Nuclear Theory·nucl-th

Wednesday·September 2, 2026

14 papers—7 primary·7 cross-listed

01
[Submitted on 31 Aug 2026]
Probing Dense Nuclear Matter at Small-x: A workflow for a global analysis framework
Junaid S. Khan · Rebecca L. Lustberg · Fredrick Olness · Peter Risse · Bjoern Schenke · Brandon Stevenson
The dipole model provides a powerful framework for describing high-energy nuclear interactions, particularly in the regime of dense gluonic matter. However, accurately evolving the dipole--nucleus scattering amplitude remains a major computational challenge because it is governed by nonlinear QCD evolution equations. To address this, we investigate a machine learning (ML) model as an efficient surrogate for the conventional numerical evolution. These ML-based approximations dramatically reduce the computational cost of global analyses while maintaining the accuracy required to describe a broad range of experimental data. We systematically evaluate the ML results for accuracy, computational efficiency, and ability to capture essential features of dipole evolution in nuclear environments. These computational advancements will enable global analyses of diverse datasets within both the dipole and parton model frameworks, providing a more rigorous probe of nuclear structure in the dense regime. Comparing both descriptions within a common fitting framework can provide precise constraints on the gluon distributions and advance our understanding of the quark and gluon structure of nuclei, particularly in the small-x region.
Comments:
7 pages, 3 figures, proceedings of the 33rd International Workshop on Deep Inelastic Scattering and Related Subjects (DIS2026), 4-8 May 2026, Bologna, Italy
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2609.00230 [pdf]
0 citations
02
[Submitted on 31 Aug 2026]
Symmetry-Reduced Variational Quantum Simulation of the $U (5) \to S U (3)$ Quantum Phase Transition in the Interacting Boson Model
Faisal Etminan🇮🇷
The spherical-to-deformed quantum phase transition of the Interacting Boson Model (IBM) is investigated using the variational quantum eigensolver (VQE). The $U (5)$ -- $S U (3)$ transitional Hamiltonian is studied with $χ = - 7 /2$ . We develop a symmetry-preserving, minimum-qubit VQE framework for collective nuclear models, achieving a substantial reduction in qubit requirements without compromising the finite-size quantum-phase-transition physics. The transition is characterized through the normalized $d$ -boson occupation and ground-state energy derivatives. Finite-size results are found to approach the analytic critical point $ξ_{c} = 8/17 ≃ 0.470588$ , with an independent order-parameter extrapolation yielding $ξ_{\infty} = 0.46986 (61)$ . The VQE reproduces ground-state energies and structural observables to numerical precision. These results demonstrate the potential of symmetry-reduced VQE for efficient quantum simulations of collective nuclear dynamics and quantum phase transitions.
Comments:
34 pages, 8 Figures, 4 tables
Subjects:
Nuclear Theory (nucl-th); Quantum Physics (quant-ph)
arXiv:
2609.00349 [pdf]
0 citations
03
[Submitted on 31 Aug 2026]
What Are We Talking About When We Talk About Nuclear Reactions
Gregory Potel
This introductory Chapter will try to briefly address 1. the basic physical ingredients that determine the nuclear spectrum and the associated energy scales; 2. the connection between the observed experimental results, typically in the form of cross sections, and the underlying nuclear structure presented in the previous point. The nature and scope of the present Chapter is to provide a roadmap of the field of nuclear reactions theory, and to set the stage for the more detailed discussions in the companion Chapters. The aim is to provide a conceptual framework that will allow the reader to understand how the different reaction theory approaches fit together, and how they relate to the underlying physics of nuclear reactions. The reader will find in other chapters in this volume detailed discussions about the methods addressing two seemingly quite distinct phenomena: direct and compound nuclear reactions. We hope that this brief Chapter will help them realize that whenever we are talking about either of these, we are talking about the same thing: nuclear reactions.
Comments:
Invited chapter to the Encyclopedia of Nuclear Physics (Elsevier)
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2609.00410 [pdf]
0 citations
04
[Submitted on 1 Sept 2026]
Neural-Network-Based Variational Method in Nuclear Density Functional Theory: Application to the Kohn--Sham method
Kenta Yoshimura · Kazuyuki Sekizawa
We extend the neural-network-based variational method for nuclear density functional theory to the Kohn--Sham scheme, representing the complex spinor components of the single-particle orbitals by multi-layer perceptrons. We show that neural-network optimization of a given energy density functional, combined with an orthonormalization post-processing step, is mathematically equivalent to the variational condition projected onto the tangent space of the wave-function manifold spanned by the network parameters, and that the training optimizes not only the expansion coefficients but also the basis functions themselves. We assess the method from three points of view. In the first place, we examine how the results depend on the number of units, the number of layers, and the arithmetic precision, and find that quantitative accuracy requires both a sufficient width and a sufficient depth, while single-precision arithmetic is sufficient to represent the nuclear density distribution. In the second place, the binding energies and charge radii of several closed-shell nuclei agree with conventional Skyrme--Hartree--Fock results, and the quadrupole deformations of open-shell nuclei are consistent with reference calculations that include pairing and with experiment. In the third place, we confirm that a neural-network single-particle basis can represent the three-dimensional configurations of the fundamental pasta phases: spheres, rods, and slabs. The framework offers a new perspective on computational nuclear theory, well suited to the forthcoming generation of GPU- and AI-oriented high-throughput supercomputers.
Comments:
13 pages, 3 figures, 5 tables
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2609.00836 [pdf]
0 citations
05
[Submitted on 1 Sept 2026]
Hyperonic Softening versus Nucleonic Three-Body Repulsion in Hypernuclear Matter within a microscopic approach
Mahboubeh Shahrbaf
We investigate cold homogeneous matter composed of neutrons, protons, and $Λ$ hyperons within our hyperonic extension of the lowest-order constrained variational (LOCV) method, hereafter denoted LOCVY. Our earlier LOCVY calculation, based on two-baryon interactions, is extended by supplementing the Argonne $v_{18}$ nucleonic interaction with the Urbana IX three-nucleon force, reduced within the variational framework to a correlation-weighted density-dependent effective two-nucleon interaction. The $N Λ$ and $ΛΛ$ interactions are kept unchanged, allowing the present calculation to isolate the competition between hyperon-induced softening and nucleonic three-body repulsion. The energy per baryon is calculated for fixed $Λ$ fractions $Y_{Λ} = 0$ , $0.1$ , and $0.2$ in matter with a symmetric nucleonic component and in the proton-free neutron-- $Λ$ limit. Direct differences between calculations with and without the three-body force quantify its density-dependent contribution, while a complementary decomposition into $N N$ , $N Λ$ , and $ΛΛ$ terms identifies the microscopic origin of the stiffening. The Urbana contribution becomes increasingly repulsive with density and opposes, but does not generically remove, the softening associated with a finite $Λ$ content. We further investigate the saturation properties for several prescribed $Λ$ fractions, with and without the nucleonic three-body force, to clarify how strangeness and many-body interactions modify the saturation point and the agreement with empirical nuclear-matter properties.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2609.00851 [pdf]
0 citations
06
[Submitted on 1 Sept 2026]
Femtoscopy as a New Probe of the Nuclear Equation of State
Xialei Jiang🇨🇳 · Jiaxing Zhao🇩🇪 · Yingjie Zhou🇩🇪 · Xiaofeng Luo🇨🇳
Femtoscopic correlations are widely regarded as precision probes of hadronic interactions through vacuum final-state interactions after kinetic freeze-out. Here we demonstrate that, in baryon-rich heavy-ion collisions, the nuclear mean field generates an additional dynamical contribution to femtoscopic correlations during the transport evolution. Using the Parton-Hadron-Quantum-Molecular Dynamics (PHQMD) transport approach, we investigate proton-proton, proton- $Λ$ , three-proton, and proton-proton- $Λ$ correlations in Au+Au collisions at $s_{NN} = 3$ , 4.5, 7.7, and 19.6 GeV. We find that the nuclear mean field produces a characteristic low- $k^{*}$ enhancement that is strongest at the lowest beam energies and gradually disappears with increasing collision energy. Furthermore, both the stiffness and the momentum dependence of the nuclear equation of state leave distinct signatures in the femtoscopic correlation functions, with higher-order correlations exhibiting substantially enhanced sensitivity compared with conventional two-particle observables. Our results demonstrate that femtoscopy extends beyond its traditional role as a tool for studying hadronic interactions and serve as a new class of microscopic observables for the nuclear equation of state, complementary to collective flow and subthreshold strangeness production, thereby opening a new avenue for exploring dense baryonic matter in low-energy heavy-ion collisions.
Comments:
6 pages, 4 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2609.00897 [pdf]
0 citations
07
[Submitted on 1 Sept 2026]
Superfluidity and Vortex Dynamics in Neutron Stars
Bennett Link · Armen Sedrakian
Neutron stars contain several forms of quantum condensed matter whose microscopic properties control macroscopic rotational dynamics and magnetic behavior of these fascinating objects. This review surveys superfluidity and superconductivity in compact stars, with emphasis on phenomena associated with quantized vorticity and magnetic-flux structures, and the possible connections to observed phenomena. We first summarize the microphysics of nucleonic pairing, including spin-singlet $^{1} S_{0}$ neutron pairing in the inner crust, proton superconductivity in the outer core, and spin-triplet $^{3} P_{2}$ -- $^{3} F_{2}$ neutron pairing at higher densities, together with the principal many-body uncertainties affecting the corresponding pairing gaps. We then discuss the dynamics of neutron vortices, including pinning, vortex creep, and dissipative motion, and the role of vortex dynamics in angular-momentum exchange between the superfluid and the observable crustal component. We give special attention to proton flux tubes in type-II superconducting cores, the possible realization of type-I superconductivity, and vortex--flux-tube interactions. We also review collective rotational phenomena, including Tkachenko oscillations of the vortex lattice and free precession, and their possible relation to long-term variability in pulsar timing. Finally, we discuss the possible deconfinement of hadronic matter into quark matter, the formation of color-superconducting phases, and the topological defects associated with these phases, together with their possible observational consequences. Throughout the review, we identify key open questions connecting microscopic pairing, mesoscopic defect dynamics, and observable neutron-star phenomena.
Comments:
Invited review for Encyclopedia of Nuclear Physics, 42 pages, 15 figures,
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); Solar and Stellar Astrophysics (astro-ph.SR)
arXiv:
2609.01022 [pdf]
0 citations
08
[Submitted on 31 Aug 2026] (cross-list from hep-ph)
Magnetic field-induced enhancement and quenching of Urca emission in quark matter
William Gyory🇺🇸 · Igor A. Shovkovy🇺🇸
Using first-principles field-theoretic methods, we investigate neutrino emission from strongly magnetized dense quark matter under conditions relevant to compact stars. We account for Landau-level quantization of both electron and quark states and show that it strongly modifies the kinematics of Urca processes. In particular, quark quantization restricts the available phase space in which both quark and electron energies can simultaneously lie near their respective Fermi surfaces. At moderately strong magnetic fields, before pronounced quark quantization sets in, the emission rate tends to increase on average with increasing field strength. In the regime of very strong fields, however, the increasingly restricted phase space first gives rise to Shubnikov--de Haas-type oscillations and then to resonance-like spikes near a discrete sequence of Urca-resonant magnetic field values, separated by regions of strong suppression. Finally, the emission rate becomes nearly completely quenched once $∣ e B ∣ ≳ 6 μ_{e} μ_{u}$ , corresponding to approximately $B ≳ 1.5 \times 1 0^{19} \mbox G$ for the representative set of model parameters considered. We also find significant anisotropy in the longitudinal momentum emission near the Urca-resonant magnetic field values.
Comments:
33 pages, 8 multipanel figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Theory (nucl-th)
arXiv:
2609.00157 [pdf]
0 citations
09
[Submitted on 31 Aug 2026] (cross-list from astro-ph.HE)
A NICER view of PSR J1614 $-$ 2230: a massive and compact millisecond pulsar
Lucien Mauviard · Sebastien Guillot · Lami Suleiman · Yves Kini · Denis González-Caniulef · Christine Kazantsev · Pierre Stammler · Devarshi Choudhury · Bas Dorsman · Mariska Hoogkamer · Daniela Huppenkothen · Tuomo Salmi and 8 other authors
Using pulse profile modeling, we obtain the mass-radius measurement of a millisecond pulsar (MSP) with data from the Neutron Star Interior Composition ExploreR, XMM-Newton and the Chandra X-ray Observatory. We report here the radius of PSR J1614 $-$ 2230, the second most massive MSP confirmed by radio timing. All of the data sets are well described by a simple model composed of two circular hot spots. The final result yields an equatorial radius of $R_{eq} = 10.0 6_{- 0.87}^{+ 1.25}$ km, and a gravitational mass of $M = 1.93 7_{- 0.013}^{+ 0.012} M_{⊙}$ (equally tailed 68% credible intervals). Although a non-thermal component was previously reported at higher energies, we find no sign of it in either our phase-averaged or phase-resolved spectral analyses. Using new relations linking the compactness to oblateness or surface gravity, and tailored to the spin frequency of PSR J1614 $-$ 2230, we infer a configuration with one hot spot near the pole, and another near the equator. The tight mass posterior is essentially informed by radio timing, while the radius constraint is not as tight due to the low source signal (8.5 $σ$ X-ray pulse significance). However, over all geometries and atmosphere models tested, the radius posterior tends toward low values ( $≲ 12.08$ km, 90th percentile in all cases).
Comments:
27 pages, 11 figures and 5 tables. Submitted to ApJ. Data files available in Zenodo
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Theory (nucl-th)
arXiv:
2609.00172 [pdf]
0 citations
10
[Submitted on 31 Aug 2026] (cross-list from astro-ph.HE)
Equation of state and neutron star properties with new mass-radius constraints from PSR~J1614--2230, PSR~J2124--3358, and 47~Tuc~X7
Melissa Mendes · Isak Svensson · Hannah Gottling · Kai Hebeler · Achim Schwenk · Nathan Rutherford · Lucien Mauviard · Christine Kazantsev · Yves Kini · Denis Gonzalez-Caniulef · Sebastien Guillot · Anna Watts
We study the impact of new mass-radius information from PSR J1614-2230, PSR J2124-3358, and 47 Tuc X7 in a combined equation of state inference based on chiral effective field theory constraints at nuclear densities and using different high-density extensions, including perturbative QCD constraints. The largest impact stems from the heavy-mass PSR J1614-2230 star, which shifts heavy neutron stars to smaller radii by around 0.4 km. Moreover, the combined astrophysical NICER, LIGO/Virgo, and X-ray information drives the radius posterior to a more data-driven distribution, which is less sensitive to the high-density extension. For the equation of state, the new mass-radius information significantly tightens the pressure and speed-of-sound posterior distributions, especially around three times saturation density. Finally, we make predictions for the poorly constrained masses of PSR J2124-3358 and 47 Tuc X7 based on the combined equation of state analysis and the other astrophysical sources.
Comments:
13 pages, 9 figures
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2609.00173 [pdf]
0 citations
11
[Submitted on 31 Aug 2026] (cross-list from astro-ph.SR)
A Data-Driven Model for $r$ -Process Production Patterns
Chen-Qi Li · Yong-Zhong Qian · Axel Gross · Zewei Xiong
Using the elemental abundances in 68 metal-poor (MP) stars, we present a data-driven model for $r$ -process production patterns covering Sr to U. We show that essentially all the $r$ -process patterns in those and other test stars can be adequately explained as mixtures of Patterns 1 and 2, which provides theoretical insights into the empirical categories of limited- $r$ , $r$ -I, and $r$ -II stars. We carry out an extensive survey of the yield templates produced by parametric $r$ -process calculations. We propose that Pattern 2 may be dominated by a single template and points to regularity in $r$ -process production by a subset of neutron star mergers (NSMs), while Pattern 1 is the average superposition of multiple templates and reflects production by other NSMs and perhaps also some magneto-rotational supernovae. We raise possible systematic issues with abundance ratios for elements measured in different ionization states, and highlight the need for examining the Os, Ir, and Pt measurements for HD~122563, which is dominated by Pattern 1 with a prominent Pt peak in our model. If this result is confirmed, the meaning of the limited- $r$ category requires drastic revision. Further measurements of a wider range of $r$ -process elements in a larger sample of MP stars are critical to test and improve our model.
Comments:
Accepted for publication in The Astrophysical Journal (ApJ), 48 pages
Subjects:
Solar and Stellar Astrophysics (astro-ph.SR); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2609.00303 [pdf]
0 citations
12
[Submitted on 1 Sept 2026] (cross-list from hep-ph)
Investigating three-body resonances in $α α Ω/ Ω_{ccc}$ clusters within the $_{Ω/ Ω_{ccc}}^{9} Be$ nucleus
Hao Zhou🇨🇳 · Xiang Liu🇨🇳
We investigate the bound and resonant states of the $α + α + Ω$ and $α + α + Ω_{ccc}$ three-body systems, corresponding to $_{Ω}^{9} Be$ and $_{Ω_{ccc}}^{9} Be$ , within the Gaussian expansion method combined with the complex scaling method. The $α Ω$ and $α Ω_{ccc}$ interactions are constructed by folding the $N Ω$ and $N Ω_{ccc}$ potentials obtained from lattice QCD calculations by the HAL QCD Collaboration with the nucleon density distribution of the $α$ particle. The uncertainty associated with the $α$ -particle matter radius is also examined. For the $Ω$ sector, the strong $N Ω$ attraction generates deeply bound $0_{1}^{+}$ , $2_{1}^{+}$ , and $4_{1}^{+}$ states in $_{Ω}^{9} Be$ , accompanied by a pronounced contraction of the $α α$ core, demonstrating a strong gluelike effect of the $Ω$ baryon. An unconventional inversion between the $0_{1}^{+}$ and $4_{1}^{+}$ levels is also predicted. In contrast, the $Ω_{ccc}$ baryon produces considerably weaker attraction: the $0_{1}^{+}$ state of $_{Ω_{ccc}}^{9} Be$ is weakly bound, whereas the $2_{1}^{+}$ and $4_{1}^{+}$ states remain resonances. Their resonance energies and widths exhibit a clear dependence on the strength of the $α Ω_{ccc}$ interaction. These results reveal qualitatively different gluelike behaviors of the $Ω$ and $Ω_{ccc}$ baryons and provide predictions for the spectroscopy of exotic multistrange and triply charmed hypernuclei.
Comments:
13 pages, 6 figures and 3 tables
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2609.00932 [pdf]
0 citations
13
[Submitted on 1 Sept 2026] (cross-list from astro-ph.HE)
The Radius of the Neutron Star PSR J0614-3329 from NICER Data
M. C. Miller · A. J. Dittmann · I. M. Holt · F. K. Lamb · C. Chirenti · Z. Arzoumanian · J. Berteaud · S. Bogdanov · K. C. Gendreau · A. K. Harding · W. C. G. Ho · C. Kalapotharakos and 5 other authors
Neutron star radius measurements, particularly using X-ray data collected with the Neutron star Interior Composition Explorer (NICER), have provided invaluable information for models of cold, catalyzed matter at densities above that of nuclear saturation. Here we present an analysis of NICER data on the 318-Hz pulsar PSR J0614-3329, which has a mass ~1.4-1.5 solar masses determined from radio observations. The best-fitting model we explore has three uniform-temperature circular hot spots and yields a symmetric 68% credible range for the equatorial circumferential radius of 9.88-12.77 km. We also explore joint fits to the NICER data and the X-ray Multi-Mirror (XMM-Newton) data on this pulsar, but find that the models that best fit both data sets systematically underpredict the XMM-Newton data when, as is standard, it is assumed that the XMM-Newton background is known from observations of surrounding fields. Finally, we discuss the implications of our results, combined with data on other neutron stars, for the properties of the dense matter in neutron star cores.
Comments:
15 pages, 8 figures, submitted to The Astrophysical Journal. Posterior samples available on Zenodo via doi:10.5281/zenodo.22131748
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc); Nuclear Theory (nucl-th)
arXiv:
2609.00965 [pdf]
0 citations
14
[Submitted on 1 Sept 2026] (cross-list from hep-ph)
Amplitude structure of $3 \to 3$ scattering in a Mandelstam variable representation
Xu Zhang · Feng-Kun Guo
We construct a dispersive representation of the relativistic $3 \to 3$ scattering amplitude for three identical spinless particles in the $S$ -wave. The two-particle subenergy, instead of the total energy, is used as the dispersive variable. This choice keeps the physical dispersive contour free of the kinematical cuts that complicate total-energy dispersion relations. By separating discontinuities across the two-particle subenergy cuts from that across the three-body cut, we derive a linear integral equation with one-particle exchange as the driving term. We further show that the solution satisfies three-body unitarity as a consequence of two-body unitarity, analyticity, and crossing symmetry. For pair-wise interactions, this representation can be rewritten into the form used for isobar-spectator scattering. Finally, we give prescriptions for contour deformation and the subtraction of poles in the two-body subsystem amplitudes, which continue the amplitude onto adjacent unphysical Riemann sheets and thus provide direct access to the analytic structure relevant for three-body resonance poles.
Comments:
15 pages, 5 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
arXiv:
2609.00985 [pdf]
0 citations

Affiliations

first authorsco-authorsvia INSPIRE