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Nuclear Theory·nucl-th

Wednesday·September 2, 2026

14 papers—7 primary·7 cross-listed

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  1. 01

    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.

    nucl-thhep-ph0 citations
  2. 02

    Symmetry-Reduced Variational Quantum Simulation of the 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 -- transitional Hamiltonian is studied with . 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 -boson occupation and ground-state energy derivatives. Finite-size results are found to approach the analytic critical point , with an independent order-parameter extrapolation yielding . 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.

    nucl-thquant-ph0 citations
  3. 03

    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.

    nucl-th0 citations
  4. 04

    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.

    nucl-th0 citations
  5. 05

    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 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 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 and 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 fractions , , and in matter with a symmetric nucleonic component and in the proton-free neutron-- limit. Direct differences between calculations with and without the three-body force quantify its density-dependent contribution, while a complementary decomposition into , , and 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 content. We further investigate the saturation properties for several prescribed 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.

    nucl-th0 citations
  6. 06

    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-, three-proton, and proton-proton- correlations in Au+Au collisions at , 4.5, 7.7, and 19.6 GeV. We find that the nuclear mean field produces a characteristic low- 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.

    nucl-th0 citations
  7. 07

    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 neutron pairing in the inner crust, proton superconductivity in the outer core, and spin-triplet -- 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.

    nucl-thastro-ph.HEastro-ph.SR0 citations

Affiliations

first authorsco-authorsvia INSPIRE