Bulletin of the American Physical Society
2016 Fall Meeting of the APS Division of Nuclear Physics
Volume 61, Number 13
Thursday–Sunday, October 13–16, 2016; Vancouver, BC, Canada
Session CG: Nuclear Structure Theory I |
Hide Abstracts |
Sponsoring Units: DNP Chair: Francesca Sammarruca, University of Idaho Room: Pavilion Ballroom B |
Friday, October 14, 2016 8:30AM - 8:42AM |
CG.00001: Ab initio no-core configuration interaction calculations of electromagnetic observables for $p$-shell nuclei using natural orbitals Chrysovalantis Constantinou, Mark A. Caprio, James P. Vary, Pieter Maris The goal of \textit{ab initio} nuclear theory is to provide quantitative predictions of nuclear observables, by solving the many-body problem starting from the internucleon interaction. The solution of the many-body problem involves large spaces with dimensions that grow fast with the number of nucleons and single-particle states included in the space. Convergence of nuclear observables in the employed space using an adequate set of single-particle orbitals is essential for making quantitative predictions. Long-range nuclear observables, such as the matrix elements of the $E2$ operator, converge slowly when conventional oscillator single-particle orbitals are used for no-core configuration interaction (NCCI) calculations. Natural orbitals, obtained by diagonalizing the one-body density matrix from an initial NCCI calculation in the harmonic oscillator basis, provide accelerated convergence since they are adapted to the properties of the many-body wave function of the nucleus under study. We explore the convergence of electromagnetic observables of $p$-shell nuclei obtained using natural orbitals for NCCI calculations. [Preview Abstract] |
Friday, October 14, 2016 8:42AM - 8:54AM |
CG.00002: The nuclear geometric Yang-Mills equation for incompressible nuclei Nicholas Sparks, George Rosensteel The geometric Yang-Mills equation for the Bohr-Mottelson collective model provides a way of relating angular momentum degrees of freedom to the internal (Kelvin circulation) degrees of freedom. It is well known that nuclei are highly incompressible. The correct mathematical description for nuclear incompressibility involves an equation of constraint for constant volume. An alternative yet equivalent description involves treating this constraint in a purely differential geometric way. The relationship between these two seemingly different approaches is explored here. [Preview Abstract] |
Friday, October 14, 2016 8:54AM - 9:06AM |
CG.00003: SU(3) gauge symmetry for collective rotational states in deformed nuclei George Rosensteel, Nick Sparks How do deformed nuclei rotate? The qualitative answer is that a velocity-dependent interaction causes a strong coupling between the angular momentum and the vortex momentum (or Kelvin circulation). To achieve a quantitative explanation, we propose a significant extension of the Bohr-Mottelson legacy model in which collective wave functions are vector-valued in an irreducible representation of SU(3). This SU(3) is not the usual Elliott choice, but rather describes internal vorticity in the rotating frame. The circulation values C of an SU(3) irreducible representation, say the (8,0) for $^{20}$Ne, are C = 0, 2, 4, 6, 8, which is the same as the angular momentum spectrum in the Elliott model; the reason is a reciprocity theorem in the symplectic model. The differential geometry of Yang-Mills theory provides a natural mathematical framework to solve the angular-vortex coupling riddle. The requisite strong coupling is a ``magnetic-like" interaction arising from the covariant derivative and the bundle connection. The model builds on prior work about the Yang-Mills SO(3) gauge group model (J. Phys. A 48 (2015) 445203). [Preview Abstract] |
Friday, October 14, 2016 9:06AM - 9:18AM |
CG.00004: Isospin Considerations in Energy Level Spacings within the Shell Model Michael Quinonez, Arun Kingan, Larry Zamick The GXFP1 effective interaction with configurations confined to the f-p shell is used within the program NuShellx to generate energy levels of nucleons in $^{44}$Ti . We construct nearest neighbor spacing histograms first with all isospins present (T=0, 1, and 2) and then ones with only one isospin present e.g. all T=0. With all isospins present we get something close to a Poisson distribution with a peak in the interval 0-0.1 mean spacing units. When we have states of only one isospin and one angular momentum e.g. J=4 T=0 the distribution becomes more Wigner-like, with much fewer entries in the lowest interval. The same is true for J=4 T=1 and J=4 T=2. We relate this behavior to level repulsion. We consider variances and other methods of analyzing the distributions. [Preview Abstract] |
Friday, October 14, 2016 9:18AM - 9:30AM |
CG.00005: Ab initio treatment of fully open-shell medium-mass nuclei with the IM-SRG Ragnar Stroberg, Angelo Calci, Jason Holt, Petr Navratil, Scott Bogner, Heiko Hergert, Robert Roth, Achim Schwenk The in-medium similarity renormalization group (IM-SRG) is a recently-developed theoretical many-body framework which -- like the coupled cluster and the self-consistent Green's function approaches -- allows for the treatment of medium-mass nuclei using interactions fit at the few-body level. I will give a brief overview of how the IM-SRG may be used to decouple a shell-model type valence space. I will then describe a recent development for the approximate treatment of residual 3N forces in the valence space which extends the reach of IM-SRG to essentially all medium-mass nuclei, and I will present some selected results spanning isotopic chains from beryllium (Z=4) to nickel (Z=28). Finally, I will discuss the consistent treatment of transition operators, highlighting the potential for future applications in electroweak physics. [Preview Abstract] |
Friday, October 14, 2016 9:30AM - 9:42AM |
CG.00006: Nucleon localization within nuclear density functional theory Chunli Zhang, Bastian Schuetrumpf, Witold Nazarewicz Recently, a nucleon localization measure based on Hartree-Fock densities has been introduced to investigate $\alpha$-cluster structures in light nuclei. Compared to the local nucleonic density, the nucleon localization function (NLF) has been shown to be an excellent indicator of cluster correlations. To investigate the cluster structures in light nuclei and study the development of fission fragments in heavy nuclei, we analyse NLFs in deformed nuclei. We use both the deformed harmonic oscillator model and self-consistent nuclear density functional theory (DFT) with energy density functionals UNEDF1 and UNEDF1-HFB, which were optimized for fission studies. In this contribution, we will discuss particle densities and spatial localization functions for deformed configurations of $^{8}$Be and $^{20}$Ne and along fission pathways of $^{232}$Th and $^{240}$Pu. We illustrate the usefulness of the NLF by showing how the third hyperdeformed minimum of $^{232}$Th can be understood in terms of the ground states of $^{132}$Sn and $^{100}$Zr. [Preview Abstract] |
Friday, October 14, 2016 9:42AM - 9:54AM |
CG.00007: Survey of Reflection-Asymmetric Nuclear Deformations Erik Olsen, Yuchen Cao, Witold Nazarewicz, Nicolas Schunck Due to spontaneous symmetry breaking it is possible for a nucleus to have a deformed shape in its ground state. It is theorized that atoms whose nuclei have reflection-asymmetric or pear-like deformations could have non-zero electric dipole moments (EDMs). Such a trait would be evidence of CP-violation, a feature that goes beyond the Standard Model of Physics. It is the purpose of this project to predict which nuclei exhibit a reflection-asymmetric deformation and which of those would be the best candidates for an EDM measuring experiment. Using nuclear Density Functional Theory along with the new computer code AxialHFB and massively parallel computing we calculated ground state nuclear properties for thousands of even-even nuclei across the nuclear chart: from light to superheavy and from stable to short-lived systems. Six different Energy Density Functionals (EDFs) were used to assess systematic errors in our calculations. These results are to be added to the website Massexplorer (http://massexplorer.frib.msu.edu/) which contains results from earlier mass table calculations and information on single quasiparticle energies. [Preview Abstract] |
Friday, October 14, 2016 9:54AM - 10:06AM |
CG.00008: Nuclear spin-isospin excitations from covariant quasiparticle-vibration coupling Caroline Robin, Elena Litvinova Methods based on the relativistic Lagrangian of quantum hadrodynamics and nuclear field theory provide a consistent framework for the description of nuclear excitations, naturally connecting the high- and medium-energy scales of mesons to the low-energy domain of nucleonic collective motion. Applied in the neutral channel, this approach has been quite successful in describing the overall transition strength up to high excitation energies, as well as fine details of the low-lying distribution [1]. Recently, this method has been extended to the description of spin-isospin excitations in open-shell nuclei [2]. In the charge-exchange channel, the coupling between nucleons and collective vibrations generates a time-dependent proton-neutron effective interaction, in addition to the static pion and rho-meson exchange, and introduces complex configurations that induce fragmentation and spreading of the resonances. Such effects have a great impact on the quenching of the strength and on the computing of weak reaction rates that are needed for astrophysics modeling. Gamow-Teller transitions in medium-mass nuclei and associated beta-decay half-lives will be presented. Further developments aiming to include additional ground-state correlations will also be discussed. [1] E. Litvinova et al. PRC 78, 014312; E. Litvinova et al. PRC 79, 054312. [2] C. Robin, E. Litvinova, arXiv:1605.00683, submitted to EPJA. [Preview Abstract] |
Friday, October 14, 2016 10:06AM - 10:18AM |
CG.00009: Revisiting Grodzins Systematics of B(E2) values Boris Pritychenko, Michael Birch, Balraj Singh Using Grodzin's formalism as modified by S. Raman {\it et al.}, {\sc Phys. Rev.} {\bf C 37}, (1988) 805 and D. Habs {\it et al.}, CERN Proposal INTC-P-156 (2002) we analyze systematics of our latest evaluated B(E2) data for all the even-even nuclei in Z=2-104 range published in At. Data Nucl. Data Tables 107 (2016). The analysis indicates a low predictive power of systematics for a large number of cases, and a strong correlation between B(E2) fit coefficients and nuclear shape, shell closing effects. These findings provide a strong rationale for introduction of individual or elemental (grouped by Z) fit parameters. The current systematics estimates of quadrupole collectivities in even-even nuclei yield complementary values for comparison with experimental results and theoretical calculations. The complete list of fit parameters will be presented and possible implications will be discussed. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700