Nuclear Theory·nucl-th

Thu·Sep 24, 2026Thursday·September 24, 2026

10 papers—8 primary·2 cross-listed

01
Complexity of Nuclear States for 48Ca
L. López-Hernández · D. A. Lara Bustillos · Carlos E. Vargas · V. Velázquez
In complex systems theory, there are different ways to describe a system in terms of information, such as emergence (Shannon entropy), self-organization, and com- plexity. These measures provide information about the dynamic behavior of a complex system. We study the differences in entropy and complexity for many-body systems undergoing a transition from a regular to a chaotic regime. To do this, we analyze the eigenvectors of the 48 Ca nucleus for different quadrupole-type two-body interactions. We obtain the eigenvectors by diagonalizing the two-body Hamiltonian for 48 Ca us- ing the Antoine code. We then calculate the entropy and complexity for the different quadrupole-type interactions. The differences found in information entropy and com- plexity are clear when comparing a regular system with a chaotic one. We find that the complexity of the regular and chaotic states of 48 Ca shows differences associated with its internal interactions.
nucl-thquant-phEntropy 2026, 28, 878
02
Multi-Model Analysis of the Astrophysical $S (E)$ Factor for the $^{9} Be (p, α)^{6} Li$ Reaction and Its Impact on Astrophysical Reaction Rates
Xue-Jian Wang · Wei-Ke Nan · Qing Wang · Tian-Yu Tao · Qun-Gang Wen · Jian-You Guo · Cheng-Bo Li · Hui-Ming Jia
The $^{9} Be (p, α)^{6} Li$ reaction is a destruction process for $^{9} Be$ in stars and the Big Bang. The Trojan Horse Method (THM) is a well-established indirect technique that enables the determination of reaction cross sections within the Gamow energy region while avoiding the uncertainties associated with low-energy extrapolations of the $S (E)$ factor and electron-screening effects. In this work, the bare-nucleus THM data reported by Wen \textit{et al.} are systematically analyzed using polynomial fitting, a double Breit--Wigner model, and the $R$ -matrix formalism. The applicability and physical implications of these theoretical approaches in describing the low-energy $S (E)$ factor of the $^{9} Be (p, α)^{6} Li$ reaction are investigated and compared. Since the THM data have been incorporated into the NACRE II reaction-rate compilation, leading to improved accuracy in reaction-rate evaluations, the refined theoretical analysis presented here provides further insight into the underlying reaction dynamics and establishes a more reliable foundation for stellar reaction-rate calculations. The results obtained in this work offer valuable reference for future high-precision experimental investigations and the development of theoretical models in nuclear astrophysics.
nucl-thastro-ph.SRnucl-exThe Astrophysical Journal, 1008:119 (9pp)…
03
Exploring the short-range correlations in $^{16}$ O+ $^{16}$ O collisions at the LHC
Qi Liu · Shanjin Wu · Huichao Song
Short-range correlations (SRCs) dominate the nuclear force at short distances, including the repulsive core and intermediate-range attraction, and are one of the most fascinating aspects of the nucleon-nucleon (NN) interaction. In this work, we investigate the effects of SRCs on the final-state observables in $^{16}$ O+ $^{16}$ O collisions at $s_{N N} = 5.36$ ~TeV, using the iEBE-VISHNU hybrid model with {T\raisebox{-0.5ex}{R}ENTo} initial conditions. We embed the nucleon configurations of $^{16}$ O generated from variational Monte Carlo (VMC) simulations with realistic SRCs in the initial stage, along with uncorrelated VMC samples and Woods--Saxon distributions implementing a hard repulsive core or short-range attraction as comparison runs. We find that SRCs reduce both $v_{2} {2}$ and $v_{2} {4}$ in the most central collisions, with the decrease of $v_{2} {4}$ being more pronounced due to the event-by-event flow fluctuations. Meanwhile, SRCs noticeably enhance the correlation between the elliptic flow and the mean transverse momentum, $ρ_{2} (v_{2}^{2}, [p_{T}])$ . These effects are mainly attributed to the strong repulsive core of the SRCs, which suppresses the probability of finding nucleon pairs at short relative distances and renders the initial geometry more uniform. This interpretation is supported by the calculations based on Woods--Saxon distributions with a hard repulsive core, which reproduce similar results, while the contribution from a pure intermediate-range attraction is negligible. Our results demonstrate that relativistic nuclear collisions provide a complementary probe of the short-range structure of the nuclear force, beyond the traditional nuclear experiments at low energies.
nucl-thhep-ph
04
Shell structure and spontaneous decay of superheavy $Z = 124$ isotopes with the deformed relativistic Hartree-Bogoliubov theory in continuum
Yumeng Wang · Lang Liu · Cong Pan
Shell structure and spontaneous decay of $Z = 124$ isotopes are systematically investigated using the deformed relativistic Hartree-Bogoliubov theory in continuum (DRHBc) with the PC-PK1 density functional. By accounting for deformation and continuum effects, the neutron drip line is predicted to be located at $N = 320$ , and eight potential multi-neutron emitters beyond the neutron drip line are identified. The results, compared with the spherically constrained case, highlight the critical role of deformation effects in determining the ground-state properties of superheavy nuclei. In addition, potential neutron shell closures emerge at $N = 258$ and $350$ , alongside subshell closures at $N = 232$ and $320$ . The results disfavor $Z = 124$ as a possible proton magic number and suggest $Z = 120$ and $138$ as more favorable candidates for proton shell closures in the superheavy region. Finally, the competition between $α$ decay, $β$ decay, and spontaneous fission is analyzed by calculating half-lives within various semi-empirical formulas. The results indicate that $α$ decay is the predominant mode on the proton-rich side, whereas spontaneous fission and $β^{-}$ decay gradually become dominant with increasing neutron number.
nucl-thnucl-ex
05
Strangeness Production in Heavy-Ion Collisions: Color Ropes or Hydrodynamic Evolution?
Carl Rosenkvist · Hannah Elfner
We investigate strangeness production and transverse dynamics in heavy-ion collisions at $s_{NN} \approx 2.5 - 20 GeV$ using the transport approach SMASH (Simulating Many Accelerated Strongly-interacting Hadrons), its extension with rope hadronization, and the SMASH+vHLLE hybrid approach. Results from the Pythia-based heavy-ion model Angantyr, with and without rope hadronization, are included for comparison. We study midrapidity particle yields and average transverse masses as functions of the number of wounded nucleons, as well as their energy dependence. For the $K^{+} / π^{+}$ ratio, SMASH+vHLLE overpredicts strangeness production at low energies but describes the higher-energy behavior reasonably well. SMASH+Ropes reproduces the ratio up to $s_{NN} \sim 10 GeV$ but does not capture the turnover at higher energies. In contrast, the transverse-mass observables favor the hybrid approach, while the non-thermal models considered here do not generate sufficient collective transverse expansion. These results show that strangeness enhancement alone does not uniquely distinguish microscopic string interactions from a locally equilibrated medium. Simultaneously constraining strangeness production and transverse dynamics is therefore essential for disentangling thermal and non-thermal mechanisms in heavy-ion collisions.
nucl-thhep-ph
06
The compressible liquid drop model with curvature included algebraically for the pasta phases in neutron stars
Dmitry Kobyakov
In the compressible liquid drop model (CLDM), the curvature energy term has been included in many works in the literature, and its effects on the presence of pasta phases have also been extensively investigated. However, the analytical part of the inclusion used to cease once a 4-order algebraic equation for the optimized size of the nucleus was written. In this paper, an optimization is suggested to the analytical part of the solution of the CLDM equations. Solving analytically the 4-order algebraic equation proves to be helpful for a straightforward identification of the denied parameter ranges in which the CLDM has no real-root solutions. Using a particular nuclear force derived from the chiral effective field theory, I investigate effects on the ground state of the nucleus curvature. Surprisingly, the inclusion has lead to a significant modification of the range of baryon density in which the bubble phases are found, disfavoring the bubble phases from the ground state. This shows a strong difference between the predictions of the CLDM with the nucleus size obtained when including the curvature term and that obtained from the $w_{s} = 2 w_{C + L}$ approximation. The importance of the curvature energy in the CLDM is linked with its ability to change qualitatively the ground state. This paper presents an analytical extension to the CLDM solution, which is ready to be used with any other nuclear model in the future, in order to optimize the inclusion of the nuclear curvature energy, and is not limited to one nuclear model.
nucl-thastro-ph.HEastro-ph.SR
07
Fission Evaluation Tools and Analytics (FETA)
N. Schunck
We present a new Python package called FETA to compute fission observables. In comparison to existing fission event modeling codes on the market, FETA is a modular, flexible, and code-agnostic wrapper around a statistical reaction theory program. In this paper, we report on version 2.0 of FETA, which simulates the prompt decay of the fragments with the LLNL-developed Hauser-Feshbach code YAHFC. We discuss the design philosophy of FETA, present some validation results for the neutron-induced fission of 239Pu, and briefly outline the structure of the package.
nucl-th
08
Strange Quark Stars and Spontaneous Scalarization
Mina Mehraeen Nazdik · Zeinab Rezaei
Strange quark matter, as one of the most extreme dense states in astrophysics, can be explored through relativistic compact objects. Hypothetical relativistic stars composed of dense strange quark matter are characterized by the equation of state of that matter. The spontaneous scalarization of strange quark stars is influenced by the equation of state of strange quark matter. Here, we investigate how the equation of state of strange quark matter influences the spontaneous scalarization of these stars. Considering Normal, color-flavor-locked (CFL), and CFLm quark matter in the bag models and applying the scalar-tensor gravity, we calculate the structure of scalarized strange quark stars. We investigate how the effective bag constant, perturbative QCD parameter, CFL pairing gap, and strange quark mass control the mass-radius relation, the central scalar field, the scalarization thresholds, and the scalar charge. Our results demonstrate that strange quark stars in scalar-tensor gravity are viable, testable objects, and they establish a complete framework for constraining both the gravitational theory and the properties of cold quark matter with current and future multimessenger observations.
nucl-thastro-ph.HE
09
Analytical Solution of the Nonlinear Boltzmann Equation For Multicomponent Systems
Linyuan Wei · Yi Wang · Jin Hu · Baoyi Chen
We present exact analytical solutions to the nonlinear relativistic Boltzmann equation for homogeneous, isotropic massless multi-component systems with non-isotropic scattering cross sections. For a two-component system, we identify three distinct classes of exact solutions, each corresponding to specific constraints among initial energy densities, particle number densities, and scattering cross sections. These solutions comprise the equilibrium state and two novel classes: a hybrid structure featuring a non-equilibrium Maxwell-Juttner distribution coupled with a nontrivial distribution; the former is unprecedented in kinetic theory, while the latter refers to nontrivial dynamics shared by both species, which is novel in the relativistic context.
↳ cond-mat.stat-mechhep-phnucl-th
10
Simulating the emission source function in very peripheral relativistic heavy-ion collisions
Angel Reina Ramírez · Volodymyr Magas · Juan M. Torres-Rincon
We present a microscopic femtoscopic investigation of the space-time emission source in low-multiplicity (80--90\% centrality) $Pb - Pb$ collisions at $s_{N N} = 5.02 TeV$ , using a hybrid transport framework coupling SMASH initial conditions, 3+1D viscous hydrodynamics (vHLLE), and a SMASH hadronic cascade afterburner. Access to the full space-time evolution of the produced particles allows for the direct reconstruction of emission source functions in both the Longitudinally Comoving System and the Pair Rest Frame. We study identical pairs of mesons ( $π π$ , $K K$ ) and baryons ( $pp$ ), as well as cross-species combinations, while explicitly isolating the contributions from primordial particles, hadronic rescattering, and long-lived resonance decays. Our analysis shows that simple Gaussian fits are inadequate for precision source analyses, whereas a combined Gaussian plus exponential parametrization better captures the compact core and the extended tail. Finally, the extracted Gaussian core radii, $R_{core}$ , for our very peripheral collisions demonstrate an approximate $m_{T}$ -scaling behavior rather similar to the one observed in pp reactions.
↳ hep-phnucl-th