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Nuclear Theory·nucl-th

Wednesday·August 13, 2025

7 papers—4 primary·3 cross-listed

All7Primary4Cross-lists3
  1. 01

    [Submitted on 11 Aug 2025]

    The DNA of nuclear models: How AI predicts nuclear masses

    Kate A. Richardson🇺🇸 · Sokratis Trifinopoulos🇺🇸 · Mike Williams🇺🇸

    Obtaining high-precision predictions of nuclear masses, or equivalently nuclear binding energies, , remains an important goal in nuclear-physics research. Recently, many AI-based tools have shown promising results on this task, some achieving precision that surpasses the best physics models. However, the utility of these AI models remains in question given that predictions are only useful where measurements do not exist, which inherently requires extrapolation away from the training (and testing) samples. Since AI models are largely black boxes, the reliability of such an extrapolation is difficult to assess. We present an AI model that not only achieves cutting-edge precision for , but does so in an interpretable manner. For example, we find that (and explain why) the most important dimensions of its internal representation form a double helix, where the analog of the hydrogen bonds in DNA here link the number of protons and neutrons found in the most stable nucleus of each isotopic chain. Furthermore, we show that the AI prediction of can be factorized and ordered hierarchically, with the most important terms corresponding to well-known symbolic models (such as the famous liquid drop). Remarkably, the improvement of the AI model over symbolic ones can almost entirely be attributed to an observation made by Jaffe in 1969 based on the structure of most known nuclear ground states. The end result is a fully interpretable data-driven model of nuclear masses based on physics deduced by AI.

    Comments:
    19 pages, 11 figures
    Subjects:
    Nuclear Theory (nucl-th); cs.AI (cs.AI); Machine Learning (cs.LG); Nuclear Experiment (nucl-ex)
    arXiv:
    2508.08370 [pdf]
    3 citations
  2. 02

    [Submitted on 12 Aug 2025]

    In-medium similarity renormalization group for a pairing-plus-particle-hole model

    L. H. Chen · Y. G. Yao · B. C. He

    We benchmark two implementations of the in-medium similarity renormalization group (IMSRG) method, IMSRG(2) and IMSRG(2*), for the low-lying states of a pairing-plus-particle-hole model with varying numbers of fermions. In IMSRG(2), all operators are truncated up to the normal-ordered two-body terms, whereas IMSRG(2*) includes an additional term to partially account for higher-body contributions. The results are compared against exact solutions. We find that IMSRG(2*) consistently outperforms IMSRG(2) for both ground and excited states, although achieving convergence for excited states remains more challenging in strongly correlated systems than for the ground state.

    Comments:
    7 pages, 10 figures
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2508.08595 [pdf]
    PRC(2026)·0 citations
  3. 03

    [Submitted on 12 Aug 2025]

    Impact of shape coexistence on the symmetric to asymmetric fission mode transition in Th isotopes

    Shengyuan Chen · Zeyu Li · Minghui Zhou · Zhipan Li

    We study the evolution of fission modes along the Th isotopic chain using a microscopic framework combining the time-dependent generator coordinate method and finite-temperature covariant density functional theory. Theoretical fission fragment charge distributions agree well with experiments, and reveal a rapid symmetric-to-asymmetric transition from to 234. By analyzing the collective potential energy surfaces and time evolution of collective probability density distributions, we demonstrate that this fission mode transition is strongly correlated with the rapidly deepening asymmetric fission valley a phenomenon driven by the reduction of deformation energies of both the heavy and light fragments formed in the asymmetric fission valley. Further analysis attributes the decrease of light-fragment deformation energies to the onset of a coexisting large-deformed minimum in neutron-rich Kr and Sr isotopes (dominated isotopes for light asymmetric peak), which arises from a deformed proton shell closure near . Notably, we identify, for the first time, the pivotal role of the light fragment and its shape coexistence structure on the fission mode transition in Th isotopes in a fully microscopic framework.

    Comments:
    7 pages, 7 figures, Submitted to Physical Review C
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2508.08616 [pdf]
    PRC(2026)·2 citations
  4. 04

    [Submitted on 12 Aug 2025]

    Spacetime Curvature as a Probe of Exotic Core Phases in Neutron Stars within Modified Gravity

    Sayantan Ghosh🇮🇳 · Bharat Kumar🇮🇳 · Subhash Mahapatra🇮🇳

    In this study, we investigate the effect of Energy-Momentum Squared Gravity (EMSG) on the curvature of neutron stars (NSs) by using three relativistic mean-field (RMF) equations of state (EOSs) and three hadron-quark phase transition (HQPT) EOSs. Neutron stars, with their extreme densities and strong gravitational fields, provide an ideal laboratory for testing General Relativity (GR) in the high-curvature regime and for exploring possible deviations via modified gravity. EMSG extends GR by including nonlinear terms involving the energy-momentum tensor, characterized by a coupling parameter . We focus on the Kretschmann, Ricci, and Weyl curvature scalars, analyzing their dependence on baryon density and radial coordinate for varying values of . Our results indicate that EMSG can significantly alter the curvature profiles of neutron stars. In particular, the magnitude of both Weyl and Kretschmann scalars increases (decreases) for a positive (negative) EMSG parameter, with the former exhibiting a larger dependence. Similarly, the surface curvature (SC) is notably affected by . Interestingly, we further observe distinct discontinuities in the curvature profiles at hadron-quark phase transitions, especially in the soft and intermediate HQPT models. These signatures may provide observable imprints of exotic core phases in neutron stars.

    Comments:
    Comments are welcome
    Subjects:
    Nuclear Theory (nucl-th); General Relativity and Quantum Cosmology (gr-qc); High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th)
    arXiv:
    2508.08866 [pdf]
    PRD(2026)·6 citations

Affiliations

first authorsco-authorsvia INSPIRE