Nuclear Theory·nucl-th

Tuesday·February 3, 2026

18 papers—15 primary·3 cross-listed

01
Numerical simulations of non-relativistic stochastic fluids via the Metropolis algorithm
Mattis Harhoff🇩🇪 · Sören Schlichting🇩🇪 · Lorenz von Smekal🇩🇪
Stochastic hydrodynamics provides a dynamical framework for the evolution of fluctuations in heavy-ion collisions, but poses significant challenges in numerical simulations. We present an algorithm for the simulation of non-relativistic stochastic fluids in two spatial dimensions in a box. We use the robust Metropolis algorithm, handling fluctuations and dissipation at once by systematically replacing dissipative terms in the hydrodynamic equations by random forces. The algorithm can easily be modified for numerical simulations of other hydrodynamic theories. We present test cases as well as numerical calculations of the renormalization of shear viscosity.
nucl-thhep-phJ.Subatomic Part.Cosmol.(2026)·0 citations
02
The Role of Ab Initio Beta-Decay Calculations in Light Nuclei for Probes of Physics Beyond the Standard Model
Grigor H. Sargsyan🇺🇸 · Garrett B. King🇺🇸 · Ayala Glick-Magid🇮🇱 · Chien-Yeah Seng🇺🇸
Precision beta decay experiments serve as powerful probes of physics beyond the Standard Model, enabling stringent tests of fundamental symmetries of nature. In particular, these experiments primarily focus on precise determinations of the Cabibbo-Kobayashi-Maskawa matrix element Vud and the search for exotic weak currents, both of which depend critically on theoretical calculations of radiative, recoil-order, and isospin-breaking corrections with quantified uncertainties. In recent years, ab initio nuclear many-body methods--grounded in realistic nucleon-nucleon interactions and systematically improvable approximations--have advanced considerably in their ability to compute these higher-order corrections for various nuclei. This review provides a comprehensive overview of state-of-the-art ab initio calculations of beta-decay corrections, encompassing both radiative corrections and recoil-order terms, and examines their significance for precision tests of the Standard Model. We discuss the theoretical formalisms employed, including the integration of effective field theory frameworks with many-body approaches. Particular attention is given to recent results for superallowed Fermi decays (e.g., 10C -> 10B and 14O -> 14C) and allowed Gamow-Teller transitions (e.g., 6He -> 6Li, 8Li -> 8Be, 8B -> 8Be), where ab initio calculations have achieved unprecedented precision. We also highlight emerging calculations for unique forbidden decays, which offer complementary sensitivity to BSM physics. Finally, we outline future directions aimed at extending the reach of ab initio calculations to heavier nuclei and additional decay modes, thereby strengthening the synergy between theory and experiment in the ongoing search for new physics.
nucl-thPPNP(2026)·2 citations
03
General Radial-Composition Correlations in Two-Component Many-Body Systems
Y. Lei
The linear correlation between RMS radius difference and composition asymmetry in two-component many-body systems is a robust feature observed across nuclear experiments, diverse nuclear structural models, molecular dynamic simulations for bimetallic clusters, and galactic modeling with self-interacting dark matter. We identify the short-range attractive central force as the key ingredient for its emergence, a mechanism underpinned by the coordinate transformation under low-energy harmonic-oscillator approximation, the virial theorem, and Pauli principle/hard core potential, in many-fermion system/classic many-body system.
nucl-th0 citations
04
Model Study of Eigen-Microstate Signatures of Criticality in Relativistic Heavy-Ion Collisions
Ranran Guo🇨🇳 · Jin Wu🇨🇳 · Mingmei Xu🇨🇳 · Zhiming Li🇨🇳 · Zhengning Yin🇨🇳 · Yufu Lin🇨🇳 · Lizhu Chen🇨🇳 · Yanhua Zhang🇨🇳 · Jinghua Fu🇨🇳 · Xiaosong Chen🇨🇳 · Yuanfang Wu🇨🇳
We present a comprehensive model study of the eigen-microstate approach (EMA) for identifying critical fluctuations in relativistic heavy-ion collisions. Using UrQMD and two stochastic baseline models, we demonstrate that EMA is insensitive to conventional short-range correlations and effectively filters out non-critical backgrounds. Critical fluctuations embedded via event-level or particle-level replacement with CMC events generate characteristic cluster-like eigen-microstate patterns and enhanced leading eigenvalues, with event-level criticality producing stronger responses. The eigen microstates exhibit the same pattern across different scales, demonstrating that the fractal nature of critical fluctuations is captured by the eigen microstates. Finite-size scaling of eigenvalue ratios exhibits fixed-point behavior, confirming the largest eigenvalue as an effective order-parameter-like quantity. These results demonstrate that EMA offers a robust and background-independent method for critical-point searches in the RHIC Beam Energy Scan and future heavy-ion experiments.
nucl-thhep-ph0 citations
05
Spin alignment, tensor polarizabilities, and local equilibrium for spin-1 particles
Wojciech Florkowski🇵🇱 · Sudip Kumar Kar🇵🇱 · Valeriya Mykhaylova🇵🇱
Different bases for the spin-1 density matrix are discussed to clarify the connection between its components and observables measured in heavy-ion collisions. The theoretical advantage of using the adjoint representation for spin matrices is emphasized. Next, the equilibrium spin density matrix and the corresponding Wigner function are introduced. With appropriate definitions of the energy-momentum and spin tensors, this framework allows for the formulation of perfect spin hydrodynamics in the same way as previously done for spin-1/2 particles. Together, these results provide a unified description of spin-1/2 and spin-1 particles.
nucl-thhep-exhep-phActa Phys.Polon.B(2026)·4 citations
06
Structure evolution of ground and excited states in the exotic nucleus $^{22}$ Al
Z. C. Xu · H. Y. Shang · S. M. Wang · Y. G. Ma
Recent experimental studies on proton-rich nuclei in the $s d$ shell have revealed intriguing near-threshold phenomena, including exotic structures associated with mirror-symmetry breaking. In particular, a halo-like structure has been suggested for the $1^{+}$ state of $^{22}$ Al based on the large isospin asymmetry observed in the $^{22}$ Si/ $^{22}$ O mirror Gamow-Teller transitions. Recent mass measurements further indicate that the ground state of $^{22}$ Al is weakly bound, with a single-proton separation energy of about 100 keV. To investigate how the continuum affects the structure and decay properties of this proton-dripline nucleus, we employ the state-of-the-art Gamow shell model. This approach utilizes valence-space effective interactions and operators derived from chiral forces. Our calculations identify the ground state of $^{22}$ Al as a $4^{+}$ state, with a $3^{+}$ state as the first excitation. Despite their diffuse nature under weak binding, the Thomas-Ehrman shift for these states is found to be negligible due to their small $s$ -wave components. In contrast, the excited $1_{1}^{+}$ state possesses a significantly larger $s$ -wave component, resulting in a more pronounced halo-like structure.
nucl-thPRC(2026)·1 citation
07
Physics Informed Bayesian Machine Learning of Sparse and Imperfect Nuclear Data
Jiaming Liu · Yang Su · N.C. Shu · Y.J. Chen · J.C. Pei
The prevailing data-driven machine learning has been plagued by the absence of physics knowledge and the scarcity of data. We implement the physics-model informed prior into Bayesian machine learning to evaluate the energy dependence of independent fission product yields, which are crucial for advanced nuclear energy applications but only sparse and imperfect experimental data are available. The informative prior is the posterior after learning the generated data from fission models. Furthermore, cumulative fission yields are included as a physical constraint via a conversion matrix to provide augmented energy dependence. Our work demonstrated a truly Bayesian machine learning by incorporating comprehensive physics knowledges as a powerful tool to exploit the sparse but expensive nuclear data.
nucl-th0 citations
08
Helium-3 relativistic wave function in light-front dynamics
Zhimin Zhu · Ziqi Zhang · Kaiyu Fu · V.A. Karmanov
The relativistic wave function of $^{3}$ He nucleus is calculated in the framework of Light-Front Dynamics. It is determined by 32 spin-isospin components, each of which depends on five scalar variables. For NN interaction, the one-boson exchange model is assumed, but without a potential approximation. The relativistic effects manifest themselves in deviation of the relativistic components from the non-relativistic input, in the appearance of the components absent in the non-relativistic limit, and in dependence of solutions on specific variables that don't exist in the non-relativistic wave function.
nucl-th0 citations
09
Physics-based method for generating probability table using random-matrix approach
K. Fujio · T. Kawano · A.E. Lovell · D. Neudecker · N.A.W. Walton
We develop a new method for generating probability tables based on a solid theoretical foundation. The fluctuating cross sections are calculated using the GOE- $S$ -matrix model, in which the Gaussian Orthogonal Ensemble (GOE) is incorporated into the calculation of the scattering ( $S$ ) matrix. The calculated cross sections are then converted into the probability tables in the same manner as in NJOY. Using $^{238}$ U and $^{239}$ Pu as target nuclei, we determine the optimal model parameters based on the convergence behavior of the average cross sections. The statistical uncertainty of the probability tables is examined as a function of the number of ladders. We demonstrate that the probability tables calculated at 0 K are qualitatively comparable with those calculated using the conventional single-level Breit-Wigner formalism, albeit we observe some local differences due to requisite unitality for the $S$ matrix.
nucl-thnucl-ex0 citations
10
Is $^{40}$ Mg a Borromean halo nucleus? A case built on the electric-dipole response
Jagjit Singh · J. Casal · N. R. Walet · W. Horiuchi · W. Satuła
We investigate the low-energy electric-dipole response of $^{40}$ Mg using a $^{38}$ Mg $+ n + n$ three-body model. This model is implemented using a three-body hyperspherical formalism with an analytical transformed harmonic oscillator basis. In this study, two different neutron-neutron interactions are considered: a scalar Gaussian density-dependent central potential and a more realistic finite-range potential which includes central, spin-orbit, and tensor components. We examine how electric-dipole response is affected by the choice of the interaction.
nucl-thActa Phys.Polon.Supp.(2026)·1 citation
11
Universal Relations and Correlation Analysis of Proto-Neutron Star Properties in Energy-Momentum Squared Gravity
Sayantan Ghosh
Proto-neutron stars (PNSs) are the hot, lepton-rich remnants of the core collapse supernovae, which go through a cooling phase and become cold, stable Neutron stars (NSs). Since PNSs are also superdense objects with strong gravitational fields, we can use them to probe general relativity (GR) in the high-curvature regime, similar to NSs. In this study, we analyze the macroscopic properties like mass, radius, compactness, tidal deformability, $f$ -mode oscillations and gravitational binding energy of PNSs using four different relativistic mean-field (RMF) equations of state (EOSs) with fixed entropy per baryon ( $S$ =1, 2) and varying the lepton fractions ( $Y_{l}$ ). The variation of $S$ and $Y_{l}$ has a noticeable effect on these properties. Extending our study beyond GR, we explore these effects within the framework of Energy-Momentum Squared Gravity (EMSG). This modified gravity theory adds the squared energy-momentum terms to the field equations with a free parameter $α$ . In the weak-field regimes, EMSG remains indistinguishable from GR, but in the strong-field regimes, such as PNSs or NSs, it shows measurable deviations. Varying the free parameter $α$ , we observe significant changes in the macroscopic properties of the PNSs. After that, we focus on the universal relations of the macroscopic properties and the correlations of the universal relations. We find that, despite significant changes in the macroscopic properties induced by the variations of $S$ , $Y_{l}$ and $α$ , the correlations remain strong and nearly unaffected.
nucl-thgr-qchep-phJHEAp(2026)·3 citations
12
A global potential constrained by the Bohr-Sommerfeld quantization condition for $α$ -decay half-lives of even-even nuclei
Nguyen Gia Huy · Do Huy Tho · Mai Doan Quang Huy · Nguyen Le Anh
The $α$ decay provides valuable constraints on nuclear structure and plays an essential role in identifying heavy and superheavy nuclei. We study $α$ -decay half-lives of 178 even-even nuclei within a semi-classical WKB framework using a phenomenological Woods-Saxon $α$ -nucleus potential. The potential depth is determined by imposing the Bohr-Sommerfeld quantization condition (BSQC), ensuring a physically consistent description of the quasibound $α$ -daughter system. To facilitate large-scale calculations, a global parametrization of the BSQC-constrained potential depth is constructed. The resulting half-lives reproduce experimental data with comparable accuracy for both the direct BSQC approach and the fitted prescription, providing a first step toward a global and computationally efficient description of $α$ decay.
nucl-thNPA(2026)·0 citations
13
Impact of Two-Body Currents on Semi-Exclusive Lepton-Nucleus Reactions
N. Rocco🇺🇸 · N. Steinberg🇺🇸
We generalize the spectral-function formalism to describe two-nucleon knockout processes in exclusive kinematics. Significant improvements are introduced both in the treatment of the current operators entering the $Δ$ -current contribution and in the modeling of correlations between the two struck nucleons, including a consistent treatment of isospin dependence and the explicit incorporation of angular correlations. The framework is validated through comparisons with relativistic Fermi-gas calculations and with semi-exclusive electron-nucleus scattering data. Our results demonstrate that an accurate description of nuclear dynamics plays a crucial role in modeling this reaction mechanism. We further present a study of selected electroweak observables relevant to neutrino-scattering experiments.
nucl-thhep-th3 citations
14
Investigation of the shape of uranium in relativistic $^{238}$ U+ $^{238}$ U collisions with nuclear densities from covariant density functional theory
Yuan Li · Hao-jie Xu · Dandan Zhang · Guo-Liang Ma
Relativistic $^{238}$ U+ $^{238}$ U collisions have recently been used to extract the quadrupole shape of $^{238}$ U. In this study, we employ state-of-the-art three-dimensional (3D) lattice covariant density functional theory (CDFT) with pairing correlations to calculate the density of uranium, including its octupole and hexadecaople deformations, as input for hydrodynamic simulations of these collisions. We find that while the CDFT density well describes elliptic flow, a clear mismatch emerges with transverse-momentum-related observables, indicating a tension in the effective quadrupole deformation. Furthermore, constraining the octupole deformation with triangular flow $v_{3}$ proves to be difficult due to significant sensitivity to the uncertain nuclear structure of the gold reference system. Our results underscore the necessity of realistic nuclear densities for both colliding species and highlight the need for further investigation of correlations related to both flow and transverse momentum to fully characterize nuclear deformation.
nucl-thnucl-ex4 citations
15
Radiative decay and electromagnetic moments in $^{229}$ Th determined within nuclear DFT
A. Restrepo-Giraldo · J. Dobaczewski · J. Bonnard · X. Sun
Using the nuclear DFT approach with symmetry breaking and restoration, we investigate the electromagnetic properties of the ground and isomeric states in $^{229}$ Th. We determine the magnetic dipole transition strength B(M1; $3/ 2_{1}^{+} \to 5/ 2_{1}^{+})$ between these two states and discuss the effects of parity breaking, configuration mixing, and time-odd core polarization. We also determine the corresponding spectroscopic magnetic dipole and octupole, and electric quadrupole moments. Because the octupole deformability of the Skyrme functionals used here is not described in sufficient detail, we analyze the results using a set of Skyrme functionals and perform a regression aligned with the measured electric octupole moments of neighboring even-even nuclei. Without parameter adjustment, the results compare favorably with the experimental data but also indicate the need to systematically adjust the octupole degrees of freedom in future functional parametrizations.
nucl-th3 citations

Affiliations

first authorsco-authorsvia INSPIRE