Nuclear Theory·nucl-th

Thursday·June 4, 2026

11 papers—5 primary·6 cross-listed

01
Comment on "Partial conservation of seniority in semi-magic nuclei" by Chong Qi
Kai Neergård
This review misrepresents parts of one of my publications and fails to mention important parts.
nucl-thnucl-ex1 citation
02
NuGNN: a Graph Neural Network for Nuclear Reaction Network Equations
C. H. Kim · K. Y. Chae · S. Ko · M. R. Mumpower · M. S. Smith
Nuclear reaction networks are a major computational bottleneck in astrophysical simulations when large isotope sets are required, because of the stiffness of the network equations and the repeated calls to Jacobian-based solvers required by implicit methods. In this work, we develop a deep learning surrogate solver for a large 690-isotope nuclear reaction network under general Type I X-ray burst conditions using a graph neural network, NuGNN. Unlike conventional fully connected or convolutional neural networks, NuGNN directly reflects the structure of the reaction network through heterogeneous isotope and reaction nodes and message-passing along reaction connections. The model is trained on data spanning many orders of magnitude in stellar temperature and density and in simulation time step size. We compare NuGNN with a Res-U-Net and fully connected neural network and find that NuGNN consistently achieves significantly better accuracy with errors of only a few percent. More importantly, when implemented in the network evolution code in place of the original solver, NuGNN successfully reproduces the final abundance patterns, whereas the other architectures fail to do so. We also show that the trained model can substantially improve computational speed, demonstrating its practical potential for large-scale simulations. These results show that graph neural networks provide a robust and promising framework for accurate surrogate modeling of large nuclear reaction networks.
nucl-th0 citations
03
Physics of many-body resonances with complex scaling and applications to light unstable nuclei
Takayuki Myo
We review the exotic phenomena in light unstable nuclei with a focus on many-body resonances, which can decay into more than two constituents, and are frequently observed in unstable nuclei above the three-body threshold energy. The complex scaling transformation of the Schrödinger equation is a powerful method for describing many-body resonances, because it separates the continuum spectra into resonant and non-resonant continuum ones. Since the asymptotic wave functions of the resonances are regularized in the complex scaling, many-body resonances are described using the $L^{2}$ basis functions in the eigenvalue problem. The properties of many-body resonances can then be discussed in the same way as those of the bound states. We apply the complex scaling to the system consisting of a stable nucleus and valence nucleons and investigate many-body resonances in neutron-rich and proton-rich light nuclei. Using the eigenstates obtained with the complex scaling, we construct the extended completeness relation and the Green's function. They are used to calculate the level densities and the general transition strengths into many-body unbound states. We also discuss the interpretation of the complex expectation values associated with resonances, which remains an open problem. We propose a possible scheme for it in terms of the complex-scaled Green's function.
nucl-thnucl-exAAPPS Bull.(2026)·0 citations
04
Analisys of $0^{-}$ excitations in $^{16}$ O from inelastic scattering of polarized protons of intermediate energy
M.S. Onegin
Comparison of the calculation of inelastic proton scattering from $^{16}$ O with excitation of $0^{-}$ levels with $T = 0, 1$ with accessible experimental data at different energies of incident protons is presented. The role of antisymmetrization in reaction formalism and the manifestation of the pion condensation in nuclear are discussed. To obtain more solid conclusions on these points more experimental data are needed.
nucl-th0 citations
05
Numerical study of the three-boson bound-state problem in partial-wave and vector-variable formulations
Wolfgang Schadow · Mohammadreza R. Hadizadeh
We present a systematic benchmark of the three-boson bound-state problem in momentum space, comparing one-dimensional (1D) spectator-amplitude, two-dimensional (2D) partial-wave, and three-dimensional (3D) vector-variable formulations. The benchmark controls the interaction representation by embedding the same finite partial-wave interaction space in each formulation, so that discrepancies reflect discretization, interpolation, and quadrature errors. This enables direct 1D--2D--3D comparisons for separable interactions, controlled 2D--3D tests for local interactions, and comparison with the full local interaction in the 3D vector-variable formulation. Binding energies agree at the $1 0^{- 6}$ ~MeV level for separable interactions and at the few- $1 0^{- 6}$ to $1 0^{- 5}$ ~MeV level for local interactions. The 2D and 3D equations are also solved in both $t$ -matrix-driven and bare-potential-driven forms, whose agreement validates the permutation geometry, quadrature, and interpolation. Fourier transforms to coordinate space yield consistent norm decompositions and spatial observables, providing an independent check of the momentum-space solutions.
nucl-th0 citations
06
Canonical statistical hadronization with local baryon conservation for higher-order cumulants
Mario Ciacco🇮🇹 · Sourav Kundu🇨🇭 · Volodymyr A. Kuznietsov🇺🇸 · Maximiliano Puccio🇨🇭 · Volodymyr Vovchenko🇺🇸
We study higher-order cumulants of the conserved baryon number at the LHC within the canonical ensemble with local baryon conservation. We generalize the density correlations approach of [Phys. Rev. C 110, L061902 (2024)] to incorporate the effect of Gaussian local conservation in spatial rapidity space in cumulants up to 6th order. Gaussian local conservation improves upon the commonly employed $V_{c}$ approach, yielding comparable predictions at midrapidity, but marked differences for larger rapidity acceptances. Our coordinate-space results are in exact agreement with the diffusion master equation approach for all cumulant ratios up to $κ_{6} / κ_{2}$ . Using the blast-wave model to apply kinematic cuts, we obtain predictions for net-proton cumulants in O--O and Pb--Pb collisions at the LHC that establish an ideal hadron gas baseline. We find that local baryon conservation alone can drive $κ_{6} / κ_{2}$ to small or even negative values in restricted acceptance, a behavior often associated with chiral criticality. The conservation baseline must therefore be carefully accounted for when interpreting upcoming LHC measurements.
↳ hep-phnucl-th2 citations
07
Quantum Simulation of Nucleon-Antinucleon Interaction in Large- $N$ QCD $_{2}$ on an IBM Quantum Nighthawk Processor
Cameron V. Cogburn🇺🇸 · Sebastian Grieninger🇺🇸 · Dmitri E. Kharzeev🇺🇸
We report a quantum simulation of the nucleon--antinucleon interaction in large- $N$ two-dimensional quantum chromodynamics (QCD $_{2}$ ) on the IBM Quantum Nighthawk processor. In the large- $N$ limit, QCD $_{2}$ admits a bosonized description in which baryons emerge as topological solitons (kinks) of an effective mesonic field theory, providing a controlled, nonperturbative framework for baryon--antibaryon dynamics. We formulate the problem by mapping the continuum bosonized Hamiltonian to a spin-chain representation equivalent to an XXZ model with anisotropy set by the QCD parameters. In this mapping, nucleon and antinucleon states correspond to kink and antikink excitations, respectively, while their interaction is encoded in the spin correlations of the chain. Using Jordan--Wigner encoding, we implement the resulting XXZ Hamiltonian on a finite set of qubits and realize it via a variational ground state ansatz and postselected nonunitary disorder operator insertions optimized for the Nighthawk architecture. We then show the kink--antikink interaction potential built from the conditional energies of these nonunitary string operators can be robustly extracted from the quantum hardware due to structured error cancelation. The resulting potential exhibits the expected attractive behavior. The quantum simulation results are benchmarked against exact diagonalization, ideal statevector evaluation showing good agreement. To connect the device result to the continuum field theory, we extract the potential in the continuum limit using large- $L$ matrix product state calculations.
↳ quant-phhep-phnucl-th2 citations
08
Boson Models with Interactions of Arbitrary Order
P. Van Isacker🇫🇷
The paper considers quantal many-boson systems that are described by a rotationally invariant and boson-number conserving Hamiltonian. The properties of a generic model are studied which treats N bosons of p different kinds with non-zero angular momenta l_1,l_2,...,l_p, possibly augmented with a (number of) scalar s boson(s). The order k of the interaction between the bosons is arbitrary and closed formulas are given for matrix elements between N-boson states for any k if p=1 and p=2. A recursive procedure is defined for arbitrary k and p. With the expressions derived in the paper it is possible to express symbolically a Hamiltonian matrix element between N-boson states as a linear combination of k-body interaction matrix elements. More generally, the formulas allow the evaluation of matrix elements of tensor operators that are not necessarily scalar nor boson-number conserving. The numerical implementation of the formalism is discussed and illustrated with a few examples.
↳ quant-phnucl-thSymmetry(2026)·0 citations
09
TMD factorization in diffractive heavy-quark production in photon-nucleus collisions
Paul Caucal🇫🇷 · Patricia Gimeno-Estivill🇫🇮 · Edmond Iancu🇫🇷 · Tuomas Lappi🇫🇮 · Farid Salazar🇺🇸
Using the Colour Glass Condensate effective theory, we study the diffractive production of a massive quark-antiquark pair accompanied by a gluon in coherent photon-nucleus collisions at high energy. This partonic configuration provides the leading twist contribution to the cross section in the correlation limit where two of the partons are hard and nearly back to back in the transverse plane, while the third one is semi-hard, with a transverse momentum of the order of the nuclear saturation momentum. We consider two scenarios: (i) a hard quark-antiquark pair together with a semi-hard gluon; in this case we demonstrate transverse momentum dependent (TMD) factorization with a mass-dependent ''hard'' factor and the standard expression for the gluon diffractive TMD, and (ii) a hard antiquark-gluon pair and a semi-hard quark; in this case we find TMD factorization with a mass-independent ''hard'' factor and a mass-dependent quark diffractive TMD, which represents a new result. We show that increasing the quark mass reduces (or even washes out) the effects of gluon saturation on the quark diffractive TMD. In particular, it leads to the suppression of the Cronin peak that we observe in the massless limit. Our results are the basis for future phenomenological studies of quarkonium and open charm production in the saturation regime in ultraperipheral collisions at the Large Hadron Collider, and in deep inelastic scattering at the Electron-Ion Collider.
↳ hep-phnucl-th1 citation
10
Contact interaction treatment of {\pi} and {\rho} elastic and transition tensor form factors
Ke-Yu Guo🇨🇳 · Ke-Xin Zeng🇨🇳 · Xin-Yu Bai🇨🇳 · Chen Chen🇨🇳 · Craig D. Roberts🇨🇳
Predictions for tensor charges and form factors, elastic and transition, involving $π$ - and $ρ$ -mesons and their scalar and axialvector diquark partners, are delivered using a symmetry-preserving treatment of a vector*vector contact interaction (SCI). Two distinct SCI regularisation schemes are employed, with the results showing little sensitivity. Although, as typical in SCI analyses, the form factors are stiff; their infrared behaviour may be considered physically reliable. Notable amongst related quantities are the following: the pion tensor charge is approximately $0.36$ and the associated tensor form factor radius is practically the same as the pion charge radius; the $ρ$ -meson tensor charge is roughly 80% of that for the proton; and diquark tensor charges and form factors are semiquantitatively alike with those of their $π$ , $ρ$ partners. In addition to being interesting in themselves, the SCI predictions can serve as baselines for future studies with a closer connection to QCD.
↳ hep-phhep-exhep-latnucl-ex+10 citations
11
Thermodiffusive coupled-transport phenomena in dense quark matter
Kamaljeet Singh🇮🇳 · Kangkan Goswami🇮🇳 · Raghunath Sahoo🇮🇳
Coupled-transport phenomena reveal that heat, charge, and particle flows are intrinsically interconnected, providing deeper insight into the microscopic dynamics of a medium than independent transport processes. We study the behavior of the coupled-transport coefficients in hot and dense quark matter within the framework of the 2+1 flavor Nambu--Jona--Lasinio model at finite temperature and quark chemical potential. These coefficients characterize coupled-transport phenomena, where particle diffusion is driven by temperature gradients (Soret effect) and heat flow is induced by gradients in chemical potential (Dufour effect). These coefficients are estimated by solving the relativistic Boltzmann transport equation using the relaxation time approximation with temperature-dependent cross sections. We study the scaled Soret and Dufour coefficients as functions of temperature and quark chemical potential across the QCD phase diagram. We aim to understand the intricate behavior of the coupled-transport coefficients near the chiral symmetry restoration region. Our results indicate that coupled-transport coefficients are sensitive to the chiral phase transition and provide the first systematic insight into the cross-coupled-transport properties in dense quark matter.
↳ hep-phhep-exhep-thnucl-ex+10 citations

Affiliations

first authorsco-authorsvia INSPIRE