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Nuclear Theory·nucl-th

Monday·March 2, 2026

7 papers—5 primary·2 cross-listed

All7Primary5Cross-lists2
  1. 01

    [Submitted on 26 Feb 2026]

    Hyperon-Induced Inhomogeneous Pion Condensation and Moat Regimes in Neutron Star Cores

    Theo F. Motta🇧🇷 · Randall H. V. Pradinett🇧🇷 · Gastão Krein🇧🇷

    We perform a stability analysis of the homogeneous ground state of nuclear matter against inhomogeneous perturbations of the pion condensate. In -equilibrium, restricting the baryon species to nucleons only, we observe no instability; however, at high densities, the pseudoscalar density-density correlations assume a moat regime, i.e. a damped oscillatory patterned spatial correlation, which in momentum space appears as a non-zero global minimum for some finite three-momentum. When hyperons are permitted to appear, this minimum can cross down to negative values, which configures an instability towards an inhomogeneous pion condensate which ultimately will affect the equation of state.

    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
    arXiv:
    2602.23433 [pdf]
    PRD(2026)·1 citation
  2. 02

    [Submitted on 27 Feb 2026]

    Particle number projected energies at finite temperature

    Jiawei Chen · Yu Qiang · Junchen Pei

    In this work, the particle number projection at finite temperature is incorporated into self-consistent Skyrme density functional calculations. In particular, the energies of compound nuclei as a function of deformations are calculated rigorously based on projected densities. Results show that the even-odd staggering effect in partition function gradually diminishes as the system approaches the critical temperature. The obtained fission barriers are similar to that without projection at finite temperature, although projected energies are different. The nuclear level density at the ground state and the barrier are also studied using the projection method and the discrete Gaussian method.

    Comments:
    7 pages, 4 figures
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2602.23642 [pdf]
    PRC(2026)·0 citations
  3. 03

    [Submitted on 27 Feb 2026]

    Is nucleon spin thermalized in intermediate-energy heavy-ion collisions?

    Jun Xu🇨🇳

    Despite the success of the spin-thermalized assumption in explaining hyperon spin polarizations in relativistic heavy-ion collisions, challenges begin to arise especially at lower collision energies. The present study compares the nucleon spin polarization during the collision process and at the freeze-out stage from a non-relativistic spin-dependent transport model with spin-thermalized approaches in intermediate-energy heavy-ion collisions, where the relativistic effect and the temperature gradient have shown to be unimportant. It is found that both the global and local spin polarizations are largely overestimated from spin-thermalized approaches, compared to those generated by the spin-orbit mean-field potential in transport simulations.

    Comments:
    7 pages, 6 figures
    Subjects:
    Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
    arXiv:
    2602.23793 [pdf]
    APS Open Science(2026)·1 citation
  4. 04

    [Submitted on 27 Feb 2026]

    factor of C(,)O at low energies in cluster effective field theory

    Shung-Ichi Ando

    The C(,)O reaction at low energies is studied by constructing an effective field theory. We choose a separation scale at ~MeV, where is the initial -C energy in center-of-mass frame, just below the sharp resonant state of O, and include two open channels, -C and -O, and resonant , , states of O in the study. Parameters of the theory are fitted to experimental data, factor of C(,)O at the energies below ~MeV, including the data sets recently reported by the LUNA and JUNA collaborations, and the factor of C(,)O is extrapolated to the Gamow peak energy ~MeV in the low mass AGB stars. We discuss an uncertainty in the estimate of the factor and confirm that the main part of the uncertainty emerges from the parameter fit of the near-breakup threshold state of O.

    Comments:
    28 pages, 4 figures
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
    arXiv:
    2602.23794 [pdf]
    1 citation
  5. 05

    [Submitted on 27 Feb 2026]

    Theoretical Studies of alpha Clustering in Nuclei and Beyond

    Takaharu Otsuka · Alexander Volya · Naoyuki Itagaki

    This article comprises three sections. Section 2 starts with a review of ab initio no-core shell model calculations by Monte Carlo Shell Model. Alpha clustering arises for 8,10,12Be and 12C with Daejeon16 and JISP16 interactions, even in the ground state of 12C. Hoyle state is shown to be dominated by alpha clustering in triangular configurations. As the ground and Hoyle states show strong deformations, they are good cases to investigate rotational excitations. As an original work, the recently proposed fully quantum (mechanical) formulation for deformation and rotation is extended to cluster states. Dual rotational modes are proposed: compact-object and distant-object rotations. The former is found in many heavy nuclei, whereas the latter can be found for clustering states. While 8Be is an example for the latter, 12C is a rare example that both modes appear. Atomic molecules and hadrons can be viewed similarly. Possible relevance to fission is mentioned. Section 3 presents a general framework for an extended no-core shell model with cluster-nucleon configuration interaction, combining traditional shell-model-like configurations with explicit microscopic configurations representing cluster degrees of freedom. The section reviews the microscopic origins of cluster substructures in light nuclei, emphasizing how nucleonic degrees of freedom, nucleon-nucleon interactions, and continuum coupling naturally extend the traditional shell model into configuration-interaction frameworks that incorporate clustering and reaction dynamics. Section 4 presents that although the cluster structure is robust in Be-C nuclei, some jj-coupling shell model components are mixed in the ground state of 12C. Using the antisymmetrized quasi cluster model, we can clearly model this competition between the cluster and shell components. The spin-orbit interaction is key.

    Comments:
    52 pages, 21 figures; 2nd version -> Fig. 9 was slightly revised, one wording was modified (prolonged -> elongated) in the main text -> 60 pages, revisions -> minor change -> ACCEPTED by EPJA, abstract mentions Sect. 5, ref. 48 arXiv to EPJ-Conf
    Subjects:
    Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
    arXiv:
    2602.24175 [pdf]
    EPJA(2026)·1 citation
  6. 06

    [Submitted on 27 Feb 2026] (cross-list from astro-ph.HE)

    Realistic Equations of State Informing Neutron Star Post-Merger Gravitational-Wave Frequencies

    Spencer J. Magnall🇦🇺 · Nilaksha Barman🇮🇳 · Debarati Chatterjee🇮🇳 · Paul D. Lasky🇦🇺 · Simon Goode🇦🇺

    Binary neutron star mergers are thought to produce hot, rapidly rotating neutron stars with masses that can far exceed their Tolman-Oppenheimer-Volkoff mass. The gravitational-wave emission from such remnants provides a unique opportunity to measure the nuclear equation of state at densities and temperatures not available to terrestrial experiments. Current detector design is informed by gravitational-wave signals from general relativistic hydrodynamics simulations of neutron star mergers, typically with hybrid thermal treatments for the equation of state, where a cold equation of state is modified by adding a thermal component. We use realistic equations of state based on the relativistic mean field model with consistent treatment of thermal effects to compute the distribution of expected peak gravitational-wave frequencies. Marginalising over equation of state and progenitor neutron star masses, we show the peak frequency of emission ranges from to 4 kHz. The width of this distribution suggests the need for broadband observatories with kHz sensitivity, and calls into question some of the so-called post-merger optimised configurations. We show the proposed KAGRA high-frequency design is well-suited to measuring post-merger remnants when compared to the KAGRA broadband design.

    Comments:
    8 pages, 5 figures, to be submitted
    Subjects:
    High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc); Nuclear Theory (nucl-th)
    arXiv:
    2602.23646 [pdf]
    MNRAS(2026)·1 citation
  7. 07

    [Submitted on 27 Feb 2026] (cross-list from nucl-ex)

    High-Precision Mass Measurements of Proton-Rich Rh, Pd, Cd isotopes in the vicinity of 100Sn and Impact on X-Ray Burst and Supernova Nucleosynthesis

    D. S. Hou · W. D. Xian · M. Rosenbusch · M. Wada · P. Schury · A. Takamine · Y. Luo · J. Lee · H. Ishiyama · S. Nishimura · C. Y. Fu · A. Dohi and 46 other authors

    Using the ZeroDegree multi-reflection time-of-flight mass spectrograph of the CRISMASS project at RIKEN Radioactive Isotope Beam Factory, we performed high-precision mass measurements of proton-rich nuclei near the doubly magic nucleus 100Sn, achieving uncertainties on the order of 10 keV. The masses of 91Rh, 92Pd, and 96Cd were determined for the first time with high precision, and the accuracy of several additional masses was substantially improved. Incorporating the new data into X-ray burst simulations significantly reduces the abundance uncertainties in the = 90-100 region, shifting the reaction flow toward = 90 production and suppressing the synthesis of heavier nuclei. Further investigation of the -process indicates that 99Rh plays a significant role in the reaction flow within the mass region studied. These high-precision mass measurements refine the mass surface near 100Sn and provide critical constraints on models of proton-rich nucleosynthesis.

    Subjects:
    Nuclear Experiment (nucl-ex); Astrophysics of Galaxies (astro-ph.GA); Nuclear Theory (nucl-th)
    arXiv:
    2602.23776 [pdf]
    0 citations

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first authorsco-authorsvia INSPIRE