Open-Shell Nuclei and Excited States from Multi-Reference Normal-Ordered Hamiltonians

Abstract

We discuss the approximate inclusion of three-nucleon interactions into ab initio nuclear structure calculations using a multi-reference formulation of normal ordering and Wick's theorem. Following the successful application of single-reference normal ordering for the study of ground states of closed-shell nuclei, e.g., in coupled-cluster theory, multi-reference normal ordering opens a path to open-shell nuclei and excited states. Based on different multi-determinantal reference states we benchmark the truncation of the normal-ordered Hamiltonian at the two-body level in no-core shell-model calculations for p-shell nuclei, including 6-Li, 12-C, and 10-B. We find that this multi-reference normal-ordered two-body approximation is able to capture the effects of the 3N interaction with sufficient accuracy, both, for ground-state and excitation energies, at the computational cost of a two-body Hamiltonian. It is robust with respect to the choice of reference states and has a multitude of applications in ab initio nuclear structure calculations of open-shell nuclei and their excitations as well as in nuclear reaction studies.

6 pages, 4 figures, v2: update to published version

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• In-Medium Similarity Renormalization Group Approach to the Nuclear Many-Body Problem
• Symmetry-projected variational calculations with the numerical suite TAURUS I. Variation after particle-number projection
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• Pre-processing the nuclear many-body problem: Importance truncation versus tensor factorization techniques
• Structure of the exotic ${}^9$He nucleus from the no-core shell model with continuum
• Tensor-decomposition techniques for ab initio nuclear structure calculations. From chiral nuclear potentials to ground-state energies
• Nucleus giant resonances from an improved isospin-dependent Boltzmann-Uehling-Uhlenbeck transport approach
• Bayesian uncertainty quantification for nuclear matter incompressibility
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