nucl-th — Pith

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nucl-th 2026-05-13 Recognition

Nuclei D-term kinks at magic neutron numbers

Mass radius and D-term of atomic nuclei in relativistic mean field theory

Relativistic mean field calculations find the gravitational form factor D peaks and dips with shell closures, creating kinks in mass and机械机械

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Based on relativistic mean field theory for atomic nuclei, we compute the mass radius and other radii associated with the energy momentum tensor for dozens of spin-0 nuclei across the nuclear chart. We also compute the D-term of these nuclei, the forward limit of the gravitational form factor $D(t=0)=D$. The dependence on the neutron number $N$ is systematically studied for calcium (Ca), nickel (Ni), zirconium (Zr), tin (Sn) and lead (Pb) isotopes. Remarkably, $|D|$ does not monotonically increase with $N$. Instead, it exhibits local maxima and minima when $N$ equals a magic number and even a sub-magic number. This results in characteristic kinks in the mass, scalar, tensor and shear radii of these isotopes. Our work for the first time elucidates the strong sensitivity of the various mechanical properties of nuclei to the nuclear shell structure.

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nucl-th 2026-05-13 2 theorems

Generalized IMSRG gives first ab initio anapole moment for 29Si

Ab initio calculation of symmetry-breaking observables

Extending the flow equations to weak operators produces predictions for parity-violating moments in nuclei used in new-physics searches.

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Symmetry-violating observables such as the nuclear anapole and Schiff moments provide sensitive probes of the fundamental symmetries of nature and physics beyond the Standard Model. Their interpretation has been hindered, however, by the lack of ab initio nuclear structure calculations in the medium-mass and heavy nuclei of interest to experimentalists. To provide them, we introduce a new version of the in-medium similarity renormalization group (IMSRG) designed to target parity-violating operators. By generalizing the IMSRG flow equations to evolve the weak symmetry-breaking Hamiltonian - and the anapole or Schiff operators - alongside the strong nuclear Hamiltonian, we construct a systematically improvable framework for computing these parity-violating moments. We benchmark the method against the no-core shell model in light nuclei and obtain the first ab initio predictions of the anapole moment in $^{29}$Si and the Schiff moments in $^{129}$Xe. These heavier systems are of direct experimental interest.

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nucl-th 2026-05-12 1 theorem

Hybrid model unifies transport and thermal clustering in heavy-ion collisions

Freeze-out model of light nuclei formation in heavy-ion collision transport

It predicts yields, spectra and flows in Au+Au at 1.23 A GeV while handling non-uniform temperatures and collective flows.

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Cluster production plays an important role in heavy-ion collisions at intermediate beam energies, where light nuclei contribute substantially to final-state yields and to other observables that are used to infer the nuclear equation of state. In this letter, we propose a new approach for clustering that combines dynamical transport and thermal cluster production for mid-rapidity particles. The resulting hybrid coarse-graining model matches nucleon and light-cluster descriptions at freeze-out while properly accounting for thermal non-uniformity and collective transport in the hot, strongly interacting systems created in heavy-ion collisions. To illustrate the capabilities of this model, yields at 4~fm impact parameter, spectra and elliptic flows at 7.4~fm ($20\text{--}30\%$ centrality) are predicted at mid-rapidity for semi-peripheral Au$+$Au collisions at an incident energy of $E_\text{lab}=1.23~A\mathrm{GeV}$.

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nucl-th 2026-05-12 1 theorem

Proof validates Strutinsky energy theorem

Rigorous proof of the Strutinsky energy theorem and foundations of nuclear density functional theory

It clarifies the shell-correction decomposition and supports nuclear density functionals

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We have derived a rigorous theoretical proof of the Strutinsky energy theorem. This proof not only provides a proper interpretation of the shell-correction decomposition, resolving decades of confusion, but also lays a foundation for constructing nuclear density functionals.

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nucl-th 2026-05-12 2 theorems

Neutron vortex cores larger than magnetic penetration depth in outer core

The mean-field theory of superfluid-superconducting vortex states in the outer core of neutron stars

Entrainment effects invalidate the thin-line London approximation for neutron vortices across the entire outer core region.

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Purpose: Characterize superfluid-superconducting vortex states at arbitrary pressures with $T_{cp}\neq T_{cn}$, assuming both proton and neutron mean-fields are formed by spin-0 Cooper pairs. Method: The existing mean-field theory is extended to account for $T_{cp}\neq T_{cn}$. The pressure dependence of the pairing gap energy $\Delta_{\alpha0}$ is quantitatively established on the basis of the effective chiral field theory. To link $T_{c\alpha}$ with $\Delta_{\alpha0}$, I use the weak-coupling result $T_{c\alpha}\approx0.57\Delta_{\alpha0}$. A quadratic scaled-temperature ($T/T_{cp}$) dependence of the thermodynamic magnetic field is postulated in analogy with pure superconductors. The $T/T_{c\alpha}$-dependence of the gap $\Delta_{\alpha T}$ is inferred from the many-body approximations for the pure neutron matter. Results: An empirical $T/T_{c\alpha}$-dependence for the mean-field is constructed to account for the interplay between the condensation and the magnetic energies. The superfluid entrainment is found to increase the size of the vortex core and to decrease the effective magnetic penetration depth. The size of the neutron vortex core is found to be larger than the magnetic penetration depth in the outer core. Conclusions: The usual approximation of infinitely thin vortex line (the London's approximation) for the neutron vortex is found to be irrelevant in the entire outer core and for the proton vortex is found to be limited to vicinity of the crust-core transition. The developed mean-field theory paves the way to study the vortex microscopic structure, the angular momentum, the magnetization and the vortex-fluxtube interaction energy.

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nucl-th 2026-05-12 Recognition

Microscopic model matches cold-fusion cross sections

New perspective on cold fusion reactions: A microscopic description

Hartree-Fock-Bogoliubov surfaces supply the barriers for the fusion-by-diffusion model, reproducing data for 48Ca+208Pb and showing an near-

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A microscopic framework that combines the Hartree-Fock-Bogoliubov (HFB) approach with the fusion by diffusion (FBD) model is proposed to investigate the synthesis mechanism of superheavy nuclei (SHN). For the reaction $^{48}\text{Ca}+^{208}\text{Pb}$, the calculated evaporation-residue cross section (ERCS) reproduces the experimental data reasonably well. The method enables self-consistent extraction of the fusion injection point and inner barrier from HFB potential-energy surfaces (PES), thereby incorporating nuclear structure effects while eliminating phenomenological tuning at the fusion stage. For cold-fusion reactions, the PES features a hyperasymmetric valley driven by shell effects. This $^{208}$Pb anchored valley connects the entrance channel to compound nucleus formation and provides an exit channel for cluster decay. We further investigate the cold-fusion reactions $^{54}\text{Cr}+^{208}\text{Pb}$ and $^{58}\text{Fe}+^{208}\text{Pb}$, obtaining a near-exponential decrease of $P_{\text{CN}}$ with compound-nucleus charge $Z$, consistent with established systematics. This approach demonstrates a self-consistent framework that can reduce uncertainties in the fusion stage of SHN production.

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nucl-th 2026-05-11 Recognition

Lambda quasiparticle binds at -29.55 MeV in nuclear matter

Quasiparticle properties of a single Λ impurity in symmetric nuclear matter with a regulated NΛ interaction

Regulated contact force fitted to vacuum data yields empirical depth, mostly from static term plus small dynamical correction.

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We explore the quasiparticle properties of a single $\Lambda$ hyperon propagating through symmetric nuclear matter using the Green's function formalism. The $N\Lambda$ interaction is described by a non-local regulated low-momentum contact potential with a leading-order constant term and a next-to-leading-order derivative correction. The two coupling constants in the ${}^1S_0$ and ${}^3S_1$ channels are fixed by matching the vacuum on-shell $T$ matrix to the scattering length and effective range obtained from modern next-to-next-to-leading-order chiral effective field theory. Using this effective interaction, we calculate the retarded $\Lambda$ self-energy from the in-medium $N\Lambda$ ladder $T$ matrix, which sums repeated $N\Lambda$ scattering in the nucleonic medium. At saturation density, the zero-momentum quasiparticle pole is found at $E_{\rm qp}(0,\rho_{\rm sat})=-29.55~{\rm MeV}$, in good agreement with the empirical depth of the single $\Lambda$ potential in nuclear matter. The self-energy decomposition gives a static Born contribution $\Sigma_\Lambda^{\rm Born}(0)=-26.36~{\rm MeV}$ and a dynamical correlation contribution ${\rm Re}\,\Sigma_\Lambda^{\rm corr,R}(0,E_{\rm qp})=-3.19~{\rm MeV}$, showing that repeated in-medium $N\Lambda$ scattering is needed to reproduce the empirical binding scale. The quasiparticle remains narrow and well defined, with a large residue $Z(0)=0.98$, a small damping width $\Gamma(0)=0.023~{\rm MeV}$, and a sharp spectral peak near the quasiparticle energy. At finite momentum, the $\Lambda$ quasiparticle becomes less bound, with $E_{\rm qp}(k,\rho_{\rm sat})$ increasing from $-29.55~{\rm MeV}$ at $k=0$ to $-6.49~{\rm MeV}$ at $k=1~{\rm fm}^{-1}$, while the residue and width change only weakly. A low-momentum fit gives $m_\Lambda^*/m_\Lambda=0.747$, consistent with the range obtained in Brueckner calculations with Nijmegen hyperon--nucleon potentials.

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nucl-th 2026-05-11 2 theorems

Few-nucleon parity violation extends to complex nuclei for Standard Model tests

Hadronic parity violation: successes, challenges, and future prospects

Precision results in simple systems now support benchmarks and new-physics searches in heavier nuclei.

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Hadronic parity violation concerns the study of the interplay of the weak- and strong-interaction dynamics that yields low energy, parity-violating observables in systems of hadrons and nuclei. We explain its essential features, as well as our current understanding of its observed effects, describing recent theoretical and experimental progress in a pedagogical context. We provide a broad overview of ongoing research efforts to show how precision studies of few-nucleon systems can be extended to studies of complex nuclei and, ultimately, to new benchmarks for computations in the Standard Model, as well as to new searches for the dynamics beyond it.

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nucl-th 2026-05-11 2 theorems

Thirring model energy density bounded within factor of two

The massive Thirring / sine-Gordon model with non-zero current density

Exact Bethe ansatz solution shows model-independent bounds from current density constrain the zero-temperature equation of state tightly at高

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This paper determines the zero-temperature equation of state for the massive Thirring / sine-Gordon model. This demonstrates recently derived model-independent upper and lower bounds on the zero-temperature equation of state with fixed number density from systems with a non-zero current density. That approach is potentially valuable as Monte Carlo calculations with a current density avoid the sign problem in the Euclidean formulation. An advantage to illustrating these bounds in the massive Thirring / sine-Gordon model is that the relevant calculations with both a number density and a current density can be done using a Bethe ansatz. For this model, optimal bounds constrain the energy density as a function of number density by a factor of two from above and below at high densities for all choices of couplings. The lower bound becomes exact at low densities, while the upper bound approaches the worst constraint of a factor of 4.90.

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nucl-th 2026-05-11 Recognition

Deuteron breakup alters Xi d correlation functions

Xi-deuteron low-energy s-wave phase shifts and momentum correlation functions in Faddeev formulation

Faddeev calculations using chiral and lattice XiN models predict differences experiments could use to refine the forces.

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The low-energy $\Xi$-deuteron scattering is investigated through the solution of Faddeev equations, employing three sets of the currently available parametrization of the $\Xi$-nucleon interactions. One of these is the chiral NLO interaction parametrized by the J\"{u}lich group, and the other two are based on the calculations by the HAL-QCD method. The $s$-wave phase shifts in the $J=3/2$ and $J=1/2$ states are presented. Three-body wave functions in coordinate space are constructed from the Faddeev amplitudes in momentum space. These functions are used in the calculation of $\Xi d$ momentum correlation functions. The effects of the deuteron breakup are significant in the $J=3/2$ channel. The differences in the magnitude of the calculated correlation function show the quantitative difference of the $\Xi N$ interactions in the spin-isospin channels. The prospective experimental data on the $\Xi d$ momentum correlation function could contribute to a better description of the $\Xi N$ interactions.

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nucl-th 2026-05-11 Recognition

Resonance direct theory fits photoneutron data for Pb

Analysis of the energy and angular distributions of photoneutrons from natPb, 197Au, natSn, natCu, natFe, and natTi using resonance direct theory

Calculations that add the direct process to pre-equilibrium and compound models agree with 16.6 MeV experiments and link high-energy anisot

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Photoneutron double-differential cross sections in the giant dipole resonance (GDR) region were calculated to investigate the underlying nuclear reaction mechanisms, with particular emphasis on the role of the direct process. Contributions from direct, pre-equilibrium, and compound processes were all taken into account. Wilkinson's resonance direct (RD) theory, based on the independent particle model, was applied to describe high-energy neutron emission from the direct process. The angular distribution of neutrons emitted via the RD mechanism was formulated using the Agodi and Courant formalism, which was incorporated into the RD framework. Neutron emission from the pre-equilibrium and compound processes was calculated using the two-component exciton model and the Hauser-Feshbach formalism, respectively. The calculated results were compared with experimental data obtained at NewSUBARU using 16.6-MeV quasi-monochromatic linearly-polarized photon beams. Good agreement between calculations and measurements was observed for Pb, Au, and Sn, confirming the validity of the proposed model. Furthermore, the angular anisotropies of photoneutrons emitted from these elements were investigated, revealing considerable contributions from the RD process at high neutron energies. This study provides a deeper understanding of photoneutron emission mechanisms in the GDR energy region.

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nucl-th 2026-05-08

Isospin ratios in heavy-ion collisions constrain symmetry energy

Probing the density dependence of nuclear symmetry energy through isospin transport in heavy-ion reactions

INDRA-FAZIA data plus BUU calculations give density-dependent limits relevant to neutron stars and supernovae

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The density dependence of the nuclear symmetry energy remains one of the key uncertainties in contemporary nuclear physics, with significant implications for the structure of exotic nuclei, the dynamics of heavy-ion collisions, and the properties of astrophysical objects such as neutron stars and core-collapse supernovae. However, extracting robust constraints requires observables that are minimally affected by final-state interactions and are reliably predicted by transport models. This review synthesizes recent theoretical and experimental advancements in constraining the symmetry energy by leveraging isospin diffusion in heavy-ion reactions within the Fermi energy domain. Recent results from the INDRA-FAZIA collaboration, including isospin transport ratio data, and Boltzmann-Uehling-Uhlenbeck (BUU) transport model calculations are highlighted. Confidence regions for the symmetry energy are extracted from isospin transport ratios and isospin diffusion currents by utilizing state-of-the-art nuclear functionals, including both ab initio and phenomenological approaches, with a particular focus on the density regions probed by these experiments. The resulting constraints will aid future Bayesian studies of the nuclear equation of state and contribute to a more unified understanding of dense matter in both terrestrial experiments and astrophysical environments.

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nucl-th 2026-05-08

Electrons can deplete nuclear isomers via inelastic scattering

Isomer depletion via nuclear excitation by inelastic electron scattering

Calculations for three key isomers show excitations to higher levels enable decay and energy release.

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Isomer depletion via the process of nuclear excitation by inelastic electron scattering is investigated theoretically. A comprehensive study on low-energy nuclear excitations by inelastic electron scattering is performed to analyze the impact of the nuclear and ion charge, the nuclear transition energy, and the nuclear transition multipolarity on the cross section of the process. We apply the analysis to the case of isomer depletion, in which an excitation from the isomeric state to a nuclear level above the isomeric state can lead to decay to a nuclear level below the isomer itself and hence lead to the release of the energy stored in the isomer. For this purpose, the isomer depletion of $\mathrm{{}^{93m}{Mo}}$, $\mathrm{{}^{152m}{Eu}}$, and $\mathrm{{}^{178m}{Hf}}$, which represent the most important scenarios of isomer depletion, are studied. Our results demonstrate the capability of the process of nuclear excitation by inelastic electron scattering for isomer depletion.

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nucl-th 2026-05-08

Crust neutron radii shift with symmetry-energy slope L

Relativistic mean-field study of the neutron star inner crust using the asymmetric finite difference method

RMF calculations find binding energies drop and neutron sizes change as L rises or effective mass increases.

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The ground-state properties of neutron-rich nuclear clusters in the inner crust of neutron stars are investigated within the Wigner-Seitz approximation using a relativistic mean-field framework. The radial Dirac equations are solved with an asymmetric finite-difference scheme, by which the hermiticity is preserved and spurious states are eliminated. Calculations are performed for representative Wigner-Seitz cells employing TM1-based interactions with different symmetry-energy slope parameters $L$, as well as a parametrization with a larger nucleon effective mass. It is found that the binding energy per nucleon decreases systematically with increasing $L$, while a larger effective mass leads to further reduction, particularly at higher densities. Quantum shell effects, which are absent in the Thomas-Fermi approximation, give rise to oscillatory density distributions and modify neutron properties. Within the Wigner-Seitz cell, the resulting neutron root-mean-square radius and chemical potential are shown to be sensitive to both $L$ and the effective nucleon mass, underscoring their important roles in determining the microscopic structure of the neutron-star inner crust.

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nucl-th 2026-05-07

Axial-vector current yields full unpolarized electroweak nucleon responses

Axial-vector Current and General Unpolarized Electroweak Single-nucleon Responses

General forms plus tested approximations clarify how weak form factors enter free and bound-nucleon reactions.

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The present study provides an extension to our recent work on the vector (V) electromagnetic single-nucleon current and associated response functions, both for unpolarized situations and in situations where the target nucleon is polarized. Here the axial-vector (A) single-nucleon current matrix element is developed in detail and the full set of vector and axial-vector currents used to obtain the electroweak VV, AA and VA response functions. Only the unpolarized case is studied in the present work. The general forms for all of these elements are developed together with various approximation schemes in which numerical studies are provided to indicate where these approximations may be expected to be valid. The results of this work provide the basis for a deeper understanding of the roles played by the various single-nucleon form factors in weak interaction reactions on free nucleons and when using the standard ``prescription for nuclear physics'' in reactions involving nucleons in nuclei.

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nucl-th 2026-05-07

Small density jumps let hybrid stars match NICER pulsar sizes

Can a hybrid star with constant sound speed parametrization explain the new NICER mass-radius measurements ?

Constant sound speed models for quark cores work when the phase transition jump is low, but fail for large jumps that cannot support heavy 2

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We present a reanalysis of NICER observations of PSR J0740+6620 and PSR J0030+0451 to test the consistency of various nuclear equations of state (EoS) within the framework of hybrid star models. In particular, we examine how different surface temperature models for PSR J0030+0451, categorized as Scenarios A, B, and C, lead to significantly different mass-radius estimates. We perform a comprehensive study constraining the parameters of the constant speed of sound (CSS) model based on representative observational categories. Our findings indicate that for certain hadronic equations of state, including both density-independent and density-dependent cases, the results remain consistent for lower values of the energy density discontinuity, while discrepancies emerge as the discontinuity increases. Scenarios involving large jumps in energy density are generally disfavored by the requirement of supporting massive neutron stars, whereas higher values of the speed of sound in the quark matter phase tend to yield better agreement with observational trends. These results underscore the importance of phase transition characteristics in aligning hybrid star models with current astrophysical observations. We further constrain the CSS parameters using observational data from PSR J0740+6620 and PSR J0952-0607 by computing the maximum mass supported by these parameter sets.

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nucl-th 2026-05-07

Effective mass and symmetry energy control mixed phase width in hot hybrid stars

Characterizing the quark-hadron mixed phase in compact star cores : sensitivity to nuclear saturation and quark-model parameters at finite-temperature

Thermal effects narrow the coexistence region while strong quark vector repulsion enables massive pulsars to match NICER radius data.

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A thorough knowledge of the quark-hadron phase transition in hot and dense matter is essential for constraining the equation of state of neutron stars. In this work, we study the thermodynamics of the quark-hadron mixed phase at finite temperature using the Gibbs construction and examine its impact on hybrid star matter. We systematically explore the role of nuclear saturation properties, including the effective nucleon mass, incompressibility, symmetry energy coefficient, and its slope, together with quark matter parameters such as the bag constant and the vector coupling strength. We find that the width of the mixed phase is mainly controlled by the effective mass and symmetry energy, while the roles of incompressibility and symmetry energy slope are comparatively weak, particularly at higher temperatures. Thermal effects substantially modify the phase structure: increasing temperature reduces the mixed-phase width and softens the equation of state in the coexistence region due to Gibbs phase equilibrium constraints. These effects are reflected in the behavior of the speed of sound, the trace anomaly, and its derivative. Variations in the symmetry energy, effective mass, and quark parameters significantly affect the hadron-quark transition, stellar radii, and maximum mass, while finite temperature softens the equation of state and enhances radius jumps in the mixed phase. Strong vector repulsion is essential to reconcile massive pulsar observations with NICER constraints, whereas weaker repulsion favors more compact, low-mass configurations.

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nucl-th 2026-05-07 2 theorems

Longitudinal spin acceleration creates Lambda polarization quadrupole

Modeling Λ polarization in Au+Au collisions at sqrt{s_{rm NN}}=200 GeV using relativistic spin hydrodynamics

The pattern arises when spin acceleration couples to transverse expansion and matches data from 200 GeV Au+Au collisions.

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We investigate spin polarization dynamics in relativistic heavy-ion collisions using ideal relativistic spin hydrodynamics, employing non-boost-invariant longitudinal solutions as the hydrodynamic background. Operating in the small-polarization regime, where spin evolves perturbatively on top of the bulk expansion, we first analyze a $(1+1)$D setup with transverse homogeneity. In this framework, symmetry-constrained initial conditions for the spin potential lead to non-trivial evolution and generate both local and global $\Lambda$ hyperon polarization consistent with qualitative experimental trends, though they fail to reproduce observed azimuthal structures. To address this limitation, we extend the framework by incorporating transverse flow and spatial anisotropy at freeze-out, constructing a $novel$ $(1+1+2)$D model that preserves the longitudinal dynamics. We demonstrate that the inclusion of a longitudinal spin acceleration component, coupled with transverse expansion, results in the emergence of a quadrupole pattern in the longitudinal polarization. The resulting momentum-dependent and integrated observables exhibit qualitative and reasonably good quantitative agreement with experimental data for Au+Au collisions at $\sqrt{s_{\rm NN}}=200$ GeV. Finally, we provide predictions for the in-plane transverse spin polarization, an observable that, to our knowledge, has not yet been experimentally measured.

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nucl-th 2026-05-07

Relativistic model matches nuclear level densities to experiments

Nuclear level densities in the relativistic Hartree-Bogoliubov plus combinatorial framework

Using three relativistic functionals, calculations reproduce s-wave resonance spacings as well as leading global models, with effective mass

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A systematic study of nuclear level densities has been carried out within the relativistic Hartree-Bogoliubov plus combinatorial framework. Calculations were performed for even-even nuclei with available experimental data, based on the relativistic energy density functionals DD-ME2, DD-PC1, and PC-PK1. The overall performance of the model is assessed against experimental data. On this basis, the effects of different functionals, pairing correlations, deformation, and other relevant factors on nuclear level densities are examined. The results show that the present framework provides a good description of the experimental level density and reproduces the s-wave neutron resonance spacings with an accuracy comparable to that of the best existing global models. Furthermore, differences among the adopted relativistic density functionals in the nucleon effective mass at saturated nuclear matter are transmitted to the predicted level densities and constitute the main source of the differences among the results obtained with the three functionals.

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nucl-th 2026-05-07

Neodymium isotopes show stability at 92 neutrons

Nuclear Structure and Shape Evolution of Nd Isotopes

RMF calculations of binding energies and deformations across the full even-even chain locate shape transitions around that point.

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In this work, we have analyzed the structural properties of even-even $^{126-188}Nd_{60}$ isotopes. For this we have used axially deformed Relativistic Mean Field (RMF) model with PK1 and NL-SH parametrization. In structural properties, We have estimated and analyzed binding energy per nucleon (B.E./A), two neutron separation energy ($S_{2n}$), differential variation of two neutron separation energy ($dS_{2n}$), quadrupole deformation parameter ($\beta_{2}$), root mean square nuclear charge radius ($r_{ch}$), neutron skin thickness ($r_{np}$) and single particle energy (SPE) levels of Nd isotopes. Some bulk properties are also compared with experimentally accessible results and with results of Finite Range Droplet Model (FRDM). To understand the shape evolution around N = 92, the variation of the potential energy curves (PECs) with quadrupole deformation parameter are also investigated. From all the investigations, We observe some sign of stability at N = 92 and shape transitions around it.

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nucl-th 2026-05-07

Sky3s Skyrme force changes neutrino rates by up to 10 times

Charged current neutrino processes in hot nuclear matter with a recent Skyrme parametrization constrained by microscopic calculations

Calculations for hot nuclear matter show order-of-magnitude differences from SLy4 and milder finite-temperature violations of beta balance.

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Neutrino processes are important in the modeling of supernova explosions, proto-neutron star evolution, and binary neutron star mergers. We study neutrino production and absorption in proto-neutron star and supernova matter and direct Urca neutrino emission of neutron star matter in the framework of the random phase approximation (RPA). As interactions, we employ the recent extended Skyrme parametrization Sky3s whose effective masses and spin-dependent terms were adjusted to microscopic calculations, and the SLy4 parametrization that was used in previous calculations of neutrino rates. The rates obtained for Sky3s differ from those for SLy4 by up to one order of magnitude for some processes and energy regions. We also determine the electron, muon, and proton fractions that lead to a stationary composition of matter for a density above the direct Urca threshold, and find that with Sky3s the standard $\beta$ equilibrium condition is not as badly violated at finite temperature as predicted in the literature. There are also minor differences between the full RPA and the common Landau approximation, but they are probably not significant for astrophysical simulations. We conclude that it would be worthwhile to repeat the calculation of neutrino rates for the use in astrophysical simulations, and the corresponding simulations, with several and better constrained interactions than SLy4, such as Sky3s.

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nucl-th 2026-05-07

Fluctuations barely shift bottomonium R_AA and v2

Effects of event-by-event hydrodynamic fluctuations on bottomonium dynamics in Pb--Pb collisions at sqrt{s_{NN}} = 5.02 TeV

Event-by-event simulations in Pb-Pb at 5.02 TeV find only marginal differences from smooth media for suppression and flow.

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We investigate the effects of event-by-event hydrodynamic fluctuations on bottomonium nuclear modification factors and elliptic flow in Pb--Pb collisions at $\sqrt{s_{NN}}=5.02$ TeV. The internal evolution of the heavy quarkonium is described by a time-dependent Schr\"odinger equation with a temperature-dependent complex heavy-quark potential, while the hot QCD medium evolution is simulated using the iEBE-VISHNU event-by-event viscous hydrodynamic framework. By incorporating both fluctuating and smooth hot media, we observe that both $R_{AA}$ and $v_2$ of various bottomonium states are marginally affected by the medium fluctuations. By realistically simulating the dynamical evolution of bottomonium within a large set of event-by-event fluctuating hot QCD medium, this work provides key insights into the behavior of heavy-quarkonium observables in relativistic heavy-ion collisions.

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nucl-th 2026-05-07

Cherenkov angles and jet drift reveal medium properties

Medium Characterization with Hard Probes: From Cherenkov Light in QED to Jet Drift in QCD

A refractive-index fit for argon produces angular excess; flow deflection yields unique v2 and acoplanarity signals across collision systems

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This dissertation presents a unified framework for medium characterization with hard probes spanning from Cherenkov light in quantum electrodynamics (QED) to jet drift in quantum chromodynamics (QCD). We first develop a dispersive fit to the refractive index $n(\lambda)$ of liquid argon (LAr) by incorporating anomalous dispersion at the 106.6 nm resonance for the first time. We show that the angular distribution of Cherenkov radiation is highly sensitive to the peak of the refractive index and contributes a significant excess over isotropic scintillation in certain angular bins. This work is important for precision Particle Identification (PID) for experiments like DUNE and CCM. Transitioning to high-energy nuclear collisions, we utilize ``jet drift'' -- the flow-induced deflection of partons -- as a tomographic probe of the Quark-Gluon Plasma (QGP). Using the Anisotropic Parton Evolution (APE) Monte Carlo simulation across various collision systems (PbPb, AuAu, and UU), we disentangle how the jet modification depends on medium size, temperature, and geometry. We show that jet drift exhibits distinct systematics in observables like the elliptic flow ($v_2$) and dihadron acoplanarity ($\Delta\phi$), which helps disentangle it from conventional energy loss. Together, these studies demonstrate how the angular and kinematic signatures of hard probes revolutionize our ability to resolve the fundamental properties of matter.

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nucl-th 2026-05-06

This preprint is a pedagogical review that starts from classical damped driven…

What is a resonance? And why does it matter?

A pedagogical exposition deriving the concept of quantum resonances from classical oscillations and mapping their manifestations in nuclear…

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The resonance phenomenon is of central importance in many areas of physics, with particular significance in the study of nuclear structure and reactions. Starting from the classical framework of damped driven oscillations, this text introduces and analyzes quantum-mechanical resonances in a pedagogical and systematic fashion, with emphasis on applications in nuclear physics. Building on the formal theory of resonances, the text elucidates the relationship between experimental observations, phenomenological insights, and computational methods used to characterize and describe resonant states. The discussion encompasses the diverse manifestations of nuclear resonances, ranging from few- to many-body systems, all the way to collective phenomena and to exotic systems that appear near the limits of nuclear stability. References to the relevant literature are provided to assist readers who wish to explore specific topics in more depth.

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nucl-th 2026-05-06

Four-body DWBA unifies pair and single-particle breakup observables

Inclusive breakup of three-body projectiles: A unified four-body framework for pair-detected and single-particle observables

Derives consistent expressions for both detection channels of three-body projectiles from one Hamiltonian and recovers known limits.

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Inclusive breakup of three-body projectiles $a=i+j+k$ on a target $A$ admits two distinct inclusive observables: detection of a correlated pair $b=(ij)$ with $k+A$ unresolved, and detection of a single particle $i$ with $jk+A$ unresolved. A four-body DWBA sum-rule framework is derived for both channels from a common Hamiltonian. For the pair-detected channel, the unresolved propagator remains the two-body $k+A$ Green function and all three-body projectile effects enter through a pair-projected source built from $\Phi_a$; a reference pair-target optical interaction splits this source into a target-elastic reference part and an explicit pair-target coupling part, yielding a state-resolved semi-inclusive coincidence observable and an amplitude-level diagnostic of the two-body cluster approximation. For the single-particle channel, the unresolved propagator is the three-body $jk+A$ resolvent, whose reference-channel Feshbach reduction reproduces the Carlson-Frederico-Hussein (CFH) absorptive kernel $W_j+W_k+W_{3B}$; the additional source $V_{iA}-U_{iA}$ drives target excitations, with its direct $g_Q$ component yielding target-excited CFH-like kernels under a diagonal-intermediate-states approximation. Prior forms are derived for both partitions, with reduced post-prior identities at the single-channel level (pair-detected) and at the CFH-optical level (single-particle). For $^{6}$Li$=\alpha+n+p$, the explicit deuteron-target coupling has an E1/E2/monopole tidal structure evaluated on the full three-body wave function. The framework is validated by recovery of the two-body IAV, CFH, and detected-cluster limits, and separates exact DWBA identities from later optical and diagonal-target approximations.

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nucl-th 2026-05-05

Chiral symmetry always breaks near the AdS boundary

Chiral symmetry breaking and inhomogeneous phases in thermal anti-de Sitter spacetime

The unique inhomogeneous condensate persists close to the boundary while curvature and temperature compete, even after the Hawking-Page jump

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We study the spontaneous breaking of chiral symmetry in an AdS spacetime at finite temperature using the quark-meson model. The condensate $\sigma$ is typically inhomogeneous in AdS and is determined from the differential gap equation. We demonstrate that there are no free integration constants in the regular solutions to the differential equation and find that the solution to the boundary value problem is unique. We find that chiral symmetry is always broken close to the AdS boundary. We construct the phase diagram of the system as a function of the AdS curvature and temperature. These two parameters have opposing effects: temperature tends to restore chiral symmetry, whereas negative curvature favors its spontaneous breaking. We also consider how the phase diagram is modified when the Hawking-Page phase transition is taken into account.

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nucl-th 2026-05-05

Three-body model gives 22.492 eV b for 7Be(p,γ)8B S-factor

Structure of the ⁸B and ⁸Li nuclei and the astrophysical S₁₇(0)-factor of the ⁷Be(p,γ)⁸B direct capture process within a three-body model

The zero-energy value from ANC matching lies near the input of one successful solar model and above the standard recommendation.

abstract click to expand

The structure of the ground $(2^+)$ and excited $(1^+)$ bound states of the $^8$B and $^8$Li nuclei is studied within the framework of the $\alpha+^3$He($^3$H)+$p(n)$ three-body potential cluster model based on the hyperspherical Lagrange-mesh method. The two-body $\alpha-^3$He($^3$H), $\alpha$-N, and $^3$He($^3$H)-N realistic potentials have been applied from the literature. Convergent theoretical estimates for the three-body binding energy and matter radius have been obtained with the maximal hypermomentum $K_{max}=22$ and 28 for the ground and excited $1^+$ states, respectively. The ANC value of the virtual transition of the $^8$B nucleus is estimated self-consistently by matching the overlap integral of the $^8$B three-body and the $^7$Be two-body wave functions with it's asymptotics. The obtained values are $0.211$~fm$^{-1/2}$ and $0.739$~fm$^{-1/2}$ in the spin 1 and spin 2 channels, respectively. For the ANC values of the $^8$Li nucleus the estimates $0.220$~fm$^{-1/2}$ and $0.774$~fm$^{-1/2}$ are extracted. For the zero-energy astrophysical factor of the direct nuclear capture process $^7$Be(p,$\gamma)^8$B an estimate $22.492\pm0.014$ eV b was obtained based on the asymptotic theory developed by D. Baye [Phys. Rev. C {\bf 62}, 065803 (2000)]. The most important contribution comes from the spin 2 channel with $S^{(2)}_{17}(0)=20.838 \pm 0.014$ eV b, while the spin 1 channel yields $S^{(1)}_{17}(0)=1.654 \pm 0.003$ eV b. These results for $S_{17}(0)$ are in a good agreement with the estimate $20.8\pm0.7{\rm(th)}\pm1.4{\rm(exp)}$ eV b of the SF II, but larger than the recommended value $20.5\pm0.70$ eV b of the SF III. At the same time, our estimate is very close to the value 22.4 eV b used in the most successful Solar Model BAR2M [W.~Yang and Z.~Tian, AJ {\bf 970}, 38 (2024)].

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nucl-th 2026-05-05

Three-body model gives S_17(0) = 22.49 eV b for 7Be capture

Structure of the ⁸B and ⁸Li nuclei and the astrophysical S₁₇(0)-factor of the ⁷Be(p,γ)⁸B direct capture process within a three-body model

Asymptotic normalization constants from the α + ³He + p wave function separate the spin-1 and spin-2 contributions at zero energy.

abstract click to expand

The structure of the ground $(2^+)$ and excited $(1^+)$ bound states of the $^8$B and $^8$Li nuclei is studied within the framework of the $\alpha+^3$He($^3$H)+$p(n)$ three-body potential cluster model based on the hyperspherical Lagrange-mesh method. The two-body $\alpha-^3$He($^3$H), $\alpha$-N, and $^3$He($^3$H)-N realistic potentials have been applied from the literature. Convergent theoretical estimates for the three-body binding energy and matter radius have been obtained with the maximal hypermomentum $K_{max}=22$ and 28 for the ground and excited $1^+$ states, respectively. The ANC value of the virtual transition of the $^8$B nucleus is estimated self-consistently by matching the overlap integral of the $^8$B three-body and the $^7$Be two-body wave functions with it's asymptotics. The obtained values are $0.211$~fm$^{-1/2}$ and $0.739$~fm$^{-1/2}$ in the spin 1 and spin 2 channels, respectively. For the ANC values of the $^8$Li nucleus the estimates $0.220$~fm$^{-1/2}$ and $0.774$~fm$^{-1/2}$ are extracted. For the zero-energy astrophysical factor of the direct nuclear capture process $^7$Be(p,$\gamma)^8$B an estimate $22.492\pm0.014$ eV b was obtained based on the asymptotic theory developed by D. Baye [Phys. Rev. C {\bf 62}, 065803 (2000)]. The most important contribution comes from the spin 2 channel with $S^{(2)}_{17}(0)=20.838 \pm 0.014$ eV b, while the spin 1 channel yields $S^{(1)}_{17}(0)=1.654 \pm 0.003$ eV b. These results for $S_{17}(0)$ are in a good agreement with the estimate $20.8\pm0.7{\rm(th)}\pm1.4{\rm(exp)}$ eV b of the SF II, but larger than the recommended value $20.5\pm0.70$ eV b of the SF III. At the same time, our estimate is very close to the value 22.4 eV b used in the most successful Solar Model BAR2M [W.~Yang and Z.~Tian, AJ {\bf 970}, 38 (2024)].

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nucl-th 2026-05-05

Bayesian filter fits fission yields with full correlations

New Procedure for the Evaluation of Fission Product Yields: Application to the Spontaneous Fission of ²⁵²Cf

Kalman method on 252Cf data produces means, covariances and consistent multiplicity predictions

abstract click to expand

Over the last decade, there has been significant improvement in the understanding and modeling of the decay of fission fragments by both prompt and delayed emission. These model improvements open the door for performing consistent evaluations across multiple fission observables, providing not only mean values but also covariances between observables. One such model is the Hauser-Feshbach Fission Fragment Decay model implemented in $\texttt{BeoH}$, which uses distributions of initial conditions of fission fragments to perform a Hauser-Feshbach decay for prompt neutron and $\gamma$-ray emission and evaluated decay data to calculate cumulative fission product yields. This manuscript describes a new evaluation procedure for independent and cumulative fission product yields, including full correlations among the fission products. We use a Bayesian Kalman filter to fit both experimental cumulative fission product yields and those from the ENDF/B-VIII.0 evaluated library, producing mean values and covariances. In addition to comparing the fission products from these optimizations, we calculate prompt and delayed neutron and $\gamma$-ray multiplicities using the fitted parameters and compare to some available experimental data. We see reasonable agreement, even when these quantities are not included in the optimization.

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nucl-th 2026-05-05

Generalized recursion yields gauge-invariant gluon amplitudes directly

Gluon production in the Color Glass Condensate from BCFW recursion

In the Color Glass Condensate, this skips gauge-dependent fields when extracting the leading-order spectrum from color current sources.

abstract click to expand

In the Color Glass Condensate framework, the colliding projectiles are described as classical color currents. Gluon production at leading order in the coupling is obtained from the retarded solution of the classical Yang-Mills equations, with these currents acting as sources. However, while the final gluon spectrum is gauge invariant, the classical color field $A^\mu$ from which it is obtained is gauge dependent. This makes the intermediate steps of this approach unnecessarily complicated, as some effort is spent to also determine the gauge dependent part of $A^\mu$, which is then discarded when one calculates a gauge invariant observable. In this work, we use a generalization of BCFW recursion applicable to off-shell gluons in order to calculate directly the gauge independent gluon production amplitude. This approach allows all manipulations to be performed in terms of gauge invariant amplitudes instead of gauge dependent Feynman diagrams, and therefore provides a gauge agnostic way to obtain the result.

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nucl-th 2026-05-05 3 theorems

Neural network reconstructs nuclear potential from phase shifts

Constructing Inverse Potentials from Scattering Phase Shifts using Physics-Informed Neural Networks: Application to Neutron-Alpha Scattering

A Gaussian envelope built into the network keeps the potential finite-range and yields a 60 MeV attractive well whose barrier structure fits

abstract click to expand

We develop a physics-informed neural networks (PINNs) framework for the inverse scattering problem in nuclear physics and apply it to the $P_{3/2}$ partial wave of neutron-alpha elastic scattering. The radial potential is represented by a feed-forward network whose output is multiplied by a Gaussian envelope, embedding the finite-range condition directly into the architecture rather than through a soft penalty term. This distinction proves essential: without the envelope, the optimizer produces potentials with non-vanishing tails and the resulting phase shifts remain inconsistent with the data regardless of training duration, demonstrating that hard structural constraints are indispensable for physically meaningful solutions to nuclear inverse problems. Phase shifts are generated at each scattering energy by numerically integrating the variable-phase equation with a fourth-order Runge-Kutta scheme, making the entire pipeline end-to-end differentiable.Training converges stably to a loss near $3\times10^{-4}$ and recovers a smooth, purely attractive central potential with a well depth of $-60.47$~MeV. Adding the centrifugal barrier to the learned potential reveals a well-defined barrier-well structure that naturally accounts for the $P_{3/2}$ resonance. The extracted resonance parameters, $E_{r} = 0.95$~MeV and $\Gamma_{r} = 0.78$~MeV, together with the P-wave effective-range parameters, are in good agreement with expected values. A leave-one-out analysis confirms that the reconstruction is stable against the removal of any single data point. These results establish physics-guided machine learning as a reliable route to potential reconstruction from nuclear scattering data.

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nucl-th 2026-05-05 3 theorems

Feshbach-Villars equation extended to two spin-0 particles

Relativistic Feshbach-Villars Equation for Two Spin-0 Particles

Center-of-mass motion separates, leaving a relative-coordinate equation of the same type.

abstract click to expand

The Feshbach-Villars version of the relativistic quantum mechanics can be extended for two-body systems in such a way that the center-of-mass motion is separated off. The procedure results in an equation of Feshbach-Villars-type in terms of the relative coordinate.

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nucl-th 2026-05-04

Coupled MHD evolution suppresses low-mass dilepton spectrum

Relativistic BDNK MHD Evolution in a Boost-Invariant Medium and Its Impact on Dilepton Production

Enhanced cooling from temperature and magnetic field feedback reduces emission in boost-invariant medium compared to non-coupled cases.

abstract click to expand

In this work, we explore a Bemfica--Disconzi--Noronha--Kovtun (BDNK)-type formulation of relativistic magnetohydrodynamics, providing a causal and stable first-order description of dissipative fluids. We derive coupled evolution equations for the temperature and magnetic field in a boost-invariant Bjorken background, restricting to $(0+1)$D dynamics while retaining all relevant first-order gradients. By varying the transport coefficients, we disentangle the interplay and mutual backreaction between the thermal and electromagnetic sectors. We find that, for comparable transport coefficients, the magnetic field responds more strongly to changes in the temperature evolution, while its feedback on the temperature remains subleading. We further analyze the number density evolution, which is sensitive to both temperature gradients and magnetic-field dynamics. We also investigate implications for dilepton production, where the magnetic field modifies the emission rate via the relaxation time in a kinetic-theory framework. The coupled evolution leads to a suppression of the low-mass dilepton spectrum, primarily driven by enhanced cooling in the presence of positive coupling between temperature gradients and magnetic-field evolution, as compared to scenarios without such feedback.

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nucl-th 2026-05-04 4 theorems

Duality maps black holes to nuclei and caps stable charge at 82

The atomic nucleus as a bound system of 3A quarks

Refined mapping from extremal AdS5 black holes to subnuclear systems predicts lead-208 as the heaviest stable nucleus and a specific glueb

abstract click to expand

The atomic nucleus, viewed as a system of bound quarks, should, in principle, be described within an effective theory of low-energy quantum chromodynamics. This paper provides an overview of recently developed models that embody essential features of the desired effective theory. The Fermi gas model helps explain why the number of $d$ quarks is approximately equal to that of $u$ quarks in stable light nuclei up to ${\rm {}^{40}_{20}Ca}$. A modified bag model accounts for the deviation from this rule in heavier nuclei. With this model, the static properties of a wide range of stable nuclei can be described with reasonable accuracy. To make the most of the modified bag model, it is useful to invoke gauge/gravity duality. A refined version of duality states: ``The dynamics inside an extremal black hole in ${\rm AdS}_5$ is mapped onto the corresponding dynamics of a stable subnuclear system in ${\mathbb R}_{1,3}$''. This version of duality allows one to predict the primary decay channel of the lightest glueball. Another implication is that this framework explains why the periodic table contains a finite number of stable elements. Duality makes it possible to calculate the maximum allowed charge $Z_{\rm max}$ of stable heavy nuclei: $Z_{\rm max}\approx 82$, which is the charge of the ${\rm {}^{208}_{82}Pb}$ nucleus.

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nucl-th 2026-05-04

Stochastic fields lower nuclear ground-state energies

Multireference Covariant Density Functional Theory with Stochastic Basis

Multireference covariant DFT with random external perturbations yields tighter nuclei and softer bands in 20Ne, 24Mg and 28Si.

abstract click to expand

Multireference density functional theory (MR-DFT) provides a pivotal microscopic framework for the description of the ground state properties, low-lying nuclear spectra and transition properties of atomic nuclei. Conventionally, practical implementations of MR-DFT rely on empirically chosen generator coordinates, which may omit relevant collective degrees of freedom and thus fail to capture sufficient collective correlations. Here we introduce the stochastic-basis multireference density functional theory (MR-SDFT). This is an extended scheme that augments the MR-DFT toolkit by (i) generating a diverse ensemble of mean-field reference configurations via a stochastic external field and (ii) selecting a compact subspace with Projection-Selection method. The chosen reference configurations are then linearly superposed within the MR-DFT framework to yield spectroscopic observables. Applying this framework to \nuclide[20]{Ne}, \nuclide[24]{Mg} and \nuclide[28]{Si} with the covariant density functional theory (CDFT), it is demonstrated that the MR-SCDFT leads to lower ground-state energies, smaller point-proton rms radius, and a softer ground-state band compared to the conventional MR-CDFT.

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nucl-th 2026-05-04

Two-body currents increase neutrino cross sections

Two-body current and axial form factor effects in charged-current quasielastic neutrino-nucleus scattering within the NEUT event generator

The boost comes from transverse response enhancement, with axial form factor updates adding further changes tested against T2K and MINERvA

abstract click to expand

We present a charged-current quasielastic neutrino-nucleus scattering model based on an unfactorized representation of the spectral function, employing relativistic momentum distributions for bound nucleons and the relativistic distorted-wave impulse approximation with an energy-dependent relativistic potential to describe the scattered nucleon. The model incorporates two-body meson-exchange currents contributing to one-particle-one-hole final states and tests several axial form factor parametrizations, including recent LQCD and MINERvA fits. It is implemented in the NEUT event generator and benchmarked against T2K and MINERvA ${\nu}_{\mu}$-$^{12}$C CC0${\pi}$ measurements. We find that two-body meson-exchange currents lead to a sizeable increase of the total cross section, arising from an enhancement of the transverse response, which is the dominant component in charged-current neutrino scattering. On the other hand, recent fits of the axial form factor predict larger values than the standard dipole form, yielding a systematic enhancement of the cross section. The LQCD+MINERvA parametrization tends to overestimate the data, while the MINERvA-only fit provides a more moderate increase. Overall, no single configuration consistently provides the best agreement with the different datasets.

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nucl-th 2026-05-04

Λp spectrum structures depend on ΣN scattering lengths

Hyperon-nucleon interaction through the K^-dtoπΛ N reaction

Calculations of K- d to π- Λ p reaction show threshold features that vary with the sign of the I=1/2 scattering length and can constrain the

abstract click to expand

The hyperon-nucleon interaction is investigated through the final-state interaction in the $K^-d\to\pi^-\Lambda p$ reaction. We focus on the $\Lambda N$-$\Sigma N$ coupled-channel interaction, which produces characteristic structures around the $\Sigma N$ thresholds in the $\Lambda p$ invariant mass spectrum. The spin-triplet $\Sigma N\to\Lambda p$ conversion amplitude is constructed within the $K$-matrix formalism using scattering lengths in the isospin basis. We first examine the dependence of the conversion amplitude on the $\Sigma N$ scattering lengths and find that the threshold structure is particularly sensitive to the sign of the real part of the $I=1/2$ scattering length. We then calculate the $\Lambda p$ invariant mass spectrum of the $K^-d\to\pi^-\Lambda p$ reaction, including the contributions from the background diagrams. The resulting spectra show characteristic structures around the $\Sigma N$ thresholds, whose shapes depend on the choice of the interaction parameters. These results suggest that the $\Lambda p$ invariant mass spectrum can serve as a useful observable for constraining the $\Lambda N$-$\Sigma N$ coupled-channel interaction.

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nucl-th 2026-05-04

Metropolis walk matches overdamped Langevin for fission

Comparative Study of Langevin and Random Walk Models for Nuclear Fission in the Overdamped Regime

Lighter actinides produce identical mass distributions; heavier nuclei show extra symmetric splits from residual inertia.

abstract click to expand

We present a comparative study of Langevin dynamics and a Metropolis random walk model applied to thermal neutron-induced fission of $^{229}$Th, $^{235}$U, $^{239}$Pu, $^{245}$Cm, $^{249}$Cf, and $^{255}$Fm. Both methods are implemented within an identical four-dimensional Fourier-over-Spheroid framework, using potential energy surfaces derived from the macroscopic-microscopic model. We show that the Metropolis walk corresponds to the overdamped limit of the Langevin equations and confirm this correspondence numerically by Langevin calculations performed in the strongly damped regime and with quantum corrections to the random force switched off. Under these conditions, the two approaches produce essentially identical mass distributions for the lighter actinides. Systematic deviations develop for the heavier actinides, where the Langevin dynamics yields a non-negligible symmetric fission component absent in the random walk results. We trace this difference to the kinematic structure of the Metropolis sampling and to the residual inertial dynamics retained in the Langevin framework. A parallel comparison of Langevin calculations with and without the quantum-corrected effective temperature $T^*$ isolates the contribution of zero-point fluctuations and suggests that their standard phenomenological treatment may overestimate their impact in certain cases. Both approaches qualitatively reproduce the asymmetric peak positions and their systematic evolution across the actinide chain, while a common quantitative limitation -- the narrowness of the predicted distributions -- points to the role of higher-dimensional deformation modes not included in the present parametrization.

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nucl-th 2026-05-04

Multiple rho mass solutions appear from quark dimension reduction in magnetic fields

rho mesons in finite magnetic field and finite temperature

Lowest solutions rise or saturate with field strength, match lattice data, then drop toward quark-mass sums at high temperature.

abstract click to expand

The mass spectra of $\rho$ mesons ($\rho_{Q=\pm 1}^{s_z=0,\pm 1}$ and $\rho_{Q=0}^{s_z=0,\pm 1}$) at finite magnetic field and temperature are studied in frame of the two-flavor Nambu-Jona-Lasinio model. Fully considering the breaking of translational invariance induced by external magnetic field, the analytical form of $\rho$ meson propagators have been derived in the Ritus scheme and Schwinger scheme, which gives the same algebraic formula. When solving the pole equation of $\rho$ meson propagators, multiple solutions of the meson mass appear due to the dimension reduction of their constituent quarks in magnetic fields. At vanishing temperature, we focus on the $\rho$ meson masses $M_{\rho}$ corresponding to the lowest value solution of the pole equation. $M_{\rho^{-}_+}$, $M_{\rho^{0}_+}$ and $M_{\rho^{\pm}_0}$ increase with magnetic field. $M_{\rho^{+}_+}$ firstly decreases and then becomes saturated with increasing magnetic field. $M_{\rho^0_0}$ is not sensitive to magnetic field. These results are consistent with the available LQCD simulations. At finite temperature, we discuss the lowest four/five solutions of $\rho$ meson masses $M^{i=0,1,2,3,4}_{\rho}$. With fixed magnetic field, they decrease with temperature, and approach the mass sum of their constituent quarks at high temperature. The mass solution $M^{i}_{\rho}$ for different mesons $\rho_+^{0,\pm}$ and $\rho_0^{0,\pm}$ may become degenerate at finite magnetic field and temperature.

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nucl-th 2026-05-01

Thermal hadron changes calculable by EFTs and lattice QCD

Hadron properties at finite temperature

Review combines imaginary-time formalism, chiral methods and lattice data to connect finite-temperature theory with collision observables.

abstract click to expand

This review provides an overview of thermal effects on hadron properties, focusing on the theoretical frameworks used to describe in-medium modifications of masses, decay widths, and spectral functions. We examine the application of finite-temperature quantum field theory -- specifically the imaginary-time formalism (ITF) -- to analyze both light- and heavy-hadron sectors. For light hadrons, we discuss the role of chiral symmetry restoration and the different definitions of thermal masses in effective field theories, like chiral perturbation theory. In the heavy-flavor sector, we review recent progress in describing open-heavy mesons and quarkonia using self-consistent unitarized approaches and nonrelativistic effective field theories. All these results are complemented by analyses of recent lattice-QCD calculations using the Euclidean formulation of QCD at finite temperature, relevant to extract screening masses and reconstructed spectral functions. Finally, we discuss the phenomenological impact of the thermal modifications on experimental observables in relativistic heavy-ion collisions, including numerical simulations, dilepton spectra, transport coefficients, and hadron femtoscopy. By combining phenomenological considerations with robust theoretical tools, this review provides a coherent picture of how thermal effects emerge in the hadronic phase and how they can be systematically studied within controlled frameworks. Ultimately, the discussion serves as a bridge between experimental observations in relativistic heavy-ion collisions and fundamental developments in finite-temperature QCD and effective field theories for hadronic systems.

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nucl-th 2026-05-01

Parity-doublet nucleons link chiral restoration to neutron-star equations of state

Chiral Symmetry and Its Restoration in QCD

Effective models show how positive- and negative-parity baryons become degenerate as the chiral condensate melts, allowing consistent dense-

abstract click to expand

We first note the peculiar property of the pion as the pseudoscalar particle, which play the essential role in realizing the basic properties of the nuclear matter such as the density/energy saturations. Then, we introduce the notion of chirality using the Dirac equation, and show how chiralities are mixed in the massive Dirac field with an emphasis on the similarity with the Bogoliubov-Valatin theory of superconductivity. After noting the approximate chiral symmetry in QCD in the light quark sector, we introduce the notion of the spontaneous symmetry breaking, and the Nambu-Goldstone theorem. A remark is given on the U(1)$_A$ anomaly and its physical consequences. Several chiral quark models of the Nambu-Jona-Lasinio type are introduced with an emphasis to the relevance to QCD, and discuss some consequences of the models. A three-flavor linear sigma model with the determinant term is examined, and discuss the origin of the mass term of the $\eta'$ meson. A parity-doublet model for nucleons is introduced, and the current active effort is described to construct the equation of state of nuclear and neutron-star matter incorporating the parity-doubling in the baryon sector and the occurrence of the restoration of chiral symmetry in the QCD matter. An intuitive account is given on how the chiral condensate may be reduced on the basis of Hellmann-Feynman theorem. We describe some experiments to explore the chiral restoration in hot and/or dense medium, such as the pionic atoms, lepton-pair production in relativistic-heavy-ion collisions, an attempt to produce $\eta'$-mesonic nuclei, and so on.

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nucl-th 2026-05-01

Electron decay energy is linear in mass number A for Z<47

Linear Dependence of Electron-Decay Maximum Energy on the Mass Number A Along Isotopic Chains For Z<47

Even-A and odd-A nuclei follow separate near-unit fits, yielding simple slope and intercept parameters for each element.

abstract click to expand

We investigate the systematics of the maximum Electron-decay energy E as a function of the mass number A along isotopic chains with a fixed proton number across Z<47. By making use of the available curated nuclear data, we find that, for each fixed Z, the decay energy can be described to excellent accuracy by a linear dependence on A, provided that even-A and odd-A isotopes are treated separately. This yields two straight-line trends for each element, which are characterized by the slope and intercept parameters that can be systematically tabulated across the studied range. The corresponding fits are remarkably accurate, where the coefficients of determination are typically almost unity. Such an element-by-element empirical regularity does not appear to have been previously tabulated in a compact systematic form in the nuclear physics literature. We hence provide a simple and compact parameterization of Electron-decay energetics along isotopic chains with respect to our stated scope, whereby the approach at hand may prove useful for the analysis of decay-energy evolution, behavioral classification, and preliminary estimates of Electron-decay properties. The broader theoretical motivation that initially led us to search for such a regularity is discussed only after the confirmation of our results through experimental data is established.

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nucl-th 2026-05-01

Momentum-dependent mean field fits STAR data at 3 GeV

Proton and kaon production in Au+Au collisions at sqrt{s_{rm NN}}=3 GeV

Proton and kaon spectra and flows in Au+Au collisions are reproduced only when the nuclear potential depends on particle momentum.

abstract click to expand

Within an extended isospin- and momentum-dependent Boltzmann-Uehling-Uhlenbeck transport model, we study the protons, $K^+$ mesons and $\Lambda$ hyperons production in Au+Au collisions at $\sqrt{s_{\rm NN}}=3$ GeV. For the collision in 0-10% centrality, we study the transverse momentum spectra and rapidity dependent mean transverse momentum for protons. For the collision in 10-40% centrality, we study the directed and elliptic flows for protons and $K^+$ mesons. The results show that the momentum-dependent nuclear mean field with an incompressibility $K_0=230$ MeV can fit fairly the STAR experimental data, while the momentum-independent nuclear mean field with both $K_0=230$ MeV and $K_0=380$ MeV can only partially describe the experimental results. In addition, we also study the directed and elliptic flows for the associated $\Lambda$, observations reveal the same conclusions as for kaons. These findings indicate that the momentum dependence of nuclear mean field plays a significant role in understanding nuclear matter properties in heavy-ion collisions at $\sqrt{s_{\rm NN}}=3$ GeV.

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nucl-th 2026-05-01

Lattice QCD predicts 3.5 MeV binding for J/ψ with n and 10Be

Examination of the cbar{c}+n+¹⁰Be bound-state problem within three cluster models based on QCD charmonium-nucleon interactions

Three-cluster calculations with folded HAL QCD potentials yield weakly bound states of 2-3.5 MeV and radii near 2.5 fm for J/ψ and η_c plus

abstract click to expand

The possible bound state of the $c\bar{c}+n+^{10}$Be system, representing a hypothetical charmonium-nucleus configuration, is investigated. The analysis is conducted within a three-cluster framework, in which the binary subsystems are treated as $n+^{10}\textrm{Be}$, $^{10}\textrm{Be}+c\bar{c}$, and $c\bar{c}+n$. The hyperspherical harmonics method is employed to provide a convenient description of this three-cluster configuration. The calculations are performed using effective $^{10}\textrm{Be}\textrm{-}c\bar{c}$ potentials constructed via the single-folding procedure. These potentials have been derived recently on the basis of state-of-the-art lattice QCD results from the HAL QCD Collaboration, which provided interactions for the spin-$3/2$ $J/\psi N$, spin-$1/2$ $J/\psi N$, spin-$1/2$ $\eta_{c}N$, and spin-averaged $J/\psi N$ channels, all obtained at nearly physical pion masses. The numerical results indicate that the central binding energies of the spin-$3/2$ $J/\psi+n+^{10}$Be, spin-$1/2$ $J/\psi+n+^{10}$Be, and spin-$1/2$ $\eta_{c}+n+^{10}$Be systems are 3.47, 3.55, and 1.91 MeV, respectively. The corresponding root-mean-square nuclear matter radii are predicted to be approximately 2.49, 2.48, and 2.60 fm.

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nucl-th 2026-05-01

Coulomb barrier isolates s-wave neutron tails near threshold

Probing Near-Threshold s-Wave Components in Heavy Nuclei via Coulomb-Assisted Neutron Transfer

Low-energy backward (d,p) reactions localize transfer to exterior wave functions, revealing near-threshold s-wave strength distributions.

abstract click to expand

We propose a method to probe weakly bound s-wave neutron components near the neutron emission threshold in heavy nuclei using Coulomb-assisted neutron transfer reactions. Weakly bound s-wave neutrons have large asymptotic amplitudes, which are difficult to access directly with conventional methods. This work focuses on the $(d,p)$ reaction at low incident energies and backward angles, where the reaction is localized in the nuclear exterior due to the Coulomb barrier. Under these conditions, the transition amplitude becomes sensitive to the asymptotic part of the single-particle wave function. Finite-range DWBA calculations show that the cross section for weakly bound states exhibits a weak dependence on incident energy, while that for strongly bound states decreases rapidly with decreasing energy. Contributions from orbitals with $l \geq 1$ are suppressed by the centrifugal barrier, resulting in selectivity for s-wave components. This method provides a probe of the strength distribution of weakly bound s-wave components near threshold and the asymptotic structure of their wave functions.

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nucl-th 2026-05-01 2 theorems

Analytical hydro model with core-corona fits quarkonium spectra at LHC

Quarkonium p_{rm T} spectra in heavy--ion collisions at LHC energies within a hydrodynamic core--corona framework

Cylindrical symmetry plus Hubble-like flow plus thermal-nonthermal split reproduces charmonium and bottomonium pT data from ALICE and CMS.

abstract click to expand

We present a systematic study of the transverse momentum ($p_{\rm T}$) spectra of charmonium (J/$\psi$, $\psi(2S)$) and bottomonium ($\Upsilon(nS)$) states in Pb-Pb collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV within an analytical relativistic hydrodynamics framework. The medium evolution is described assuming cylindrical symmetry with boost-invariant longitudinal expansion and Hubble-like transverse flow. Quarkonium spectra are evaluated using the Cooper-Frye formalism on a constant-temperature freeze-out hypersurface, supplemented by a core--corona approach to include both thermal and non-thermal contributions. The model describes the measurements from ALICE and CMS over a broad $p_{\rm T}$ range. For charmonium, both the spectra and the $\psi(2S)$/J/$\psi$ ratio are well reproduced, while deviations at high $p_{\rm T}$ for J/$\psi$ indicate additional hard production mechanisms. In the bottomonium sector, the $\Upsilon(nS)$ spectra and their yield ratios are successfully described, consistent with the expected sequential suppression pattern. These results demonstrate that an analytical hydrodynamic approach combined with a core-corona framework provides a unified and transparent description of quarkonium production in heavy--ion collisions at LHC energies.

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nucl-th 2026-05-01

Hydrodynamic core-corona model matches quarkonium spectra at LHC

Quarkonium p_{rm T} spectra in heavy--ion collisions at LHC energies within a hydrodynamic core--corona framework

Reproduces charmonium and bottomonium pT distributions and ratios over a broad range in Pb-Pb collisions at 5.02 TeV.

abstract click to expand

We present a systematic study of the transverse momentum ($p_{\rm T}$) spectra of charmonium (J/$\psi$, $\psi(2S)$) and bottomonium ($\Upsilon(nS)$) states in Pb-Pb collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV within an analytical relativistic hydrodynamics framework. The medium evolution is described assuming cylindrical symmetry with boost-invariant longitudinal expansion and Hubble-like transverse flow. Quarkonium spectra are evaluated using the Cooper-Frye formalism on a constant-temperature freeze-out hypersurface, supplemented by a core--corona approach to include both thermal and non-thermal contributions. The model describes the measurements from ALICE and CMS over a broad $p_{\rm T}$ range. For charmonium, both the spectra and the $\psi(2S)$/J/$\psi$ ratio are well reproduced, while deviations at high $p_{\rm T}$ for J/$\psi$ indicate additional hard production mechanisms. In the bottomonium sector, the $\Upsilon(nS)$ spectra and their yield ratios are successfully described, consistent with the expected sequential suppression pattern. These results demonstrate that an analytical hydrodynamic approach combined with a core-corona framework provides a unified and transparent description of quarkonium production in heavy--ion collisions at LHC energies.

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nucl-th 2026-04-30 2 theorems

Momentum conservation corrects jet correlators for medium effects

Probing Jet-Medium Interactions in Heavy-Ion Collisions Using Energy-Energy Correlators

This allows comparisons between heavy-ion and proton collisions to test jet energy loss inside the quark-gluon plasma followed by fragmenta

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Energy-energy correlators (EECs) provide a sensitive probe of both perturbative and nonperturbative dynamics in relativistic heavy-ion collisions. Jet-medium interactions enhance particle multiplicity within the jet cone, which must be properly accounted for when extracting the EEC of jet shower hadrons in experiments. To address this issue, we develop an augmentation method that exploits momentum conservation between the near-side and away-side regions, using $\gamma$-jet events with 0-10\% centrality in Pb+Pb collisions at $\sqrt{s_{NN}} = 5.02$ TeV simulated with the CoLBT-hydro model. This approach yields an experimentally reconstructed EEC that shows improved agreement with the EEC of hadrons originating primarily from jet parton splittings. Comparing EECs of jets from Pb+Pb and p+p collisions with different matching conditions can be sensitive to jet medium interaction dynamics, and provide a novel means to test the scenario of jet energy loss in the QGP, followed by fragmentations outside the QGP.

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nucl-th 2026-04-30

Anisotropy scaling functions collapse across species in hydro simulations

Species-Resolved Scaling of Azimuthal Anisotropy: Constraining Attenuation, Collective Expansion, and Hadronic Dynamics in Hydrodynamic Simulations

Robust collapse of v2 and v3 scaling constrains attenuation and collective expansion in Pb+Pb collisions at two LHC energies.

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Species-resolved azimuthal anisotropy scaling functions are constructed from identified particle $v_2$ and $v_3$ obtained from event-by-event iEBE-VISHNU simulations for Pb+Pb collisions at $\sqrt{s_{NN}}=2.76$ and $5.02$~TeV. The scaling functions exhibit a robust collapse across transverse momentum, centrality, particle species, and beam energy, indicating a common and tightly constrained scaling structure. High scaling fidelity yields quantitative agreement with the data-defined reference through an energy-dependent attenuation baseline $\beta_0$ in central to mid-central collisions and a centrality-dependent modification of the effective attenuation in more peripheral collisions, with only a weak dependence on $\sqrt{s_{NN}}$. The multiplicity dependence of the extracted scaling parameters reflects the interplay of EOS-driven collective expansion, finite system lifetime, and hadronic re-scattering. These results demonstrate that the scaling framework provides a quantitative, constraint-driven probe of the hydrodynamic response, enabling the disentanglement and constraint of the coupled contributions to azimuthal anisotropy.

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nucl-th 2026-04-30

χEFT forces concentrate nuclear wave functions in U(4) symmetry

Unmasking Hidden Wigner's Symmetry from First Principles

Majority of ^4He, ^6Li and ^6He states fit into few supermultiplet representations without prior constraints, enabling smaller accurate NCSM

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We present quantitative evidence that high-quality internucleon forces derived from $\chi$EFT exhibit a striking dominance of Wigner's supermultiplet symmetry, without invoking the large-$N_c$ limit of QCD or assumptions about specific nuclei. We trace the manifestation of this symmetry in nuclear structure using the \textit{ab initio} Symmetry Adapted Model (SAM) and identify suppressed spin-isospin polarizability. Our calculations show that a majority of $\rm ^4He$, $\rm ^6Li$, and $\rm ^6He$ wave functions is concentrated in a few $\rm U(4)$ irreducible representations, without imposing any \textit{a priori} constraints on the model space. This emergent feature points to a strategy for reducing explosive many-body bases of the NCSM while retaining physically important configurations needed to compute observables.

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nucl-th 2026-04-30

Nuclear models agree within 1% on neutron-star outer-crust effects

Outer-Crust Equations of State for Neutron Stars

Differences in deep-crust composition change radius and moment of inertia by less than one percent in crust-sensitive stars.

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The equation of state of the neutron-star outer crust is sensitive to nuclear mass predictions and provides a direct connection to properties of nuclei throughout the nuclide map, including those beyond experimental reach. We quantify the impact of contemporary nuclear mass models on the composition and thermodynamic properties of the outer crust, and assess the consequences for crust-dominated neutron-star configurations near the minimum-mass limit. We constructed four outer-crust equations of state based on the relativistic energy density functional and machine-learning mass model tables. The equilibrium composition of cold catalyzed matter in $\beta$-equilibrium was obtained by minimizing the Gibbs free energy per baryon, and the resulting equations of state were implemented in neutron-star structure calculations. The different mass inputs lead to variations in the equilibrium nuclide sequence, distinct last bound nuclei, and moderate shifts in the neutron-drip density. In contrast, the associated thermodynamic properties, as well as the minimum-mass neutron-star configurations, remain closely aligned across the four outer-crust equations of state. The model dependence of the outer crust is primarily reflected in the detailed nuclide composition and in the precise location of neutron drip. Nevertheless, the considered outer-crust equations of state yield closely consistent predictions for the relevant neutron-star observables, providing a reliable input for stellar modelling.

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nucl-th 2026-04-30 Recognition

Nuclear mass models leave outer-crust equations of state consistent

Outer-Crust Equations of State for Neutron Stars

Composition changes but thermodynamic properties and minimum neutron star masses align across four models

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The equation of state of the neutron-star outer crust is sensitive to nuclear mass predictions and provides a direct connection to properties of nuclei throughout the nuclide map, including those beyond experimental reach. We quantify the impact of contemporary nuclear mass models on the composition and thermodynamic properties of the outer crust, and assess the consequences for crust-dominated neutron-star configurations near the minimum-mass limit. We constructed four outer-crust equations of state based on the relativistic energy density functional and machine-learning mass model tables. The equilibrium composition of cold catalyzed matter in $\beta$-equilibrium was obtained by minimizing the Gibbs free energy per baryon, and the resulting equations of state were implemented in neutron-star structure calculations. The different mass inputs lead to variations in the equilibrium nuclide sequence, distinct last bound nuclei, and moderate shifts in the neutron-drip density. In contrast, the associated thermodynamic properties, as well as the minimum-mass neutron-star configurations, remain closely aligned across the four outer-crust equations of state. The model dependence of the outer crust is primarily reflected in the detailed nuclide composition and in the precise location of neutron drip. Nevertheless, the considered outer-crust equations of state yield closely consistent predictions for the relevant neutron-star observables, providing a reliable input for stellar modelling.

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nucl-th 2026-04-30

Neutron skin data tighten symmetry energy limits for neutron stars

Neutron Stars and Neutron Skins: Connecting Finite Nuclei to Dense Matter

Bayesian fusion of nuclear experiments and models links lab nuclei to dense matter properties.

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This is a brief overview of the connection between neutron skin thickness in finite nuclei and the equation of state of neutron-rich matter, with applications to neutron stars. Multiple experimental probes are discussed, including dipole polarizability, parity-violating electron scattering, heavy-ion fragmentation, quasi-free scattering, and ultraperipheral collisions. A consistent picture emerges from Bayesian analyses combining experimental data and energy density functionals, providing constraints on the symmetry energy and its slope.

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nucl-th 2026-04-30

Multi-particle correlators amplify non-flow bias in small systems

Effectiveness of nonflow suppression using multi-particle correlators

Toy models of particle decay and momentum conservation show higher-order correlators deviate further from true flow than standard estimators

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As flow estimators, multi-particle correlators, particularly the higher-order ones, are generally regarded as effective tools for suppressing non-flow contributions. In this work, however, using two well-known toy models that simulate non-flow effects, we demonstrate that multi-particle correlators can, especially in small systems, yield estimates that deviate even further from the underlying flow harmonics than those obtained from other conventional approaches. The two toy models considered here are designed to mimic non-flow effects arising from particle decay and global momentum conservation, such that the {\it apparent} harmonic coefficients become significantly different from the {\it input} values. We provide an analytic explanation for the observed behavior of flow estimates based on multi-particle correlators. Specifically, in the toy model mimicking particle decay, we elucidate the oscillations observed in $v_2\{2\}$ and $v_2\{4\}$. For the other toy model simulating momentum conservation, we show that multi-particle cumulants introduce a deformation in the collective flow that is unique to multi-particle correlators. Additionally, we compare these results with those obtained using the maximum-likelihood estimation method, a recently proposed flow estimator that serves as a viable alternative to traditional techniques.

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nucl-th 2026-04-30

Two modes explain 99.5% of spectral fluctuations in heavy-ion collisions

Thermal and geometric normal modes of spectral fluctuations in heavy-ion collisions

PCA plus physical rotation isolates thermal and geometric contributions that drive observed v0(pT) and v02(pT) signals.

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The transverse momentum spectrum of charged particles in ultra-relativistic heavy-ion collisions fluctuates event-by-event, encoding signatures of underlying collective dynamics. Such fluctuations originate from a combined effect of thermal and geometric fluctuations in the initial state. We present a direct decomposition of these spectral fluctuations through principal component analysis performed on the joint covariance structure of normalized spectrum, mean transverse momentum and elliptic flow squared. The first two leading modes explain 99.5\% of the total variance, and are orthogonally rotated by imposing physical constraints motivated by the initial state thermal and geometric response. The resulting thermal and geometric modes bear direct analogy with the vibrational normal modes of a linear triatomic molecule. The thermal mode entirely drives the experimentally measured $v_0(p_T)$, while the geometric mode contributes substantially to $v_{02}(p_T)$ in non-central collisions, providing a transparent explanation of its characteristic low-$p_T$ sign change. The study establishes the first physically motivated interpretation of principal component modes in the field of heavy-ion collisions and provides an experimental window into the thermo-geometric structure of the QGP initial state.

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nucl-th 2026-04-30

Truncation may explain Hoehler pole clustering in pi N scattering

Possible explanation of Hoehler's clustering: effective partial-wave mixing induced by truncation

Cutting the partial-wave series for practical extraction mixes angular momenta and lets poles from different waves share content at common e

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Hoehler noted that resonance poles obtained from different partial waves in $\pi N$ scattering appear to bunch together near a small set of common complex energies, and suggested that this could indicate mixing between angular momenta. Here, we examine whether at least part of this pattern could arise effectively from the extraction procedure itself. Exact partial-wave unitarity preserves the separation of angular momenta in the infinite problem, whereas practical pole extraction from bilinear observables requires truncation of the partial-wave series. Combined with the truncation-induced mixing mechanism established in Ref.~\cite{Svarc2026}, this provides a natural source by which fitted partial-wave coefficients can inherit overlapping pole-bearing content, thereby offering a plausible contribution to Hoehler-type clustering.

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nucl-th 2026-04-29

Low-rank Hamiltonian updates shrink A-body problems to small matrices

Exact emulation of few-body systems at low cost

At fixed energy the full A-body equation collapses exactly to a matrix whose size equals only the rank of the update, enabling cheap exactem

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Effective field theories have established themselves as key pillars of modern nuclear physics. They enable a quantitative understanding of the strong nuclear force, provided low-energy constants that parametrize short-distance physics can be determined from experimental data. This, however, often becomes prohibitively expensive due to a significant computational cost of solving the A-body problem. The computational challenge is particularly severe for three-body forces, which are at the frontier of nuclear and atomic physics and play an important role in the equation of state of neutron stars. Here we prove that for a parametric low-rank update of a Hamiltonian, the A-body problem at a fixed energy exactly reduces to a low-dimensional matrix equation regardless of the size of the Hilbert space. As a proof-of-principle, we present exact and computationally cheap snapshot-based emulators for few-body scattering and bound states. Unlike alternatives, our emulators can be used far away from the snapshot region without loss of precision and yield accurate results for parameter values not accessible using conventional solution techniques. Our approach is not restricted by the interaction type, number of particles, and methods for generating snapshots and can be applied to mitigate the computational burden of the A-body problem to a broad class of problems in nuclear, atomic, and molecular physics.

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nucl-th 2026-04-29

Neural networks minimize Skyrme functionals for nuclear densities

Neural-Network-Based Variational Method in Nuclear Density Functional Theory: Application to the Extended Thomas-Fermi Model

The perceptron-based variational method matches extended Thomas-Fermi binding energies to 0.5% and reproduces pasta structures.

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We propose a neural-network-based variational framework for nuclear Density Functional Theory based on the extended Thomas--Fermi (ETF) model, in which proton and neutron number densities are represented by multilayer perceptrons and determined by direct minimization of a Skyrme-type energy density functional. We clarify the mathematical connection to the conventional Euler--Lagrange formulation, showing that stationarity in parameter space corresponds to a projected Euler--Lagrange condition on the neural-network trial-density manifold. The basic validity of the framework is examined through three sets of calculations: a Woods--Saxon potential benchmark, ground-state calculations of finite nuclei ($^{40}$Ca, $^{90}$Zr, and $^{208}$Pb), and nuclear pasta phases. The binding energies of finite nuclei agree with existing ETF calculations to within $0.5\%$, and representative pasta structures including spheres, rods, and slabs are reproduced. We also find that single-precision arithmetic yields results comparable to double precision, suggesting that the present framework is well suited to GPU environments in which low-precision computation is advantageous.

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nucl-th 2026-04-29 Recognition

Neural networks minimize nuclear densities directly

Neural-Network-Based Variational Method in Nuclear Density Functional Theory: Application to the Extended Thomas-Fermi Model

Multilayer perceptrons reproduce ETF binding energies to 0.5 percent and pasta structures while working with single-precision arithmetic.

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We propose a neural-network-based variational framework for nuclear Density Functional Theory based on the extended Thomas--Fermi (ETF) model, in which proton and neutron number densities are represented by multilayer perceptrons and determined by direct minimization of a Skyrme-type energy density functional. We clarify the mathematical connection to the conventional Euler--Lagrange formulation, showing that stationarity in parameter space corresponds to a projected Euler--Lagrange condition on the neural-network trial-density manifold. The basic validity of the framework is examined through three sets of calculations: a Woods--Saxon potential benchmark, ground-state calculations of finite nuclei ($^{40}$Ca, $^{90}$Zr, and $^{208}$Pb), and nuclear pasta phases. The binding energies of finite nuclei agree with existing ETF calculations to within $0.5\%$, and representative pasta structures including spheres, rods, and slabs are reproduced. We also find that single-precision arithmetic yields results comparable to double precision, suggesting that the present framework is well suited to GPU environments in which low-precision computation is advantageous.

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nucl-th 2026-04-29

Fission barriers generated for 3300 heavy nuclei with BSkG3

Large-scale fission data generation with BSkG3

Calculations cover triaxial and octupole shapes plus odd nuclei to supply rates needed for r-process models.

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Modeling fission properties, such as barriers and rates, is highly challenging. The most microscopic methods available are based on energy density functionals (EDFs) and rely on a limited set of collective coordinates to describe the evolution of a fissioning nucleus from its ground state to scission. Leveraging the efficiency of the MOCCa nuclear structure code and the predictive power of the BSkG3 EDF, we systematically study fission properties of the heaviest nuclei (roughly 3,300) accounting for (1) axial, triaxial and octupole moment; (2) all nuclei, including odd and odd-odd systems; and (3) fission paths determined via the least-action principle. We present the set of primary fission barriers and spontaneous fission half-lives we obtain and discuss their implications for r-process nucleosynthesis.

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nucl-th 2026-04-29

Coulomb shifts He-3 radii by 4% in pionless EFT

Coulomb Effects and Wigner-SU(4) Symmetry in He-3 Charge and Magnetic Properties

Corrections reach four percent for charge and magnetic radii but only 0.2 percent for the magnetic moment, requiring inclusion at N2LO.

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This work studies the non-perturbative Coulomb corrections to the He-3 binding energy, magnetic moment, and charge and magnetic radii in leading-order (LO) Pionless Effective Field Theory (Pionless EFT). The splitting between He-3 and H-3 binding energy is found to be 0.85(3) MeV. The Coulomb corrections to the He-3 point charge radius and full magnetic radius are found to be 0.043(2) fm and 0.036(2) fm, respectively. These corrections are 4% of the LO predictions without Coulomb and should be taken into account at next-to-next-to-leading order or beyond in Pionless EFT to achieve the desired EFT accuracy. The Coulomb correction to the He-3 magnetic moment is found to be -0.0041(1)$\mu_N$, only 0.2% of the LO prediction without Coulomb. The impact of Wigner-SU(4) symmetry in the presence of the non-perturbative Coulomb interaction is also discussed and used to help explain the hierarchy of Coulomb effects in He-3 observables.

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nucl-th 2026-04-29

³H clustering peaks at ¹²B in boron from asymmetry boost

Effect of neutron-proton asymmetry on the ³H clustering in Boron isotopes

The SF(³H)/SF(α) ratio isolates how neutron-proton imbalance counters neutron skin suppression across the isotopic chain.

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To investigate the influence of neutron-proton asymmetry on the formation of asymmetric clusters, we perform a systematic comparative study of $^{3}$H and $\alpha$ cluster preformation in the Boron isotopic chain ($^{11-14}$B). Within the framework of Antisymmetrized Molecular Dynamics (AMD), we compute the nuclear wave functions and subsequently extract the reduced width amplitudes (RWA) and spectroscopic factors (SF). The results show that the $\alpha$ cluster SF exhibits a monotonic decrease with increasing neutron number, consistent with the established suppression effect of the neutron skin. In contrast, the $^{3}$H cluster SF displays a non-monotonic behavior, peaking at $^{12}$B. This distinct trend indicates that the formation of the asymmetric $^{3}$H cluster is subject to a competition between suppression from the neutron skin and an enhancement driven by the neutron-proton asymmetry of the parent nucleus. We successfully isolate this enhancement effect by analyzing the ratio of the SFs, SF($^{3}$H)/SF($\alpha$). This approach not only quantifies the enhancement but also proposes the SF ratio as a robust experimental observable for probing insights into asymmetric clustering phenomena.

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nucl-th 2026-04-28

Scaled thermal masses align viscosity calculations for quark-gluon plasma

Chapman-Enskog calculation of the shear viscosity of quark-gluon plasma including all 2leftrightarrow 2 scatterings at finite temperature

Screening masses scaled by 0.4 align viscosity calculations and give eta/s of 0.15 at the transition for coupling at 3T

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We use the Chapman-Enskog method to investigate the shear viscosity of the quark-gluon plasma with a focus on its relation to parton cross sections. We use the recently obtained analytical expression for the shear viscosity $\eta$ of a massless quark-gluon gas at chemical equilibrium with Boltzmann statistics and all $2\leftrightarrow 2$ scatterings with arbitrary cross sections. Here we apply this general expression to cross sections at finite temperature that are based on perturbative-QCD and screened with scaled thermal masses $\sqrt{\kappa}\,m_D$ and $\sqrt{\kappa}\,m_F$. We find that the Chapman-Enskog results on $\eta \, g^4/T^3$ versus $m_D/T$ at $\kappa=1$ are qualitatively similar to but higher than the corresponding leading-order results from the AMY framework. We then find that using $\kappa=0.4$ allows the Chapman-Enskog results to match well the corresponding AMY results as it includes the effect of using thermal masses (instead of self-energies) to screen the cross sections. In addition, we show that the shear viscosity-to-entropy density ratio $\eta/s$ is very sensitive to the choice of momentum scale $Q$ in the strong coupling, where the choice of $Q=3T$ leads to $\eta/s \sim 0.15$ for $N_f=0$ or 3 at the QCD phase transition temperature $T_c$. These results lay the foundation for mapping parton cross sections to given shear viscosity in parton transport models and QCD effective kinetic theory.

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nucl-th 2026-04-28

Nuclear many-body theory extends Fermi beta-decay model to neutrino scattering in nuclei

Neutrino Cross Sections: Low Energy

The resulting cross sections and mean free paths improve modeling of neutrino transport in supernovae and neutron-star cooling.

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Low-energy neutrino interactions with isolated nucleons are accurately described by the effective theory based on Fermi's groundbreaking description of neutron $\beta$-decay. On the other hand, the extension of this scheme to the case of neutrino interactions with nuclear matter -- the understanding of which is critical for the description of a variety of astrophysical processes -- involves non trivial difficulties, originating from the complexity of nuclear structure and dynamics. This chapter provides a concise introduction to the formalism of nuclear many-body theory, suitable to perform theoretical calculations of the nuclear matter response to neutrino interactions, as well as a detailed analysis of the relevant reaction mechanisms. The neutrino mean free path in nuclear matter and its implications for the description of astrophysical processes are also discussed.

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nucl-th 2026-04-28

One transformation generates both forces and currents for deuteron breakup

Field-theoretical description of the deuteron breakup in the clothed particle representation

The same clothing transformation that produces the Kharkiv potential also yields consistent one- and two-body electromagnetic operators for

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We present a field-theoretical description of the deuteron electrodisintegration reaction d(e,e'p)n induced by unpolarized and polarized electrons. The approach combines the Lehmann-Symanzik-Zimmermann in(out) formalism with the clothed particle representation in the instant form of relativistic dynamics, providing a fully relativistic and gauge-independent framework based on the Fock-Weyl criterion. Within the method of unitary clothing transformations, one and the same transformation that generates the relativistic nucleon-nucleon interaction (the Kharkiv potential) also induces a fresh family of electromagnetic current operators. As a result, one-body and two-body (meson-exchange) currents emerge on a common footing. We compute differential cross sections and polarization observables with the inclusion of final-state interaction effects and meson-exchange current contributions, and compare the results with Saclay and Jefferson Lab data as well as with earlier theoretical predictions. The role of relativistic ingredients (one- and two-body currents, Fermi-motion effects, etc.) and the interplay between them are analyzed in several kinematic regimes of the experiments at Saclay and Jefferson Lab.

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nucl-th 2026-04-28

The paper calculates how pairing and shell corrections to nuclear free energy evolve with…

Survival of Pairing Correlations and Shell Effects at Scission in Finite-Temperature Nuclear Fission: Implications for Odd-Even Staggering

Pairing correlations persist near scission in hot fission and explain odd-even staggering in charge yields, while shell corrections are…

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We investigate the finite-temperature evolution of microscopic free-energy corrections in nuclear fission, focusing on pairing and shell effects near scission. The analysis is based on a finite-temperature BCS treatment combined with the Strutinsky method and is performed for representative deformation points along the fission path. Both pairing and shell contributions exhibit regular thermal attenuation, but their deformation dependencies differ substantially. In particular, pairing remains strongly deformation-dependent in the scission region, and its free-energy contribution differs markedly between the constant and surface-dependent pairing-strength prescriptions. The shell correction near scission is also significant at low temperature and is progressively suppressed with increasing excitation energy. These results support the interpretation of odd-even staggering in fragment charge yields as a manifestation of pairing correlations surviving into the strongly deformed pre-scission configuration. They also show that pairing and shell effects should be treated separately in finite-temperature dynamical calculations, with distinct deformation- and temperature-dependent attenuation laws.

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nucl-th 2026-04-28

The paper proposes a theoretical mechanism for exciting nuclei with non-resonant x-ray…

Nuclear non-resonant photoexcitation assisted by electron recombination

A third-order nuclear excitation process via non-resonant photon absorption assisted by electron recombination through a virtual nuclear…

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We investigate theoretically a nuclear excitation mechanism involving absorption of non-resonant photons leveraged by the coupling to the atomic shell. The nuclear non-resonant photoexcitation is assisted by electron recombination which compensates the energy mismatch between photon and nuclear transition energies, reminiscent of parametric up-conversion in non-linear media. This third-order process proceeds via a virtual nuclear state rather than virtual electronic states, distinguishing this mechanism from the electronic bridge. We investigate the process on the example of a so-far not observed 14.2 keV hard x-ray transition in 193Pt driven by an x-ray free-electron laser. Although the calculated cross section is small, it can be compensated by the vast number of non-resonant photons from the x-ray laser pulse. By enabling nuclear excitation through non-resonant photons, this up-conversion-like mechanism suggests new directions for non-linear x-ray interactions mediated by nuclear transitions.

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nucl-th 2026-04-27

Nuclear effects cancel in valence quark region

On the Cancellation of Nuclear Effects in the Valence Region

World data show the cross-section ratio for nuclei versus deuterium averages 0.9985 in the 0.25 to 0.35 x range.

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Deep-inelastic $e/\mu$ scattering data off targets ranging from deuterium to lead indicate that the nuclear modifications to the structure functions of bound nucleons are minimal in the kinematic region around the peak of the valence quark distributions. An analysis of world measurements of the isoscalar cross-section ratios $\sigma^A/\sigma^{{}^2\text{H}}$ in the region of $0.25 \leq x \leq 0.35$ shows a remarkable cancellation across all nuclei, with an average value of $0.9985 \pm 0.0022$. We discuss these results and possible interpretations in the context of a microscopic model of nuclear modifications of the structure functions.

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nucl-th 2026-04-27

Ab initio matrix elements for neutrinoless double-beta decay are smaller

Ab initio short-range nuclear matrix elements for neutrinoless double-beta decay

Converged calculations for four key isotopes give values below most phenomenological estimates and new sterile-neutrino constraints.

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We present converged ab initio calculations of short-range neutrinoless double-beta ($0\nu\beta\beta$) decay nuclear matrix elements for the key experimental isotopes $^{76}$Ge, $^{82}$Se, $^{130}$Te and $^{136}$Xe. Starting from different nuclear forces derived from chiral effective field theory, we apply the in-medium similarity renormalization group to obtain an effective valence-space Hamiltonian along with consistently transformed $0\nu\beta\beta$-decay operators. We then obtain a range of values for the matrix elements that is consistent with, but generally smaller than, those from phenomenology. Finally, we combine our results with current limits from $0\nu\beta\beta$-decay searches to obtain constraints for the sterile-neutrino mixing-mass parameter space when considering the inclusion of a fourth sterile neutrino.

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nucl-th 2026-04-27

Pseudo-SU(3) model accounts for 0+ piling in rare earth nuclei

The 0+-spectrum in rare earth nuclei within the pseudo-SU(3) shell model

Valence-shell space respecting Pauli rules produces the observed clustering and natural transition strengths.

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The study of the structure of the 0+ spectrum in heavy nuclei has drawn much attention in the last two decades. In this contribution we study their properties from a microscopic point of view. The pseudo-SU(3) model (\tilde{SU}(3)) is applied to some rare earth nuclei, namely to Sm, Gd, Dy, Er, Yb and Hf isotopes. It is shown that the 0+ spectrum, and the accumulation of states at certain energies, can be well understood using this microscopic model, which takes into account the Pauli Exclusion Principle (PES). Intentionally, a very simple model Hamiltonian is applied and only the valence shell is taken into account, in order to high-lighten certain cross features. It is demonstrated that the microscopic Hilbert space is essential in understanding the accumulation of 0+-states. A discussion to other models is provided. Also the dominance of B(E2)-transitions from the {\gamma}-band over those from the \b{eta}-band turns out to be trivial, in contrast to within some collective models.

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nucl-th 2026-04-27

Cluster Faddeev model matches fusion cross sections for light nuclei

Fusion of light nuclei in a multicluster realization of the three-body problem

Calculations for helium and lithium reactions reproduce experimental data from 1 keV to 20 MeV when nuclei are treated as clusters.

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This work describes a few-body dynamics method based on the Faddeev integral equations in momentum space for determining the total cross sections of fusion and breakup reactions with two- and three-body final channels in the continuum, employing a cluster representation of the colliding nuclei. Total cross sections were obtained for the reactions $^3\text{He}(T,D)^4\text{He}$, $^3\text{He}(T,np)^4\text{He}$, $^3\text{He}(T,nD)^3\text{He}$, $^3\text{He}(^3\text{He},2p)^4\text{He}$, $^3\text{He}(^3\text{He},pD)^3\text{He}$, $^7\text{Li}(^3\text{He},\phantom{0}^4\text{He})^6\text{Li}$, $^7\text{Li}(^3\text{He},D^4\text{He})^4\text{He}$, and $^7\text{Li}(^3\text{He},T^3\text{He})^4\text{He}$, in which both the projectile and the target nucleus were treated in a cluster representation. The work also implements a two-potential method to determine the Coulomb $t-$matrix and to account for Coulomb effects in short-range dynamics in momentum space. Calculations of the initial-state Coulomb interaction were performed; furthermore, an estimate was obtained for the magnitude of the off-shell effect of the Coulomb $t-$matrix, as well as the magnitude of the atomic electron anti-screening effect on the Coulomb interaction of the colliding nuclei. The calculated contribution of the cluster mechanism to the total cross section of the considered fusion reactions in the kinetic energy range $T\in[1~\text{keV},20~\text{MeV}]$ is in good agreement with known experimental data.

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nucl-th 2026-04-27

Quasi-parton neural network yields four-dimensional QCD equation of state

Four-dimensional QCD equation of state from a quasi-parton model with physics-informed neural networks

Trained only on zero-chemical-potential lattice data, the model extrapolates to finite baryon, charge, and strangeness densities for heavy-

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The equation of state (EoS) of strongly interacting matter at finite temperature and chemical potentials (baryon, charge, and strangeness) is a crucial input for hydrodynamic simulations of relativistic heavy-ion collisions. We construct a four-dimensional EoS using a deep-learning-assisted quasi-particle model (DLQPM) within a physics-informed neural network (PINN) framework, in which the masses of light quarks, strange quarks, and gluons are parameterized as functions of temperature and chemical potentials ($T, \mu_B, \mu_Q, \mu_S$). The model is constrained by lattice QCD data at vanishing chemical potentials and provides a thermodynamically consistent extrapolation to finite $\mu_{B,Q,S}$. The DLQPM accurately reproduces the lattice-calculated cumulants $\chi^{B,Q,S}_{i,j,k}$ at $\mu_{B,Q,S}=0$, and its predicted EoS at various chemical potentials agrees well with results from the generalized $T'$-expansion method in lattice QCD. Furthermore, the calculated baryon-strangeness correlation $C_{BS}$ is consistent, within uncertainties, with preliminary STAR data. This work offers a reliable EoS for exploring the QCD phase structure in the beam energy scan region.

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nucl-th 2026-04-27

QED corrections shift parity asymmetry by under 1 percent

The parity-violating asymmetry including QED corrections in high-energy electron-nucleus collisions

Nonperturbative Dirac solutions for Al, Ca, Pb and C show the combined vertex, self-energy and vacuum-polarization effects stay small at GeV

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The parity-violating asymmetry, accounting for the vector and axial-vector vertex plus self-energy correction as well as for vacuum polarization, is calculated nonperturbatively by solving the corresponding Dirac equation for the electronic scattering states. Investigating the nuclei $^{27}$Al, $^{48}$Ca and $^{208}$Pb at collision energies in the GeV region and at forward scattering angles matching the experimental geometries, it is found that the combined QED effects change the parity-violating asymmetry by less than one percent. The same is true for $^{12}$C and $^{208}$Pb at an energy of 150 MeV.

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nucl-th 2026-04-24

eGCM captures quantum fluctuations in nuclear transfer

Multi-Nucleon Transfer Reactions and the Creation and the Evolution of the Compound Nucleus

An extension of the Generator Coordinate Method implemented in the continuum produces reaction dynamics that differ from mean-field results.

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There is no microscopic quantum approach based on the many-body time-dependent Schr\"{o}dinger equation which capable to describe the formation and the evolution of a compound nucleus. The most advanced microscopic approach developed so far to describe multi-nucleon transfer (MNT) reactions in complex nuclear systems (with total number of nucleons $\gg 100$) is the time-dependent Hartree Fock (TDHF) mean field theory. In any mean field approach, however, the mean field is an expectation value of a quantum operator, thus classical in nature and unable to describe its quantum fluctuations, which are often expected to be crucial. Quantum fluctuations can be in principle be included in a configuration interaction (CI) framework, which in the case of reactions has to be implemented in the continuum. Here we describe the first such implementation within a novel extension of the well known Generator Coordinate Method (GCM), dubbed the enhanced GCM (eGCM), applied to the MNT reaction $^{48}$Ca+$^{208}$Pb near the Coulomb barrier, which demonstrates major qualitative differences with either TDHF or GCM previous approaches.

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nucl-th 2026-04-24

Drip lines for Z=122 superheavy nuclei located by deformed theory

Ground-state properties of superheavy Z=122 isotopes within the deformed relativistic Hartree-Bogoliubov theory in continuum

Calculations identify the boundaries of stability and point to possible magic neutron numbers at 184, 258 and 350.

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The ground-state properties of superheavy $Z = 122$ isotopes are investigated using the deformed relativistic Hartree-Bogoliubov theory in continuum (DRHBc). Bulk properties, including binding energies, Fermi energies, nucleon separation energies, quadrupole deformations, and root-mean-square radii, are calculated. The results are compared with those obtained from the relativistic continuum Hartree-Bogoliubov (RCHB) theory. By examining the dependence on the angular-momentum cutoff and the effects of triaxial and octupole deformations, a strategy for determining the ground states is suggested. Furthermore, based on an analysis of the Fermi and nucleon separation energies, the proton and neutron drip lines for $Z = 122$ isotopes are determined within both the DRHBc and RCHB frameworks. The possible magic numbers $N=184$, 258, and 350 are also suggested. Finally, the evolution of single-particle levels, deformation, charge and neutron radii as well as average pairing gaps with increasing neutron number, is discussed.

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nucl-th 2026-04-24 2 theorems

Drip lines located for Z=122 superheavy isotopes

Ground-state properties of superheavy Z=122 isotopes within the deformed relativistic Hartree-Bogoliubov theory in continuum

Deformed continuum calculations identify stability boundaries and candidate magic neutron numbers at 184, 258, and 350.

abstract click to expand

The ground-state properties of superheavy $Z = 122$ isotopes are investigated using the deformed relativistic Hartree-Bogoliubov theory in continuum (DRHBc). Bulk properties, including binding energies, Fermi energies, nucleon separation energies, quadrupole deformations, and root-mean-square radii, are calculated. The results are compared with those obtained from the relativistic continuum Hartree-Bogoliubov (RCHB) theory. By examining the dependence on the angular-momentum cutoff and the effects of triaxial and octupole deformations, a strategy for determining the ground states is suggested. Furthermore, based on an analysis of the Fermi and nucleon separation energies, the proton and neutron drip lines for $Z = 122$ isotopes are determined within both the DRHBc and RCHB frameworks. The possible magic numbers $N=184$, 258, and 350 are also suggested. Finally, the evolution of single-particle levels, deformation, charge and neutron radii as well as average pairing gaps with increasing neutron number, is discussed.

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nucl-th 2026-04-24

Octupole correlations explain transfer intensity jumps near N=90

Octupole correlation effects on two-neutron transfer intensity in rare-earth nuclei

Model calculations show that octupole mixing reproduces the observed sudden changes in (p,t) and (t,p) intensities across shape transitions.

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Impacts of octupole correlations on the low-lying $0^+$ states and two-neutron transfer intensities in rare-earth nuclei are investigated in terms of the interacting boson model that is based on the nuclear density functional theory. The octupole degrees of freedom are not only essential building blocks to describe properties of negative-parity states in the model, but also influence low-spin positive-parity states including excited $0^+$ states. The calculation produces a large number of low-energy $0^+$ states that contain significant amounts of octupole components, indicating important roles played by the octupole degrees freedom in this mass region. Octupole correlations are shown to make sizable contributions to the $(p,t)$ and $(t,p)$ transfer intensities and, in particular, to reproduce the discontinuous changes of these quantities near those nuclei with $N\approx88$ or 90, which are observed experimentally as a signature of the shape phase transition.

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nucl-th 2026-04-23

Conformal prediction adds guaranteed bands to neutron star EOS uncertainties

Conformal prediction for uncertainties in the neutron star equation of state

It works as post-processing on Bayesian samples without assuming any particular error distribution.

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We study uncertainties in the equation of state of neutron stars using conformal prediction as a distribution-free and model-agnostic method that provides coverage guarantees. In particular, we apply the Conformalized Quantile Regression (CQR) method to posterior samples calculated from Bayesian inference, creating reliable uncertainty bands without assuming a specific form of the underlying distribution. We first construct CQR bands as a postprocessing step to the posterior samples of neutron star mas-radius relations provided by the NMMA collaboration and to Quantum Monte Carlo calculations of pure neutron matter. In all cases, empirical coverage studies confirm the robustness of the method.

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nucl-th 2026-04-23

Cluster-superfluid phonon coupling weaker than hydrodynamics

Interaction between nuclear clusters and superfluid phonons in the neutron-star inner crust

Microscopic response shows phonon amplitude suppressed inside nuclear clusters, cutting the effective interaction strength.

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The interaction between lattice vibrations of nuclear clusters and superfluid phonons associated with neutron superfluidity plays an important role in the dynamics of the neutron-star inner crust. While this coupling has been discussed mainly within macroscopic approaches such as hydrodynamics and effective field theory, its microscopic origin and the value of the effective coupling constant have remained unclear. In this work, we derive the interaction between nuclear clusters and superfluid phonons starting from a microscopic description of inner-crust matter. Using nuclear density functional theory, we analyze the response of a neutron superfluid around a single nuclear cluster within the quasiparticle random-phase approximation. From this microscopic response, we obtain the interaction between the cluster and the surrounding superfluid. Matching this result to the long-wavelength effective description, we determine the coupling constant in an effective Hamiltonian describing the mixing between lattice and superfluid phonons. The resulting coupling strength is found to be significantly smaller than previous hydrodynamical estimates. This reduction originates from the suppression of the superfluid phonon amplitude inside and around the nuclear cluster. Our results provide a microscopic determination of the coupling parameter governing lattice-superfluid phonon mixing in the neutron-star inner crust.

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nucl-th 2026-04-23

Minimal force gives cutoff-independent bindings to calcium

Cutoff-independent predictions from nuclear lattice effective field theory

Interactions fixed only on nuclei with three or fewer nucleons reproduce 40Ca energies with just a few MeV variation across cutoffs.

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Cutoff independence is an essential requirement for the predictive power of nuclear \textit{ab initio} calculations based on effective field theory (EFT). While it is conventionally assumed that such invariance necessitates high-order interactions and complex many-body forces, we present a minimal chiral nuclear force that exhibits remarkable cutoff independence across a broad range from light to medium-mass nuclei and sub-saturated nuclear matter. Our framework comprises only contact terms up to next-to-leading order, a single three-nucleon contact force, and a leading-order one-pion-exchange potential, all constrained strictly in the $A \leq 3$ sector. Despite its simplicity, this interaction accurately reproduces experimental binding energies up to $^{40}\text{Ca}$ with unexpectedly small residual cutoff dependencies of only a few MeV. We demonstrate that the use of a lattice-inspired \emph{absolute}-momentum regulator efficiently suppresses high-momentum modes, resolving the overbinding problem for soft chiral forces without invoking complex many-body forces. These results establish a robust and economic foundation for EFT-based \textit{ab initio} calculations in both continuum and lattice frameworks.

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