Bulletin of the American Physical Society
2015 Fall Meeting of the APS Division of Nuclear Physics
Volume 60, Number 13
Wednesday–Saturday, October 28–31, 2015; Santa Fe, New Mexico
Session DE: Mini-Symposium on Toward a Predictive Model of Nuclei II |
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Chair: Jason Holt, TRIUMF Room: Sweeney Ballroom D |
Thursday, October 29, 2015 10:30AM - 10:42AM |
DE.00001: Microscopic Shell Model Calculations for the Fluorine Isotopes Bruce R. Barrett, Erdal Dikmen, Pieter Maris, James P. Vary, Andrey M. Shirokov Using a formalism based on the No Core Shell Model (NCSM), we have determined miscroscopically the core and single-particle energies and the effective two-body interactions that are the input to standard shell model (SSM) calculations [1]. The basic idea is to perform a succession of a Okubo-Lee-Suzuki (OLS) transformation, a NCSM calculation, and a second OLS transformation to a further reduced space, such as the {\it sd}-shell, which allows the separation of the many-body matrix elements into an ``inert'' core part plus a few valence-nucleons calculation. In the present investigation we use this technique to calculate the properties of the nuclides in the Fluorine isotopic chain, using the JISP16 nucleon-nucleon interaction. The obtained SSM input, along with the results of the SSM calculations for the Fluorine isotopes, will be presented.\\[4pt] [1] E. Dikmen, {\it et al}., Phys. Rev. C {\bf 91}, 064301 (2015). [Preview Abstract] |
Thursday, October 29, 2015 10:42AM - 10:54AM |
DE.00002: Ab-Initio Excited States from the In-Medium Similarity Renormalization Group Nathan Parzuchowski, Scott Bogner, Heiko Hergert The recently developed In-Medium Similarity Renormalization Group (IM-SRG) has had great success in the direct ab-initio calculation of scalar observables of the ground states of medium mass nuclei. To extend these calculations to excited states and response, we employ equations-of-motion (EOM) methods, which make approximations to the overall structure of excited states. We obtain an effective Hamiltonian by solving a set of IM-SRG flow equations specific to these approximations. Promising results are obtained for low-lying excited states in closed-shell nuclei. These calculations provide a simple framework for the calculation of electromagnetic and weak transition strengths, and can be extended straightforwardly to open-shell nuclei using a multi-reference framework. [Preview Abstract] |
Thursday, October 29, 2015 10:54AM - 11:06AM |
DE.00003: Improving the In-Medium Similarity Renormalization Group via approximate inclusion of three-body effects Titus Morris, Scott Bogner The In-Medium Similarity Renormalization Group (IM-SRG) has been applied successfully not only to several closed shell finite nuclei, but has recently been used to produce effective shell model interactions that are competitive with phenomenological interactions in the SD shell. A recent alternative method for solving of the IM-SRG equations, called the Magnus expansion, not only provides a computationally feasible route to producing observables, but also allows for approximate handling of induced three-body forces. Promising results for several systems, including finite nuclei, will be presented and discussed. [Preview Abstract] |
Thursday, October 29, 2015 11:06AM - 11:18AM |
DE.00004: Electric dipole excitations in calcium isotopes Irina Egorova, Elena Litvinova New results obtained for electric dipole strength in the chain of calcium isotopes with the mass numbers A = 40, 42, 44 and 48 are presented. Starting from the covariant mean-field theory, phonon spectra and phonon-nucleon coupling vertices for the phonons with spin $J \leq 6$ of normal parity were obtained as a self-consistent relativistic random phase approximation solution. Calculations for the dipole nuclear response were performed using the time blocking approximation. For the open-shell nuclei, both quasiparticle and phonon spectra include effects of the superfluid pairing on the equal footing. For the double magic nuclei the phonon space is extended by including phonons of pairing type and the corresponding effects on the spectra are discussed. [Preview Abstract] |
Thursday, October 29, 2015 11:18AM - 11:30AM |
DE.00005: ABSTRACT WITHDRAWN |
Thursday, October 29, 2015 11:30AM - 11:42AM |
DE.00006: Collective rotation from \textit{ab initio} theory Mark A. Caprio, Pieter Maris, James P. Vary The challenge of \textit{ab initio} nuclear theory is to quantitatively predict the complex and highly-correlated behavior of the nuclear many-body system, starting from the underlying internucleon interactions. We may now seek to understand the wealth of nuclear collective phenomena through \textit{ab initio} approaches. No-core configuration interaction (NCCI) calculations for $p$-shell nuclei give rise to rotational bands, as evidenced by rotational patterns for excitation energies, electromagnetic moments, and electromagnetic transitions. In this talk, the intrinsic structure of these bands is discussed, and the predicted rotational bands are compared to experiment. [Preview Abstract] |
Thursday, October 29, 2015 11:42AM - 11:54AM |
DE.00007: Quantum Nuclear Pasta Calculations with Twisted Angular Boundary Conditions Bastian Schuetrumpf, Witold Nazarewicz Nuclear pasta, expected to be present in the inner crust of neutron stars and core collapse supernovae, can contain a wide spectrum of different exotic shapes such as nuclear rods and slabs. There are also more complicated, network-like structures, the triply periodic minimal surfaces, already known e.g. in biological systems. These shapes are studied with the Hartree-Fock method using modern Skyrme forces. Furthermore twisted angular boundary conditions are utilized to reduce finite size effects in the rectangular simulation boxes. It is shown, that this improves the accuracy of the calculations drastically and additionally more insights into the mechanism of forming minimal surfaces can be gained. [Preview Abstract] |
Thursday, October 29, 2015 11:54AM - 12:06PM |
DE.00008: Nuclear response theory for isospin transfer in relativistic framework Caroline Robin, Elena Litvinova Nuclear response theory for isospin transfer modes has numerous applications extending across the field of nuclear physics from beta decay, neutrino scattering, electron capture, two-neutrino and neutrino-less double beta decay to weak processes in stars. Precise information on such modes of excitation as Gamow-Teller resonance and spin-dipole resonance is needed to compute weak reaction rates, which are important for astrophysical modeling. In this work we present a theoretical approach to nuclear spin-isospin response. It is based on the relativistic Lagrangian and includes explicitly effective meson degrees of freedom to describe nucleon-nucleon interaction, and, at the same time, emergent collective phenomena which can be quantified consistently as an additional nucleon-nucleon interaction induced by the nuclear medium. Pion-nucleon interaction is considered with the free-space coupling constant [1,2]. The recent development introduces pairing correlations of the superfluid type, which are needed for a correct description of open-shell nuclei [3]. New results of calculations for Gamow-Teller resonance and for spin-dipole resonance in medium-mass nuclei will be presented and discussed. \\[4pt] [1] T. Marketin, E. Litvinova, D. Vretenar, P. Ring, Phys. Lett. B 706, 477 (2012).\\[0pt] [2] E. Litvinova, B.A. Brown, D.-L. Fang, T. Marketin, R. G. T. Zegers, Phys. Lett. B 730, 307 (2014).\\[0pt] [3] C. Robin, E. Litvinova, to be published. [Preview Abstract] |
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