Nuclear Theory·nucl-th

Tuesday·November 12, 2024

15 papers—8 primary·7 cross-listed

01
[Submitted on 9 Nov 2024]
Elliptic and quadrangular flow of protons in the high baryon density region
Shaowei Lan🇨🇳 · Zuowen Liu🇨🇳 · Like Liu🇨🇳 · Shusu Shi🇨🇳
The collective flow provides valuable insights into the anisotropic expansion of particles produced in heavy-ion collisions and is sensitive to the equation of the state of nuclear matter in high-baryon-density regions. In this paper, we use the hadronic transport model SMASH to investigate the elliptic flow ( $v_{2}$ ), quadrangular flow ( $v_{4}$ ), and their ratio ( $v_{4} / v_{2}^{2}$ ) in Au+Au collisions at high baryon density. Our results show that the inclusion of baryonic mean-field potential in the model successfully reproduces experimental data from the HADES experiment, indicating that baryonic interactions play an important role in shaping anisotropic flow. In addition to comparing the transverse momentum ( $p_{T}$ ), rapidity, and centrality dependence of $v_{4} / v_{2}^{2}$ between HADES data and model calculations, we also explore its time evolution and energy dependence across $s_{N N} =$ 2.4 to 4.5 GeV. While the ratio $v_{4} / v_{2}^{2}$ for high- $p_{T}$ particles approaches 0.5, which aligns with expectations from hydrodynamic behavior, we emphasize that this result primarily reflects agreement with the HADES measurements rather than a definitive indication of ideal fluid behavior. These findings contribute to understanding the early-stage dynamics in heavy-ion collisions at high baryon density.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2411.06196 [pdf]
Universe(2025)·1 citation
02
[Submitted on 9 Nov 2024]
Imprints of high-density nuclear symmetry energy on the crustal fraction of neutron star moment of inertia
Nai-Bo Zhang · Bao-An Li
The density dependence of nuclear symmetry energy $E_{sym} (ρ)$ remains the most uncertain aspect of the equation of state (EOS) of supradense neutron-rich nucleonic matter. Implications of observational crustal fraction of neutron star (NS) moment of inertia $Δ I / I$ on the $E_{sym} (ρ)$ are examined in the present work, utilizing an isospin-dependent parameterization of NS EOS. We find that symmetry energy parameters significantly influence the $Δ I / I$ , while the EOS of symmetric nuclear matter has a negligible effect. An increase in the slope $L$ and skewness $J_{sym}$ of symmetry energy results in a larger $Δ I / I$ , whereas an increase in the curvature $K_{sym}$ leads to a reduction in $Δ I / I$ . Additionally, we discuss the imprints of observational $Δ I / I$ on the symmetry energy for NSs with masses of 1.0 M $_{⊙}$ or 1.4 M $_{⊙}$ . Our results indicate that the $Δ I / I$ has the potential to set a lower limit of symmetry energy at densities exceeding $3 ρ_{0}$ , particularly when $L$ is constrained to values less than $60$ MeV, thereby enhancing our understanding of supradense NS matter.
Comments:
10 pages, 5 figures, published on Particles
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2411.06238 [pdf]
Particles(2025)·2 citations
03
[Submitted on 9 Nov 2024]
Divergence and resummation of the moment expansion for an ultrarelativistic gas in Bjorken flow
Caio V. P. de Brito🇧🇷 · David Wagner🇮🇹 · Gabriel S. Denicol🇧🇷 · Dirk H. Rischke🇩🇪
In this letter, we demonstrate for the first time that the moment expansion for an ultrarelativistic gas undergoing Bjorken flow diverges. We then show how this series can be resummed using the Borel-Padé method and use this to determine the single-particle distribution function of the gas. Finally, we compare the exact resummed solution of the single-particle distribution function with solutions of the Boltzmann equation in the hydrodynamic limit and verify that the system displays considerable deviations from local equilibrium.
Comments:
Main text (8 pages, 5 figures) + Supplemental Material (12 pages, 6 figures)
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Theory (hep-th)
arXiv:
2411.06267 [pdf]
PRD(2026)·7 citations
04
[Submitted on 11 Nov 2024]
Finite nuclei in an extended Nambu-Jona-Lasinio model
Cheng-Jun Xia🇨🇳 · Yu-Ting Rong🇨🇳 · Ting-Ting Sun🇨🇳
We propose a new theoretical framework to investigate the properties of finite nuclei based on an extended Nambu-Jona-Lasinio (eNJL) model, where the Dirac sea, the spontaneous chiral symmetry breaking, and the quark degrees of freedom are considered by extending the SU(3) NJL model and treating baryons as clusters of quarks. The eNJL model can then be readily adopted to examine the matter states ranging from baryonic matter to quark matter in a unified manner. In this work, by assuming spherically symmetric finite nuclei and neglecting the center-of-mass or rotational corrections, we systematically investigate the properties of finite nuclei based on the eNJL model with additional pairing correlations. It is found that our model generally reproduces the binding energies of the 2495 nuclei ( $A > 2$ ) from the 2016 Atomic Mass Evaluation (AME2016) with the root-mean-square deviations $5.38$ MeV. The deviations are mainly attributed to the too large shell gaps at magic numbers $N (Z) = 28$ , 50, and 82 as well as the spurious shell closures at $N (Z) = 34$ , 58, and 92. Meanwhile, the obtained charge radii of 906 nuclei are systematically smaller than the experimental values with root-mean-square deviations $0.127$ fm. In our future study, we expect to reduce the uncertainties of our predictions by carefully calibrating the density dependence of coupling constants and considering deformations with microscopic collective corrections from the nucleons in the Fermi sea and quarks in the Dirac sea.
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2411.06679 [pdf]
0 citations
05
[Submitted on 11 Nov 2024]
Non-Hermitian quantum mechanics approach for extracting and emulating continuum physics based on bound-state-like calculations: Detailed description
Xilin Zhang🇺🇸
This work applies a reduced basis method to study the continuum physics of a finite quantum system -- either few or many-body. Specifically, I develop reduced-order models, or emulators, for the underlying inhomogeneous Schrödinger equation and train the emulators against the equation's bound-state-like solutions at complex energies. The emulators rapidly and accurately interpolate and extrapolate the matrix elements of the Hamiltonian resolvent operator (Green's function) across a parameter space that includes both complex energy and other real-valued physical inputs in the Schrödinger equation. The spectra, discretized and compressed as the result of emulation, and the associated resolvent matrix elements (or amplitudes), have the defining characteristics of non-Hermitian quantum mechanics calculations, featuring complex eigenenergies with negative imaginary parts and branch cuts moved below the real axis in the complex energy plane. Therefore, one now has a method that extracts continuum physics from bound-state-like calculations and emulates those extractions in the input parameter space. Building on a prior Letter [arXiv:2408.03309], this article provides the full theoretical details, a comprehensive analysis of the method's performance, and a brief discussion of how it can be coupled with existing continuum approaches to perform emulations in their input parameter spaces.
Comments:
42 pages, 26 figures, the companion paper of arXiv:2408.03309, with the supplemental material attached as an arXiv ancillary file, close to the version to be published at Physical Review C
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Atomic Physics (physics.atom-ph); physics.chem-ph (physics.chem-ph); Computational Physics (physics.comp-ph)
arXiv:
2411.06712 [pdf]
PRC(2025)·11 citations
06
[Submitted on 11 Nov 2024]
Collective modes in relativistic cold asymmetric nuclear matter within the covariant Vlasov approach
Aziz Rabhi · Olfa Boukari · Sidney S. Avancini · Constança Providência
A covariant relativistic approach based on the Vlasov equation is applied to the study of infinite asymmetric nuclear matter. We use several Walecka-type hadronic models and obtain the dispersion relations for the longitudinal modes. The isovector and isoscalar collective modes are determined for a wide range of densities as a function of isospin asymmetry and momentum transfer within a set of eleven relativistic mean field models with different nuclear matter properties. Special attention is given to beta-equilibrium matter. It is shown that the possible propagation of isoscalar and isovector-like modes depends directly on the density dependence of the symmetric nuclear matter equation of state and of the symmetry energy, with a stiff equation of state favouring the propagation of isoscalar like collective modes at high densities, and a stiff symmetry energy defining the behavior of the isovector like modes which propagate for densities below two times saturation density. The coupling of the nuclear modes to the electron plasmon is also discussed.
Comments:
18 pages, 11 figures, 3 tables. Accepted for publication in Physical Review C
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); Instrumentation and Methods for Astrophysics (astro-ph.IM)
arXiv:
2411.06960 [pdf]
PRC(2025)·2 citations
07
[Submitted on 11 Nov 2024]
Probing nuclear structure and the equation of state through pre-equilibrium dipole emission in charge-asymmetric reactions
Leonid Shvedov · Stefano Burrello · Maria Colonna · Hua Zheng
We investigate the pre-equilibrium dipole response in the charge-asymmetric reaction $^{40}$ Ca+ $^{152}$ Sm, of recent experimental interest, at several beam energies within the range $[5, 11]$ AMeV and different collision centralities. By employing Skyrme-like effective interactions for the nuclear mean field, we probe the role of the different ingredients performing theoretical calculations based on the time-dependent Hartree-Fock approach or a semi-classical transport model that also includes two-body correlations. A comparative analysis between these approaches allowed us to disentangle the role of deformation effects in the entrance channel from the ones associated with structure details of genuine quantal nature on the dipole emission. Moreover, we also investigate the impact of the occurrence of residual two-body collisions on the reaction dynamics. This study contributes to the understanding of the microscopic processes that determine the complex dynamics of low-energy heavy-ion collisions along the fusion-fission path, which is relevant to super-heavy element synthesis, unraveling interesting connections with the characteristics of the nuclear effective interaction and the associated equation of state.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2411.07159 [pdf]
PRC(2025)·4 citations
08
[Submitted on 11 Nov 2024]
Astrophysical constraints on nuclear EOSs and coupling constants in RMF models
Cheng-Jun Xia🇨🇳 · Wen-Jie Xie🇨🇳 · Mohemmedelnazier Bakhiet🇨🇳
Utilizing various astrophysical constraints on neutron star structures, we carry out a Bayesian analysis on the density-dependent behaviors of coupling constants in RMF models as well as the nuclear matter properties at supranuclear densities. The effective nucleon interactions in the isoscalar-scalar, isoscalar-vector, and isovector-vector channels are considered, where the corresponding coupling constants ( $α_{S}, α_{V}, α_{T V}$ ) are fixed by dividing entire density range into three regions with six independent parameters. In this work we focus on constraining the density-dependent point-coupling constants at supranuclear densities, while the coupling constants at subsaturation densities are derived from the covariant density functional DD-ME2. For those consistent with astrophysical observations, the coupling constants generally decrease with density and approach to small positive values at large enough densities, which qualitatively agrees with various RMF models. The posterior probability density functions and their correlations of the coupling constants and various nuclear matter properties are examined as well. At $1 σ$ level, the constrained coupling constants at density $1.5 n_{0}$ ( $2.5 n_{0}$ ) are $α_{S} = 3. 1_{- 0.05}^{+ 0.1} (1.5 5_{- 0.2}^{+ 0.85}) \times 1 0^{- 4} MeV^{- 2}$ , $α_{V} = 2. 3_{- 0.0}^{+ 0.1} (1. 3_{- 0.1}^{+ 0.55}) \times 1 0^{- 4} MeV^{- 2}$ , and $α_{T V} = 2.0 5_{- 0.4}^{+ 0} (2.0 5_{- 0.5}^{+ 0}) \times 1 0^{- 5} MeV^{- 2}$ . At larger densities, we find the lower limit of $α_{T V}$ is not well constrained, so that more extensive calculations with larger number of free parameters are necessary.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2411.07170 [pdf]
PRD(2024)·14 citations

Affiliations

first authorsco-authorsvia INSPIRE