Nuclear Theory·nucl-th

Thursday·May 22, 2025

12 papers—7 primary·5 cross-listed

01
[Submitted on 20 May 2025]
Relaxation Time Approximation for a multi-species relativistic gas
Gabriel S. Rocha · Gabriel S. Denicol
We generalize a recent prescription for the relaxation time approximation for the relativistic Boltzmann equation for systems with multiple particle species at finite temperature. This is performed by adding counter-terms to the traditional Anderson-Witting ansatz for each particle species. Our approach allows for the use of momentum-dependent relaxation times and the obedience of local conservation laws regardless of the definition of the local equilibrium state. As an application, we derive the first order Chapman-Enskog corrections to the equilibrium distribution and display results for the hadron-resonance gas. We also demonstrate that our collision term ansatz obeys the second law of thermodynamics.
Comments:
20 pages, 1 figure -- v2: matches published version
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2505.14823 [pdf]
PRD(2025)·3 citations
02
[Submitted on 20 May 2025]
An Overview of the MUSES Calculation Engine and How It Can Be Used to Describe Neutron Stars
Mateus Pelicer · Veronica Dexheimer · Joaquin Grefa
For densities beyond nuclear saturation, there is still a large uncertainty in the equations of state (EoS) of dense matter that translate into uncertainties in the internal structure of neutron stars. The MUSES Calculation Engine provides a free and open-source composable workflow management system, which allows users to calculate the EoS of dense and hot matter that can be used, e.g. to describe neutron stars. For this work, we make use of two MUSES EoS modules, Crust Density Functional Theory and Chiral Mean Field model, with beta-equilibrium with leptons enforced in the Lepton module, then connected by the Synthesis module using different functions: hyperbolic tangent, Gaussian, bump, and smoothstep. We then calculate stellar structure using the QLIMR module and discuss how the different interpolating functions affect our results.
Comments:
6 figures, 1 table
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE)
arXiv:
2505.14921 [pdf]
Universe(2025)·3 citations
03
[Submitted on 20 May 2025]
Deformation of Jets Induced by Ambient Medium Flow
Arjun Sengupta🇺🇸 · Rainer J. Fries🇺🇸
The evolution of jets showers in high energy nuclear collisions is influenced in various ways by the presence of a surrounding medium. The interaction of jet constituents with the medium can happen during the partonic stage of the jet, during hadronization, and even during its hadronic stage. We demonstrate how flow of the ambient medium in a direction transverse to the jet can introduce both dipole and quadrupole defomations. We propose to analyze the $n = 1$ and $n = 2$ harmonic deformations of soft and semi-hard hadrons or subjets in a jet with respect to the jet core using the method of $q$ -vectors. We discuss simulations which show how the transverse shapes and their preferred angles evolve when the ambient environment of jets changes from the vacuum to a parton medium without flow and finally to a medium with various rates of transverse flow. Our study includes the effects of both flow during the development of the parton shower and hadronization. The existence of dipole deformations, and the correlation of the angles of dipole and quadrupole deformations could constitute promising experimental signals for the presence and size of ambient transverse flow.
Comments:
Contribution to Hard Probes 2024; 5 pages, 4 figures; submitted to EPJ Web of Conferences
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2505.14928 [pdf]
EPJ Web Conf.(2025)·2 citations
04
[Submitted on 20 May 2025]
Low-energy $^{12}$ C continuum states in three- $α$ model
Souichi Ishikawa
The electric multipole strength distributions for transitions from the $^{12} C (0_{1}^{+})$ ground state to $3 α$ ( $0^{+}$ , $1^{-}$ , $2^{+}$ , and $3^{-}$ ) continuum states are studied in terms of $3 α$ model. Several sets of the $3 α$ Hamiltonian are introduced phenomenologically with conventional $α$ - $α$ interaction potentials and $3 α$ potentials with different range parameters. The transition strength distributions are obtained from wave functions of $3 α$ bound- and continuum states calculated by the Faddeev three-body formalism. From these strength distributions, the resonance parameters (energy, $3 α$ -decay width, and transition strength) of $3 α$ resonance states are extracted. Dependencies of these observables on interaction potential models are studied to examine the introduced interaction models. Using the transition strength distributions, excitation-energy spectra in the $^{12} C (α, α^{'}) 3 α$ reaction are calculated to compare with experimental data.
Comments:
23 pages, 7 figures
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2505.14981 [pdf]
PRC(2025)·2 citations
05
[Submitted on 21 May 2025]
Robust extrapolation using physics-related activation functions in neural networks for nuclear masses
C. H. Kim · K. Y. Chae · M. S. Smith
Given the importance of nuclear mass predictions, numerous models have been developed to extrapolate the measured data into unknown regions. While neural networks -- the core of modern artificial intelligence -- have been recently suggested as powerful methods, showcasing high predictive power in the measured region, their ability to extrapolate remains questionable. This limitation stems from their `black box' nature and large number of parameters entangled with nonlinear functions designed in the context of computer science. In this study, we demonstrate that replacing such nonlinear functions with physics-related functions significantly improves extrapolation performance and provides enhanced understanding of the model mechanism. Using only the information about neutron (N) and proton (Z) numbers without any existing global mass models or knowledge of magic numbers, we developed a highly accurate model that covers light nuclei (N, Z > 0) up to the drip lines. The extrapolation performance was rigorously evaluated using the outermost nuclei in the measurement landscape, and only the data in the inner region was used for training. We present details of the method and model, along with opportunities for future improvements.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2505.15363 [pdf]
0 citations
06
[Submitted on 21 May 2025]
Quadrupole Strength in Isobaric Triplets
B. C. Backes · J. Dobaczewski · D. Muir · W. Nazarewicz · P.-G. Reinhard · M. A. Bentley · R. Wadsworth
The dependence of the $E 2$ matrix elements on isospin projection $T_{z}$ is linked to the conservation of the isospin symmetry. To study this conjecture, we calculated the $B (E 2 : 2^{+} \to 0^{+})$ rates for the even-even $T = 1$ mirror nuclei with $42$ $\leq$ $A$ $\leq$ $98$ within nuclear density functional theory, employing the generalized Bohr Hamiltonian, and carrying out angular momentum projection. We demonstrated that collective effects are crucial for describing experimental data near the $N = Z$ line without invoking explicit beyond-Coulomb isospin symmetry-breaking corrections. We also determined the $B (E 2 ↓)$ values for odd-odd $T_{z} = 0$ nuclei $^{70} B r$ and $^{78} Y$ in doubly-blocked configurations. We discussed the requirements for accurately describing isobaric analog states and emphasized how current theoretical results should be interpreted within the study of isospin symmetry across isospin triplets.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2505.15375 [pdf]
PRC(2025)·1 citation
07
[Submitted on 21 May 2025]
Enhancing the creation of elements in laser-assisted heavy-ion fusion reactions
Nicholas Thomson · Laura Moschini · Alexis Diaz-Torres
Low-energy fusion of heavy ions is a fascinating coupling-assisted quantum tunnelling problem, whose understanding is crucial for advancing the synthesis of new elements and isotopes. Quantum dynamical coupled-channels calculations of laser-assisted $^{16}$ O + $^{238}$ U fusion are presented for both a central collision and the total fusion cross-sections, suggesting that laser-nucleus interaction can enhance the average $^{16}$ O + $^{238}$ U fusion probability by $6 - 60%$ at subbarrier energies using quasi-static laser fields of intensity $1 0^{27} - 1 0^{29}$ Wcm $^{- 2}$ and photon's energy of $1$ eV. Femtosecond laser pulses are shown to reduce this enhancement by many orders of magnitude.
Comments:
7 pages, 7 figures
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2505.15390 [pdf]
PRC(2025)·1 citation

Affiliations

first authorsco-authorsvia INSPIRE

Relaxation Time Approximation for a multi-species relativistic gas

An Overview of the MUSES Calculation Engine and How It Can Be Used to Describe Neutron Stars

Deformation of Jets Induced by Ambient Medium Flow

Low-energy 12C continuum states in three-α model

Robust extrapolation using physics-related activation functions in neural networks for nuclear masses

Quadrupole Strength in Isobaric Triplets

Enhancing the creation of elements in laser-assisted heavy-ion fusion reactions

Affiliations

Low-energy $^{12}$ C continuum states in three- $α$ model