Stress distributions in the deuteron are related to form factors of the asymmetric energy-momentum tensor through three-dimensional Fourier transforms. There are eleven such form factors, which we calculate in an impulse approximation. We compare the obtained form factors to prior results for the six form factors that have been previously calculated. We then elaborate on the formalism for relating the form factors to internal distributions of mass, mass flux, momentum, stresses, and forces, and obtain results for all of these distributions. We obtain the principal stresses for the symmetric part of the stress tensor, and show that the antisymmetric part describes the reorientation of fermion spin by torsion stress when the nucleon moves between the S and D waves. Force distributions in the nucleons depend on the so-called nonconserved form factors through the Cauchy momentum equation, and are nonradial owing to the presence of tensor forces and spin-orbit coupling.

The nuclear equation of state, which determines the structure and properties of neutron stars, remains subject to substantial theoretical uncertainties, leading to model dependence in predicted observables. Universal relations have emerged as a powerful tool to mitigate this dependence by linking neutron star observables in a framework-independent manner. In this work, we introduce a new universal relation that bridges finite nuclei and neutron stars through the dimensionless quantity $\zeta ={\beta }_{1.4}{\tilde{L}}^{-1}$, which couples the compactness of a $1.4M_{\odot }$ neutron star to the slope of the nuclear symmetry energy at saturation. The relation is examined under a broad set of relativistic energy density functionals with point-coupling and meson-exchange interactions, as well as nonrelativistic Skyrme functionals. We demonstrate that $\zeta$ exhibits a strong exponential correlation with the electric dipole polarizability ${\alpha }_D$ in finite nuclei across all considered equations of state. By exploiting experimental ${\alpha }_D$ data for selected neutron-rich nuclei, we constrain $\zeta$ and translate these constraints into equation-of-state independent bounds on the neutron star radius $R_{1.4}$ and the symmetry-energy slope $L$, providing insights into the properties of neutron star matter.

Background: The coupled-channel framework provides a good description for nuclear reactions, provided all relevant channels are included. However, practical applications are often performed in a reduced model space with only a single channel. To effectively account for the effects of missing channels, approximations developed for elastic scattering differ from those for fusion reactions.

Purpose: In this work, we investigate these different approximations used for fusion reactions and elastic scattering (or other direct reactions), by bringing them under the same coupled-channel framework.

Method: We perform coupled-channel calculations for reactions around the Coulomb barrier with a tightly bound projectile (${}^{16}\mathrm{O}+{}^{144}\mathrm{Sm}$). We also perform continuum discretized coupled-channel calculations to study elastic (${}^8\mathrm{B}+{}^{58}\mathrm{Ni}$) and fusion (${}^6\mathrm{Li}+{}^{198}\mathrm{Pt}$) of loosely bound projectiles in the same energy regime.

Results: We contrast the coupled-channel results with those obtained in a single-channel approach with different assumptions for the effective interactions to shed light on the relevant absorption terms required for the two different reaction channels. Our results clearly show that, when the relevant channels are included in the coupled-channel framework, one can describe elastic and fusion cross sections using the same original Hamiltonian. However, our results also reveal a lack of consistency between the effective interaction required to successfully model direct processes and that used to describe fusion reactions when the problem is reduced to a smaller set of channels.

Conclusions: From our results, we can track the reason for this inconsistency: it stems from the contribution of nonelastic channels to fusion, a contribution that is lost when reducing the coupled-channel equations to a single equation in the elastic channel. In the cases discussed here, this lost information, while crucial in fusion processes, has no impact on elastic scattering.

We develop a fully relativistic theoretical framework for calculating nuclear excitation cross sections induced by muon beams, covering a broad range of incoming energies from 1 to 1000 MeV. Focusing on experimentally accessible isotopes, ${}^{115}\mathrm{In}$ and ${}^{90}\mathrm{Zr}$, we calculate excitation cross sections to various nuclear states. To enhance relevance for potential experiments, we also estimate the effective cross sections for excitation to long-lifetime isomeric states, suitable for postexcitation detection. Additionally, we compare the excitation cross sections for ${\mu }^{-}$, ${\mu }^{+}$, and electrons, and we assess the impact of muon penetration into the nucleus on these cross sections.

Background: With the recent progress in lifetime measurements, there has been strong experimental and theoretical interest in studying the evolution of the collectivity in the long Te isotopic chain.

Purpose: The purpose of the present work is to investigate the structure of low-lying excited states in even-even Te nuclei as well as the $\nu h_{11/2}$ band in the odd-mass systems within the interacting boson model framework.

Methods: A new open-source Python package is developed to evaluate the eigenvalues and eigenfunctions of a Hamiltonian which contains both the standard ${\widehat{n}}_d$ and $\widehat{Q}·\widehat{Q}$ terms as well as higher-order terms which could be essential for triaxial deformation and mixed symmetry effects.

Results: Systematic calculations of low-spin yrast and nonyrast states in even-even ${}^{108-124}\mathrm{Te}$ and odd-even ${}^{109-125}\mathrm{Te}$ nuclei have been carried out using the newly developed Python package and compared with the neighboring Cd isotopes. From the resulting eigenfunctions, the reduced transition probabilities $B\left(\mathrm{E}2\right)$ are calculated and compared to adopted values. Due to the vibrational-like structure of the spectra of the Te nuclei, the Hamiltonian is dominated by the vibrational term, which is reflected in the $B\left(\mathrm{E}2\right)$ values. This alone does not explain the low $B_{4/2}$ ratios observed in some Te nuclei. However, it is demonstrated via the contour plot that the $B_{4/2}$ ratios can be highly sensitive to the higher-order terms of the Hamiltonian within specific parameter domains.

Conclusions: We demonstrate that inclusion of higher-order interactions can provide a possible explanation of the anomaly observed in certain Te isotopes. The results highlight both the importance of extended IBM Hamiltonians and the utility of pyIBM as a modern computational tool for collective nuclear structure studies.

In the present work, we have generalized the projected shell model (PSM) approach to include the quasiparticle excitations from two major oscillator shells, and have also extended the basis space to five-quasiparticle configurations for odd-mass nuclei. The magnetic and antimagnetic rotational structures observed in odd-neutron Pd- and Cd-isotopes have been investigated as a first major application of the new development. It is shown that the PSM approach provides a reasonable description of the observed properties of magnetic and antimagnetic rotational bands.

Potential energy surfaces of superheavy nuclei are investigated within the multidimensionally constrained relativistic mean-field model. The results are analyzed using the Strutinsky shell-correction method, with particular emphasis on ${}^{296}\mathrm{Lv}$ and isotopic chains of $Z=114$ and $Z=120$. The analysis reveals that triaxial degrees of freedom substantially reduce the barrier height along the triaxial fission pathway compared to the axial fission path in ${}^{296}\mathrm{Lv}$. A steplike behavior emerges in proton shell corrections for $Z=114$ isotopes, contrasting with the smoother patterns observed in $Z=120$ isotopes, is attributed to the differences in the ground-state deformations. The observed correlation between fission-barrier maxima and shell-correction minima points to the shell closures at neutron numbers $N=172$ and $N=184$ at $Z=114$ and 120.

The saturation of symmetric nuclear matter—reflected in the nearly constant interior density of heavy nuclei—is a defining property of nuclear matter. Modern relativistic energy density functionals (EDFs) calibrated exclusively to the properties of finite nuclei, make robust predictions with quantified uncertainties about the bulk properties of symmetric nuclear matter in the vicinity of the saturation density. Following the same fitting protocol, nonrelativistic Skyrme EDFs systematically predict higher saturation densities than their relativistic counterparts. To investigate this tension in the bulk limit, we study the ground-state properties of hypothetical symmetric macroscopic nuclei containing thousands of nucleons. Using both relativistic and nonrelativistic EDF frameworks, we extract the corresponding liquid-drop parameters. We find a clear correlation between the volume and surface energy coefficients: Skyrme models, which saturate at higher densities, develop softer and more diffuse surfaces with lower surface energies, whereas relativistic EDFs, which saturate at lower densities, produce more defined and less diffuse surfaces with higher surface energies. This compensating behavior allows both classes of models to reproduce empirical nuclear radii despite their distinct saturation properties. Our analysis suggests that the apparent disparity in saturation densities arises from the intrinsic balance among saturation density, bulk binding energy, and surface tension, rather than from the fitting protocol.

Pairing correlations are ubiquitous in low-energy states of atomic nuclei. To incorporate them within nuclear density functional theory, often used for global computations of nuclear properties, pairing functionals that generate nucleonic pair densities and pairing fields are introduced. Many pairing functionals currently used can be traced back to zero-range nucleon-nucleon interactions. Unfortunately, such functionals are plagued by deficiencies that become apparent in large model spaces that contain unbound single-particle (continuum) states. In particular, the underlying computational schemes diverge as the single-particle space increases, and the results depend on how marginally occupied states are incorporated. These problems become more pronounced for pairing functionals that contain gradient-density dependence, such as in the Fayans functional. To remedy this, finite-range pairing functionals are introduced. In this study, this is done by folding the pair density with Gaussians. We show that a folding radius of about 1 fm offers the best compromise between quality and stability, and substantially reduces the pathological behavior in different numerical applications.

We investigate the ground-state properties of asymmetric nuclear matter and its response to a static perturbation using the density-functional theory framework. Our method, which extends the finite-nucleon-number technique of [Phys. Rev. C 107, 044311 (2023)] to the case of isospin-asymmetric matter, allows us to study the impact of external isoscalar and isovector fields on the system. In particular, the densities and static response functions in the different isospin channels, and as a function of isospin asymmetry, are evaluated. Finite-size effects are discussed by comparing with random-phase approximation predictions in the thermodynamic limit. A peculiar nonmonotonic behavior of the isovector response function is analyzed.

A systematic analysis of the relationship between spontaneous fission and $\alpha$-decay half-lives is performed for actinides and superheavy nuclei in the ground state. The ratio of logarithmic half-lives exhibits regular trends with nuclear mass and charge numbers, showing almost constant behavior at fixed neutron excess. Based on these systematics, a new semiempirical formula is proposed that relates spontaneous fission half-lives to $\alpha$-decay half-lives and neutron excess. The formula contains only three fitted parameters and provides a unified description for nuclei of different parities without introducing separate hindrance factors. It reproduces experimental spontaneous fission half-lives with a mean absolute deviation of 0.94 orders of magnitude for the dataset of 78 nuclei. A detailed comparison of the predicted half-lives calculated using microscopic-macroscopic and self-consistent microscopic models, more complex empirical parametrizations, and the new formula is presented. The formula can be used to predict spontaneous fission half-lives and validate experimental data, and it provides a criterion to determine the dominant decay mode ($\alpha$ decay or spontaneous fission). The existence of a fundamental relationship between spontaneous fission and $\alpha$-decay processes is discussed.

We present results on the production of ${\pi }^{\pm }, K^{\pm }, p$, and $\overline{p}$ in $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{s_{\mathrm{NN}}}=54.4\mathrm{GeV}$ using the STAR detector at RHIC, at midrapidity ($\left|y\right|<0.1$). Invariant yields of these particles as a function of transverse momentum are shown. We determine bulk properties such as integrated particle yields ($dN/dy$), mean transverse momentum ($\langle p_T\rangle$), particle ratios, which provide insight into the particle production mechanisms. Additionally, the kinetic freezeout parameters ($T_{\text{kin}}$ and $\langle {\beta }_T\rangle$), which provide information about the dynamics of the system at the time of freezeout, are obtained. The Bjorken energy density (${\epsilon }_{\mathrm{BJ}}$), which gives an estimate of the energy density in the central rapidity region of the collision zone at the formation time $\tau$, is calculated and presented as a function of multiplicity for various energies. The results are compared with those from the models such as A Multi-Phase Transport (AMPT) and Heavy Ion Jet INteraction Generator (HIJING) for further insights.

Astrophysical scenarios such as binary neutron star mergers, protoneutron stars, and core-collapse supernovae involve finite temperatures and strong magnetic fields. Previous studies on the effect of magnetic fields on flavor-equilibration processes relied on the Fermi surface approximation, which is not a reliable approximation in the neutrino-transparent regime of matter in supernovae or neutron star mergers. In a recent study, we went beyond the Fermi surface approximation, performing the full phase space integral to obtain direct Urca rates in a background magnetic field. In this work, we extend these calculations to incorporate the collisional broadening (modified Urca) contribution. We use the recently developed nucleon width approximation, which naturally includes the magnetic field dependence of all contributions. We demonstrate the impact of magnetic fields on the flavor-equilibrium condition for two finite-temperature equations of state with different direct Urca thresholds. We also study the impact of magnetic fields on the bulk viscous dissipation of density oscillations relevant in postmerger scenarios.

In the context of the ongoing PUMA experiment (CERN), which investigates antiproton annihilation on atomic nuclei, we study the energy shifts and widths of hydrogenic states in the $\overline{p}+{}^3\mathrm{H}$ and $\overline{p}+{}^3\mathrm{He}$ systems by performing ab initio calculations. The scattering lengths and scattering volumes are first determined by solving the Faddeev-Yakubovsky equations in configuration space. The level shifts and widths of the corresponding $\overline{p}{}^3\mathrm{H}$ and $\overline{p}{}^3\mathrm{He}$ hydrogen-like states are then obtained using the Trueman formula. A pronounced model dependence associated with the nucleon-antinucleon interaction is observed for certain states. Finally, annihilation densities are computed from the four-body wave functions. Comparison with the nuclear density distributions indicates that the antiproton-nucleus annihilation is predominantly peripheral.

In this paper we focus on the evolution of triaxiality from $\gamma$-soft toward rigid triaxial shapes in Mo and Ru chains above $N=60$. Spectral criteria for the second-order phase transition are suggested and examined. Both chains are investigated within the phenomenological algebraic collective model and in the framework of microscopic Hartree-Fock-Bogoliubov calculations with six representative parametrizations of the effective Skyrme interaction. The algebraic collective model yields energy surfaces that are softer towards prolate shapes, whereas the Skyrme results are all softer towards oblate shapes.

Noncentral heavy-ion collisions produce hot and dense nuclear matter with significant fluid vorticity, which can induce global polarizations or alignments of particles with nonzero spins along the direction of the total orbital angular momentum. This phenomenon has been observed for hyperons and vector mesons in experiments. In the present study, we demonstrate that polarized nucleons lead to global spin alignment of the unstable nucleus ${}^4\mathrm{Li}$, which can be measured through its strong decays via ${}^4\mathrm{Li}\to {}^3\mathrm{He}+p$. Assuming that ${}^4\mathrm{Li}$ is formed through the coalescence of polarized nucleons at kinetic freeze out, we obtain the angular distribution of the daughter particle ${}^3\mathrm{He}$ in the rest frame of the polarized ${}^4\mathrm{Li}$. Taking kinetic freeze-out nucleons from an isotropic and thermalized fireball of constant vorticity and including quantum corrections up to ${\hslash }^2$ in the coalescence calculation through the Moyal star product, we find that the angular distribution of ${}^3\mathrm{He}$ has a $cos\left(2{\theta }^{*}\right)$ dependence with ${\theta }^{*}$ being its angle with respect to the polarization direction of ${}^4\mathrm{Li}$. We also find that the ${}^3\mathrm{He}$ angular distribution depends on both the vorticity and the polarization of kinetic freeze-out nucleons. Future measurements on the spin alignment of ${}^4\mathrm{Li}$ in heavy-ion collisions thus offer a promising method to probe the spin dynamics, vortical structure, and spin-dependent equation-of-state of the nuclear matter produced in these collisions.

The most accurate approach to determine the compressibility of nuclear matter remains the one based on microscopic energy density functionals (EDFs). Recent analyses yield a value for nuclear incompressibility modulus $K_{\mathrm{sat}}=240\pm 20\mathrm{MeV}$, defined in nuclear matter as the second derivative of the energy per particle at saturation density. However, we demonstrate that the compressibility modulus can be reduced to values shifted by four times the suggested uncertainty, i.e., $K_{\mathrm{sat}}\approx 160\mathrm{MeV}$, by providing examples based on models where the second derivative ($K_{\mathrm{sat}}$) and third derivative ($Q_{\mathrm{sat}}$) of the energy per particle at saturation density can be independently varied, while the experimental binding energies, charge radii, and isoscalar giant monopole resonance data in ${}^{120}\mathrm{Sn}$ and ${}^{208}\mathrm{Pb}$ are enforced. The present work suggests a new methodology to access the compressibility of nuclear matter from nuclear experiments, still based on microscopic models, but using EDFs containing more flexibility than the ones employed up to now. Consequences of our results for nuclear matter at suprasaturation density are also discussed by exploring the quarkyonic crossover. We predict that, for our models with low values for $K_{\mathrm{sat}}$, the quark onset density has to be low for neutron stars to exist.

We conduct a systematic investigation of the influence of the nuclear symmetry energy on the proposed neutron decay into dark matter particles within the cores of neutron stars. Compared to the majority of previous studies that considered only pure neutron matter, the present analysis is extended to encompass $\beta$-stable nuclear matter. Furthermore, in relation to previous studies, the interactions between dark matter and baryons are incorporated and systematically studied regarding their effect on the structure of neutron stars. Our findings indicate that the nuclear symmetry energy plays a critical role in shaping the total equation of state for dense neutron star matter containing dark sector components. The strength of interactions among dark matter particles, as well as between dark matter and baryons, is shown to be pivotal in determining both the composition and the macroscopic properties of neutron stars. The concurrent tuning of interaction strengths alongside the symmetry energy parameters may facilitate a more accurate reproduction of recent observational data relevant to neutron star properties. In any case, the extent to which the proposed dark decay of the neutron is affected by the extreme conditions prevailing in the interiors of neutron stars remains an open problem.

A hybrid approach combining the Tabular Prior-data Fitted Network (TabPFN) with the Coulomb and proximity potential model (CPPM) is developed to investigate $\alpha$-particle preformation factors $P_{\alpha }$ and their impact on $\alpha$-decay half-lives. The TabPFN model, trained on 498 nuclei, accurately learns the relationship between nuclear-structure properties and $P_{\alpha }$, achieving a root-mean-square deviation of ${\sigma }_{\mathrm{rms}}=0.211$. The predicted factors reveal clear odd-even staggering and shell-closure effects, and exhibit linear correlations with both $Q_{\alpha }^{-1/2}$ and the fragmentation potential $V_{\mathrm{frag}}$. When incorporated into CPPM calculations, the machine-learning-based $P_{\alpha }$ values significantly improve half-life predictions. Similar improvements are also obtained when deformation effects are included in the potential barrier description. The capability of the model is further demonstrated through predictions for superheavy nuclei ($Z=117–120$), suggesting $N=184$ as a potential neutron magic number.

We report high-statistics measurements of fifth- and sixth-order factorial cumulants and cumulant ratios of (net-)proton multiplicity distributions in $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{s_{\mathrm{NN}}}=7.7–27\mathrm{GeV}$, using data from the STAR experiment collected during the Beam Energy Scan Phase II at RHIC. Protons and antiprotons are identified at midrapidity ($\left|y\right|<0.5$) with transverse momentum $0.4<p_T<2.0\text{GeV}/c$. The proton factorial cumulants ${\kappa }_4, {\kappa }_5$, and ${\kappa }_6$ increase with order but exhibit no sign alternation within current uncertainties, offering no evidence for a two-component structure in the proton multiplicity distribution, as might be expected near a first-order phase transition. The cumulant ratios $C_5/C_1$ and $C_6/C_2$ fluctuate around zero in collisions at 0–40% centrality. The results are consistent with both the negative predictions from lattice QCD and the positive trends obtained from the ultrarelativistic quantum molecular dynamics (UrQMD) model. At $\sqrt{s_{\mathrm{NN}}}\gtrsim 27\text{GeV}$, the $C_4/C_2$ and $C_5/C_1$ results are compatible with predictions from lattice QCD, functional renormalization group (FRG), and hadron resonance gas (HRG) models, while UrQMD describes the data better at lower energies. These measurements place constraints on baryon number fluctuations and offer valuable insights into the QCD phase structure.