Nuclear Theory·nucl-th

Wednesday·September 17, 2025

9 papers—5 primary·4 cross-listed

06
[Submitted on 15 Sept 2025] (cross-list from gr-qc)
Radial Oscillations of Viscous Neutron Stars: Zero Diffusion Case
Raissa F. P. Mendes🇧🇷 · Amanda Guerrieri🇧🇷 · João V. M. Muniz🇧🇷 · Gabriel S. Rocha🇧🇷 · Gabriel S. Denicol🇧🇷
The spectrum of radial oscillations of neutron stars is systematically studied within two frameworks of viscous relativistic hydrodynamics: the relativistic Navier-Stokes and Israel-Stewart theories. A correspondence is established between the discrete stellar eigenmodes and the continuous dispersion relation of perturbations around a homogeneous fluid, providing a basis for interpreting our numerical results. We analyze the Newtonian limit and assess the impact of relativistic corrections, such as the gravitational redshifting of microscopic relaxation timescales. We show that bulk viscosity can significantly affect the behavior of both hydrodynamic and nonhydrodynamic fundamental modes, and that, depending on the magnitude of the viscous effects, it is the nonhydrodynamic mode that becomes unstable beyond the turning point in a sequence of equilibrium configurations. These results provide a useful step toward systematic studies of neutron star quasinormal modes in the presence of viscosity.
Comments:
18 pages, 7 figures
Subjects:
General Relativity and Quantum Cosmology (gr-qc); Nuclear Theory (nucl-th)
arXiv:
2509.12330 [pdf]
PRD(2026)·7 citations
07
[Submitted on 16 Sept 2025] (cross-list from hep-ph)
Coupled-channel analysis for vector charmonia and their nature
Satoshi X. Nakamura (Shandong University)🇨🇳
High-precision $e^{+} e^{-} \to c c ˉ$ data (20 final states) from the BESIII and Belle in $s = 3.75 - 4.7$ GeV are analyzed with a semi three-body unitary coupled-channel model. Vector charmonium poles are extracted from the amplitudes obtained from the fit. We find well-known $ψ$ states listed in the PDG, and also several states near open-charm thresholds. The compositeness of the near-threshold poles suggests that $ψ (4040)$ could mainly consist of a $D^{*} D ˉ^{*}$ -molecule component, rather than a conventionally accepted quark-model $ψ (3 S)$ state. Also, $ψ (4230)$ and $ψ (4360)$ might be substantial mixtures of $D_{1} (2420) D ˉ$ , $D_{1} (2420) D ˉ^{*}$ , $D_{s}^{*} D ˉ_{s}^{*}$ , and $c c ˉ$ components.
Comments:
8 pages, 3 figures, Contribution to the Proceedings for 6th International Workshop on Future Tau Charm Facilities (FTCF), November 17-21, 2024, Guangzhou, China
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Theory (nucl-th)
arXiv:
2509.12925 [pdf]
JUSTC 55, 1207 (2025)·0 citations
08
[Submitted on 16 Sept 2025] (cross-list from hep-ph)
Nuclear Suppression in Diffractive Vector Meson Production within the Color Glass Condensate Framework
Heikki Mäntysaari🇫🇮 · Hendrik Roch🇺🇸 · Farid Salazar🇺🇸 · Björn Schenke🇺🇸 · Chun Shen🇺🇸 · Wenbin Zhao🇺🇸
We extend a recent global Bayesian analysis of diffractive $J / ψ$ production in $γ + p$ and $γ + Pb$ collisions within the color glass condensate (CGC) framework to investigate potential modifications of the nucleon structure inside nuclei. To this end, we perform fits that allow the effective nucleon structure parameters in Pb nuclei to differ from those of free protons. This approach directly addresses the question of whether the proton's spatial gluon distribution at intermediate to large $x$ is modified in the nuclear environment. We compare results obtained with shared and independent nucleon structure parameters and assess the impact on the simultaneous description of $γ + p$ data from HERA and the LHC, as well as $γ + Pb$ data from the LHC. Our findings show that there is no hint of difference in the nucleon structure beyond those already present in the CGC when embedding nucleons inside a nuclear environment.
Comments:
2nd International Workshop on the physics of Ultra Peripheral Collisions (UPC 2025)
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2509.13015 [pdf]
2 citations
09
[Submitted on 16 Sept 2025] (cross-list from gr-qc)
Rotating neutron stars within the macroscopic effective-surface approximation
A.G. Magner🇺🇦 · S.P.Maydanyuk🇺🇦 · A. Bonasera🇺🇸 · H. Zheng🇨🇳 · S.N. Fedotkin🇺🇦 · A.I. Levon🇺🇦 · T. Depastas🇺🇸 · U.V. Grygoriev🇺🇦 · A.A. Uleiev🇺🇦
The macroscopic model for a neutron star (NS) as a finite perfect fluid at the equilibrium is extended to rotating systems by incorporating the linear perturbation expansion over a small frequency $ω$ near Schwarzschild outer-inner gravitational metric within the effective-surface (ES) approach. The NS angular momentum $I$ and moment of inertia (MI) for a slow stationary azimuthal rotation around the symmetry axis are calculated by using the Kerr metric approach in spherical coordinates, and compared with Boyer-Lindquist (outer) and Hogan (inner) metric results. The volume and gradient-surface terms of the macroscopic NS energy density $E (ρ)$ (Equation of State) are taken into account at the leading order of the leptodermic parameter $a / R ≪ 1$ , where $a$ is the ES crust thickness and $R$ is the NS effective radius. The analytical macroscopic NS MI expressions, $Θ = d I / d ω = Θ ~ / (1 - T_{tφ})$ , have been obtained in terms of the statistically averaged MI, $Θ ~$ , and its time and azimuthal-angle $t, φ$ correlation, $T_{tφ}$ , as sums of the volume and surface components. The MI $Θ$ is changed significantly as function of the effective radius $R$ because of a strong gravity. We found the additional constraint for the NS radius to smaller accessible ranges which is due mainly to the $t, φ$ correlations and surface contributions. The adiabaticity conditions for applicability of the linear perturbation theory is carried out for several neutron stars with a strong gravity and relatively large rotation periods.
Comments:
34 pages, 13 figures, 3 tables
Subjects:
General Relativity and Quantum Cosmology (gr-qc); High Energy Astrophysical Phenomena (astro-ph.HE); Solar and Stellar Astrophysics (astro-ph.SR); Nuclear Theory (nucl-th)
arXiv:
2509.13129 [pdf]
1 citation

Affiliations

first authorsco-authorsvia INSPIRE

Radial Oscillations of Viscous Neutron Stars: Zero Diffusion Case

Coupled-channel analysis for vector charmonia and their nature

Nuclear Suppression in Diffractive Vector Meson Production within the Color Glass Condensate Framework

Rotating neutron stars within the macroscopic effective-surface approximation

Affiliations