Path Integral Quantum Monte Carlo Calculations of Light Nuclei

TL;DR

This paper introduces a path-integral quantum Monte Carlo method for calculating properties of light nuclei, demonstrating its efficiency and accuracy compared to existing techniques, especially for non-commuting operators.

Contribution

The paper develops a novel path-integral quantum Monte Carlo approach tailored for light nuclei, capable of handling complex interactions and operators more efficiently than traditional methods.

Findings

Accurate ground-state energies for triton and alpha particle.

Consistent results with Green's function Monte Carlo for commuting operators.

Effective calculation of response functions without increased variance.

Abstract

We describe a path-integral ground-state quantum Monte Carlo method for light nuclei in continuous space. We show how to efficiently update and sample the paths with spin-isospin dependent and spin-orbit interactions. We apply the method to the triton and alpha particle using both local chiral interactions with next-to-next-to-leading-order %(N$^2$LO) and the Argonne interactions. For operators, like the total energy, that commute with the Hamiltonian, our results agree with Green's function Monte Carlo and auxiliary field diffusion Monte Carlo calculations. For operators that do not commute with the Hamiltonian and for Euclidean response functions, the path-integral formulation allows straightforward calculation without forward walking or the increased variance typical of diffusion methods. We demonstrate this by calculating density distributions, root mean square radii, and Euclidean response functions for single-nucleon couplings.