Understanding the Effect of Chiral NN Parametrization on Nuclear Shapes From an Ab Initio Perspective

The ab initio symmetry-adapted no-core shell model naturally describes nuclear deformation and collectivity, and is therefore well-suited to studying the dynamics and coexistence of shapes in atomic nuclei. For the first time, we analyze how these features in low-lying states of 6Li and 12C are impacted by the underlying realistic nucleon-nucleon interaction. We find that the interaction parametrization has a notable but limited effect on collective shapes in the lowest 6Li and 12C states, while collective structures in the excited 2+ state of 12C are significantly more sensitive to the interaction parameters and exhibits emergent shape coexistence.Comment: 4 pages + references, 3 figures, CGS17 (2023) conference proceedings contributio

Emergent symplectic symmetry in atomic nuclei

Exact symmetry and symmetry-breaking phenomena play a key role in gaining a better understanding of the physics of many-particle systems, from quarks and atomic nuclei, through molecules and galaxies. In nuclei, exact and dominant symmetries such as rotational invariance, parity, and charge independence have been clearly established. Beyond such symmetries, the nature of nuclear dynamics appears to exhibit a high degree of complexity, and only now, we show the fundamental role of an emergent approximate symmetry in nuclei, the symplectic Sp(3,ℝ) symmetry, as clearly unveiled from ab initio studies that start from realistic interactions. In this article, we detail and enhance our recent findings presented in [T. Dytrych, K.D. Launey, J.P. Draayer, D.J. Rowe, J.L. Wood, G. Rosensteel, C. Bahri, D. Langr, R.B. Baker, Phys. Rev. Lett. 124, 042501 (2020)], that establish Sp(3,ℝ) as a remarkably good symmetry of the strong interaction, and point to the predominance of a few equilibrium nuclear shapes (deformed or not) with associated vibrations and rotations that preserve the symplectic Sp(3,ℝ) symmetry. Specifically, we find that the structure of nuclei below the calcium region in their ground state, as well as in their low-lying excited states and giant resonances, respects this symmetry at the 60–80% level

Untangling simple patterns in intricate atomic nuclei

In this review, we present a symmetry-guided strategy that utilizes exact as well as partial symmetries for enabling a deeper understanding of and advancing ab initio studies for determining the microscopic structure of atomic nuclei. These symmetries are critical toward untangling simple patterns within an overarching complexity that defines nuclei, and naturally provide a physically relevant basis. Such basis, for large-scale calculations, allows the model space size to be reduced through a very structured selection of the basis states, and guides extensions of the ab initio theory beyond current limitations. This is key to facilitating studies of the structure and reactions of isotopes across the nuclear chart, using QCD-inspired interactions and high performance computing (HPC) resources. This, in turn, can guide explorations of orderly patterns in nuclei and how they emerge from first principles

New Insights into Backbending in the Symmetry-adapted Framework

We provide new insights into backbending phenomenon within the symmetry-adapted framework which naturally describes the intrinsic deformation of atomic nuclei. For $^{20}\text{Ne}$, the canonical example of backbending in light nuclei, the ab initio symmetry-adapted no-core shell model shows that while the energy spectrum replicates the backbending from experimental energies under the rigid rotor assumption, there is no change in the intrinsic deformation or intrinsic spin of the yrast band around the backbend. For the traditional example of $^{48}\text{Cr}$, computed in the valence shell with empirical interactions, we confirm a high-spin nucleus that is effectively spherical, in agreement with previous models. However, we find that this spherical distribution results, on average, from an almost equal mixing of deformed prolate shapes with deformed oblate and triaxial shapes. Microscopic calculations confirm the importance of spin alignment and configuration mixing, but surprisingly unveil no anomalous increase in moment of inertia. This finding opens the path toward further understanding the rotational behavior and moment of inertia of medium-mass nuclei.Comment: 11 pages, 7 figure

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

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

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