Nuclear Theory·nucl-th

Thursday·September 11, 2025

13 papers—9 primary·4 cross-listed

01
Wave-Breaking Phenomena in Quark-Gluon Plasma
Biswarup Paul🇮🇳
We investigate the onset of wave-breaking in the quark-gluon plasma (QGP) formed in heavy-ion collisions at both RHIC and the LHC. A nonlinear longitudinal color field is coupled to a three-dimensional viscous hydrodynamic background constrained by experimental conditions: Pb-Pb at $s_{NN} = 5.02$ TeV (LHC) and Au-Au at $s_{NN} = 200$ GeV (RHIC). The instantaneous wave-breaking threshold is determined from the in-medium plasma frequency, while the field evolution follows a nonlinear Landau equation with Debye screening and expansion damping. At the LHC, the higher initial temperature and density drive the system above the threshold within $τ ≲$ 2.3 fm/ $c$ , whereas at RHIC the cooler and more dilute medium delays wave-breaking to $τ ≃ 2.8$ ~fm/ $c$ . Scans over initial temperature, density, thermalization time, QGP lifetime, and collision system (RHIC vs LHC) confirm the robustness of this instability against parameter variations. These results identify wave-breaking as a universal microscopic mechanism for the early loss of coherence and rapid onset of hydrodynamics in the QGP, providing a common explanation for the fast equilibration observed at both RHIC and the LHC.
nucl-thhep-phnucl-ex0 citations
02
The IBM Description of the B(E2) Anomaly: Dynamical Triaxiality and Configuration Mixing
Wei Teng · Sheng Nan Wang · Xian Zhi Zhao · Yu Zhang
A theoretical investigation has been carried out to examine the effects of dynamical triaxility and configuration mixing on the $B (E 2)$ anomaly, characterized by $B_{4/2} = B (E 2; 4_{1}^{+} \to 2_{1}^{+}) / B (E 2; 2_{1}^{+} \to 0_{1}^{+}) < 1.0$ and $R_{4/2} = E (4_{1}^{+}) / E (2_{1}^{+}) \geq 2.0$ , within the framework of the interacting boson model (IBM). The results indicate that the effective $γ$ deformation may undergo substantial changes with increasing angular momentum in the $B (E 2)$ anomaly system governed by an IBM Hamiltonian involving rotor-like terms. Further calculations reveal that mixing between normal and intruder states may facilitate the emergence of $B (E 2)$ anomaly, thereby providing additional theoretical insights into this unusual phenomenon.
nucl-thhep-phNPA(2025)·5 citations
03
Triaxial rotor modes in finite-N boson systems
Yu Zhang · ShengNan Wang · Feng Pan · Chong Qi · J P Draayer
We propose an algebraic approach to elucidate the dynamic characteristics of triaxial rotor modes in nuclei by mapping a triaxial rotor Hamiltonian to the interacting boson model (IBM) one within a finite- $N$ framework. Our method unveils striking features not observed in conventional modes, exemplified by the $B (E 2)$ anomaly, characterized by $B (E 2; 4_{1} - - 2_{1}^{+}) / B (E 2; 2_{1} - - 0_{1}^{+}) << 1$ . Using specific examples, we demonstrate that the peculiar properties of low-lying states in both neutron-rich and neutron-deficient Os nuclei can be comprehensively understood through the proposed Hamiltonian, which incorporates both rigid and soft triaxial rotor modes. This algebraic method not only offers fresh insights into triaxial dynamics but also showcases its capability in uncovering emergent exotic collective modes in nuclear structure.
nucl-thPRC(2024)·22 citations
04
Nuclear Mass Predictions Using a Neural Network with Additive Gaussian Process Regression-Optimized Activation Functions
H. X. Liu🇨🇳 · S. Manzhos🇯🇵 · X. H. Wu🇨🇳
Nuclear masses are machine-learned as a function of proton and neutron numbers. The neural network with additive Gaussian process regression-optimized activation functions (GPR-NN) method is employed for the first time for this purpose. GPR-NN combines the advantages of both neural networks and Gaussian process regression, in that it possesses the expressive power of an NN, in principle allowing modeling any kind of dependence of nuclear mass on the features, and robustness of a linear regression with respect to overfitting. A study of the GPR-NN approach for interpolation and extrapolation in nuclear mass predictions is presented. It is found that the optimal hyperparameters for the GPR-NN approach in interpolation and extrapolation are different. If an appropriate set of hyperparameters is adopted, the GPR-NN approach can achieve good extrapolation performance for nuclear mass prediction, which could potentially help improve the mass predictions of a large number of currently experimentally unknown nuclei.
nucl-thPRC(2026)·0 citations
05
Renormalizability and nonrenormalizability of nonlocal potentials
N. Jacobi · A. M. Gasparyan · E. Epelbaum
We consider separable toy models of the nucleon-nucleon interaction inspired by chiral effective field theory. We show that nonlocality of the long-range forces causes the need for nonlocal counter terms, or even makes the whole approach nonrenormalizable.
nucl-thPRC(2025)·0 citations
06
A comprehensive view of nuclear shapes, rotations and vibrations from fully quantum mechanical perspectives
Takaharu Otsuka🇯🇵
The nuclear quadrupole collective states at low excitation energies are described in a novel, fully quantum mechanical and systematic manner as compared to traditional pictures initiated by Aage Bohr. The ellipsoidal shapes are shown to be triaxial in virtually all strongly deformed nuclei, in contrast to the Ansatz of axially symmetric shapes. The rotational bands of such triaxially deformed nuclei are described in a fully quantum mechanical way, i. e., without resorting to quantized free rotation of rigid body. The excitation energies within a rotational band, exhibiting the $J (J + 1)$ dependence on angular momentum $J$ , are shown to basically represent the change of binding energies due to nuclear forces. This differs from the interpretation á la Aage Bohr as rotational kinetic energies. The $K$ quantum numbers are shown to be practically conserved for triaxial ellipsoids, which turned out to be a real but positive surprise to many people in the field. The so-called $γ$ bands are shown to be $K$ =2 $^{+}$ rotations rather than $γ$ -vibrations, leading to a nice description of the so-called $γ γ$ 4 $^{+}$ state as a $K$ =4 $^{+}$ rotation. Vibrational modes are also shown to emerge in this study. Thus, the whole picture of low-energy quadrupole collective motion of heavy nuclei has been renewed in a fully quantum mechanical fashion, which differs from the traditional picture but appears to be simpler and more natural.
nucl-thnucl-exEPJ Web Conf.(2025)·3 citations
07
Lattice calculation of the Sn isotopes near the proton dripline
Fabian Hildenbrand · Serdar Elhatisari · Ulf-G. Meißner · Helen Meyer · Zhengxue Ren · Andreas Herten · Mathis Bode
We present the first $ab initio$ lattice calculations of the proton-rich tin isotopes $^{99}$ Sn to $^{102}$ Sn using nuclear lattice effective field theory with high-fidelity two- and three-nucleon forces. For a given set of three-nucleon couplings, we reproduce binding energies with $\sim 1%$ accuracy for the even-even systems, and obtain energy splitting and two-nucleon separation energies in agreement with experiment. Our results confirm the $N = 50$ shell closure and reveal that the binding energy of $^{99}$ Sn lies below values extrapolated from heavier isotopes.
nucl-thhep-lathep-phnucl-exPRL(2026)·13 citations
08
NuLattice: Ab initio computations of atomic nuclei on lattices
M. Rothman · B. Johnson-Toth · G. Hagen · M. Heinz · T. Papenbrock
We introduce NuLattice, a Python software package for ab initio computations of atomic nuclei on lattices. The computational tools consist of Hartree Fock, the coupled cluster method, the in-medium similarity renormalization group, and full configuration interaction. At present, the employed interactions are from pion-less effective field theory at leading order and consist of two-body and three-body contacts. We present results for light nuclei $^{2}$ H, $^{3, 4}$ He, $^{8}$ Be, $^{12}$ C, and $^{16}$ O. NuLattice algorithms exploit the sparsity and locality of lattice interactions, and as a result computations can be run on laptops.
nucl-thEPJA(2026)·7 citations
09
Two-particle two-hole excitations in semi-inclusive neutrino-nucleus scattering
Valerio Belocchi🇮🇹 · Maria Benedetta Barbaro🇮🇹 · Arturo De Pace🇮🇹 · Marco Martini🇫🇷
A calculation of the two-particle two-hole contribution to the semi-inclusive $(ν_{μ}, μ^{-} N)$ cross section on carbon is performed in the framework of the relativistic Fermi gas model. The process is driven by meson-exchange currents encompassing all contributions involving the exchange of a single pion and the excitation of a $Δ$ resonance. The calculation is validated against the inclusive $(ν_{μ}, μ^{-})$ response functions already existing in the literature, and then extended for the first time to the semi-inclusive channel. Results are presented both at fixed neutrino energy and folded with the T2K neutrino flux.
nucl-thhep-exhep-phPRD(2025)·5 citations

Affiliations

first authorsco-authorsvia INSPIRE