Nuclear Theory·nucl-th

Wednesday·April 29, 2026

13 papers—6 primary·7 cross-listed

01
[Submitted on 27 Apr 2026]
Chapman-Enskog calculation of the shear viscosity of quark-gluon plasma including all $2 \leftrightarrow 2$ scatterings at finite temperature
Okey Ohanaka🇺🇸 · Zi-Wei Lin🇺🇸
We use the Chapman-Enskog method to investigate the shear viscosity of the quark-gluon plasma with a focus on its relation to parton cross sections. We use the recently obtained analytical expression for the shear viscosity $η$ of a massless quark-gluon gas at chemical equilibrium with Boltzmann statistics and all $2 \leftrightarrow 2$ scatterings with arbitrary cross sections. Here we apply this general expression to cross sections at finite temperature that are based on perturbative-QCD and screened with scaled thermal masses $κ m_{D}$ and $κ m_{F}$ . We find that the Chapman-Enskog results on $η g^{4} / T^{3}$ versus $m_{D} / T$ at $κ = 1$ are qualitatively similar to but higher than the corresponding leading-order results from the AMY framework. We then find that using $κ = 0.4$ allows the Chapman-Enskog results to match well the corresponding AMY results as it includes the effect of using thermal masses (instead of self-energies) to screen the cross sections. In addition, we show that the shear viscosity-to-entropy density ratio $η / s$ is very sensitive to the choice of momentum scale $Q$ in the strong coupling, where the choice of $Q = 3 T$ leads to $η / s \sim 0.15$ for $N_{f} = 0$ or 3 at the QCD phase transition temperature $T_{c}$ . These results lay the foundation for mapping parton cross sections to given shear viscosity in parton transport models and QCD effective kinetic theory.
Comments:
19 pages, 8 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2604.25059 [pdf]
2 citations
02
[Submitted on 28 Apr 2026]
Effect of neutron-proton asymmetry on the $^{3}$ H clustering in Boron isotopes
J. L. Jin🇨🇳 · Q. Zhao🇨🇳 · P. J. Li🇨🇳 · M. Kimura🇯🇵 · D. Beaumel🇫🇷 · B. Zhou🇨🇳 · J. L. Tian🇨🇳
To investigate the influence of neutron-proton asymmetry on the formation of asymmetric clusters, we perform a systematic comparative study of $^{3}$ H and $α$ cluster preformation in the Boron isotopic chain ( $^{11 - 14}$ B). Within the framework of Antisymmetrized Molecular Dynamics (AMD), we compute the nuclear wave functions and subsequently extract the reduced width amplitudes (RWA) and spectroscopic factors (SF). The results show that the $α$ cluster SF exhibits a monotonic decrease with increasing neutron number, consistent with the established suppression effect of the neutron skin. In contrast, the $^{3}$ H cluster SF displays a non-monotonic behavior, peaking at $^{12}$ B. This distinct trend indicates that the formation of the asymmetric $^{3}$ H cluster is subject to a competition between suppression from the neutron skin and an enhancement driven by the neutron-proton asymmetry of the parent nucleus. We successfully isolate this enhancement effect by analyzing the ratio of the SFs, SF( $^{3}$ H)/SF( $α$ ). This approach not only quantifies the enhancement but also proposes the SF ratio as a robust experimental observable for probing insights into asymmetric clustering phenomena.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2604.25104 [pdf]
0 citations
03
[Submitted on 28 Apr 2026]
Coulomb Effects and Wigner-SU(4) Symmetry in He-3 Charge and Magnetic Properties
Xincheng Lin
This work studies the non-perturbative Coulomb corrections to the He-3 binding energy, magnetic moment, and charge and magnetic radii in leading-order (LO) Pionless Effective Field Theory (Pionless EFT). The splitting between He-3 and H-3 binding energy is found to be 0.85(3) MeV. The Coulomb corrections to the He-3 point charge radius and full magnetic radius are found to be 0.043(2) fm and 0.036(2) fm, respectively. These corrections are 4% of the LO predictions without Coulomb and should be taken into account at next-to-next-to-leading order or beyond in Pionless EFT to achieve the desired EFT accuracy. The Coulomb correction to the He-3 magnetic moment is found to be -0.0041(1) $μ_{N}$ , only 0.2% of the LO prediction without Coulomb. The impact of Wigner-SU(4) symmetry in the presence of the non-perturbative Coulomb interaction is also discussed and used to help explain the hierarchy of Coulomb effects in He-3 observables.
Comments:
22 pages, 11 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2604.25221 [pdf]
1 citation
04
[Submitted on 28 Apr 2026]
Large-scale fission data generation with BSkG3
Adrián Sánchez-Fernández · Wouter Ryssens · Stéphane Goriely
Modeling fission properties, such as barriers and rates, is highly challenging. The most microscopic methods available are based on energy density functionals (EDFs) and rely on a limited set of collective coordinates to describe the evolution of a fissioning nucleus from its ground state to scission. Leveraging the efficiency of the MOCCa nuclear structure code and the predictive power of the BSkG3 EDF, we systematically study fission properties of the heaviest nuclei (roughly 3,300) accounting for (1) axial, triaxial and octupole moment; (2) all nuclei, including odd and odd-odd systems; and (3) fission paths determined via the least-action principle. We present the set of primary fission barriers and spontaneous fission half-lives we obtain and discuss their implications for r-process nucleosynthesis.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2604.25418 [pdf]
0 citations
05
[Submitted on 28 Apr 2026]
Neural-Network-Based Variational Method in Nuclear Density Functional Theory: Application to the Extended Thomas-Fermi Model
Kenta Yoshimura
We propose a neural-network-based variational framework for nuclear Density Functional Theory based on the extended Thomas--Fermi (ETF) model, in which proton and neutron number densities are represented by multilayer perceptrons and determined by direct minimization of a Skyrme-type energy density functional. We clarify the mathematical connection to the conventional Euler--Lagrange formulation, showing that stationarity in parameter space corresponds to a projected Euler--Lagrange condition on the neural-network trial-density manifold. The basic validity of the framework is examined through three sets of calculations: a Woods--Saxon potential benchmark, ground-state calculations of finite nuclei ( $^{40}$ Ca, $^{90}$ Zr, and $^{208}$ Pb), and nuclear pasta phases. The binding energies of finite nuclei agree with existing ETF calculations to within $0.5%$ , and representative pasta structures including spheres, rods, and slabs are reproduced. We also find that single-precision arithmetic yields results comparable to double precision, suggesting that the present framework is well suited to GPU environments in which low-precision computation is advantageous.
Comments:
9 pages
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2604.25759 [pdf]
1 citation
06
[Submitted on 28 Apr 2026]
Exact emulation of few-body systems at low cost
Sven Heihoff · Arseniy A. Filin · Evgeny Epelbaum
Effective field theories have established themselves as key pillars of modern nuclear physics. They enable a quantitative understanding of the strong nuclear force, provided low-energy constants that parametrize short-distance physics can be determined from experimental data. This, however, often becomes prohibitively expensive due to a significant computational cost of solving the A-body problem. The computational challenge is particularly severe for three-body forces, which are at the frontier of nuclear and atomic physics and play an important role in the equation of state of neutron stars. Here we prove that for a parametric low-rank update of a Hamiltonian, the A-body problem at a fixed energy exactly reduces to a low-dimensional matrix equation regardless of the size of the Hilbert space. As a proof-of-principle, we present exact and computationally cheap snapshot-based emulators for few-body scattering and bound states. Unlike alternatives, our emulators can be used far away from the snapshot region without loss of precision and yield accurate results for parameter values not accessible using conventional solution techniques. Our approach is not restricted by the interaction type, number of particles, and methods for generating snapshots and can be applied to mitigate the computational burden of the A-body problem to a broad class of problems in nuclear, atomic, and molecular physics.
Comments:
13 pages, 3 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2604.25792 [pdf]
4 citations

Affiliations

first authorsco-authorsvia INSPIRE

Chapman-Enskog calculation of the shear viscosity of quark-gluon plasma including all 2↔2 scatterings at finite temperature

Effect of neutron-proton asymmetry on the 3H clustering in Boron isotopes

Coulomb Effects and Wigner-SU(4) Symmetry in He-3 Charge and Magnetic Properties

Large-scale fission data generation with BSkG3

Neural-Network-Based Variational Method in Nuclear Density Functional Theory: Application to the Extended Thomas-Fermi Model

Exact emulation of few-body systems at low cost

Affiliations

Chapman-Enskog calculation of the shear viscosity of quark-gluon plasma including all $2 \leftrightarrow 2$ scatterings at finite temperature

Effect of neutron-proton asymmetry on the $^{3}$ H clustering in Boron isotopes