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Hartree-Fock emulators for nuclei: Application to charge radii of Ca48,52

M. Companys Franzke*, A. Tichai†, K. Hebeler‡, and A. Schwenk§

  • *Contact author: margarida.companys@tu-darmstadt.de
  • †Contact author: alexander.tichai@tu-darmstadt.de
  • ‡Contact author: kai.hebeler@tu-darmstadt.de
  • §Contact author: achim.schwenk@tu-darmstadt.de
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Phys. Rev. C 114, 014330 – Published 27 July, 2026

DOI: https://doi.org/10.1103/wvyf-b2m3

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 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 the large charge-radius increase from Ca48 to Ca52 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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Phys. Rev. C 114, 014330– Published 27 July, 2026
  • Received 21 October 2025
  • Revised 22 April 2026
  • Accepted 19 May 2026
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

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