Centroids of nuclear shell-model Hamiltonians, with optimization of energy-based truncation schemes

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Hauptverfasser: Johnson, Calvin W., Keller, Austin
Format: Preprint
Veröffentlicht: 2025
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author Johnson, Calvin W.
Keller, Austin
author_facet Johnson, Calvin W.
Keller, Austin
contents The configuration-interaction shell model is an effective and widely-used approach to the nuclear many-body problem, whose main drawback is the exponential growth of the basis dimension. An useful way to character nuclear shell-model Hamiltonians is through traces, including traces in subspaces defined by orbital occupations. Such traces, or energy centroids, can be easily and efficiently computed through the monopole components of the nuclear interaction, that is, terms that go like $n_a n_b$ where $n_a$ is the occupation of the single-particle orbital labeled by $a$. These calculations can be carried out very quickly for both empirical (valence space) and no-core shell model spaces and interactions. In fact, they can be carried out so fast, one can use this to optimize an efficient, if approximate, many-body truncation scheme used in available nuclear shell-model codes such as BIGSTICK. To carry out both the traces and the optimization, we present the TRACER code, written in Fortran90 and described and available here. We give example results as well as discuss performance.
format Preprint
id arxiv_https___arxiv_org_abs_2511_03161
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Centroids of nuclear shell-model Hamiltonians, with optimization of energy-based truncation schemes
Johnson, Calvin W.
Keller, Austin
Nuclear Theory
The configuration-interaction shell model is an effective and widely-used approach to the nuclear many-body problem, whose main drawback is the exponential growth of the basis dimension. An useful way to character nuclear shell-model Hamiltonians is through traces, including traces in subspaces defined by orbital occupations. Such traces, or energy centroids, can be easily and efficiently computed through the monopole components of the nuclear interaction, that is, terms that go like $n_a n_b$ where $n_a$ is the occupation of the single-particle orbital labeled by $a$. These calculations can be carried out very quickly for both empirical (valence space) and no-core shell model spaces and interactions. In fact, they can be carried out so fast, one can use this to optimize an efficient, if approximate, many-body truncation scheme used in available nuclear shell-model codes such as BIGSTICK. To carry out both the traces and the optimization, we present the TRACER code, written in Fortran90 and described and available here. We give example results as well as discuss performance.
title Centroids of nuclear shell-model Hamiltonians, with optimization of energy-based truncation schemes
topic Nuclear Theory
url https://arxiv.org/abs/2511.03161