Nuclear Theory·nucl-th

Thursday·April 2, 2026

22 papers—13 primary·9 cross-listed

01
[Submitted on 31 Mar 2026]
An Asymptotically Causal Metamodel for Neutron Star Equations of State
Gabriele Montefusco🇫🇷 · Marco Antonelli🇫🇷 · Francesca Gulminelli🇫🇷
Nuclear metamodels - phenomenological parametrizations of the energy of nuclear matter - are convenient tools to explore the space of realistic neutron star configurations constrained by astrophysical and nuclear data. While much recent work has focused on composition-agnostic barotropic models, the metamodel approach is designed to describe the composition dependence of the relevant thermodynamic potential. We revise a previously proposed non-relativistic metamodel by introducing a more controlled high-density behaviour, improving both its causal properties and its accuracy in reproducing the pressure and the beta-equilibrium composition of microscopically motivated equations of state. Since causality is automatically enforced at high density, the fraction of discarded models due to superluminal sound speeds is substantially reduced, facilitating metamodel-based explorations of equilibrium neutron star configurations. We further assess our framework by performing a Bayesian inference of neutron star properties beyond standard observables such as masses and radii, exploiting the metamodel's ability to probe composition-dependent quantities including the dUrca threshold and the Ledoux criterion for g-mode stability.
Comments:
20 pages, 10 figures; comments are welcome
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE)
arXiv:
2604.00196 [pdf]
1 citation
02
[Submitted on 31 Mar 2026]
Statistical Mechanics of Quarkyonic Matter
Marcus Bluhm (SUBATECH, Nantes)🇫🇷 · Yuki Fujimoto (Niigata U. and Wako, RIKEN)🇯🇵 · Marlene Nahrgang (SUBATECH, Nantes)🇫🇷
We extend the theoretical formulation of Quarkyonic Matter within the IdylliQ model framework proposed in [Y. Fujimoto et al., Phys. Rev. Lett. 132, 112701 (2024) [1]] for zero temperature to non-zero temperatures. To this end, we develop a consistent statistical mechanics and grand canonical ensemble description of Quarkyonic Matter as a quantum system subject to additional inequality constraints due to the Pauli exclusion principle acting simultaneously on baryons and their constituent quarks. These constraints result in a significant reduction in the number of physically available baryon states compared to an ideal Fermi gas. As a consequence, the one-particle baryon distribution function factorizes into a thermal Fermi-Dirac distribution and a momentum-dependent density of states. This separation allows us to derive a proper definition of the entropy density that satisfies the third law of thermodynamics in the zero-temperature limit. Moreover, we find that inside Quarkyonic Matter the physical temperature and the physical baryon chemical potential differ from the Lagrange multipliers appearing in the Fermi-Dirac distribution which may have important consequences for the thermodynamics of Quarkyonic Matter.
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th)
arXiv:
2604.00247 [pdf]
2 citations
03
[Submitted on 31 Mar 2026]
Fluid Acceleration in Heavy-Ion Collisions
Song-Ze Zhong🇨🇳 · Xian-Gai Deng🇨🇳 · Xu-Guang Huang🇨🇳 · Yu-Gang Ma🇨🇳
We study the generation and space-time evolution of fluid acceleration in heavy-ion collisions using AMPT and UrQMD transport models combined with a Gaussian smearing method. The peak proper acceleration reaches several hundred MeV, with mild model dependence. Transverse acceleration points outward and is strongest at the fireball boundary due to steep pressure gradients and low enthalpy density--a persistent feature even at early times and low energies. Longitudinal acceleration shows strong collision-energy dependence: low-energy collisions exhibit early deceleration from nuclear stopping, while ultra-relativistic collisions produce sharp acceleration pulses from passing nuclei. The volume-averaged acceleration is nearly centrality independent, as extreme acceleration localizes at boundaries. These strong acceleration fields may have important implications for QGP physics, including the Unruh effect mimicking a thermal bath, potential influences on the chiral phase transition and deconfinement, and contributions to spin polarization beyond vorticity.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2604.00302 [pdf]
Nucl.Sci.Tech.(2026)·2 citations
04
[Submitted on 1 Apr 2026]
Gravitational wave spectrum from first-order QCD phase transitions based on a parity doublet model
Bikai Gao🇯🇵 · Jingdong Shao🇨🇳 · Hong Mao🇨🇳
We investigate the gravitational wave spectrum from first-order QCD phase transitions using the parity doublet model at finite baryon chemical potential. The model incorporates the chiral invariant mass $m_{0}$ , representing the portion of nucleon mass that persists even when chiral symmetry is restored. Within the model, we identify two first-order phase transition regions: the nuclear liquid--gas transition and the chiral phase transition. By solving the bounce equation and computing the Euclidean action $S_{3} / T$ , we obtain the gravitational wave spectra from both transitions. The liquid--gas transition yields $α \sim O (1)$ and $β / H \sim O (10)$ -- $O (100)$ near the endpoint of the first-order line, producing signals with peak frequencies from the millihertz to the nanohertz band that can fit the existing data. In contrast, the chiral transition produces signals suppressed by approximately five orders of magnitude, well below the sensitivity of all current and planned detectors. These results connect the chiral invariant mass to the gravitational wave spectrum, offering a novel probe of the origin of nucleon mass through gravitational wave astronomy.
Comments:
5 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2604.00465 [pdf]
PRD(2026)·1 citation
05
[Submitted on 1 Apr 2026]
Exact Construction and Uniqueness of the Coupled-Channel Green's Function
Hao Liu · Jin Lei · Zhongzhou Ren
We present a rigorous construction and uniqueness proof of the matrix Green's function for coupled radial Schrödinger equations with symmetric coupling potentials. The Green's matrix $g_{γ γ^{'}} (R, R^{'})$ is built from two fundamental sets of $N$ linearly independent solutions, regular and outgoing, of the coupled radial equations. We prove that the associated Wronskian matrix is diagonal with elements $W_{n} = - k_{n}$ and independent of the radial coordinate, and demonstrate through the symplectic structure of the $2 N$ -dimensional phase space that the resulting construction is the unique Green's matrix satisfying the defining equation with correct boundary conditions, continuity at the source point, and the prescribed derivative discontinuity. The construction applies to any system of coupled radial Schrödinger equations with symmetric coupling potentials and open channels, including coupled-channels problems arising in nuclear, atomic, and molecular scattering. As an illustrative application, we show how the Green's matrix enters the nonlocal dynamical polarization potential (DPP) within the continuum-discretized coupled-channels (CDCC) framework, where retaining the off-diagonal elements captures multistep excitation pathways beyond the weak-coupling approximation.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2604.00471 [pdf]
PRC(2026)·3 citations
06
[Submitted on 1 Apr 2026]
Absorption of 1 $P$ -wave heavy charmonium $χ_{c 1} (1 P)$ in nuclei
E. Ya. Paryev
We study the inclusive heavy charmonium $χ_{c 1} (1 P)$ photoproduction from nuclei near the kinematic threshold within the collision model, based on the nuclear spectral function, for incoherent direct photon--nucleon charmonium creation processes. The model accounts for the final $χ_{c 1} (1 P)$ absorption in nuclear medium, target nucleon binding and Fermi motion. We calculate the absolute and relative excitation functions on $^{12}$ C and $^{184}$ W target nuclei at near-threshold photon beam energies of 8.25--16.0 GeV, the absolute momentum differential cross sections and ratios of them for its production off these target nuclei at laboratory polar angles of 0 $^{\circ}$ --10 $^{\circ}$ and for photon energy of 13 GeV as well as the A-dependences of the transparency ratios for the $χ_{c 1} (1 P)$ at photon energy of 13 GeV within the different scenarios for its absorption cross section in nuclei. We demonstrate that the absolute and relative observables considered reveal distinct sensitivity to these scenarios. Therefore, they might be useful for the determination of this cross section from the comparison of them with the experimental data from the future experiments at the upgraded up to 22 GeV CEBAF facility, which is of crucial importance in understanding of charmonium production and suppression in high-energy heavy--ion collisions in a search for the quark-gluon plasma.
Comments:
23 pages, 10 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
2604.00618 [pdf]
NPA(2026)·1 citation
07
[Submitted on 1 Apr 2026]
Triaxial shapes and the angular structure of nuclear three-body correlations
Hadi Mehrabpour🇨🇳 · Giuliano Giacalone🇨🇭 · Matthew W. Luzum🇧🇷
Relativistic nuclear collisions have emerged as a new tool for probing many-body correlations of nucleons in the ground states of atomic nuclei. Here, we investigate the connection between three-nucleon correlations inside nuclei and three-particle correlations measured in collider final states. We work within a classical rigid-rotor picture of the colliding ions, whereby correlations in the lab frame arise solely from the averaging over orientations of an intrinsic-frame nucleon density with a triaxial quadrupole deformation, characterized by Bohr parameters $β_{2}$ and $γ$ . With a Gaussian Ansatz for the density, we derive the leading-order form of the resulting two- and three-body nucleon distributions and perform a detailed analysis of their harmonic structure. With this, we provide an analytical understanding of empirical results linking shape parameters to final-state observables, notably, the fact that the covariance of the squared elliptic flow ( $v_{2}^{2}$ ) with the mean transverse momentum ( $[p_{T}]$ ), as well as the skewness of $[p_{T}]$ fluctuations, are to leading order proportional to $β_{2}^{3} cos (3 γ)$ . This elucidates the connection between three-nucleon densities, nuclear triaxiality, and three-particle correlations in high-energy nuclear collisions.
Comments:
11 pages
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
2604.00619 [pdf]
5 citations
08
[Submitted on 1 Apr 2026]
A Halo: The Trigger to a New Era of Nuclear Correlations
Hiroyuki Sagawa · Xiao Lu · Shan-Gui Zhou
In this contribution to the Halo-40 Proceedings, we discuss two topics regarding halo phenomena: The first is the pairing anti-halo effect on the neutron radius of halo nuclei and its restoration due to the coupling to the continuum; the second is the soft dipole excitation of deformed halo nuclei. We demonstrate the importance of Hartree-Fock-Bogoliubov and the relativistic Hartree-Bogoliubov theory in continuum for properly taking into account the halo nature of extended wave functions in calculations of neutron radii, as well as the soft dipole excitations of halo nuclei. It was shown that the anti-halo effect is very sensitive to the continuum coupling induced by Bogoliubov-type quasi-particles, which largely cancels the anti-halo effect on the neutron radius. The soft dipole excitations of deformed halo nuclei Ne-31 and Mg-37 are discussed within the deformed Woods-Saxon model. We point out that the sharp peak just above the threshold in the dipole response is created by the halo effect, and its strength can be used to identify the magnitude of deformation and the halo configuration in the Nilsson level scheme.
Comments:
14 pages, 7 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2604.00637 [pdf]
Particles(2026)·0 citations
09
[Submitted on 1 Apr 2026]
Off-shell Chiral Dynamics in the $Λ (1405)$ Resonance and $K^{-} p$ Femtoscopic Correlations
Jia-Ming Xie🇨🇳 · Zhi-Wei Liu🇨🇳 · Jun-Xu Lu🇨🇳 · Haozhao Liang🇯🇵 · Li-Sheng Geng🇨🇳
We present the first systematic investigation of the $S = - 1$ meson--baryon interaction within a fully off-shell covariant unitarized chiral effective field theory framework up to next-to-leading order. In particular, we perform a detailed comparison with the widely used on-shell approximation. We find that the resulting scattering observables are very similar, thereby confirming the validity of key results obtained within the on-shell scheme. A notable advantage of the off-shell treatment, however, is the absence of unphysical left-hand cuts induced by the on-shell approximation. Employing the off-shell amplitudes, we compute the femtoscopic correlation functions for $K^{-} p$ and $π^{\pm} Σ^{\mp}$ pairs. The $K^{-} p$ correlation functions are found to be consistent with previously published results based on the on-shell approximation, with marginal differences attributed to slight variations in the descriptions of the scattering data. The $π^{\pm} Σ^{\mp}$ correlation functions are predicted for the first time, and are expected to provide valuable constraints on the nature of the $Λ (1405)$ resonance and the coupled-channel chiral dynamics of the $K^{-} p$ system.
Comments:
8 figures, 15 pages
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2604.00791 [pdf]
PRD(2026)·3 citations
10
[Submitted on 1 Apr 2026]
One neutron triaxial halo candidates in aluminum isotopes from reaction observables
Jia-Lin An · Shi-Sheng Zhang · Kaiyuan Zhang
Microscopic description of one neutron ( $1 n$ ) halo candidates $^{40, 42}$ Al, with particular triaxial shape, is presented by combining the triaxial relativistic Hartree-Bogoliubov theory in continuum (TRHBc) with the Glauber reaction model for the first time. In this scheme, the reaction cross sections of aluminum isotopes on a carbon target at 240 and 900 MeV/A are calculated, which exhibit a pronounced increase for $^{40, 42}$ Al + $^{12}$ C deviating from the systematic trend of their neighbours. Furthermore, the predicted longitudinal momentum distributions of the residues after $1 n$ removal reactions for $^{40, 42}$ Al + $^{12}$ C are narrower than those for $^{36, 38}$ Al + $^{12}$ C, which suggest halo structure with spatially extended density distribution. Based on the large occupation probabilities of $p$ -wave valence neutrons, we identify $^{40, 42}$ Al as the first triaxially deformed $1 n$ $p$ -wave halo candidates. This work cast a new light on the search for the heavier halo nuclei for future experiments in the mass region of $A \approx 40$ , through theoretical predictions from triaxial structure to reaction observables.
Comments:
4 pages, 2 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2604.00834 [pdf]
J.Phys.G(2026)·0 citations
11
[Submitted on 1 Apr 2026]
Predicting reaction observables for the two-neutron halo candidates $^{31}$ F and $^{39}$ Na
Jia-Lin An · Li-Yang Wang · Kaiyuan Zhang · Shi-Sheng Zhang
Microscopic description of two-neutron ( $2 n$ ) halo candidates $^{31}$ F and $^{39}$ Na has been realized from nuclear structure to reaction observables for the first time. The reliability of the Glauber reaction model has been confirmed by exactly reproducing the momentum distributions of the benchmark $2 n$ halo nucleus $^{11}$ Li, with the identical structural inputs from the former work. Combined with the structure from the deformed relativistic Hartree-Bogoliubov theory in continuum (DRHBc), the Glauber model is applied to predict the reaction observables, including the reaction cross sections (RCSs) for the fluorine and sodium isotopes bombarding a carbon target at 240~MeV/A and the longitudinal momentum distributions of the fragments after $2 n$ knockout reactions. It turns out that the calculated RCSs agree well with the available experimental data and a pronounced increase occurs to $^{29, 31}$ F + $^{12}$ C and $^{37, 39}$ Na + $^{12}$ C, which deviate from the original trend of their neighbours. Furthermore, the narrower longitudinal momentum distributions of the fragments after $2 n$ knockout reactions demonstrate that $^{31}$ F and $^{39}$ Na have the dilute $2 n$ halo structure. Such a new combination is promising to suggest new $2 n$ halo candidates for future measurements.
Comments:
6 pages, 4 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2604.00880 [pdf]
0 citations
12
[Submitted on 1 Apr 2026]
Exact interpolation between Fick and Cattaneo diffusion in relativistic kinetic theory
Lorenzo Gavassino🇬🇧
We construct a family of exactly solvable relativistic kinetic theories in $1 + 1$ dimensions whose hydrodynamic sector continuously interpolates between Fick's and Cattaneo's laws of diffusion. The interpolation is controlled by a single parameter $a \in [0, 1]$ , which tunes the microscopic scattering dynamics from infinitely soft but infinitely frequent scatterings ( $a = 0$ ), reproducing standard diffusion, to maximally hard but finite-rate scatterings ( $a = 1$ ), yielding hyperbolic Cattaneo-type transport. For intermediate values of $a$ , the dynamics combines frequent weak scatterings with rare strong randomizing events, providing a concrete microscopic realization of mixed diffusive-telegraphic behavior. Remarkably, the full quasinormal mode spectrum can be obtained analytically for all $a$ . This allows us to track explicitly how purely diffusive modes continuously deform into damped propagating modes as the collision structure is varied.
Comments:
10 pages, 4 figures, comments welcome!
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Theory (hep-th); Mathematical Physics (math-ph); math.MP (math.MP)
arXiv:
2604.00984 [pdf]
0 citations
13
[Submitted on 1 Apr 2026]
Microscopic optical potential framework applied to neutron scattering on deformed $^{48, 50}$ Cr
J. Boström · B. G. Carlsson · A. Idini
We formulate and implement a microscopic framework to derive an optical potential from the solution to an effective Hamiltonian and use it to calculate neutron scattering cross sections for the deformed nuclei $^{24}$ Mg, $^{48}$ Cr and $^{50}$ Cr. This approach is based on a symmetry-restored multi-excitation generator coordinate method (GCM), enabling the consistent treatment of both nuclear structure and reaction observables. Through this method, non-local optical potentials corresponding to a Hamiltonian can potentially be constructed for any nucleus in the whole nuclide chart. We use this to perform reaction calculations employing quadrupole deformed triaxial configurations, obtaining results for $A \approx 50$ chromium isotopes, and study the properties of the calculated non-local optical potentials. This work further advances the unified treatment of structure and reaction, within a framework that exploits the intrinsic symmetries of nuclei.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2604.01033 [pdf]
0 citations

Affiliations

first authorsco-authorsvia INSPIRE