123 research outputs found
Stochastic extension of the Lanczos method for nuclear shell-model calculations with variational Monte Carlo method
We propose a new variational Monte Carlo (VMC) approach based on the Krylov
subspace for large-scale shell-model calculations. A random walker in the VMC
is formulated with the -scheme representation, and samples a small number of
configurations from a whole Hilbert space stochastically. This VMC framework is
demonstrated in the shell-model calculations of Cr and Zn, and we
discuss its relation to a small number of Lanczos iterations. By utilizing the
wave function obtained by the conventional particle-hole-excitation truncation
as an initial state, this VMC approach provides us with a sequence of
systematically improved results.Comment: 5 pages, 4 figures, submitted to Physics Letters
Microscopic Formulation of Interacting Boson Model for Rotational Nuclei
We propose a novel formulation of the Interacting Boson Model (IBM) for
rotational nuclei with axially-symmetric strong deformation. The intrinsic
structure represented by the potential energy surface (PES) of a given
multi-nucleon system has a certain similarity to that of the corresponding
multi-boson system. Based on this feature, one can derive an appropriate boson
Hamiltonian as already reported. This prescription, however, has a major
difficulty in rotational spectra of strongly deformed nuclei: the bosonic
moment of inertia is significantly smaller than the corresponding nucleonic
one. We present that this difficulty originates in the difference between the
rotational response of a nucleon system and that of the corresponding boson
system, and could arise even if the PESs of the two systems were identical. We
further suggest that the problem can be cured by implementing term into the IBM Hamiltonian, with coupling constant derived from the
cranking approach of Skyrme mean-field models. The validity of the method is
confirmed for rare-earth and actinoid nuclei, as their experimental rotational
yrast bands are reproduced nicely.Comment: 5 pages, 5 figures; accepted for publication in Phys. Rev. C Rapid
Communication
Anomalous Properties of Quadrupole Collective States in Te and beyond
The ground and low-lying states of neutron-rich exotic Te and Sn isotopes are
studied in terms of the nuclear shell model by the same Hamiltonian used for
the spherical-deformed shape phase transition of Ba isotopes, without any
adjustment. An anomalously small value is obtained for
in Te, consistently with a recent experiment. The levels of Te
up to yrast are shown to be in agreement with observed ones. It is
pointed out that Te can be an exceptionally suitable case for studying
mixed-symmetry 1, 2 and 3 states, and predictions are made for
energies, M1 and E2 properties. Systematic trends of structure of heavier and
more exotic Sn and Te isotopes beyond Te are studied by Monte Carlo
Shell Model, presenting an unusual and very slow evolution of
collectivity/deformation.Comment: 8 pages, 7 figures, accepted for publication in Phys. Rev.
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