Nuclear Theory·nucl-th

Friday·March 6, 2026

10 papers—5 primary·5 cross-listed

01
Coupled charm and charmonium transport in a strongly coupled quark-gluon plasma
Kaiyu Fu🇺🇸 · Biaogang Wu🇺🇸 · Ralf Rapp🇺🇸
The quark-gluon plasma (QGP) is a strongly coupled medium in which both open and hidden charm particles experience substantial nonperturbative interactions. This poses a major challenge for a quantitative description of charmonium transport in ultra-relativistic heavy-ion collisions, as it requires a mutually consistent treatment of pertinent transport coefficients. In this work, we present a coupled charm-charmonium transport framework for a strongly coupled QGP based on thermodynamic $T$ -matrix interactions with recent constraints from Wilson-line correlators (WLCs) computed in lattice QCD. For the first time, the same underlying heavy-light interactions and in-medium spectral functions are used to self-consistently evaluate charm-quark diffusion and charmonium kinetics. In particular, the charmonium equilibrium limit, a critical transport parameter for regeneration, is evaluated in the presence of broad spectral functions. Charm-quark diffusion is simulated via Langevin dynamics and coupled to a Boltzmann equation for charmonium dissociation and regeneration. The equilibrium limit of the statistical model is recovered once charm quarks thermalize, and its extension to describe off-equilibrium is constructed. Preliminary applications to charmonium observables in Pb--Pb collisions at the LHC capture the measured centrality and momentum dependence fairly well.
nucl-thEPJA(2026)·1 citation
02
Single-Particle Resonant States in Relativistic Hartree-Fock Theory: A Green's Function Approach
Wei Gao · Ting Ting Sun · Wen Hui Long
Relativistic Hartree-Fock theory is combined with the Green's function method in coordinate space to study both single-particle bound and resonant states within a unified framework. Within this approach, single-particle resonance energies and widths are unambiguously extracted from the density of states, and the influence of the Coulomb exchange effects on proton resonances in $N = 82$ isotones are systematically examined. It is found that the exact treatment of Coulomb exchange terms reduces proton resonance energies of approximate $0.09 \sim 0.21$ MeV, a significantly smaller effect than that obtained from the phenomenological treatment. Moreover, except for rather narrow resonances, the proton resonance widths are visibly reduced by the Coulomb exchange terms, also being much less pronounced than the phenomenological approach. Notably, clear shell effects are observed in the isotonic evolutions of the resonance energy reductions for specific resonances. All these highlight the necessity of a microscopical and exact treatment of the Coulomb exchange terms.
nucl-thCPC(2026)·0 citations
03
Bayesian Learning of (n,p) Reaction Cross Sections with Quantified Uncertainties
Arunabha Saha · Songshaptak De
Accurate neutron-induced $(n, p)$ reaction cross sections are essential for applications in nuclear energy, radionuclide production, materials studies, and nuclear astrophysics. However, experimental data remain sparse for many isotopes, and evaluated nuclear data libraries can show systematic deviations from available measurements. We develop a Bayesian neural network (BNN) residual learning model, denoted \texttt{BNN-R5}, to improve $(n, p)$ reaction cross-section predictions. The model uses five physically motivated nuclear descriptors and does not employ experimental or evaluated cross-section values as input features. Rather than predicting the cross sections directly, \texttt{BNN-R5} learns the log-space residual between the evaluated TENDL-2023 data and experimental measurements, thereby providing a data-driven correction to the evaluated library. The model is trained using stochastic variational inference, which provides predictive mean values together with Bayesian uncertainty estimates. Across a broad range of target nuclei, the corrected cross sections generally show improved agreement with experimental data and outperform the original TENDL-2023 evaluations. Feature-importance analysis using SHapley Additive exPlanations (SHAP) identifies the pairing term $δ$ as the most influential descriptor, followed by the excitation-energy variable $ln (Δ E)$ and the neutron number $N$ , while the proton number $Z$ has the smallest overall influence. These results demonstrate that Bayesian residual learning provides a robust and interpretable framework for improving evaluated nuclear data and predicting reaction cross sections in data-sparse regions of the nuclear chart.
nucl-th0 citations
04
Six- $α$ cluster Bose-Einstein condensation and supersolid $^{12}$ C( $0_{2}^{+})$ + $^{12}$ C( $0_{2}^{+})$ molecular structure in $^{24}$ Mg
S. Ohkubo · J. Takahashi · Y. Yamanaka
We show for the first time that the low-spin ( $J \leq 4^{+}$ ) six- $α$ condensate candidate states in $^{24}$ Mg, recently reported by Fujikawa et al. [Phys. Lett. B 848, 138384 (2024)], are well described by the superfluid $α$ -cluster model (SCM). This is achieved by a rigorous treatment of the Nambu-Goldstone (NG) zero mode as the order parameter of condensation in the finite six- $α$ system. We find that a roton rotational band with a large moment of inertia is built on the first excited NG $0^{+}$ state, analogous to the roton bands observed in three-, four-, and five- $α$ condensates in $^{12}$ C, $^{16}$ O, and $^{20}$ Ne, respectively. Remarkably, our calculated roton band reproduces the well-known molecular resonance with a $^{12}$ C( $0_{2}^{+}$ )+ $^{12}$ C( $0_{2}^{+}$ ) structure ( $1 6^{+}$ ) observed at $E_{c.m.} = 32.5$ MeV in inelastic $^{12}$ C+ $^{12}$ C scattering. This result provides a unified description of both the low-spin six- $α$ condensate states and the high-spin $^{12}$ C( $0_{2}^{+}$ )+ $^{12}$ C( $0_{2}^{+}$ ) molecular resonance. Analysis of the wave functions reveals a large overlap between the SCM states and a geometrical $^{12}$ C( $0_{2}^{+}$ )+ $^{12}$ C( $0_{2}^{+}$ ) configuration. This dual nature -the coexistence of superfluidity and crystallinity- identifies these states as a signature of a supersolid.
nucl-thEPJA(2026)·0 citations
05
Emergence of the geometric contribution to the superfluid density in the inner crust of neutron stars
Giorgio Almirante🇫🇷
The geometric contribution to the superfluid density has been found to be of great importance in the inner crust of neutron stars. In this work we clarify how this contribution arises in the context of a band theory for neutrons. Specifically, we derive the dependence of the superfluid density on the magnitude of the pairing gap when the system has many bands cutting the Fermi energy, as it is the case for the neutrons in the inner crust. Also, in the perturbation theory framework, we find that it is essential to account for the corrections to the (Bogoliubov) quasi-particle states in order to get the geometric contribution. Accounting only for the corrections to the (Hartree-Fock) single-particle states leads to the conventional contribution only.
nucl-thcond-mat.quant-gasParticles(2026)·1 citation

Affiliations

first authorsco-authorsvia INSPIRE

Coupled charm and charmonium transport in a strongly coupled quark-gluon plasma

Single-Particle Resonant States in Relativistic Hartree-Fock Theory: A Green's Function Approach

Bayesian Learning of (n,p) Reaction Cross Sections with Quantified Uncertainties

Six-α cluster Bose-Einstein condensation and supersolid 12C(02+​)+12C(02+​) molecular structure in 24Mg

Emergence of the geometric contribution to the superfluid density in the inner crust of neutron stars

Affiliations

Six- $α$ cluster Bose-Einstein condensation and supersolid $^{12}$ C( $0_{2}^{+})$ + $^{12}$ C( $0_{2}^{+})$ molecular structure in $^{24}$ Mg