Recent developments in the shell model Monte Carlo approach to nuclei

TL;DR

This paper reviews recent advances in the shell model Monte Carlo method for nuclear physics, highlighting applications to nuclear collectivity, state densities, and pairing gaps, and introduces an improved technique for odd nuclei.

Contribution

It presents new applications of SMMC to describe nuclear collectivity, state densities, and pairing gaps, including a novel method to handle odd nuclei without the sign problem.

Findings

Collectivity emergence correlates with pairing and shape phase transitions.

State densities show collective enhancement factors.

New method accurately computes ground-state energies of odd nuclei.

Abstract

The shell model Monte Carlo (SMMC) approach provides a powerful method for the microscopic calculation of statistical and collective nuclear properties in model spaces that are many orders of magnitude larger than those that can be treated by conventional methods. We discuss recent applications of the method to describe the emergence of collectivity in the framework of the configuration-interaction shell model and the crossover from vibrational to rotational collectivity in families of rare-earth nuclei. We have calculated state densities of these rare-earth nuclei and find their collective enhancement factors to be correlated with the pairing and shape phase transitions. We also discuss an accurate method to calculate the ground-state energy of odd-even and odd-odd nuclei, circumventing the sign problem that originates in the projection on an odd number of particles. We have applied this method to calculate pairing gaps in families of isotopes in the iron region.