Quantum Monte Carlo calculations in the nuclear shell model by the complex Langevin method

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Hauptverfasser: Asano, Yuhma, Ito, Yuta, Nishimura, Jun, Shimizu, Noritaka
Format: Preprint
Veröffentlicht: 2025
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author Asano, Yuhma
Ito, Yuta
Nishimura, Jun
Shimizu, Noritaka
author_facet Asano, Yuhma
Ito, Yuta
Nishimura, Jun
Shimizu, Noritaka
contents The nuclear shell model is known to describe the properties of various nuclei extremely well. However, the auxiliary-field quantum Monte Carlo calculations cannot be applied to it with general interactions due to the sign problem. The model has therefore been investigated primarily by variational methods, where the accuracy of the results depends crucially on the ansatz for the wave function. Here we perform the auxiliary-field quantum Monte Carlo calculations in the case of small systems at finite temperature using the complex Langevin method (CLM), which has been successfully applied to various interesting systems with the sign problem over the decade. In particular, we show the existence of a parameter region in which the validity criterion for the CLM is satisfied and the expectation value of the energy obtained by exact diagonalization is correctly reproduced. Thus the CLM can be a complementary approach to the variational method for large systems.
format Preprint
id arxiv_https___arxiv_org_abs_2508_15116
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Quantum Monte Carlo calculations in the nuclear shell model by the complex Langevin method
Asano, Yuhma
Ito, Yuta
Nishimura, Jun
Shimizu, Noritaka
Nuclear Theory
Statistical Mechanics
High Energy Physics - Lattice
High Energy Physics - Theory
The nuclear shell model is known to describe the properties of various nuclei extremely well. However, the auxiliary-field quantum Monte Carlo calculations cannot be applied to it with general interactions due to the sign problem. The model has therefore been investigated primarily by variational methods, where the accuracy of the results depends crucially on the ansatz for the wave function. Here we perform the auxiliary-field quantum Monte Carlo calculations in the case of small systems at finite temperature using the complex Langevin method (CLM), which has been successfully applied to various interesting systems with the sign problem over the decade. In particular, we show the existence of a parameter region in which the validity criterion for the CLM is satisfied and the expectation value of the energy obtained by exact diagonalization is correctly reproduced. Thus the CLM can be a complementary approach to the variational method for large systems.
title Quantum Monte Carlo calculations in the nuclear shell model by the complex Langevin method
topic Nuclear Theory
Statistical Mechanics
High Energy Physics - Lattice
High Energy Physics - Theory
url https://arxiv.org/abs/2508.15116