Constrained-Path Quantum Monte-Carlo Approach for Non-Yrast States Within the Shell Model

TL;DR

This paper extends the constrained-path quantum Monte-Carlo method to accurately reconstruct non-yrast nuclear states within the shell model, enabling complete nuclear spectroscopy with improved efficiency and sign problem control.

Contribution

It introduces a novel approach for non-yrast state reconstruction in shell model QMC, enhancing the method's capability for comprehensive nuclear spectroscopy.

Findings

Achieves accurate binding energies for various nuclei.

Effectively controls sign and phase problems in fermionic QMC.

Demonstrates applicability in the $sd$ valence space.

Abstract

The present paper intends to present an extension of the constrained-path quantum Monte-Carlo approach allowing to reconstruct non-yrast states in order to reach the complete spectroscopy of nuclei within the interacting shell model. As in the yrast case studied in a previous work, the formalism involves a variational symmetry-restored wave function assuming two central roles. First, it guides the underlying Brownian motion to improve the efficiency of the sampling. Second, it constrains the stochastic paths according to the phaseless approximation to control sign or phase problems that usually plague fermionic QMC simulations. Proof-of-principle results in the $sd$ valence space are reported. They prove the ability of the scheme to offer remarkably accurate binding energies for both even- and odd-mass nuclei irrespective of the considered interaction.