Nuclear Theory·nucl-th

Monday·April 7, 2025

11 papers—5 primary·6 cross-listed

01
Is the central compact object in HESS J1731-347 a hybrid star with a quark core? An analysis with the constant speed of sound parametrization
Suman Pal🇮🇳 · Soumen Podder🇮🇳 · Gargi Chaudhuri🇮🇳
In this work, we investigate the possibility of the compact object in HESS J1731-347 with $M = 0.7 7_{- 0.17}^{+ 0.20} M_{⊙}$ and $R = 10. 4_{- 0.78}^{+ 0.86} k m$ to be a hybrid star with quark matter in the inner core. The observation of this low mass compact star dictates the use of softer equation of state which on the contrary cannot explain the massive compact stars. This poses a new challenge for the astrophysicists in their search for the equation of state of compact objects. The hybrid equations of state are constructed using the IUFSU parametrization based on the relativistic mean field (RMF) theory for the hadronic part and the generic constant speed of sound parametrization (CSS) for the phase transition to quark matter.The CSS framework is characterized by three key parameters, namely the transition density $(ρ_{t r})$ , the energy jumps $(Δ ε)$ and the speed of sound $(C_{s})$ . Here, our primary aim is to investigate the influence of individual CSS parameters on the formation of a object of small mass and radius compatible with HESS J1731-347 parameters. We have also examined the effect of hadronic parameters such as effective mass, symmetry energy, and the slope of the symmetry energy at saturation densities on the formation of this compact object.Finally our analysis suggests that, within a 1 $σ$ credible level, HESS J1731-347 aligns with the scenario of a stable hybrid star with early deconfinement and higher energy gap
nucl-thApJ(2025)·14 citations
02
A unified algorithm for multi-particle correlations between azimuthal angle and transverse momentum in ultra-relativistic nuclear collisions
Emil Gorm Dahlbæk Nielsen🇩🇰 · Nina Nathanson🇩🇰 · Kristjan Gulbrandsen🇩🇰 · You Zhou🇩🇰
Multi-particle correlations between azimuthal angle and mean transverse momentum are a powerful tool for probing size and shape correlations in the initial conditions of heavy-ion collisions. These correlations have also been employed to investigate nuclear structure, including potential nuclear shape phase transitions at the energy frontier. However, their implementation is highly nontrivial, and prior studies have been mostly limited to lower-order correlations, such as the modified Pearson correlation coefficient, $ρ (v_{n}^{2}, [p_{T}])$ . This paper presents a unified framework that employs a recursive algorithm, enabling the efficient evaluation of arbitrary-order correlations while maintaining computational efficiency. This framework is demonstrated using widely adopted transport models, including AMPT and HIJING. The proposed unified algorithm for multi-particle correlations between azimuthal angle and transverse momentum provides a systematic and efficient approach for multi-particle correlation analyses. Its application in experiments at the Relativistic Heavy Ion Collider and the Large Hadron Collider facilitates the exploration of nuclear structure at ultra-relativistic energies.
nucl-thnucl-exEPJC(2025)·4 citations
03
Numerical Assessment of Convergence in the Post Form Ichimura-Austern-Vincent model
Jin Lei
The Ichimura-Austern-Vincent (IAV) model provides a powerful theoretical framework for describing inclusive breakup reactions. However, its post-form representation presents significant numerical challenges due to the absence of a natural cutoff in the transition matrix integration. This work presents a systematic assessment of convergence methods for post-form IAV calculations, comparing the bin method and the Vincent-Fortune approach. We demonstrate that while the bin method offers implementation simplicity, it exhibits strong parameter dependence that compromises numerical stability. In contrast, the Vincent-Fortune method, which employs complex contour integration, achieves reliable convergence without arbitrary parameters. We further introduce a novel hybrid approach that integrates finite-range distorted wave Born approximation (DWBA) with the Vincent-Fortune technique, combining the accuracy of finite-range treatment at short distances with the numerical stability of zero-range approximations in the asymptotic region. Numerical results for deuteron and $^{6}$ Li-induced reactions confirm the efficacy of this hybrid method, showing consistent agreement with experimental data while eliminating the convergence issues that plague traditional approaches. This advancement enables more reliable calculations of nonelastic breakup cross sections and facilitates the extension of the IAV formalism beyond DWBA to incorporate continuum-discretized coupled-channels (CDCC) wave functions for a more comprehensive treatment of breakup processes.
nucl-thPRC(2025)·3 citations
04
NucleiML: A machine learning framework of ground-state properties of finite nuclei for accelerated Bayesian exploration
Anagh Venneti · Chiranjib Mondal · Sk Md Adil Imam · Sarmistha Banik · Bijay K. Agrawal
The global behavior of the nuclear equation of state (EoS) is commonly studied using data from finite nuclei (FN), heavy-ion collisions, and astrophysical observations of neutron stars (NS). The constraints derived from FN such as binding energies and charge radii play the most crucial role in shaping the EoS up to saturation density. The computational cost associated with explicitly incorporating these constraints presents a significant challenge especially when the aim is to explore the model uncertainties rather than optimizing a single model. We address this by introducing NucleiML (NML), a machine learning framework trained on ground-state properties of a few finite nuclei generated by a relativistic mean-field model. NML allows us to integrate FN and NS properties within a Bayesian inference framework in an efficient manner. The results demonstrate reasonable accuracy and a speedup of $\sim 1 0^{4}$ times for calculation of FN properties for a single parameter set, yielding roughly $\sim 1 0^{3} \times$ speed up in the Bayesian framework. The present study makes the case for extending the work to a larger set of nuclei, potentially enabling future studies of NS properties to incorporate the whole nuclear chart.
nucl-thastro-ph.HE1 citation
05
Predictions in the superheavy region from the quark-meson coupling model QMC $π$ -III
Kay Marie M. Paglinawan (1) · Anthony W. Thomas (2) · Pierre A. M. Guichon (2) · Jirina R. Stone (3) ((1) Silliman University, Dumaguete City, Philippines, (2) CSSM and ARC Centre of Excellence for Dark Matter Particle Physics, University of Adelaide, SA, Australia, (3) Department of Physics (Astrophysics), University of Oxford, Oxford, UK)
The Quark-Meson Coupling (QMC) model establishes a self-consistent relationship between the quark structure dynamics of a nucleon and the relativistic mean fields that arise within the nuclear medium. The model has been successful in calculating the ground-state observables of finite nuclei and in predicting the properties of dense nuclear matter, as well as cold, nonaccreting neutron stars. This paper focuses on the latest predictions from the model for the superheavy region, encompassing energies and deformations. Despite utilizing significantly fewer model parameters, the results have consistently improved as the model evolved, yielding better predictions for binding energies.
nucl-thPoS(2025)·1 citation
06
Optimal Observables for the Chiral Magnetic Effect from Machine Learning
Yuji Hirono🇯🇵 · Kazuki Ikeda🇺🇸 · Dmitri E. Kharzeev🇺🇸 · Ziyi Liu🇨🇳 · Shuzhe Shi🇨🇳
The detection of the Chiral Magnetic Effect (CME) in relativistic heavy-ion collisions remains challenging due to substantial background contributions that obscure the expected signal. In this Letter, we present a novel machine learning approach for constructing optimized observables that significantly enhance CME detection capabilities. By parameterizing generic observables constructed from flow harmonics and optimizing them to maximize the signal-to-background ratio, we systematically develop CME-sensitive measures that outperform conventional methods. Using simulated data from the Anomalous Viscous Fluid Dynamics framework, our machine learning observables demonstrate up to 90\% higher sensitivity to CME signals compared to traditional $γ$ and $δ$ correlators, while maintaining minimal background contamination. The constructed observables provide physical insight into optimal CME detection strategies, and offer a promising path forward for experimental searches of CME at RHIC and the LHC.
↳ hep-phnucl-exnucl-thPRC(2025)·1 citation
07
Relativistic dynamics of charmonia in strong magnetic fields
Liuyuan Wen🇨🇳 · Meijian Li🇪🇸 · Yiyu Zhou🇮🇹 · Yang Li🇨🇳 · James P. Vary🇺🇸
We investigate the properties of charmonium systems in strong external magnetic fields using a relativistic light-front Hamiltonian approach within the Basis Light-Front Quantization (BLFQ) framework. By solving the eigenvalue problem for the invariant mass squared operator with confinement potentials and one-gluon-exchange interactions, we obtain the mass spectrum and wave functions under varying magnetic fields. Our results reveal significant spectral modifications via the Zeeman effect, including $η_{c}$ - $J / ψ$ mixing and magnetic sublevel splitting. Momentum density analysis demonstrates wave function deformation, with transverse momentum broadening and longitudinal narrowing under strong fields, alongside structural shifts in parton distributions such as double-hump profiles in excited states. Relativistic corrections and center-of-mass coupling critically drive these dynamics, highlighting the necessity of a relativistic framework for QCD bound states in extreme magnetic environments.
↳ hep-phnucl-thphysics.atom-phPRD(2025)·6 citations
08
Hybrid framework of Fermi-Dirac spin hydrodynamics
Zbigniew Drogosz🇵🇱
We outline the hybrid framework of spin hydrodynamics, combining classical kinetic theory with the Israel-Stewart method of introducing dissipation. We obtain the local equilibrium expressions for the baryon current, the energy-momentum tensor, and the spin tensor of particles with spin 1/2 following the Fermi-Dirac statistics and compare them with the previously derived versions where the Boltzmann approximation was used. The expressions in the two cases have the same form, but the coefficients are governed by different functions. The relative differences between the tensor coefficients in the Fermi-Dirac and Boltzmann cases are found to grow exponentially with the baryon chemical potential. In the proposed formalism, nonequilibrium processes are studied including mathematically possible dissipative corrections. Standard conservation laws are applied, and the condition of positive entropy production allows for transfer between the spin and orbital parts of angular momentum.
↳ hep-phnucl-thMDPI Physics(2025)·3 citations
09
Exact Wigner function for chiral spirals
Samapan Bhadury🇵🇱 · Wojciech Florkowski🇵🇱 · Sudip Kumar Kar🇵🇱 · Valeriya Mykhaylova🇵🇱
The exact solution of the Dirac equation for fermions coupled to an external periodic chiral condensate (chiral spiral) is used to obtain the exact formula for the Wigner function (up to the quantum loop corrections). We find that the resulting expressions for various coefficients of the Wigner function exhibit properties that cannot be reproduced within the standard semiclassical expansion. The formula for the axial vector component of the Wigner function can be conveniently used to study spin polarization effects and illustrate connections between the spin density matrix and axial current. In particular, we find that during an adiabatic change of the periodic potential into a uniform one, the polarization vector is twisted from its original direction.
↳ hep-phnucl-thPRD(2025)·1 citation
10
Quenching through the QCD chiral phase transition
Adrien Florio🇩🇪 · Eduardo Grossi🇮🇹 · Aleksas Mazeliauskas🇩🇪 · Alexander Soloviev🇸🇮 · Derek Teaney🇺🇸
We present a detailed numerical and analytical study of the out-of-equilibrium dynamics of Model G, the dynamical universality class relevant to the chiral phase transition. We perform numerical 3D stochastic (Langevin) simulations of the $O (4)$ critical point for large lattices in the chiral limit. We quench the system from the high-temperature unbroken phase to the broken phase and study the non-equilibrium dynamics of pion fields. Strikingly, the non-equilibrium evolution of the two-point functions exhibits a regime of growth, a parametrically large enhancement, and a subsequent slow relaxation to equilibrium. We analyze our numerical results using dynamic critical scaling and mean-field theory. The growth of the two point functions is determined by the non-linear dynamics of an ideal non-abelian superfluid, which is a limit of Model G that reflects the broken chiral symmetry. We also relate the non-equilibrium two-point functions to a long-lived parametric enhancement of soft pion yields relative to thermal equilibrium following a quench.
↳ hep-lathep-phnucl-thPRD(2025)·9 citations
11
Supercooled Goldstone Bosons at the QCD Chiral Phase Transition
Adrien Florio🇩🇪 · Eduardo Grossi🇮🇹 · Aleksas Mazeliauskas🇩🇪 · Alexander Soloviev🇸🇮 · Derek Teaney🇺🇸
We discuss a universal non-equilibrium enhancement of long-wavelength Goldstone bosons induced by quenches to the broken phase in Model G -- the dynamical universality class of an $O (4)$ -antiferromagnet and the chiral phase transition in QCD. Scaling arguments for the coarsening dynamics describing the formation of the chiral condensate predict a parametric enhancement in the infrared spectra of Goldstones, a prediction confirmed by stochastic simulations of the transition. The details of the enhancement are determined by the non-linear dynamics of a superfluid effective theory, which is a limit of Model G reflecting the broken $O (4)$ symmetry. Our results translate to a parametric enhancement of low-momentum pions in heavy-ion collisions at the LHC, which are underpredicted in current hydrodynamic models without critical dynamics.
↳ hep-phhep-latnucl-exnucl-thPRL(2025)·14 citations

Affiliations

first authorsco-authorsvia INSPIRE