Speaker
Description
Understanding the structure of heavy and neutron-rich nuclei is essential for the rapid neutron-capture process (r-process). The simulation of this process, which synthesizes half of the elements heavier than iron, relies on accurate predictions of nuclear masses and reaction rates (neutron capture, photo absorption, beta decay, etc.) for thousands of neutron-rich nuclei. However, since experimental data are scarce in this exotic region of the nuclear chart, theoretical models are crucial to bridge this gap.
Models based on nuclear energy density functionals (EDFs) represent our current best hope to provide this plethora of data. Such an approach describes a nucleus in terms of its constituent nucleons while the equations remain sufficiently tractable for global application. We are building a new class of EDF-based models aimed at providing all necessary data to astrophysical applications: the Brussels-Skyrme-on-a-Grid or BSkG-series [1-6]. Exploiting the concept of spontaneous symmetry breaking to the utmost, the BSkG models accord the nucleus an extreme amount of freedom: nuclear shapes range from spheres and axially symmetric ellipsoids but also exhibit triaxial deformation, reflection asymmetry, non-zero angular momentum or all of these combined! Global tabulations of accurate predictions of these models are available for (i) nuclear ground-state quantities like masses, radii and deformation, (ii) more involved quantities including fission properties [7] and (iii) nuclear level densities (NLD), which are in excellent agreement with Oslo data where available [8].
Our next big goal is the prediction of photon strength functions (PSF) across the entire nuclear chart through quasi-particle random phase approximation (QRPA) calculations. This way, we will complete the nuclear data required to predict consistently electromagnetic reactions rates from a single nuclear-structure model, thereby making r-process simulations more robust to nuclear input. This project is also of interest to nuclear structure: extending our symmetry-broken solver to QRPA calculations will allow us to study the effect of exotic deformation modes, e.g. triaxial, octupole, …, on nuclear PSFs.
In this talk, I will start by discussing the BSkG series of models and discuss some key points on how spontaneous symmetry breaking helps us improve our global description of the properties of nuclei, and in particular our predictions of nuclear level densities [8]. Then, I will highlight some of the recent achievements made in the construction of our symmetry-broken QRPA solver and show the first BSkG predictions of PSFs for triaxially-deformed systems.
[1] G. Scamps et al., EPJA 57, 333 (2021).
[2] W. Ryssens et al., EPJA 58, 246(2022).
[3] G. Grams et al., EPJA 59, 270 (2023).
[4] W. Ryssens et al., EPJA 59, 96 (2023).
[5] G. Grams et al., EPJA 61, 35 (2025).
[6] G. Grams et al., arXiv:2601.05968 (2026).
[7] A. Sánchez-Fernández, PLB 874, 140287 (2026).
[8] S. Goriely et al. PRC 113, 014320 (2026).