Isospin-projected nuclear level densities by the shell model Monte Carlo method

TL;DR

This paper introduces an efficient isospin projection method within the shell model Monte Carlo framework, enabling accurate calculations of isospin-dependent nuclear level densities, especially relevant for nuclei where neutron and proton numbers are similar.

Contribution

The paper presents a novel isospin projection technique that is exact for isoscalar observables and avoids the sign problem in shell model Monte Carlo calculations.

Findings

Isospin-dependent corrections are significant for N~Z nuclei.

The method accurately captures isospin effects in nuclear level densities.

Application to the $pf+g_{9/2}$ shell demonstrates its effectiveness.

Abstract

We have developed an efficient isospin projection method in the shell model Monte Carlo approach for isospin-conserving Hamiltonians. For isoscalar observables this projection method has the advantage of being exact sample by sample. The isospin projection method allows us to take into account the proper isospin dependence of the nuclear interaction, thus avoiding a sign problem that such an interaction introduces in unprojected calculations. We apply our method in the calculation of the isospin dependence of level densities in the complete $pf+g_{9/2}$ shell. We find that isospin-dependent corrections to the total level density are particularly important for $N \sim Z$ nuclei.