Bulletin of the American Physical Society
2011 Fall Meeting of the APS Division of Nuclear Physics
Volume 56, Number 12
Wednesday–Saturday, October 26–29, 2011; East Lansing, Michigan
Session MD: Nuclear Theory III: Ab Initio and Density Functionals |
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Chair: Bruce Barrett, University of Arizona Room: Heritage |
Saturday, October 29, 2011 8:30AM - 8:42AM |
MD.00001: Ab initio studies of light nuclei Christian Forss\'en The ab initio no-core shell model (NCSM) is a well-established theoretical framework aimed at an exact description of nuclear structure starting from high-precision interactions between the nucleons. We consider realistic two- and three-nucleon interactions and will also discuss techniques based on unitary transformations that provide many-body Hamiltonians with superior convergence properties. The performance of the NCSM within nuclear physics will be exemplified by showing results from studies of light nuclei. [Preview Abstract] |
Saturday, October 29, 2011 8:42AM - 8:54AM |
MD.00002: Ab Initio No Core Full Configuration Calculations for Lithium Isotopes Robert Cockrell Ab Initio No Core Full Configuration methods are employed to obtain nuclear densities for several light nuclei with a realistic NN interaction, JISP16. We calculate binding energies for various states of interest as well as dipole and quadrupole moments and select M1 and E2 transitions. The One Body Density Matrix is used to determine the densities and shapes of the ground state and various excited states of these Lithium isotopes. We discuss the opportunities to use these densities to construct Nuclear Energy Density Functionals. [Preview Abstract] |
Saturday, October 29, 2011 8:54AM - 9:06AM |
MD.00003: Importance truncation and the further development of the No-Core Shell Model Michael Kruse, Petr Navratil, Bruce Barrett The No-Core Shell Model, an ab-initio approach to calculating observables of light nuclei, has been shown to be successful in describing p-shell nuclei properties. With the inclusion of the resonating group method, the approach can be extended to describe nuclear reactions. However, the calculations require a large number of basis states for full convergence. By using perturbation theory, one can formulate a procedure, for selecting only those states that one considers ``important.'' This selection procedure is able to drastically reduce the size of the basis, yet captures enough of the physics present, comparing well with full space calculations. I will show calculations in which we calculate the wave functions of Helium-8 (in an importance truncation setting), which are used as input for the n+He-8 scattering calculations. Those theoretical calculations are then compared to recent experiments. [Preview Abstract] |
Saturday, October 29, 2011 9:06AM - 9:18AM |
MD.00004: Ab initio calculation of the optical model Helber Dussan, Seth Waldecker, Willem Dickhoff, Herbert M\"uther, Artur Polls We explore the effects of short-range correlations in nuclei for positive and negative energies starting from a microscopically generated irreducible self-energy. This approach is an attempt to develop an optical potential obtained from a realistic nucleon-nucleon interaction. In this first study we use a CD Bonn self-energy obtained for $^{40}$Ca. Our results are compared with the ones found using the dispersive optical model (DOM) and with experimental data available for $^{40}$Ca. Finally we outline further necessary developments to obtain a purely {\it ab initio} optical potential that can reproduce experimental data. [Preview Abstract] |
Saturday, October 29, 2011 9:18AM - 9:30AM |
MD.00005: Ab Initio Configuration-Interaction Calculations in SU(3)-scheme Basis Tomas Dytrych The predictive power of ab initio no-core shell model (NCSM) depends critically on the choice of a realistic nuclear interaction, and on the adequacy of basis to describe a system of strongly interacting nucleons. To include many-body correlations important for the description of nuclear collective dynamics and geometry, we embedded the SU(3) coupling scheme of the Elliot SU(3) model into the NCSM framework. The SU(3)-scheme basis provides a microscopic description of nuclei in terms of mixed shape configurations, and offers a symmetry-guided framework for winnowing a model space while retaining the ability to remove center-of-mass spurious excitations exactly. The resulting SU(3) no-core shell model (SU3-NCSM) harnesses powerful computational techniques of the group theory while taking the advantage of massively parallel computing systems. The foundation principles of SU(3)-NCSM will be discussed and the results for some p-shell nuclei will be presented. [Preview Abstract] |
Saturday, October 29, 2011 9:30AM - 9:42AM |
MD.00006: Properties of trapped neutrons interacting with realistic nuclear Hamiltonians Pieter Maris, James Vary Neutron drops can provide useful microscopic input to a universal nuclear energy density functional. We have computed the ground state energy of neutrons trapped in harmonic wells of different strength and compare results from different Hamiltonians, including realistic two-body interactions as well as different three-body forces. In addition to the total energy of the system, we also compute the internal energies and radii. Excitation energies for different spin states provides information about spin-orbit splittings. These results can be used as a benchmark for different many-body techniques, test different nuclear interactions far from stability, and to constrain properties of nuclear energy-density functionals. [Preview Abstract] |
Saturday, October 29, 2011 9:42AM - 9:54AM |
MD.00007: Fission Barriers of Actinide Nuclei with New Nuclear Density Functionals Jordan McDonnell, Markus Kortelainen, Witold Nazarewicz, J.A. Sheikh, Mario Stoitsov, Nicolas Schunck We survey the fission of isotopes of Ra, Th, U, and Pu through nuclear density functional theory. We compare the fission barriers predicted by new universal nuclear energy density functionals (UNEDF) to the predictions of previous Skyrme functionals and experimental data, validating the ability of the new functionals to predict fission observables. We also study the dependence of fission observables on nuclear temperature, finding barrier heights to decrease and mass yields to be more symmetric with increasing temperature for all functionals studied. [Preview Abstract] |
Saturday, October 29, 2011 9:54AM - 10:06AM |
MD.00008: Widths of nuclear states from ab initio calculations Kenneth Nollett \textit{Ab initio} calculations of nuclear structure from the bare nucleon-nucleon interaction describe the energy spectra of light nuclei quite accurately, but the usual pseudobound calculations do not yield widths when those levels are unbound. Computing widths from scattering wave functions is difficult and computationally expensive, but one can also compute widths directly from the pseudobound calculations using an integral relation. The integral is short-ranged and thus well-suited to quantum Monte Carlo methods. I will present computed widths for one-nucleon emission from unbound states of light nuclei, concentrating on relatively narrow states without large alpha widths. For most states, these are the first ever \textit{ab initio} calculations of widths. A closely related integral yields asymptotic normalizations of bound states, and I will also present the first \textit{ab initio} calculations of many of these quantities. [Preview Abstract] |
Saturday, October 29, 2011 10:06AM - 10:18AM |
MD.00009: Ab initio DFT for nuclear physics Lucas Platter The description of heavy nuclei using a microscopic Hamiltonian that describes the nucleon-nucleon interaction is one of the ultimate challenges in nuclear theory. I will discuss recent progress towards this goal made with ab intio density functional theory (ADFT). ADFT aims at obtaining a density functional from many-body perturbation theory and using modern methods borrowed form chemical physics to solve for ground state observables of large nuclei. In particular, I will highlight the density matrix expansion [1] and the optimized effective potential [2] method as tools to deal with non-local functionals that appear naturally within such an approach. \\[4pt] [1] S. Bogner, R. J. Furnstahl and L. Platter, Eur.Phys.J. A39 (2009) 219. \\[0pt] [2] J. Drut and L. Platter, Phys. Rev. C in press. [Preview Abstract] |
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