Nuclear Theory·nucl-th

Wednesday·April 2, 2025

20 papers—9 primary·11 cross-listed

01
[Submitted on 31 Mar 2025]
On the Approach Towards Equilibrium Through Momentum-Dependent Relaxation:Insights from Evolution of the Moments in Kinetic Theory
Reghukrishnan Gangadharan🇮🇳 · Sukanya Mitra🇮🇳 · Victor Roy🇮🇳
We investigate the impact of momentum-dependent relaxation time approximation in the Boltzmann equation within the Bjorken flow framework by analyzing the moments of the single-particle distribution function. The moment equations, which form an infinite hierarchy, provide important insights about the system dynamics and the approach towards equilibrium for systems far from equilibrium. The momentum-dependent collision kernel couples moments through both the energy exponents and the angular dependence via various-order Legendre polynomials, resulting in an intricate system of infinitely coupled equations. A naive truncation of the coupled equations results in diverging moments at late times. We outline strategies for solving the coupled system, including a novel approach for managing the divergences and non-integer moments. We show a significant influence of momentum dependent relaxation time on the time evolution of the moments, particularly for higher-order moments and system with smaller shear viscosity over entropy density, emphasizing the importance of incorporating such dependence for a more accurate description of the system dynamics with low shear viscosity such as the quark-gluon-plasma produced in high-energy heavy-ion collisions.
Comments:
17 pages, 11 figures. Edit 2: Added analytic proof for the positivity of the modified collision kernel. Some typos were corrected
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2504.00126 [pdf]
PRD(2025)·4 citations
02
[Submitted on 31 Mar 2025]
A weak entanglement approximation for nuclear structure: a progress report
Calvin W. Johnson · Oliver C. Gorton
We report on a recently proposed approach, inspired by quantum informationtheory, for calculating low-energy nuclear structure in the framework of the configuration-interaction shell-model. Empirical evidence has demonstrated that the many-proton and many-neutron partitions of nuclear configuration-interaction wave functions are weakly entangled, especially away from $N = Z$ . This has been developed into a practical methodology, the Proton And Neutron Approximate Shell-model (PANASh). We review the basic ideas and present recent results. We also discuss some technical developments in calculations.
Comments:
9 pages, 4 figures. Submitted to the proceedings of NTSE (Nuclear Theory in the Supercomputing Era) 2024
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2504.00273 [pdf]
J.Subatomic Part.Cosmol.(2025)·5 citations
03
[Submitted on 1 Apr 2025]
Transition magnetic moments for $Δ \to p$ transition in asymmetric nuclear matter
Suneel Dutt🇮🇳 · Arvind Kumar🇮🇳 · Harleen Dahiya🇮🇳
In the present work we calculate the transition magnetic moments for the radiative decays of $Δ$ baryon to proton $(Δ \to p)$ in isospin asymmetric nuclear medium at finite temperature using chiral SU(3) quark mean field model. Within the framework of chiral SU(3) mean field model, the properties of baryons in asymmetric medium are modified through the exchange of scalar fields $(σ, ζ, δ)$ and vector fields $(ω, ρ)$ . The isospin asymmetry of medium is taken into account via scalar-isovector field $δ$ and vector iso-vector field $ρ$ . We calculate the in-medium masses of quarks, proton and $Δ$ baryon in asymmetric matter within the chiral SU(3) quark mean field model and use these as input in the chiral constituent quark ( $χ$ CQM) model to calculate the in-medium transition magnetic moments for $(Δ \to p)$ transition for different values of isospin asymmetry of hot and dense medium. For calculating the magnetic moments of baryons, contributions of valence quarks, quark sea and orbital angular momentum of quark sea are considered in these calculations.
Comments:
7 pages. Contribution to the Proceedings for The XVIth Quark Confinement and the Hadron Spectrum Conference (QCHSC24) 19-24 August, 2024 Cairns Convention Centre, Cairns, Queensland, Australia
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2504.00442 [pdf]
PoS(2025)·0 citations
04
[Submitted on 1 Apr 2025]
Illustrating the liquid gas transition of nuclear matter in QCD
Fei Gao🇨🇳 · Yi Lu🇨🇳 · Si-xue Qin🇨🇳 · Zhan Bai🇨🇳 · Lei Chang🇨🇳 · Yu-xin Liu🇨🇳
We demonstrate that the liquid-gas transition of nuclear matter can be rigorously described with the quantum chromodynamics by combining the quark gap equation and the Faddeev equation of nucleon. Our investigation focuses on this transition at zero temperature and finite chemical potential, revealing a finite difference between the gas and liquid solution of the quark propagator. This difference emerges from the shift of the nucleon pole mass in medium, which is generated in the nucleon channel of the quark gap equation. We prove that such a difference is precisely the contour contribution from the shift of the nucleon pole. The resulting discontinuity manifests as a first-order phase transition and fundamentally determines both the nuclear binding energy and the saturation density. We then derive an analytical relation between the binding energy and the sigma term of the nucleon, yielding a binding energy of $E / A = 15.9 MeV$ . Furthermore, by establishing the relation between the nuclear saturation density and the vector charge of nucleon in association with the binding energy, we determine the saturation density to be $n_{B}^{0} = 0.15 fm^{- 3}$ .
Comments:
7 pages, 4 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th); Nuclear Experiment (nucl-ex)
arXiv:
2504.00539 [pdf]
PRD(2025)·4 citations
05
[Submitted on 1 Apr 2025]
Electric and magnetic $γ$ -ray strength functions at finite-temperature
Amandeep Kaur · Esra Yüksel · Nils Paar
The $γ$ -ray strength function ( $γ$ SF) is essential for understanding the electromagnetic response in atomic nuclei and modeling astrophysical neutron capture rates. We introduced a microscopic description of both electric dipole (E1) and magnetic dipole (M1) $γ$ SFs that includes finite-temperature effects within relativistic density functional theory. The temperature dependence of the total electromagnetic $γ$ SFs shows significant modification in the low-energy region due to thermal unblocking effects, essential for agreement with recent particle- $γ$ coincidence data from the Oslo method. An investigation of the electric and magnetic contributions to the total $γ$ SF in hot nuclei indicates that the M1 mode becomes more prominent in the low-energy region, different than what is known at zero temperature. This microscopic approach offers new insights into the interplay between E1 and M1 $γ$ SFs at finite-temperature, and opens new perspectives for future studies of $(n, γ)$ reactions and nucleosynthesis in hot stellar environments.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2504.00699 [pdf]
0 citations
06
[Submitted on 1 Apr 2025]
A Novel Deep Learning Method for Detecting Nucleon-Nucleon Correlations
Yu-Jing Huang🇨🇳 · Zhu Meng🇨🇳 · Long-Gang Pang🇨🇳 · Xin-Nian Wang🇨🇳
This study investigates the impact of nucleon-nucleon correlations on heavy-ion collisions using the hadronic transport model SMASH in $s_{NN} = 3$ GeV $^{197} Au$ + $^{197} Au$ collisions. We developed an innovative Monte Carlo sampling method that incorporates both single-nucleon distributions and nucleon-nucleon correlations. By comparing three initial nuclear configurations - a standard Woods-Saxon distribution (un-corr), hard-sphere repulsion (step corr), and ab initio nucleon-nucleon correlations (nn-corr)- we revealed minimal differences in traditional observables except for ultra-central collisions. When distinguishing between un-corr and nn-corr configurations, conventional attention-based point cloud networks and multi-event mixing classifiers failed (accuracy ~50%). To resolve this, we developed a novel deep learning architecture integrating multi-event statistics and high-dimensional latent space feature correlations, achieving 60\% overall classification accuracy, which improved to 70\% for central collisions. This method enables the extraction of subtle nuclear structure signals through statistical analysis in high-dimensional latent space, offering a new paradigm for studying initial-state nuclear properties and quark-gluon plasma characteristics in heavy-ion collisions. It overcomes the limitations of traditional single-event analysis in detecting subtle initial-state differences.
Comments:
18 pages, 13 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2504.00790 [pdf]
PRC(2026)·8 citations
07
[Submitted on 1 Apr 2025]
Universal critical behavior of generaliezd susceptibilities of net-baryon number at small quark mass
Xue Pan🇨🇳 · Peng Yang🇨🇳 · Lingling Cao🇨🇳
In the limit of small quark masses, the angle between the temperature axis and the applied magnetic field direction in the three-dimensional Ising model vanishes as $m_{q}^{2/5}$ when mapped onto the QCD $T - μ_{B}$ phase plane. By selecting two distinct small angles and projecting the Ising model results onto QCD, we have investigated the universal critical behavior of the sixth-, eighth-, and tenth-order susceptibilities of the net-baryon number. When considering only the leading critical contribution, the negative dip in the $μ_{B}$ dependence of the generalized susceptibilities is not universal, in contrast to the observation in the case where the angle is $9 0^{\circ}$ . Its existence depends on the mapping parameters and the distance to the phase transition line. After incorporating the sub-leading critical contribution, the negative dip is enhanced to some extent but remains a non-robust feature. In contrast, the positive peak structure persists in all cases and represents a robust characteristic of generalized susceptibilities of the net-baryon number near the critical point.
Comments:
13 pages, 9 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th)
arXiv:
2504.00832 [pdf]
IJMPE(2025)·0 citations
08
[Submitted on 1 Apr 2025]
Exploring the role of $d^{*}$ hexaquarks on quark deconfinement and hybrid stars
Marcos O. Celi🇨🇱 · Mauro Mariani🇨🇱 · Rajesh Kumar🇺🇸 · Mikhail Bashkanov🇬🇧 · Milva G. Orsaria🇨🇱 · Alessandro Pastore🇫🇷 · Ignacio F. Ranea-Sandoval🇨🇱 · Veronica Dexheimer🇺🇸
We investigate the impact of the $d^{*}$ (2380) hexaquark on the equation of state (EoS) of dense matter within hybrid stars (HSs) using the Chiral Mean-Field model (CMF). The hexaquark is included as a new degree of freedom in the hadronic phase, and its influence on the deconfinement transition to quark matter is explored. We re-parametrize the CMF model to ensure compatibility with recent astrophysical constraints, including the observation of massive pulsars and gravitational wave events. Our results show that the presence of $d^{*}$ significantly modifies the EoS, leading to a softening at high densities and a consequent reduction in the predicted maximum stellar masses. Furthermore, we examine the possibility of a first-order deconfinement phase transition within the context of the extended stability branch of slow stable HSs (SSHSs). We find that the presence of hexaquarks can delay the deconfinement phase transition and reduce the associated energy density gap, affecting the structure and stability of HSs. Our results suggest that, as the hexaquark appearance tends to destabilize stellar configurations, fine tuning of model parameters is required to obtain both the presence of hexaquarks and quark deconfinement in these systems. In this scenario, the SSHS branch plays a crucial role in obtaining HSs with hexaquarks that satisfy current astrophysical constraints. Our work provides new insights into the role of exotic particles like $d^{*}$ in dense matter and the complex interplay between hadronic and quark degrees of freedom inside compact stellar objects.
Comments:
20 pages, 10 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE)
arXiv:
2504.00981 [pdf]
PRD(2025)·6 citations
09
[Submitted on 1 Apr 2025]
Scattering Observables from Few-Body Densities and Compton Scattering on 6Li
Alexander Long · Harald W. Griesshammer
The dynamics of scattering on light nuclei is numerically expensive using standard methods. Fortunately, recent developments allow one to factor the relevant quantities for a given probe into a convolution of an $n$ -body Transition Density Amplitude (TDA) and the interaction kernel for a given probe. These TDAs depend only on the target, and not the probe; they are calculated once for each set of kinematics and can be used for different interactions. The kernels depend only on the probe, and not on the target; they can be reused for different targets and different kinematics. The calculation of TDAs becomes numerically difficult for more than four nucleons, but we discuss a new solution through the use of a Similarity Renormalization Group transformation, and a subsequent back-transformation. This technique allows for extending the TDA method to heavier nuclei such as 6Li. We present preliminary results for Compton scattering on 6Li and compare with available data, anticipating an upcoming, more thorough study. We also discuss ongoing extensions to pion-photoproduction and other reactions on light nuclei.
Comments:
10 pages (pdflatex), including 5 figures as 5 .pdf files
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2504.00989 [pdf]
PoS(2026)·1 citation

Affiliations

first authorsco-authorsvia INSPIRE