Nuclear Theory·nucl-th

Wednesday·November 26, 2025

10 papers—5 primary·5 cross-listed

01
Relaxation of a single-particle excitation in a Fermi system within the diffusion approximation of kinetic theory
Sergiy V. Lukyanov
The time evolution of the Wigner distribution function for a single-particle excitation in a Fermi system was studied within the framework of the diffusion approximation of kinetic theory by numerically solving a nonlinear diffusion equation with constant kinetic coefficients. A method was proposed to separate the dissipative processes into contributions from the relaxation of the single-particle excitation and from the relaxation of the nuclear core, with a distinct relaxation time introduced for each process. The influence of the diffusion and drift coefficients on the characteristic relaxation time scale was analyzed. It was found that the resulting relaxation times exhibit a discrepancy relative to the kinetic coefficient estimates known from previous studies.
nucl-thPRC(2026)·2 citations
02
Covariant equations of motion of massive spinning particles in a background Yang-Mills field
Jie Zhou🇨🇳 · Ying Shan Zhao🇨🇳 · Yifeng Sun🇨🇳
The dynamics of a spinning colored particle in a background non-Abelian Yang-Mills field is of broad interest in many areas of physics. A physically important application arises in relativistic heavy-ion collisions, where hard probes such as heavy quarks and jets propagate through the strong early-time classical color fields collectively referred to as the glasma. The standard framework for describing the classical dynamics of colored particles in a background Yang-Mills field is provided by the Wong equations, but it does not incorporate spin degrees of freedom. Although several extensions of the Wong equations have been proposed to include spin, they generally fail to satisfy all the necessary requirements simultaneously, such as Lorentz covariance, allowance for an arbitrary chromomagnetic moment, and preservation of the required physical constraints. In this work, we extend the framework of a relativistic classical spinning particle in an electromagnetic field to describe spin-1/2 quarks propagating in a generic background non-Abelian Yang-Mills field. By systematically applying the Dirac-Bergmann algorithm, we derive a self-consistent set of equations of motion for the particle's coordinates, momenta, spin, and color charge that satisfies all these requirements. This formalism provides a more complete and physically consistent description of spinning colored particles in background Yang-Mills fields, and offers a suitable framework for studying momentum diffusion and spin polarization phenomena of hard probes in heavy-ion collisions, particularly in the glasma.
nucl-thhep-thPRD(2026)·2 citations
03
Discrete non-orthogonal shell model for nuclear structure: Towards heavy elements
Duy-Duc Dao🇫🇷 · Frédéric Nowacki🇫🇷
We present recent developments of the Discrete Non-Orthogonal Shell Model (DNO-SM) for nuclear structure studies far from stability. Exact shell-model solutions are obtained for typical open-shell light sd and pf nuclei using non-orthogonal Slater determinants consistently derived from the variation after projection approach. The latter represents a powerful method to include correlations from particle-hole excitations. Applications to proton-rich nuclei at the N $\sim$ Z line show the important role of these correlations to probe the structure transition in the $^{84, 86}$ Mo isotopes. We finally present a first complete description of low-lying spectroscopy in the superheavy 254 No, reproducing excellently various band structures and isomers in this challenging nucleus.
nucl-thEPJ Web Conf.(2025)·1 citation
04
Toward a Unified Understanding of the Dense Matter Equation of State
Kshitij Agarwal🇮🇹 · Johannes Jahan🇺🇸 · Behruz Kardan🇩🇪 · Peter T. H. Pang🇳🇱 · Tom Reichert🇺🇸 · Alexandra C. Semposki🇺🇸
Efforts to understand the equation of state (EOS) of dense nuclear matter at supra-saturation densities have grown more sophisticated over the past decade, driven by a surge in high-precision data from both terrestrial experiments and astrophysical observations. While for the former, heavy-ion collisions (HIC) represent a unique opportunity to constrain the EOS in a controlled laboratory setting, the latter can be precisely probed thanks to the advent of multi-messenger astronomy (MMA). However, as we move away from understanding drawn from individual sources and limited statistics to the era of precision physics with improved datasets, the need for a systematic way to combine them becomes clear. In this article, we trace the individual methods for extracting the EOS both for HIC and MMA. We then review the current state-of-the-art collaborative efforts to combine these individual sources of information, focusing on: the Nuclear Physics and Multi-Messenger Astrophysics (NMMA) framework, which relies on Bayesian inference methods; the Modular Unified Solver for the Equation of State (MUSES) calculation engine, which integrates EOS priors with HIC data and produces predictions for key neutron star properties; and the Bayesian Analysis of Nuclear Dynamics (BAND) framework, which uses cutting-edge Bayesian methods to produce reliable and trustworthy predictions for nuclear and astrophysical problems. We highlight the scientific advances with respect to the EOS and neutron star properties made possible by each framework and outline the remaining challenges that must be addressed to build a coherent, predictive picture of dense nuclear matter across all relevant regimes. We conclude with a detailed discussion of how these frameworks might be integrated with each other to form a unified workflow for future EOS predictions.
nucl-thastro-ph.HEastro-ph.SRgr-qc+16 citations
05
Anisotropic flows in Au+Au collisions at $s_{NN} = 2.4 GeV$ with a Skyrme pseudopotential
Xin Li🇨🇳 · Si-Pei Wang🇨🇳 · Rui Wang🇮🇹 · Zhen Zhang🇨🇳 · Jie Pu🇨🇳 · Chun-Wang Ma🇨🇳 · Lie-Wen Chen🇨🇳
Within the framework of the lattice Boltzmann-Uehling-Uhlenbeck transport model, we present a systematic study of proton anisotropic flow observables measured by the HADES collaboration, by utilizing the recently developed density-, momentum- and isospin-dependent N $5$ LO Skyrme pseudopotential. In particular, we investigate the impacts of the momentum dependence of nucleon mean-field potentials, the stiffness of symmetric nuclear matter (SNM) EOS, the high-density behaviors of the symmetry energy and the in-medium modification of nucleon-nucleon elastic cross sections on proton $v_{1}$ , $v_{2}$ , $v_{3}$ , and $v_{4}$ in Au+Au collisions at $s_{NN} = 2.4 GeV$ . Our results show that the proton anisotropic flows are strongly sensitive to the momentum dependence of nucleon mean-field potential as well as the incompressibility coefficient $K_{0}$ of SNM. In addition, the transverse momentum dependence of the proton $v_{2}$ exhibits a modest sensitivity to the higher-order skewness coefficient $J_{0}$ and kurtosis coefficient $I_{0}$ of SNM as well as the momentum dependence of the symmetry potential, while the transverse momentum dependence of the proton $v_{1}$ is shown to modestly depend on the in-medium modification of nucleon-nucleon elastic cross sections. Moreover, the high-density symmetry energy seems to have limited effects on the proton anisotropic flows. These findings highlight the necessity of considering the momentum dependence of nucleon mean-field potentials including the symmetry potential, the higher-order characteristic parameters of SNM EOS beyond $K_{0}$ , and the in-medium modification of nucleon-nucleon elastic cross sections, in future Bayesian transport model analyses on proton anisotropic flows in heavy-ion collisions at HADES energies, thereby to extract information on nuclear matter EOS as well as the associated underlying nuclear effective interactions.
nucl-thastro-ph.HEhep-phnucl-exPRC(2026)·1 citation
06
Universal Relations with Dynamical Tides
Jayana A. Saes🇺🇸 · Abhishek Hegade K. R.🇺🇸 · Nicolás Yunes🇺🇸
Observations of neutron stars and the precise measurement of their macroscopic properties have provided valuable insights into fundamental physics, both by constraining the behavior of nuclear matter under extreme conditions and by enabling tests of general relativity in the strong-field regime. In this context, equation-of-state-insensitive or ``quasi-universal'' relations between key observables, such as the compactness, dimensionless static tidal deformability, and moment of inertia, play a crucial role in connecting different measurable observables while minimizing uncertainties due to the yet unknown equation-of-state. In this work, we identify new quasi-universal relations between the static, dimensionless tidal deformability ( $Λ^{(0)}$ ) and its leading-order dynamical correction ( $Λ^{(2)}$ ), as well as between $Λ^{(0)}$ and a combination of these parameters ( $Λ^{(0)} / Λ^{(2)} \equiv M ω_{*}$ ), obtained from the small-frequency expansion of the relativistic tidal response. We test these relations across a representative set of 59 equations of state, finding that the equation-of-state dependence does not exceed $\sim$ 5\% for the $Λ^{(0)}$ -- $Λ^{(2)}$ relation and $\sim 2.8%$ for the $Λ^{(0)}$ -- $M ω_{*}$ relation. This indicates a high degree of universality and offers a simplified framework for incorporating dynamical tidal effects into gravitational-wave modeling. Furthermore, we compare the dynamical tidal response against different recent strategies (a Taylor expansion and a one-mode approximation) to model the dynamical tide. We find that both models are capable of capturing the frequency-dependent behavior of the dynamical tidal deformability, with the one-mode approximation agreeing better with the dynamical response than the Taylor expansion in most of the parameter space.
↳ gr-qcnucl-thPRD(2026)·7 citations
07
First determination of fragmentation functions in an exotic-hadron candidate
S. Kumano🇨🇳
In recent years, there are experimental reports on exotic-hadron candidates, which have different quark configurations from ordinary $q q ˉ$ and $q q q$ constituents. However, it is not easy to confirm their exotic nature from global observables such as masses, spins, parities, and decay widths. At high energies, internal quark and gluon configurations could become more apparent because hadrons should be described by fundamental degrees of freedom of quarks and gluons in quantum chromodynamics. One of such possibilities is to use the fragmentation functions (FFs). In this work, accurate FFs of an exotic hadron candidate $f_{0}$ (980) are determined for the first time by an global analysis of experimental data on $e^{+} + e^{-} \to f_{0} (980) + X$ with recent precise measurements of the Belle collaboration. From the global analysis, we found that their second moments have a relation $M_{u} = M_{d} ≪ M_{s} \sim M_{g}$ for up-quark, down-quark, strange-quark, and gluon FFs. Furthermore, the function $D_{s}^{f_{0}} (z)$ is distributed in the larger- $z$ region in comparison with the functions $D_{u}^{f_{0}} (z)$ , $D_{d}^{f_{0}} (z)$ , and $D_{g}^{f_{0}} (z)$ . These facts support that the $f_{0} (980)$ has the $s s ˉ$ configuration at high energies. This is a new finding that $f_{0} (980)$ should be considered mainly as the $s s ˉ$ state, which is different from our usual understanding as a tetraquark (or $K K ˉ$ ) hadron from low-energy studies. Our results could indicate the transition of the internal configuration picture that $f_{0} (980)$ looks like a $q q ˉ$ state at high energies although it is described by tetra-quark or $K K ˉ$ molecule state at low energies. It sheds light on a new direction in exotic hadron physics.
↳ hep-phhep-exhep-latnucl-ex+10 citations
08
Matrix approximations of operators
B.G. Giraud🇫🇷 · S. Karataglidis🇿🇦 · K. Murulane🇿🇦 · R. Peschanski🇫🇷
The approximate representation of operators by finite matrices is analysed in terms of accuracy and convergence. The identity operator, for example, can be reconstructed using a basis of harmonic oscillator states leading to a narrow peak approximation of the $δ$ function, but this peak may be perturbed by small, residual, oscillations. The peak does not shrink nor grows quickly, and the oscillations only diminish slowly as the size of the matrix increases. For the kinetic energy operator, a triple peak (one positive, two negative) representation of $- δ^{''}$ is obtained, but that is affected also by residual oscillations. Again, convergence is slow as the matrix dimension increases. We find compact formulas to explain such oscillations. Similar observations are found for representations of local interactions, while separable potentials are better represented. As a comparison, in the context of a toy model, the effects of choosing an alternative single particle basis are studied. A formal approach for the approximation of operators is considered for comparison. We conclude with a word of caution for (finite) matrix approximations of operators.
↳ math-phhep-thmath.MPnucl-th0 citations
09
New framework for extracting GPDs from exclusive photon electroproduction
Jian-Wei Qiu🇺🇸 · Nobuo Sato🇺🇸 · Zhite Yu🇺🇸
Recently, a new framework for studying generic $2 \to 3$ hard exclusive reactions, referred to as single-diffractive hard exclusive processes, has been introduced to provide a cleaner separation of the underlying physical mechanisms. In this work, we expand this formalism to the case of exclusive real-photon electroproduction off a nucleon, $e (ℓ) + N (p) \to e (ℓ^{'}) + N (p^{'}) + γ (q^{'})$ , which represents the classical channel for accessing generalized parton distributions (GPDs) in nucleons and nuclei. This extension enables a more systematic and physically transparent formulation of the reaction dynamics, paving the way for improved extractions of GPDs from experimental data as compared to existing approaches.
↳ hep-phhep-exhep-latnucl-ex+1PRD(2026)·0 citations
10
Precision thermodynamics of the strongly interacting Fermi gas in two dimensions
S. Ramachandran · S. Jensen · Y. Alhassid
The two-species cold atomic Fermi gas with attractive short-range interactions in two spatial dimensions undergoes a Bardeen-Cooper-Schrieffer (BCS) to a Bose-Einstein Condensate (BEC) crossover as a function of $ln (k_{F} a)$ , where $a$ is the scattering length. However, the nature of this crossover in the strong coupling regime $ln (k_{F} a) \sim 1$ remains poorly understood. In this work we use canonical-ensemble auxiliary-field quantum Monte Carlo methods on discrete lattices to calculate several thermodynamical quantities in the strongly interacting regime, and eliminate systematic errors by extrapolating to continuous time and taking the continuum limit. In particular, we present results for the condensate fraction, spin susceptibility, contact, energy equation of state, and the free energy staggering gap. We identify signatures of a pseudogap regime, in which pairing correlations survive above the critical temperature for superfluidity, in the spin susceptibility and in the free energy staggering gap. These results can be used as a benchmark for future experiments.
↳ cond-mat.quant-gascond-mat.supr-conhep-latnucl-thEur.Phys.J.ST(2026)·0 citations

Affiliations

first authorsco-authorsvia INSPIRE