Bulletin of the American Physical Society
88th Annual Meeting of the Southeastern Section of the APS
Volume 66, Number 16
Thursday–Saturday, November 18–20, 2021; University Center Club, Florida State University, Tallahassee, Florida
Session E02: Advances in Theoretical Nuclear Physics I |
Hide Abstracts |
Chair: Alexander Volya, Florida State University Room: Pensacola |
Thursday, November 18, 2021 2:00PM - 2:30PM |
E02.00001: DMRG description of the island of inversion isotopes 28-33F Invited Speaker: Kevin Fossez Neutron-rich nuclei near the limits of nuclear stability will be one of the main areas of study at the Facility for Rare Isotope Beams (FRIB) coming online in 2021. These systems exhibit features common to all open quantum systems due to their weakly bound or unbound character, and also reveal interesting information about the nuclear interaction due to their extreme neutron-to-proton ratios and emergent behaviors. This is particularly visible in the so-called island of inversion (IOI), a region of the nuclear chart around $Z=10$ and $N=20$ where nuclear structure deviates from the standard shell model predictions due to deformation and continuum effects. Recently, two experiments on the neutron-rich isotopes $^{28,29}$F have revealed an unexpectedly large influence of continuum effects which effectively extends the IOI to these nuclei. In this work, I will show the mechanisms leading to these observations using state-of-the-art large-scale shell model calculations including continuum states and based on a core of $^{24}$O and an effective two-body interaction with only three adjustable parameters. I will also present new predictions in the isotopes $^{25-33}$F to motivate future experiments at FRIB. [Preview Abstract] |
Thursday, November 18, 2021 2:30PM - 2:45PM |
E02.00002: Eigenvector Continuation for Resonance States Nuwan Yapa, Sebastian Koenig Many nuclear states found in nature are not bound, but are resonances -- meta-stable states that decay after a certain time period. Solving the quantum few-body problem to identify and study such resonance states is known to be a complex and computationally expensive task. However, a novel method known as Eigenvector Continuation (EC) has recently emerged as an intriguing tool to obtain approximate solutions for computationally expensive eigenvalue problems with great speed and accuracy. As a variational method at heart, EC provides a prescription to ``learn'' a tailored effective basis in which the desired solution is expanded. In this talk, we explore two different approaches for applying EC to resonances. First, we will demonstrate that EC works well with finite-volume calculations, where resonances are manifest as avoided crossings in the discrete spectrum of energy levels as the size of the volume is varied. Then we proceed and show that the same can be accomplished in momentum space, where we identify resonances as poles of the S-matrix analytically continued onto the second Riemann sheet in the complex energy plane. In both cases we emphasize how EC makes it possible to predict resonances using as input solely information from bound-state solutions. [Preview Abstract] |
Thursday, November 18, 2021 2:45PM - 3:00PM |
E02.00003: Systematic global study of charge radii and related indicators in covariant density functional theory. Udeshika Perera, Anatoli Afanasjev, Peter Ring A systematic global investigation of differential charge radii has been performed within the CDFT framework for the first time. Theoretical results obtained with conventional covariant energy density functionals and separable pairing interaction are compared with experimental differential charge radii in the regions of the nuclear chart in which available experimental data crosses neutron shell closures at N = 28, 50, 82, and 126. It is shown that the kinks in the charge radii at neutron shell closures are due to the underlying single-particle structure and due to the weakening or collapse of pairing at these closures. It is usually assumed that pairing is a dominant contributor to odd-even staggering (OES) in charge radii. Our analysis paints a more complicated picture. It suggests a new mechanism in which the fragmentation of the single-particle content of the groundstate in odd-mass nuclei due to particle-vibration coupling provides a significant contribution to OES in charge of radii. [Preview Abstract] |
Thursday, November 18, 2021 3:00PM - 3:15PM |
E02.00004: Global Sensitivity Analysis of Collective Observables for Light Nuclei Kevin Becker, Kristina Launey, Tomas Dytrych Collective motion plays an important role in the dynamics of atomic nuclei across the Segre chart, and ab initio studies show that these features arise from an emergent symmetry in nuclear Hamiltonians [1]. With the goal to constrain uncertainties on collective observables computed with chiral effective field theory interactions, we couple the framework of the symmetry-adapted no-core shell model with the method of global sensitivity analysis [2]. In this talk, we discuss a sensitivity analysis that determines the low-energy constants in the interaction that have the largest impact on collective observables. We generate a sufficiently large sample of unique sets of the low-energy constants, and diagonalize the associated Hamiltonians to obtain the low-lying wavefunctions for selected light nuclei. Specifically, we compute the quadrupole moments for 6Li and 12C. This opens the door for constructing nuclear potentials for precise calculations of collective nuclear observables. [1] T. Dytrych, K. D. Launey, J. P. Draayer, et al., Phys. Rev. Lett. 124, 042501 (2020) [2] A. Ekstr\"{o}m and G. Hagen, Phys. Rev. Lett. 123, 252501 (2019) [Preview Abstract] |
Thursday, November 18, 2021 3:15PM - 3:30PM |
E02.00005: Pionless EFT calculations of nuclear response functions Andrew Andis, Sebastian Koenig Nuclear response functions encode the interaction of atomic nuclei with electromagnetic (or electroweak) probes. These observables can be used to understand the details of nuclear dynamics and in particular to relate theoretical predictions to experiments. Pionless effective field theory (EFT), and in particular the expansion of light nuclei around the unitarity limit, have been shown to successfully describe the binding energies and radii of light nuclei. To further assess the predictive power of this framework, we study in this work the longitudinal response function of few-nucleon states in Pionless EFT. We implement the Lorentz Integral Transform (LIT), an established method that makes it possible to calculate continuum observables like response functions with effective bound-state methods, trading the complexity of an explicit break-up calculation for a delicate numerical inversion. We present our implementation of the LIT in momentum space, using interactions provided by Pionless EFT, as well as first results derived within this framework. [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. |
© 2025 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