Bulletin of the American Physical Society
APS April Meeting 2019
Volume 64, Number 3
Saturday–Tuesday, April 13–16, 2019; Denver, Colorado
Session R14: Theoretical Aspects of Nuclear Structure 
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Sponsoring Units: DNP Chair: Maxime Brodeur, University of Notre Dame Room: Sheraton Plaza Court 3 
Monday, April 15, 2019 1:30PM  1:42PM 
R14.00001: Improved trial wave functions with 4body correlations for Nuclear Quantum Monte Carlo Cody L Petrie, Kevin E Schmidt Quantum Monte Carlo techniques are used to study various aspects of nuclear physics with great accuracy. A major difficulty with these methods is coming up with an accurate and tractable trial wave function. Until now Auxiliary Field Diffusion Monte Carlo calculations have been done with up to 2body correlations in the trial wave function. We have extended this to include up to 4body correlations using two slightly different expansions. Using these new wave functions we have done binding energy calculations for $^{4}$He, $^{16}$O, $^{40}$Ca, and symmetric nuclear matter at saturation density. For each calculation the energy decreased with respect to calculations with 2body correlations. We also discuss applications of these new wave functions to physical systems such as particle clustering in neutron star crusts. 
Monday, April 15, 2019 1:42PM  1:54PM 
R14.00002: SelfConsistent Calculation of Chiral Effective Operator Observables in TwoNucleon Systems Robert Basili, Soham Pal, Shiplu Sarker, Pieter Maris, James P Vary We investigate the effects on twonucleon system observables when including corrections arising from Chiral Effective Field Theory to operators treated at a chiral order consistent with the chiral interaction being modeled. We provide corrections to the rootmeansquare charge radius, magnetic dipole moment, and GamowTeller transition operator at varying chiral order when using regulated chiral potentials solved with a finite matrix method in the relative Harmonic Oscillator (HO) basis. We compare groundstate observables with and without the consistent chiral operator corrections, and analyze the impact due to ultraviolet and Infrared regulation within the HO basis. We discuss the implications of these results when employing a similar treatment in ab initio NoCore Shell Model calculation for properties of light nuclei. 
Monday, April 15, 2019 1:54PM  2:06PM 
R14.00003: Nuclear response in a finitetemperature relativistic framework Herlik Wibowo, Elena Litvinova The present work formulates the nuclear response theory beyond the relativistic randomphase approximation for the case of finite temperature. We model a compound nucleus within the framework of the thermal relativistic meanfield theory, which describes the interaction between the Dirac nucleons and mesons at finite temperature. A single frequency variable BetheSalpeter equation for the nuclear response function is derived with the aid of the imaginarytime projection operator, which contains the FermiDirac occupation numbers. This approach called finite temperature relativistic time blocking approximation is utilized numerically to calculate the monopole, dipole, and quadrupole responses of the neutronrich ^{68}Ni nucleus for various temperatures. The discussion will focus on the evolution of the nuclear multipole responses and pygmy dipole resonance of the ^{68}Ni nucleus with temperature. 
Monday, April 15, 2019 2:06PM  2:18PM 
R14.00004: Dispersive optical model calculations for neutron rich nuclei Natalia Calleya, Mackenzie C. Atkinson, Willem H. Dickhoff Nuclear structure and nuclear reactions represent different energy domains, and it is clear that the two are correlated as nuclear scattering cannot be fully understood without a precise description of the nucleus itself. A consistent approach, presented in this work as the dispersive optical model (DOM), was employed to describe nuclear properties above and below the Fermi energy. Using experimental data and structure information available to constrain the parameters, it has been successfully implemented for 40Ca and 48Ca. Recently, the DOM was used to extrapolate calculations to heavier Ca isotopes, to clarify how nuclear properties evolve as one goes from stability to the drip lines. Preliminary results show agreement with expected trends and encourage further predictions for neutron rich nuclei. Also, an analysis of pertinent ground state properties was carried out to investigate asymmetry effects on nucleon densities, generating an alternative energy density profile consistent with rms radii data and particle numbers. 
(Author Not Attending)

R14.00005: NucleonNucleus Effective field theory Aaina Bansal, Thomas F Papenbrock We build a NucleonNucleus (NA) effective field theory potential to study A+1 neighbor of an Abody doublymagic nucleus by attaching a neutron to an inert core with a structure. The lowenergy coefficients of the NA EFT potential are optimized scattering data available for (n,n) process. We use the optimized NA potential to compute A+1 bound states. We study 5He, 17O and 41Ca nuclei using our approach. 
Monday, April 15, 2019 2:30PM  2:42PM 
R14.00006: Tests of ab initio nuclear theory via the isobaric multiplet mass equation in T=1 superallowed β decay systems Matthew S Martin, Kyle G Leach, Jason D Holt, S Ragnar Stroberg Precision measurements of superallowed 0+ > 0+ nuclear β decay currently provide the most precise value of the vector coupling in the weak interaction. The extraction of this quantity from these experiments assume that isospin symmetry is exact, thus requiring that theoretical isospinsymmetrybreaking (ISB) corrections must be applied. 
Monday, April 15, 2019 2:42PM  2:54PM 
R14.00007: Order and Chaos in a generalized Interacting Boson Model Declan Mulhall The spectra of a rotationaly invariant random Hamiltonian for a system of $N$ particles on 2 $j$ levels is examined. In the interacting boson model, $j$=0,2, and in the vibron model, $j$=0,1. Here a broader range of $j$ is considered. In spite of the random nature of the interaction, regular spectral structures emerge, such as rotational bands, spin0 and maximum spin ground states, and smooth yrast lines. Signatures of rotational bands are present in both the structure of the spectra near the ground state and in the $B(E2)$ values. These spectral features are usually associated with collective states, yet the usual signatures of quantum chaos are present in the wave functions of the ground state and low lying states. An explanation is framed based on the statistical mechanics of a quantum gas. 
Monday, April 15, 2019 2:54PM  3:06PM 
R14.00008: Complexenergy description of open molecular and nuclear systems Xingze Mao Open quantum systems are quantum systems whose interaction with the environment has a nonnegligible effect. Some examples are polarized molecules which can attract an excess electron to form anions or nuclei such as neutronrich lithium isotopes which can be thought of as a proton and several neutrons coupled to ^{4}He core. Describing open quantum systems is a challenge as one has to go beyond the standard Hilbert formalism to include the scattering space. The Berggren ensemble is a good tool to study open quantum systems as it treats bound states, resonances and nonresonant scattering states on the same footing. I will describe the Berggren basis, and then show how we used it to model molecular multipole anions in terms of a particleplusrotor model, with the interaction between the rotating core and the excess electron given by a multipolar deformed Gaussian potential. I will also discuss our recent effort to describe lithium isotopes from ^{6}Li to ^{11}Li using the Gamow shell model, which can be used to describe these exotic nuclei with both continuum effect and correlations between valence nucleons considered.

Monday, April 15, 2019 3:06PM  3:18PM 
R14.00009: Abinitio wavefunction approach to aperiodic helical lattices Matej Veis, Jozef Noga As a model system, a chain of hydrogen atoms is embedded onto a cylinder and its electronic groundstate is numerically investigated. The resulting helix is periodic in the curved cylindrical space, but the periodicity in the Cartesian space is not guaranteed. Aperiodic helices exist and can be generated by irrational rotations, akin to the Penrose tiling [1]. To address such systems with microscopic precision, integrals of localized functions are calculated in a given supercell, while the HartreeFock is formulated in the Fourier space associated to the helical symmetry. Second order perturbative corrections are limited to pair excitations (pairMP2). The method is thoroughly benchmarked on finite rings against coupled cluster theory [2]. The 1D thermodynamic limit is reached by extrapolation. The issue of a slow (1/R) saturation of the Coulomb field is overcame by approximating the contributions from the tails of the chain, i.e. the farfield, by a fast multipole expansion (FMM) that utilizes merely onebody properties. [1] C. Corduneanu, Almost periodic functions (Chelsea Pub. Co, New York, N.Y, 1989) [2] M. Motta et. al,Physical Review X 7 (2017), 10.1103/physrevx.7.031059. 
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