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Exactness of the normal-ordered two-body truncation of three-nucleon forces

2025/08/02 by Rothman, Maxwell, Johnson-Toth, Ben, Bonaiti, Francesca +3 · 5 citations
#FOS: Physical sciences #Nuclear Theory (nucl-th)

paper · doi:10.48550/arxiv.2508.01507

Abstract

Reference-state-based many-body methods start from Hamiltonians that are normal ordered with respect to the reference state. In low-energy nuclear physics applications normal-ordered Hamiltonians consisting of two- and three-nucleon forces are usually truncated at the two-body rank with residual three-nucleon operators being discarded. Benchmark computations have shown that this truncation is accurate, but we lack an understanding about why it works. We show that the normal-ordered two-body truncation is exact for zero-range three-body forces when nuclei are computed using the coupled cluster with singles and doubles method. As the nuclear three-nucleon force is short ranged and a three-body contact is a leading term in effective field theories of quantum chromodynamics, our result provides an analytical basis for the popular normal-ordered two-body approximation.

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