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- Scott Bogner, Aurel Bulgac, +28 authors Stefan M. Wild
- Computer Physics Communications
- 2013

The UNEDF project was a large-scale collaborative effort that applied high-performance computing to the nuclear quantum many-body problem. UNEDF demonstrated that close associations among nuclear physicists, mathematicians , and computer scientists can lead to novel physics outcomes built on algorithmic innovations and computational developments. This… (More)

- P Navrátil, V G Gueorguiev, J P Vary, W E Ormand, A Nogga
- Physical review letters
- 2007

Properties of finite nuclei are evaluated with two-nucleon (NN) and three-nucleon (NNN) interactions derived within chiral effective field theory. The nuclear Hamiltonian is fixed by properties of the A=2 system, except for two low-energy constants (LECs) that parametrize the short range NNN interaction, which we constrain with the A=3 binding energies. We… (More)

- Calvin W. Johnson, W. Erich Ormand, Plamen G. Krastev
- Computer Physics Communications
- 2013

- P Maris, J P Vary, P Navrátil, W E Ormand, H Nam, D J Dean
- Physical review letters
- 2011

We report the microscopic origins of the anomalously suppressed beta decay of ¹⁴C to ¹⁴N using the ab initio no-core shell model with the Hamiltonian from the chiral effective field theory including three-nucleon force terms. The three-nucleon force induces unexpectedly large cancellations within the p shell between contributions to beta decay, which reduce… (More)

The <i>configuration-interaction</i> (CI) method, long a popular approach to describe quantum many-body systems, is cast as a very large sparse matrix eigenpair problem with matrices whose dimension can exceed one billion. Such formulations place high demands on memory capacity and memory bandwidth --- two quantities at a premium today. In this paper, we… (More)

- W. E. Ormand
- 2008

Isospin-mixing corrections for superallowed Fermi transitions in fp-shell nuclei are computed within the framework of the shell model. The study includes three nuclei that are part of the set of nine accurately measured transitions as well as five cases that are expected to be measured in the future at radioactive-beam facilities. We also include some new… (More)

Nucleosynthesis calculations require nuclear level densities for hundreds or even thousands of nuclides. Ideally one would like to constrain these level densities by microscopically motivated yet computationally cheap models. A statistical approach suggests that low moments of the Hamiltonian might be sufficient. Recently Zuker proposed a simple… (More)

- Petr Navrátil, W Erich Ormand
- Physical review letters
- 2002

We present a qualitative improvement of the ab initio no-core shell model (NCSM) approach by implementing three-body interaction capability for p-shell nuclei. We report the first calculations using three-body effective interactions derived from realistic nucleon-nucleon potentials for 6Li, 8Be, and 10B and demonstrate that the use of three-body effective… (More)

- W. E. Ormand
- 1997

A method for making realistic estimates of the density of levels in even-even nuclei is presented making use of the Monte Carlo shell model (MCSM). The procedure follows three basic steps: (1) computation of the thermal energy with the MCSM, (2) evaluation of the partition function by integrating the thermal energy, and (3) evaluating the level density by… (More)

- Fe Y Alhassid, D J Dean, S E Koonin, G Lang, W E Ormand, W K Kellogg
- 1993

We present a practical solution to the " sign problem " in the auxiliary field Monte Carlo approach to the nuclear shell model. The method is based on extrapolation from a continuous family of problem-free Hamiltonians. To demonstrate the resultant ability to treat large shell-model problems, we present results for 54 Fe in the full f p-shell basis using… (More)