1,459 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
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.
Novel Extrapolation Method in the Monte Carlo Shell Model
We propose an extrapolation method utilizing energy variance in the Monte
Carlo shell model in order to estimate the energy eigenvalue and observables
accurately. We derive a formula for the energy variance with deformed Slater
determinants, which enables us to calculate the energy variance efficiently.
The feasibility of the method is demonstrated for the full -shell
calculation of Ni, and the applicability of the method to a system
beyond current limit of exact diagonalization is shown for the
+-shell calculation of Ge.Comment: 4 pages, 4figure
Stochastic Estimation of Nuclear Level Density in the Nuclear Shell Model: An Application to Parity-Dependent Level Density in Ni
We introduce a novel method to obtain level densities in large-scale
shell-model calculations. Our method is a stochastic estimation of eigenvalue
count based on a shifted Krylov-subspace method, which enables us to obtain
level densities of huge Hamiltonian matrices. This framework leads to a
successful description of both low-lying spectroscopy and the experimentally
observed equilibration of and states in Ni in a
unified manner.Comment: 13 pages, 4 figure
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