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arXiv · 2510.08362

Hartree-Fock emulators for nuclei: Application to charge radii of $^{48,52}$Ca

Margarida Companys Franzke·Alexander Tichai·Kai Hebeler·Achim Schwenk
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Abstract

Understanding the emergence of complex structures of nuclei from chiral effective field theory (EFT) is a central challenge. The large number of low-energy couplings (LECs) in the EFT expansion and the significant cost of $\textit{ab initio}$ many-body calculations render large-scale sensitivity studies of many-body observables computationally prohibitive, necessitating the use of emulators as low-cost surrogates. In this work, we study a Hartree-Fock emulator based on eigenvector continuation to investigate trends in nuclear charge radii of neutron-rich calcium isotopes. We systematically vary the five LECs entering the leading three-nucleon (3N) interactions, and demonstrate the precision of the emulator through cross-validation over a wide parameter space. Our findings indicate that large charge radius increase from $^{48}$Ca to $^{52}$Ca is likely not explained by variations of the leading 3N couplings. This suggests that other effects, such as sensitivities to chiral two-nucleon interactions or neglected many-body effects, e.g., associated with nuclear collectivity, play an important role.

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Margarida Companys Franzke, Alexander Tichai, Kai Hebeler, Achim Schwenk. 2025-10-09. Hartree-Fock emulators for nuclei: Application to charge radii of $^{48,52}$Ca. https://doi.org/10.1103/wvyf-b2m3

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