Speaker
Description
For much of its history, low-energy nuclear physics has been driven by phenomenological models that describe experimental observations without directly addressing their microscopic origins. Collective models based on vibrations, rotations, and shell structure have provided a remarkably successful framework for interpreting excitation spectra and other spectroscopic observables. However, rapid advances in computational power, many-body theory, and effective field theories are transforming the field. Increasingly, attempts are being made to explain nuclear structure through approaches that seek to connect emergent phenomena to the underlying nucleon-nucleon interactions and to the strong interaction.
This presentation will examine how modern studies of nuclear collectivity are contributing to this transition. Emphasis will be placed on collective quadrupole excitations, triaxiality, and shape dynamics, where traditional vibrational descriptions are increasingly being complemented by microscopic interpretations rooted in shell evolution, proton-neutron correlations, and three-nucleon forces. Recent developments, including the work of Otsuka et al. [1] on shell evolution and the emergence of triaxial collective degrees of freedom, provide a framework in which nuclear shapes and collective excitations can be understood as emergent consequences of many-body dynamics arising from the underlying nucleon interactions. In this picture, collective phenomena are no longer viewed solely as phenomenological descriptions, but as manifestations of many-body dynamics arising from nuclear forces constrained by the symmetries of QCD.
Precision measurements of electromagnetic matrix elements, transition probabilities, quadrupole moments through Coulomb-excitation observables [e.g., 2-4] provide powerful probes of the mechanisms through which collective behaviour emerges in finite nuclei. These measurements offer stringent benchmarks for modern ab initio and beyond-mean-field calculations, testing the extent to which microscopic theories can reproduce the rich spectrum of collective phenomena observed experimentally. More broadly, they highlight a fundamental shift in low-energy nuclear physics: from describing collective behaviour through phenomenological models to understanding how it emerges from nuclear interactions ultimately rooted in the strong interaction.
This work was supported in part by Australian Research Council Grant No. DP210101201 and the International Technology Center Pacific (ITC-PAC) under Contract No. FA520919PA138.
[1] T. Otsuka et al, Euro. Phys. J. A 61, 126 (2025).
[2] M. Reece et al, Phys. Rev. C 112, 034311 (2025).
[3] J. Woodside et al, Phys. Rev. C 113, 044306 (2026).
[4] T. N. Perissinotto et al, EPJ Web of Conferences 368, 00006 (2026).