<i>Ab-initio</i>shell model with a core

Lisetskiy, A. F.; Barrett, B. R.; Kruse, Michael; Navrátil, Petr; Stetcu, I.; Vary, James P.

doi:10.1103/physrevc.78.044302

Cited by 96 publications

(148 citation statements)

References 24 publications

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“…Compared to other nonperturbative approaches for the construction of nonempirical Shell model interactions, this effort is low [190][191][192]. Moreover, we note that we obtain consistent neutron-neutron, proton-neutron, and proton-proton interactions from the same IMSRG evolution.…”

Section: Valence-space Decouplingmentioning

confidence: 58%

In-medium similarity renormalization group for closed and open-shell nuclei

Hergert¹

2016

Phys. Scr.

145

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Abstract. We present a pedagogical introduction to the In-Medium Similarity Renormalization Group (IMSRG) framework for ab initio calculations of nuclei. The IMSRG performs continuous unitary transformations of the nuclear many-body Hamiltonian in second-quantized form, which can be implemented with polynomial computational effort. Through suitably chosen generators, it is possible to extract eigenvalues of the Hamiltonian in a given nucleus, or drive the Hamiltonian matrix in configuration space to specific structures, e.g., band-or block-diagonal form.Exploiting this flexibility, we describe two complementary approaches for the description of closed-and open-shell nuclei: The first is the Multireference IMSRG (MR-IMSRG), which is designed for the efficient calculation of nuclear ground-state properties. The second is the derivation of nonempirical valence-space interactions that can be used as input for nuclear Shell model (i.e., configuration interaction (CI)) calculations. This IMSRG+Shell model approach provides immediate access to excitation spectra, transitions, etc., but is limited in applicability by the factorial cost of the CI calculations.We review applications of the MR-IMSRG and IMSRG+Shell model approaches to the calculation of ground-state properties for the oxygen, calcium, and nickel isotopic chains or the spectroscopy of nuclei in the lower sd shell, respectively, and present selected new results, e.g., for the ground-and excited state properties of neon isotopes.Submitted to: Phys. Scr.

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Section: Valence-space Decouplingmentioning

confidence: 58%

In-medium similarity renormalization group for closed and open-shell nuclei

Hergert¹

2016

Phys. Scr.

145

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“…Some have been based on the ab-initio no-core shell model [12,13], via a valence-cluster expansion [14][15][16], and others on the in-medium similarity renormalization group [17]. In this Letter we use a third approach, the ab-initio coupled-cluster method [18][19][20][21][22][23], to construct effective shell-model interactions for use in open-shell and neutron-rich nuclei.…”

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confidence: 99%

“…Formalism. -To derive an effective shell-model Hamiltonian in a valence space from ab-initio coupled-cluster theory, we use the valence-cluster expansion first applied in the no-core shell model [15,42]. We expand the Hamiltonian in Eq.…”

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confidence: 99%

Ab InitioCoupled-Cluster Effective Interactions for the Shell Model: Application to Neutron-Rich Oxygen and Carbon Isotopes

et al. 2014

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We derive and compute effective valence-space shell-model interactions from ab-initio coupledcluster theory and apply them to open-shell and neutron-rich oxygen and carbon isotopes. Our shell-model interactions are based on nucleon-nucleon and three-nucleon forces from chiral effectivefield theory. We compute the energies of ground and low-lying states, and find good agreement with experiment. In particular our calculations are consistent with the N = 14, 16 shell closures in 22,24 O, while for 20 C the corresponding N = 14 closure is weaker. We find good agreement between our coupled-cluster effective-interaction results with those obtained from standard single-reference coupled-cluster calculations for up to eight valence neutrons. Introduction. -The nuclear shell model is the foundation on which our understanding of nuclei is built. One of the most important problems in nuclear structure today is to understand how shell structure changes with neutron-to-proton ratio throughout the nuclear chart. Shell structure influences the locations of the neutron and proton drip lines and the stability of matter. Examples of changes in shell structure are the appearance of new magic numbers N = 14 and N = 16 in the neutron-rich oxygen isotopes [1,2], and the emergence of an N = 34 sub-shell closure in 54 Ca [3][4][5][6].Phenomenological shell-model Hamiltonians such as the sd Hamiltonian of Brown and Wildenthal [7,8] (abbreviated USD) and the p-sd Hamiltonian of Warturburton and Brown [9] (abbreviated WBP), have successfully described properties of nuclei with proton number Z and neutron number N less than about 20. To understand the origin of shell structure, however, researchers are now trying to derive the shell model from realistic nucleonnucleon (NN) and three-nucleon forces (3NFs), without further phenomenology [3,10,11]. Within the last few years, for example, Otsuka et al. [11] showed that 3NFs play a pivotal role in placing the drip line (correctly) in the oxygen isotopes at 24 O, and Holt et al. [3] showed that the inclusion of 3NFs are necessary to explain the high 2 + state in 48 Ca .Until recently, all work to compute effective shellmodel interactions was perturbative.Lately, however, nonperturbative calculations have become possible. Some have been based on the ab-initio no-core shell model [12,13], via a valence-cluster expansion [14][15][16], and others on the in-medium similarity renormalization group [17]. In this Letter we use a third approach, the ab-initio coupled-cluster method [18][19][20][21][22][23], to construct effective shell-model interactions for use in open-shell and neutron-rich nuclei. Starting from NN interactions and 3NFs generated by chiral effective-field-theory, we compute the ground-and excited-state energies of neutronrich carbon and oxygen isotopes with up to eight neu-

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“…Recently, other methods have been explored for open-shell nuclei, including two-particle attached coupled-cluster theory [16], which leads to nonhermitian effective Hamiltonians, and the NCSM with a core [17], which requires a NCSM solution of the full problem and is therefore limited to lighter nuclei.…”

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confidence: 99%

In-medium similarity renormalization group for open-shell nuclei

2012

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We present a nonperturbative derivation of effective valence-shell Hamiltonians in the framework of the recently developed in-medium similarity renormalization group (IM-SRG). As a first application, we calculate the spectra of p-and sd-shell nuclei, 6 Li and 18 O, based on evolved chiral nucleon-nucleon interactions. For 6 Li, the spectrum is in very good agreement with ab-initio results. For 18 O, the IM-SRG provides a new method for the shell model to systematically go beyond effective interaction techniques based on diagrammatic expansions. Introduction.-Advances in ab-initio methods for nuclear structure combined with nuclear forces based on chiral effective field theory (EFT) have lead to many exciting developments for light nuclei and medium-mass nuclei around closed-shell configurations (see, e.g., Refs. [1]).For open-shell systems with many valence nucleons, however, the shell model remains the most successful approach to understand and predict nuclear structure, including the evolution of shell structure with changing neutron and proton numbers, properties of ground and excited states, and electroweak transitions [2]. Moreover, the shell model has recently revealed new insights to the impact of long-range tensor [3] and three-nucleon forces [4] in neutron-rich nuclei. These are dominated by pion exchanges, which provides a link between nuclear structure and developments in chiral EFT interactions. Despite the many successes of the shell model, the microscopic derivation of effective interactions and operators among valence nucleons from nuclear forces is still largely based on perturbative approaches where the convergence remains an open problem.

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Ab-initioshell model with a core

Cited by 96 publications

References 24 publications

In-medium similarity renormalization group for closed and open-shell nuclei

In-medium similarity renormalization group for closed and open-shell nuclei

Ab InitioCoupled-Cluster Effective Interactions for the Shell Model: Application to Neutron-Rich Oxygen and Carbon Isotopes

In-medium similarity renormalization group for open-shell nuclei

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