Monte Carlo shell-model calculations

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Abstract
We propose a quantum Monte Carlo diagonalization method (QMCD) for solving the quantum many-body interacting systems. Not only the ground state but also low-lying excited states are obtained with their wavefunctions. Consequently the level structure of low-lying states can be studied with realistic interactions. The developments in the formulation of the QMCD are described with an illustrative and intuitive example. The QMCD is finally characterized as a `importance truncation' scheme to the shell model. After testing this method for Cr, we present first results for energy levels and E2 properties of Ge, indicating its large and -soft deformation. The doubly closed shell probability of Ni is shown to be only 49% in a full pf shell calculation, in contrast to the corresponding probability of Ca which reaches 86%. The prolate deformed excited band is obtained as a result of the QMCD calculation for non-yrast states, in a good agreement to recent experimental data. This band seems to have an SU(3) (-like) structure which was originally suggested by Elliott for sd-shell nuclei.