Y. Lei

Validity of pair truncation of the nuclear shell model in {sup 46}Ca

We study the validity of pair truncation of the nuclear shell model by using the semimagic nucleus

Correlations of excited states for sd bosons in the presence of random interactions

^{46}\mathrm{Ca}

Validity of pair truncations with effective interaction in Ca isotopes

. We present low-lying states and their

NUCLEON PAIR APPROXIMATION OF THE SHELL MODEL: A REVIEW AND PERSPECTIVE

E2

NUCLEON PAIR APPROXIMATION OF THE SHELL MODEL: A BRIEF REVIEW

transition rates based on both nucleon pair approximation (NPA) and exact shell-model (SM) calculations. We also calculate overlaps between wave functions of low-lying states calculated by using the NPA and those calculated by using the SM. Our calculated results show a remarkable agreement between the NPA results and the SM results, although the NPA is a drastic truncation of the SM.

Nucleon-pair approximation of the shell model with isospin symmetry

In this work we study the yrast states of sd-boson systems in the presence of random interactions. It is found that the yrast states with spin-zero ground states among the random ensemble exhibit strong correlations, characterized by anharmonic vibration, s-boson or d-boson condensation, as well as vibrational and rotational motions. We study these correlations explicitly based on their wave functions and the features of two-body interactions in the random ensemble.

Emergence of generalized seniority in low-lying states with random interactions

Using the GXPF1A interaction for the pf shell nuclei, we calculate energy levels and E2 transition rates for the semimagic nuclei {sup 43-46}Ca within both the exact shell-model space and a number of subspaces constructed using collective nucleon pairs. We present explicitly the overlaps between wave functions of low-lying states obtained from shell-model calculations and those obtained using truncated nucleon-pair subspaces. These examples are used as touchstones of pair approximations.

Low-lying states of heavy nuclei within the nucleon pair approximation

The nuclear shell model (SM) provides a firm framework to study low-lying states in nuclei. However, the configuration space of the SM truncated to a single major shell for neutrons and protons is too huge to handle for medium-mass and heavy nuclei. In order to study properties of low-lying states, one must truncate the shell model space. Pair approximation is among one of the practical approaches along this line. The wave functions of a given nucleus can be constructed in arbitrary basis of the assumed configuration spaces. They can be built by coupling the valence particles stepwise, and this can be easily realized via the wellknown procedure of the Coefficients of Fractional Parentage (cfps). The configuration spaces can be also constructed by coupling the valence nucleon pairs with given spins. If all possible pairs are considered in the pair basis, the calculated results in the pair basis are equivalent to those of the exact shell model calculations. The Nucleon pair approximation (NPA) of the shell model refers to calculation in the nucleon pair basis with truncations of pairs, i.e., in the NPA only limited pairs are assumed to play important roles while others are neglected. The NPA is found to be very good and

Magnetic moments of low-lying states in tin isotopes within the nucleon-pair approximation

We present a brief introduction of the nucleon pair approximation (NPA) of the shell model in this paper. We review our recent calculated results which include level spectra and electromagnetic properties of low-lying states, by applying the NPA to even-even nuclei and to odd-A nuclei. We also apply this method to a few schematic systems such as single-j shell, to investigate the validity of SD-pair truncation of the shell model.