11 research outputs found
Exact isovector pairing in a shell-model framework: Role of proton-neutron correlations in isobaric analog states
We utilize a nuclear shell model Hamiltonian with only two adjustable
parameters to generate, for the first time, exact solutions for pairing
correlations for light to medium-mass nuclei, including the challenging
proton-neutron pairs, while also identifying the primary physics involved. In
addition to single-particle energy and Coulomb potential terms, the shell model
Hamiltonian consists of an isovector pairing interaction and an average
proton-neutron isoscalar interaction, where the term describes the
average interaction between non-paired protons and neutrons. This Hamiltonian
is exactly solvable, where, utilizing 3 to 7 single-particle energy levels, we
reproduce experimental data for 0 state energies for isotopes with mass
through exceptionally well including isotopes from He to Ge.
Additionally, we isolate effects due to like-particle and proton-neutron
pairing, provide estimates for the total and proton-neutron pairing gaps, and
reproduce (neutron) = (proton) irregularity. These results provide a
further understanding for the key role of proton-neutron pairing correlations
in nuclei, which is especially important for waiting-point nuclei on the
rp-path of nucleosynthesis.Comment: 10 pages, 4 figure
Symplectic Effective Field Theory for Nuclear Structure Studies
A Symplectic Effective Field Theory that unveils the observed emergence of
symplectic symmetry in atomic nuclei is advanced. Specifically, starting from a
simple extension of the harmonic-oscillator Lagrangian, an effective field
theory applied against symplectic basis states is shown to yield a Hamiltonian
system with one fitted parameter. The scale of the system can be determined
self consistently as the ratio of the average volume of a nucleus assumed to be
spherical to its volume as determined by the average number of oscillator
quanta, which is stretched by the fact that the plane-wave solution satisfies
the equations of motion at every order without the need for perturbative
corrections. As an application of the theory, results for 20Ne, 22Ne and 22Mg
are presented that yield energy spectra, B(E2) values, and matter radii in good
agreement with experimentally measured results
Symmetries and canonical transformations in nuclei
We begin with a brief historical overview of the importance of special symmetries in atomic nuclei, especially the symplectic symmetry. We then show how deforming the symplectic algebra through canonical transformations that are unitary can be used to describe the same physics that in a non-deformed picture requires huge model spaces in far smaller deformed spaces, a simplification that should proportionally reduce the complexity of using the symplectic symmetry in applications. The overarching objective is to exploit this strategy to probe more deeply into the (ab initio) structure of nuclei, short cutting a need to await the development of evermore robust computational resources for carrying out advanced microscopic nuclear structure investigations
Overlaps of deformed and non-deformed harmonic oscillator basis states
A systematic approach for expanding non-deformed harmonic oscillator basis states in terms of deformed ones, and vice versa, is presented. The objective is to provide analytical results for calculating these overlaps (transformation brackets) between deformed and non-deformed basis states in spherical, cylindrical, and Cartesian coordinates. These overlaps can be used for reducing the complexity of different research problems that employ three-dimensional harmonic oscillator basis states, for example as used in coherent state theory and the nuclear shell-model, especially within the context of ab initio symmetry-adapted no-core shell model
A 21st Century View of Nuclear Structure
Exploiting exact and special symmetries to unmask simplicity within complexity, which remains the “holy grail” of nuclear physics, will be considered within its historical context and as evolving through 21st century ab initio methods, including emerging results linked to the internal structure of nucleons. Some exemplar results for very light to medium mass nuclei will be presented, and what these may portend for heavier systems, including species beyond known lines of stability, will be proffered
A 21
Exploiting exact and special symmetries to unmask simplicity within complexity, which remains the “holy grail” of nuclear physics, will be considered within its historical context and as evolving through 21st century ab initio methods, including emerging results linked to the internal structure of nucleons. Some exemplar results for very light to medium mass nuclei will be presented, and what these may portend for heavier systems, including species beyond known lines of stability, will be proffered
Exact isovector pairing in a shell-model framework: Role of proton-neutron correlations in isobaric analog states
Nuclear Forces for Precision Nuclear Physics -- a collection of perspectives
International audienceThis is a collection of perspective pieces contributed by the participants of the Institute of Nuclear Theory's Program on Nuclear Physics for Precision Nuclear Physics which was held virtually from April 19 to May 7, 2021. The collection represents the reflections of a vibrant and engaged community of researchers on the status of theoretical research in low-energy nuclear physics, the challenges ahead, and new ideas and strategies to make progress in nuclear structure and reaction physics, effective field theory, lattice QCD, quantum information, and quantum computing. The contributed pieces solely reflect the perspectives of the respective authors and do not represent the viewpoints of the Institute for Nuclear theory or the organizers of the program
Nuclear Forces for Precision Nuclear Physics -- a collection of perspectives
This is a collection of perspective pieces contributed by the participants of the Institute of Nuclear Theory's Program on Nuclear Physics for Precision Nuclear Physics which was held virtually from April 19 to May 7, 2021. The collection represents the reflections of a vibrant and engaged community of researchers on the status of theoretical research in low-energy nuclear physics, the challenges ahead, and new ideas and strategies to make progress in nuclear structure and reaction physics, effective field theory, lattice QCD, quantum information, and quantum computing. The contributed pieces solely reflect the perspectives of the respective authors and do not represent the viewpoints of the Institute for Nuclear theory or the organizers of the program