopes

We study the oblate-prolate shape mixing in the low-lying states of proton-rich Kr isotopes using the five-dimensional quadrupole collective Hamiltonian. The collective Hamiltonian is derived microscopically by means of the CHFB (constrained Hartree-Fock-Bogoliubov) + Local QRPA (quasiparticle random phase approximation) method, which we have developed recently on the basis of the adiabatic self-consistent collective coordinate method. The results of the numerical calculation show the importance of large-amplitude collective vibrations in the triaxial shape degree of freedom and rotational effects on the oblate-prolate shape mixing dynamics in the low-lying states of these isotopes.

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arXiv2009

A Model Analysis of Triaxial Deformation Dynamics in Oblate-Prolate Shape Coexistence Phenomena

From a viewpoint of oblate-prolate symmetry and its breaking, we adopt the quadrupole collective Hamiltonian to study dynamics of triaxial deformation in shape coexistence phenomena. It accommodates the axially symmetric rotor model, the $γ$-unstable model, the rigid triaxial rotor model and an ideal situation for the oblate-prolate shape coexistence as particular cases. Numerical solutions of this model yield a number of interesting suggestions. (1) The relative energy of the excited 0+ state can be a signature of the potential shape along the $γ$ direction. (2) Specific E2 transition probabilities are sensitive to the breaking of the oblate-prolate symmetry. (3) Nuclear rotation may induce the localization of collective wave functions in the ($β, γ$) deformation space.

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