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Nuclear Theory·nucl-th

Wednesday·February 4, 2026

9 papers—4 primary·5 cross-listed

All9Primary4Cross-lists5
  1. 01

    [Submitted on 2 Feb 2026]

    Anisotropic time evolution of sound modes in Bjorken expanding holographic plasma

    Casey Cartwright🇳🇱 · Ruchi Chudasama🇺🇸 · Sergei Gleyzer🇺🇸 · Durdana Ilyas🇺🇸 · Matthias Kaminski🇺🇸 · Marco Knipfer🇺🇸 · Jun Zhang🇺🇸

    The speed of sound is a key parameter for characterizing equilibrium states. However, sound waves change their properties when propagating through rapidly evolving anisotropic media, such as the quark-gluon plasma created in heavy-ion collisions. This paper uses Super-Yang-Mills theory to numerically study the time evolution of the speed and attenuation of sound modes along with the relaxation time in a plasma undergoing Bjorken expansion from various initial states in a quasi-static approximation. The longitudinal Bjorken expansion breaks the isotropy, resulting in two distinct sound speeds that range from just below the conformal value to the speed of light. An anisotropic hydrodynamic description is constructed and its applicability is discussed. Implications for the analysis of heavy ion data are considered.

    Comments:
    16 pages, 13 figures, 6 appendices
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Theory (hep-th); Nuclear Experiment (nucl-ex)
    arXiv:
    2602.02687 [pdf]
    1 citation
  2. 02

    [Submitted on 2 Feb 2026]

    Corrections to the Smoothness and On-Shell Approximations in Femtoscopy and Coalescence

    Isaac G. Smith🇮🇱 · Kfir Blum🇮🇱

    Relativistic heavy-ion collisions produce femtometer-scale sources whose space-time structure can be constrained using two-particle femtoscopic correlations. Standard implementations rely on the smoothness and on-shell approximations, which effectively remove the relative momentum dependence of the particle emission function. We explore the validity of these approximations by deriving model-independent expansions that quantify the leading corrections for femtoscopy and coalescence with arbitrary sources and final-state interactions. The resulting first- and second-order correction terms can be evaluated with essentially the same numerical complexity as the usual Koonin-Pratt expressions; for angle-averaged correlations the first-order contributions vanish by symmetry. We illustrate the framework with explicit calculations in a blast-wave source model; for blast-wave parameter sets representative of pp and PbPb fits at LHC energies, the corrections are at or below the percent level for pp correlations and deuteron coalescence. These corrections are potentially subdominant compared to other effects, for example, corrections to the equal time approximation.

    Comments:
    3 figures
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex)
    arXiv:
    2602.02810 [pdf]
    PRC(2026)·1 citation
  3. 03

    [Submitted on 3 Feb 2026]

    Neutron skin thickness and its volume and surface contributions in berkelium isotopes

    Peng Wang · Zi-Dan Huang · Shuang-Quan Zhang · Ting-Ting Sun

    Accurate determination of the neutron skin thickness () in finite nuclei is essential for constraining the density dependence of the nuclear symmetry energy. This work presents a systematic investigation of for the transuranium berkelium (Bk) isotopes within the framework of the deformed relativistic Hartree-Bogoliubov theory in continuum (DRHBc). The results indicate an overall increase in neutron skin thickness with , which exhibits antikinks at the shell closures due to the shell effects. A decomposition of into volume and surface terms, based on two-parameter Fermi (2pF) fits to angle-averaged DRHBc densities, demonstrates that the volume term dominates as much as -- in most nuclei, consistent with the found in Pb, thereby validating the volume-surface decomposition for deformed nuclei and confirming its correlation with the symmetry energy slope . The surface term prevails only near the proton drip line, where the volume fraction drops below due to the reduced neutron-to-proton ratio. Deformation is found to slightly reduce the central radius but markedly enhance the surface diffuseness , leading to a notable increase in , primarily driven by the surface term. Furthermore, we extend the decomposition to a directional analysis by extracting 2pF parameters along the symmetry axis () and perpendicular to it (). In prolate deformed nuclei, a strong directional dependence is observed: although the nucleus is elongated along the symmetry axis, is significantly larger in the perpendicular direction. This anisotropy is weak for oblate nuclei around the shell closures.

    Comments:
    11 figures, 13 pages
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2602.03323 [pdf]
    PRC(2026)·1 citation
  4. 04

    [Submitted on 3 Feb 2026]

    Exploring Hyperon Skyrme Forces in Multi- Hypernuclei and Neutron Star Matter

    X. D. Sun🇨🇳 · S. C. Han🇨🇳 · J. N. Hu🇨🇳 · A. Li🇨🇳

    A major source of uncertainty in modeling the strangeness-rich interiors of neutron stars arises from the poorly constrained two-body and three-body interactions among hyperons and nucleons. We perform a comprehensive Bayesian analysis of the and interaction parameters within the Skyrme Hartree-Fock framework, constrained by both hypernuclei experimental data and astrophysical observations. Our results show that the parameter space of the interaction is tightly constrained by combining nuclear and astrophysical data, while the parameters of the three-body interaction remain sensitive to astrophysical inputs alone. Specifically, the local, momentum-independent two-body interaction parameter is tightly constrained and predominantly attractive, while the momentum-dependent parameters and contribute repulsive effects at high densities. A key role is played by the potential depth in pure matter, which effectively constrains the two-body interaction and governs the balance between attraction at low densities and repulsion at high densities. The repulsive components of interactions then decrease hyperon fractions and reconcile hyperon-rich equations of state with the observed neutron stars, increasing the maximum mass by up to 22\%. The inclusion of three-body forces further stiffens the EOS, raising the maximum mass by up to . Our study represents a promising step toward a complete, experimentally grounded description of dense matter across a wide range of densities and strangeness compositions.

    Comments:
    18 pages incuding APPENDIX, 9 figures, 7 tables; accepted for publication in MNRAS (2026)
    Subjects:
    Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE)
    arXiv:
    2602.03388 [pdf]
    MNRAS(2026)·14 citations

Affiliations

first authorsco-authorsvia INSPIRE