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
07
[Submitted on 23 Apr 2026] (cross-list from cond-mat.stat-mech)
Hyperstatistics
Lucas Squillante · Samuel M. Soares · Constantino Tsallis · Mariano de Souza
We propose a general approach, named by us hyperstatistics, to treat complex systems, in which Boltzmann-Gibbs statistics breaks down in domains of the system. Hyperstatistics preserves the concavity of nonadditive $q$ -entropy. We obtain analytical closed-form expressions for the here proposed $(q, n)$ -generalized Boltzmann factor $B_{q}^{n}$ considering uniform, $γ$ , Log-normal, F, and the $q$ - $γ$ probability distribution functions. Remarkably, for all investigated distribution functions, $B_{q}^{n}$ reduces to a $q$ -exponential-type function. To demonstrate the applicability of hyperstatistics, we use a table top experiment of the discharge of a capacitor considering $γ$ -distributed relaxation times, the pressure decay over time associated with the pumping of $^{4}$ He lines of a closed cycle cryostat, midrapidity data for $p$ -Pb collisions at the LHC, as well as data set for acceleration distribution in turbulent systems. Furthermore, we deduce the power-law-like dielectric response using the $q$ - $γ$ -distribution function. Our proposal is applicable to systems with inherent non-Boltzmann-Gibbsian statistics in domains of the system.
Comments:
26 pages, 5 figures, 1 table. Supplementary material upon request
Subjects:
Statistical Mechanics (cond-mat.stat-mech); High Energy Physics — Experiment (hep-ex); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th); Accelerator Physics (physics.acc-ph); Data Analysis, Statistics and Probability (physics.data-an); Instrumentation and Detectors (physics.ins-det)
arXiv:
2604.24783 [pdf]
0 citations
08
[Submitted on 27 Apr 2026] (cross-list from physics.ed-ph)
Six textbook mistakes in quantum field theory
Alexandros Gezerlis🇨🇦
This article discusses incorrect statements appearing in textbooks on quantum field theory (QFT); some of these mistakes also appear in the research literature. The focus is not on errors made by an individual author, but on conceptual muddledness that is widespread in introductory textbooks. We start from a bare-bones summary of QFT, meant to establish the notation. We then turn to our six paradigmatic themes, in each case quoting a specific example of the textbook mistake, a summary of material that is known to experts but is frequently mishandled in introductory works, pointers to authoritative references where the relevant concept is handled properly, as well as a concise correction that rectifies any issues. The goal of this work is to warn readers of the existence of several pitfalls and thereby stop these errors from further propagating in the literature on QFT.
Comments:
13 pages, 2 figures
Subjects:
physics.ed-ph (physics.ed-ph); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th); Quantum Physics (quant-ph)
arXiv:
2604.24871 [pdf]
0 citations
09
[Submitted on 27 Apr 2026] (cross-list from astro-ph.HE)
A Physics Informed Bayesian Neural Network for the Neutron Star Equation of State
J.D. Baker🇺🇸 · C.A. Bertulani🇺🇸 · R.V. Lobato🇧🇷
We present a physics-informed Bayesian neural-network framework to infer neutron-star equations of state from theoretical priors and to propagate the associated uncertainties to stellar observables. Trained on a large and representative ensemble of hadronic EoSs, the model learns $P (ϵ)$ via stochastic variational inference, incorporating soft constraints at saturation density and from perturbative QCD, together with penalties enforcing monotonicity and causality. The accepted core EoSs are matched to an SLy4 crust and evolved through a unified Tolman-Oppenheimer-Volkoff-plus-tidal solver to generate posterior predictions in the mass-radius ( $M$ - $R$ ) and mass-tidal-deformability ( $M$ - $Λ$ ) planes. The inferred posterior is consistent with NICER radius measurements and the observed $2.0 M_{⊙}$ maximum-mass constraint, yielding $R_{1.4} = 12. 1_{- 0.9}^{+ 1.4} km$ , $Λ_{1.4} = 58 0_{- 240}^{+ 520}$ , and $M_{max} ≃ 2.11 \pm 0.05 M_{⊙}$ (90\% CI). The resulting canonical tidal deformability can be assessed \emph{a posteriori} against current gravitational-wave constraints. Overall, this framework provides a flexible, non-parametric mapping from microphysical EoS uncertainties to neutron-star observables.
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Theory (nucl-th)
arXiv:
2604.24949 [pdf]
2 citations
10
[Submitted on 28 Apr 2026] (cross-list from hep-ph)
A study of $J / ψ$ mass shift and bound states: Impact of $D D$ and $D D^{*}$ meson loops
Manpreet Kaur🇮🇳 · Arvind Kumar🇮🇳
We investigate the modification of the $J / ψ$ meson mass in asymmetric nuclear matter at zero and finite temperatures employing an effective Lagrangian approach that considers the contributions of $D D$ and $D D^{*}$ meson loops. The medium dependence of $D$ meson masses is determined using the hadronic chiral SU(3) model, where scalar condensates are calculated and subsequently utilized in the QCD sum rules approach. Our findings indicate that an increase in baryonic density results in a negative mass shift of the $J / ψ$ meson. This suggests that the $J / ψ$ meson is attracted to nuclear mean fields indicating the possibility of the formation of meson-nucleus bound states. Moreover, we have also determined the binding energy and absorption decay width of the $J / ψ$ meson for both the ground and excited states of $O^{16}$ , $Ca^{40}$ , $Zr^{90}$ , and $Pb^{208}$ nuclei. These results are expected to contribute to the understanding of experimental data from upcoming studies at Jefferson lab and the facility for antiproton and ion research, where low-momentum charmed mesons can be produced and examined within nuclei.
Comments:
29 pages, 8 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2604.25449 [pdf]
PRD(2026)·1 citation
11
[Submitted on 28 Apr 2026] (cross-list from hep-ph)
Les Houches study on inclusive jet production at NNLO+NNLL
Terry Generet🇬🇧 · Joey Huston🇺🇸 · Kyle Lee🇺🇸 · Ian Moult🇺🇸 · Rene Poncelet🇵🇱 · Xiaoyuan Zhang🇺🇸
Jet production at the LHC is a powerful probe of QCD, making it ideal for precision tests and determinations of QCD parameters such as parton distribution functions and the strong coupling constant. To make the most of the abundant jet production data collected at the LHC, precise calculations are required. While state-of-the-art calculations reach next-to-next-to-leading order (NNLO) QCD accuracy, a critical assessment of the remaining uncertainties arising from non-perturbative effects and missing higher orders remains crucial for correctly interpreting comparisons between theory and data. Scale variation is nearly always used to determine effects from missing higher orders. In this article, we reassess this method in the context of inclusive jet production by performing NNLO QCD calculations supplemented by small-jet-radius resummation through next-to-next-to-leading-logarithmic accuracy (NNLL). We find that NNLL resummation can have an appreciable impact on the scale uncertainty for inclusive jet cross sections, and, for some scale choices, can lead to sizeable shifts of the central cross section. We conclude that scale variations in fixed-order and resummed calculations can drastically underestimate the impact of higher orders for commonly used jet radius parameters, and that missing higher-order estimates obtained via scale variations should be considered unreliable. Our findings add further evidence to the importance of going beyond scale variations in jet and jet substructure calculations.
Comments:
32 pages, 29 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Theory (nucl-th)
arXiv:
2604.25490 [pdf]
0 citations
12
[Submitted on 28 Apr 2026] (cross-list from hep-ph)
Coherent deeply virtual Compton scattering on helium-4 beyond leading power
Víctor Martínez-Fernández🇫🇷 · B. Pire🇫🇷 · P. Sznajder🇵🇱 · J. Wagner🇵🇱
Coherent hard exclusive reactions on light nuclei provide access to their quark and gluon structure and enable three-dimensional tomography of these complex systems. We study deeply virtual Compton scattering on a helium-4 target, including both kinematic twist-3 and twist-4 corrections, as well as next-to-leading-order corrections to the twist-2 amplitude in the strong coupling $α_{s}$ . We show that these contributions are crucial for achieving a precise description of the data and, as a result, obtain the first tomographic image of the helium-4 nucleus at the quark-gluon level.
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2604.25677 [pdf]
2 citations
13
[Submitted on 28 Apr 2026] (cross-list from hep-ph)
$cuSkyrmion$ : A CUDA-OpenGL framework for interactive simulation and visualization of nuclei as Skyrmions
Sven Bjarke Gudnason🇨🇳 · Paul Leask🇸🇪
We introduce $cuSkyrmion$ , a 3-dimensional Skyrme model computation and visualization software, that is written in $CUDA C$ for rapid computation and visualization of especially the arrested Newton flow algorithm. The programme is interactive and lets the user construct Skyrmions either with configuration files, specifying coordinates, or simply in run-time using the keyboard and mouse. Rational map ansatz constituent Skyrmions can be inserted at any time and a random generator can produce a stochastic initial configuration. The software is composed into three main modules being a computational module, a rendering module and a main programme. The rendering/visualization module can readily be used by other computational modules and a $Python$ -fork, $\texttt{skyrmion_solver}$ , has been developed demonstrating the re-usability of the code.
Comments:
LaTeX: 49 pages, 14 figures, 3 tables; V2: added section 10
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th); Computational Physics (physics.comp-ph)
arXiv:
2604.25876 [pdf]
1 citation

Affiliations

first authorsco-authorsvia INSPIRE