Papers

In lepton scattering from nuclei, it has been taken for granted that nuclear modifications do not exist for the longitudinal-transverse structure-function ratio $R$, although nuclear effects in $F_2$ have been investigated for a long time. In fact, experimental data of lepton-nucleus scattering have been analyzed with this assumption. It is obviously not appropriate because nuclear modifications exist in the function $R$ theoretically as shown in this work. In this work, we explain nucleon's Fermi motion's effects by using a convolution description for nuclear structure functions, especially on the deuteron. The longitudinal and transverse structure functions are defined by taking the virtual photon momentum direction along the $z$ axis. However, nucleons in a nucleus could move in any direction, so that nucleon's longitudinal and transverse structure functions could mix with each other in the nuclear medium. Such mixing effects could be of the order of $\vec p_\perp^{\,2}/Q^2$, where $\vec p_\perp$ is the nucleon's transverse momentum and $Q^2$ is given by $Q^2=-q^2$ with the virtual-photon momentum $q$, because the transverse Fermi-motion is the source of such a mixture. In addition, nuclear effects are different between the longitudinal and transverse structure functions in the convolution model because their $x$-dependent functional forms are different. Convolution integrals have different results between the longitudinal and transverse structure functions for nuclei. Because the experiment is in progress at the Thomas Jefferson National Accelerator Facility to measure the function $R$ for the deuteron, the numerical results are shown on the nuclear effects of $R$ in the deuteron. Hopefully, such nuclear effects are found experimentally by future experiments including heavy nuclear targets.

Alpha-decay provides an important probe of nuclear structure and the underlying nucleon-nucleon interaction, while its rigorous microscopic description from first principles remains challenging. For $\alpha$+magic core systems, a microscopic treatment of $\alpha$-cluster formation and decay has been achieved by considering both the four-body correlation on top of the core and Pauli blocking. Extending this microscopic description to open-shell nuclei should account for the configuration mixing caused by the residual interactions between valence nucleons near the Fermi surface. In this work, we improve the quartetting wave function approach (QWFA) by incorporating the pairing-induced configuration mixing using the particle-number-projected Bardeen-Cooper-Schrieffer (PBCS) method. We find that the pairing enhance the formation amplitudes of the $\alpha$-cluster in open-shell nuclei while the closed shells suppress the $\alpha$-clustering.

Low-energy nuclear structure is encoded in a broad body of experimental information across the chart of nuclides. Learning how this information is organized across observables and nuclei can provide a data-driven empirical baseline for theoretical extrapolations and experimental design. Here, we develop held-out ensembles based on NuCLR (Nuclear Co-Learned Representations), a multi-task model of nuclear data, to study charge radii and electric-quadrupole transition strengths. Out-of-fold (OOF) validation shows that shared representation improves performance over single-task learning, yielding a charge-radius $\mathrm{RMS}$ deviation of $0.0147~{\rm fm}$ and a $\mathrm{B(E2)}$ $\mathrm{RMS}$ deviation of $0.192~e^2{\rm b}^2$ across hundreds of nuclides, competitive with state-of-the-art nuclear models. Our error bars estimate the expected prediction accuracy across the nuclear chart, highlighting regions where new data would encode information beyond the learned patterns. NuCLR thus serves as a data-driven surveyor of nuclear structure and a step toward a shared, multi-observable foundation model of the nuclear chart.

A species-resolved anisotropy-response scaling framework is used to investigate the structure and formation dynamics of the $f_0(980)$ in relativistic nuclear collisions. Published measurements in high-multiplicity p+Pb collisions at $\sqrt{s_{NN}}=8.16$~TeV exhibit broad scaling closure under a single-meson response construction, with a small effective final-state response, $\zeta_{f_0}\simeq0.04$, whereas a symmetric ${\rm K\bar K}$ constituent-response construction gives substantially poorer closure. An explicitly molecular ${\rm K\bar K}$ calculation also exhibits single-meson-like scaling but gives a substantially larger effective final-state response, $\zeta_{f_0}\simeq0.16$. Thus, single-meson scaling alone is not a unique structural discriminator. The combined response construction and $\zeta_{f_0}$ constraints characterize the measured $f_0(980)$ by a single-meson-like anisotropy response with weak final-state sensitivity, distinctly different from the molecular benchmark. These results establish anisotropy-response scaling as a new experimental probe of $f_0(980)$ formation dynamics and motivate systematic tests across collision systems and beam energies.

The heavy-quark polarization in ultra-relativistic heavy-ion collisions (HICs) serves as a probe for unfolding the characteristics of deconfined QCD. The present study explores the spin alignment of $\mathrm{J/\psi}$ in the HICs by employing the rotational Brownian motion of charm quarks in the presence of a strong magnetic field. We derive an analytical expression for the polarization of the $c$-$\bar{c}$ pair based on the Fokker-Planck equation under the consideration of spin-vorticity coupling. These polarized $c$-$\bar{c}$ pairs lead to the formation of the $\mathrm{J}/\psi$ at the hadronization surface via the coalescence and fragmentation mechanisms. Correspondingly, we obtain the $m=0$ diagonal element $\rho_{00}$ of the $\mathrm{J}/\psi$ spin-density matrix, which quantifies its spin alignment along the chosen quantization axis. Our study provides a microscopic description of heavy-quark spin transport and suggests rotational diffusion as a possible mechanism underlying the observed $\mathrm{J}/\psi$ spin alignment.

In this conference proceeding we review an extension of the Chiral Mean Field (CMF) model that consistently incorporates interacting thermal mesons with self-consistent in-medium masses. In this approach, the in-medium masses of pseudoscalar and vector mesons are evaluated through the explicit chiral symmetry-breaking and vector-interaction terms in the Lagrangian respectively, before applying the mean-field approximation. These medium-modified meson properties introduce additional feedback into the CMF equations of motion, leading to a revised equation of state. The impact of this refinement is analyzed by comparing the hadronic model predictions with recent lattice QCD data and other hadronic descriptions, such as the hadron resonance gas model. The modified CMF framework, featuring an improved meson treatment (mCMF),demonstrates enhanced consistency with lattice-QCD results for thermodynamic observables across a broad range of temperatures and baryon chemical potentials.

The Chiral Mean-Field (CMF) model describes dense matter in terms of baryons and quarks interacting through scalar and vector meson mean fields. In the mean-field approximation, the meson fields are replaced by their expectation values. Their role in generating interactions and in-medium properties is retained, but explicit thermal mesonic excitations are absent. This becomes increasingly problematic at high temperature, where mesons contribute significantly to the thermodynamics of hadronic matter. Here, we keep the original CMF description of dense matter and add the thermal mesonic degrees of freedom using the mesonic sector of the Hadron Resonance Gas (HRG) module in the MUSES framework. Ground-state pseudoscalar and vector mesons account for the missing thermal excitations, while mesonic resonances provide, within the HRG picture, an effective description of mesonic interactions through resonance formation. We study how these contributions affect the pressure, entropy density, energy density, and baryon density, and compare the resulting equation of state with continuum-extrapolated lattice-QCD calculations.

Heavy-ion collisions provide unique access to the properties of QCD matter over a broad range of temperatures and baryon densities. We review recent progress in constraining the high-density phase structure of QCD, with particular emphasis on the microscopic inputs required for reliable transport modeling. We discuss cluster production, strange-particle interactions, collision dynamics at few-GeV energies, and the isospin dependence of the nuclear interaction, together with their impact on the interpretation of flow, yields, fluctuations, and possible critical signatures.

We investigate net-baryon number fluctuations in the high-density, low-temperature region of the QCD phase diagram using the parity-doublet model (PDM) under the mean-field approximation. We compute the fluctuation ratios up to sixth order around the nuclear liquid-gas (LG) phase transition, where the high-order ratios are particularly sensitive. To connect the results with heavy-ion experiments, we test several different scenarios of chemical freeze-out. We find that near the LG transition the extracted fluctuations depend strongly on the choice of freeze-out curve. We self-consistently determine four freeze-out points from preliminary results of the STAR Collaboration. Comparing the experimental data with the PDM results along these four points, we find that the model describes the low energy ($\sqrt{s_{NN}}\lesssim$ 4 GeV) data well. This suggests that nucleon interactions and the LG phase transition may contribute significantly to the fluctuations in low energy heavy-ion collisions.

Recent measurements of two-particle transverse-momentum correlations, $C_{p_T}$, in Au+Au collisions have revealed a statistically significant non-monotonic beam-energy dependence over the range $\sqrt{s_{NN}}=3.0$–$7.7$~GeV that has been interpreted as potentially indicative of critical phenomena associated with a critical end point (CEP) in the QCD phase diagram. This interpretation is assessed in light of the absence of a controlled framework establishing $C_{p_T}$ as a quantitative proxy for the underlying critical response. The implications of this limitation are examined by considering the expected finite-size and finite-time modification of critical fluctuations, substantial non-critical dynamical contributions, the lack of demonstrated critical scaling, and the sizeable discrepancy between the CEP region inferred from the observed $C_{p_T}$ non-monotonicity and that constrained by susceptibility-based measurements and finite-size scaling analyses. Taken together, these considerations indicate that the observed $C_{p_T}$ non-monotonicity does not, by itself, establish a critical origin nor provide reliable quantitative constraints on the existence or location of a possible CEP.

Charge-dependent directed flow provides a sensitive probe of early electromagnetic fields and baryon stopping in relativistic heavy-ion collisions. Recent STAR measurements show a centrality-dependent sign change in the directed flow splitting (the difference between the directed flow of protons and antiprotons), indicating that electromagnetic effects alone are not sufficient to describe this observable and that the baryon stopping $-$ in particular the component of the stopped proton distribution that is odd in rapidity and odd under reflection in the impact parameter direction $-$ must also be included. We develop a semi-analytic hydrodynamic framework that combines spectator-induced electromagnetic fields with a Glauber-based description of baryon stopping, built upon an analytic solution for the background hydrodynamic flow due to Gubser together with the simplifying assumption of a constant electrical conductivity. For Au+Au collisions at $\sqrt{s_{NN}}=200$ GeV, we find that baryon stopping gives a positive contribution to the directed flow splitting that decreases for more peripheral collisions, while electromagnetic fields give a negative contribution that is larger for more peripheral collisions. The competition between these two effects naturally reproduces the observed sign change in Au+Au collisions as a function of centrality, describes the observed rapidity dependence in the $50$–$80\%$ centrality interval, and reproduces trends seen in U+U collisions. Although the simplifying assumptions that we have made regarding the analytic background and constant conductivity limit our ability to make quantitative comparisons, our model provides a transparent explanation of how transported baryon number and spectator-induced electromagnetic fields jointly shape charge-dependent directed flow.

We investigate the effect of $\alpha$-core breakup on the strong conversion of \({}^{6}_{\Lambda\Lambda}\mathrm{He}\) into a deeply bound \(H\) dibaryon. In addition to the coherent \(H+{}^{4}\mathrm{He}\) channel, we evaluate the open final states \(H+p+{}^{3}\mathrm{H}\), \(H+n+{}^{3}\mathrm{He}\), and \(H+d+d\) using a translationally invariant Gaussian cluster description, including spin-isospin recoupling and full nonrelativistic three-body phase-space integrations. The breakup widths are normalized to Gal's intact-\(\alpha\) result. At \(B_{\Lambda\Lambda}^{H}=176~\mathrm{MeV}\), corresponding to \(m_H\simeq2055~\mathrm{MeV}\), the summed breakup width exceeds the intact-\(\alpha\) width by a factor \(R_{\mathrm{br}}=2.49\times10^{3}\). The resulting inclusive width and lifetime are \(\Gamma_{\mathrm{inc}}=3.87\times10^{-4}~\mathrm{eV}\) and \(\tau_{\mathrm{inc}}=1.70\times10^{-12}~\mathrm{s}\), respectively, compared with \(\tau_{\alpha}=4.25\times10^{-9}~\mathrm{s}\) for the intact-\(\alpha\) channel alone. The mass-dependent calculation shows that the inclusive lifetime crosses the characteristic hypernuclear weak-decay timescale near \(m_H\simeq2020~\mathrm{MeV}\) and increases rapidly as the \(H\) mass decreases. In the representative dark-matter-motivated interval \(1865\leq m_H\leq1885~\mathrm{MeV}\), we obtain \(6.59\times10^{-4}\lesssim\tau_{\mathrm{inc}}\lesssim 6.80\times10^{-3}~\mathrm{s}\), far exceeding the weak-decay timescale. Thus, although core breakup can dominate the inclusive strong width near \(m_H\simeq2055~\mathrm{MeV}\), weakly decaying double-\(\Lambda\) hypernuclei remain compatible, within the present framework, with a deeply bound \(uuddss\) state in the mass range relevant to sexaquark dark matter.

The target-fragmentation region in deeply inelastic electron-nucleus scattering provides insight into the partonic structure of the target, as hadrons measured in the final state retain information about the nonperturbative dynamics of spectator partons inside the nucleus. In QCD factorization theorems, this nonperturbative dynamics is encoded in objects known as fracture functions. In this paper, we study the extended quark fracture function in the limit where the struck (anti)quark carries a very small longitudinal momentum fraction, $x$. We first present an elementary derivation within the Color Glass Condensate effective field theory of the quark fracture function in terms of the dipole operator at small $x$. At the parton level, the quark extended fracture function is sensitive to gluon saturation when the transverse momentum $P_\perp$ of the outgoing parton produced in the target-fragmentation region is smaller than the nuclear saturation scale $Q_s$, in which regime the $P_\perp$ distribution becomes approximately flat. We then show, through a numerical study that incorporates the convolution of this parton-level result with a collinear fragmentation function, that hadronization largely washes out these saturation effects, as the convolution predominantly probes partonic transverse momenta that are typically larger than $Q_s$.

We present new results on the matching relations for gluon transverse momentum dependent parton distribution functions up to one-loop accuracy. At tree-level, employing the spinor formalism, we obtain these relations up to twist 3 accuracy for both T-even and T-odd distributions, including the hadron-mass corrections. At one-loop order, we extend the parton-in-parton approach to include higher-twist operators in the small-$b$ expansion. As a result, we derive for the first time the Wandzura-Wilczek relation for the worm-gear T distributions and establish a systematic method to include mass corrections at one-loop and twist-2 accuracies.

The double-parton scattering process off light and heavy nuclei is proposed as an effective tool to open a novel window for accurately studying the effects of nuclear binding on the internal structure of the nucleon, in the spirit of the European Muon Collaboration (EMC) effect. The key ingredient is the actual calculation of nuclear double-parton distributions that contain information about double-parton distributions and generalized-parton distributions of the nucleon, folded with nuclear light-front distributions. It allows to introduce a new quantity, which we call double-EMC ratio that appears to be much more sensitive than the standard EMC effect to both the nucleon partonic structure and to the nuclear binding. Hence, it could help solving long-standing questions about how nucleons change when they are bound in atomic nuclei.

We present a feasibility study demonstrating how recent advances in quantum-sensing technologies can facilitate stringent comparisons between theoretical predictions and experimental measurements of contact-free transitions in muonic atoms. Such comparisons can probe previously unexplored regions of the parameter space governing spin-independent muon-proton interactions and disentangle the extraction of fundamental constants from searches for physics beyond the Standard Model.

Recently, a global analysis has been performed for longitudinal spin asymmetries in polarized deep inelastic scattering (DIS) processes, combining the polarized valence quark model with the large-$N_c \& N_f$ helicity evolution equations. With a three-fold reduction in the number of free parameters, the valence quark model results in a six-fold reduction of uncertainty for the resulting prediction of total parton spin inside the proton, when compared to previous analysis performed with traditional moderate-$x$ model inspired by Born approximation. The fit based on valence quark model predicts a positive gluon hPDF and negative $g_1$ structure function at small $x$. However, the resulting increase in the $\chi^2$-statistic of the fit warrants further examination into the physical uncertainty of the valence quark model, which is a work in progress. We also summarize other possibilities of future research directions towards the end of this article.

Nuclear chirality in $^{128}$Cs is revisited within the microscopic relativistic configuration-interaction density functional (ReCD) theory. The positive-parity doublet bands are investigated by simultaneously examining their energy spectra, electromagnetic transition probabilities, $g$ factors, spectroscopic quadrupole moments, and underlying angular-momentum geometry. Without introducing additional parameters adjusted to the spectroscopic data, the ReCD calculations provide an overall satisfactory description of the available experimental observables. In particular, a comprehensive analysis of the available experimental data and the calculated spectroscopic observables indicates qualitative resemblances between the partner bands around $I = 17\hbar$. A microscopic analysis of the angular-momentum geometry through azimuthal plots reveals a distinct evolution of the rotational mode with increasing spin: chiral vibration at $I < 17\hbar$, static chirality at $I = 17\hbar$, and a transition toward planar rotation at higher spins. These results suggest that static chiral geometry in $^{128}$Cs is confined to a narrow spin region around $I = 17\hbar$ within the present ReCD calculations.

In the momentum-space few-body theory of light nuclei, where the Faddeev equations with separable two-body input close on one-variable amplitudes, the unscreened Coulomb interaction is exactly separable by the stereographic projection of Fock, with analytic form factors and strengths, and the truncation of the expansion converges at negative energies. It is derived here as an operator identity for the potential and added, without screening or fitting, as a block of separable terms to the separable nuclear input of a charged pair. The representation is compared with the screening–renormalization method and with Coulomb-distorted form factors on two-body benchmarks: the off-shell $t$~matrix, the Coulomb displacement of the $\alpha p$ Pauli-forbidden state, and the Coulomb-modified phases of the $pp$, $\alpha p$ and $\alpha\alpha$ pairs. The Feshbach–Schur projection of the Pauli-forbidden state is shown to require the Coulomb-dressed eigenstate, which the Fock block provides within the same separable problem. At positive energy a finite truncation is a screened Coulomb potential with an analytic, momentum-dependent radius.

Supernovae are major drivers of cosmic chemical evolution. They synthesize heavy elements and disperse them into the interstellar medium via their explosion shocks. Light elements are converted into heavier ones during both presupernova evolution and the explosive event itself. Supernova explosions generate nucleosynthesis environments rich in neutrons, protons, and neutrinos under unique thermodynamic conditions, which can enable the production of heavy elements beyond iron. Modern numerical simulations are constructing increasingly realistic explosion models of various supernova channels, providing more accurate nucleosynthesis conditions and chemical yields. In tandem with advances in large-scale spectroscopic surveys delivering precise, high-resolution stellar abundance data, as well as isotopic ratios from presolar grains and meteorites, our understanding of the supernova role in cosmic nucleosynthesis is poised to advance significantly. We review recent progress in modeling various supernova channels, with particular emphasis on nucleosynthesis yields derived from state-of-the-art simulations. We examine the roles of Type Ia, core-collapse, electron-capture, and pair-instability supernovae in producing intermediate-mass, iron-peak, trans-iron, and very heavy elements, as well as their characteristic chemical imprints. We also outline major theoretical uncertainties that affect yield predictions. We intend this review to serve as a timely reference for theoretical model development and a practical guide for interpreting observational abundance data.

The computation of transport coefficients in interacting quantum many-body systems is rarely analytically accessible. Here, we develop a new Krylov-space mechanism that makes the leading density dependent correction to Green-Kubo diffusivity exactly calculable in the strong-dissipation regime of a one-dimensional noisy spin-$\frac{1}{2}$ XXZ chain. This is done by showing that the density-polarization-dressed bond coherence generates a Krylov subspace where repeated action of the dissipator closes exactly on an explicitly identifiable operator family. Within this subspace, the dissipative dynamics is then mapped onto a self-similar semi-infinite chain with a boundary defect. Surprisingly, all Lanczos coefficients of the Krylov chain and its boundary Green's function can be determined exactly. The latter then determines the exact leading density-dependent correction to the diffusivity. Finally, we calculate analytically the full boundary-to-bulk Green's function and find that it decays exponentially along the emergent Krylov chain.

A nucleus is conventionally called stable when no decay has been observed. We replace this phenomenological definition with a criterion based on conservation laws alone. For this purpose, we formulate a general decay form (GDF) for finite charge-neutral nuclear systems that includes all possible final configurations allowed by known conservation laws. A nucleus is absolutely stable if no allowed configuration has lower mass. A global search over all nuclei with measured atomic masses yields 84 absolutely stable nuclei. Beyond the criterion of absolute stability, we introduce a dimensionless decay-accessibility entropy SGDF to quantify the relative accessibility of GDF-allowed decay channels. We rank all naturally occurring isotopes according to their maximum SGDF values and predict their dominant decay modes and corresponding partial half-lives. We further identify promising candidates for natural alpha and two-neutrino double-beta decays. The resulting framework also provides a nuclear-scale perspective on the far-future evolution of matter, in which nuclear decay drives matter toward combinations of these 84 absolutely stable nuclei before still slower forms of matter evolution. These findings extend the conventional phenomenological stable-radioactive classification to a conservation-law-based framework for nuclear stability and provide a quantitative roadmap for future rare-decay searches.

Thermal neutron capture on a proton, $np\to d\gamma$, is measured to a fraction of a percent; the impulse approximation misses nine percent of it. This article follows that gap through five decades of an idea of Mannque Rho's, the chiral filter. Chiral symmetry fixes the pion-exchange current that fills the gap, and power counting explains why nothing else competes. The missing nine percent becomes a prediction, correct within errors. On the unprotected side, one constant fixed by tritium beta decay predicted solar $pp$ fusion and the hep process; $g_A^*$ remains open.

We investigate the nuclear responses for the WIMP-nucleus scattering in the dark matter direct detection with particular emphasis on the inelastic channel for the $^{129}$Xe and $^{131}$Xe isotopes. Our generalization incorporates both the elastic and inelastic scattering channels. With multipole expansion of the effective operators, the angular momentum, parity and time-reversal selection rules can effectively determine the allowed transitions. Instead of the nuclear shell model, we use the state-of-the-art relativistic configuration-interaction density functional theory, which is more suitable for heavy nuclei such as xenon isotopes, to calculate the nuclear response functions. For certain interaction operators, the inelastic contribution can be comparable as its elastic counterpart and some can even dominate by up to three orders of magnitude. Additionally, the higher excited nuclear states can have comparable signal rate as the first excited states. We compare our results with the nuclear shell model calculation. The differences would have significant effects for interpreting the dark matter direct detection searches.

We study bottomonium $\Upsilon$($n$S) production in ${\rm O}+{\rm O}$ collisions at $\sqrt{s_{NN}}=5.36$~TeV, including both cold nuclear-matter (CNM) effects and final-state interactions in a short-lived quark-gluon plasma. The CNM baseline is calculated using the EPPS21 nuclear parton distribution functions together with coherent energy loss and transverse momentum broadening. Hot-medium effects are evaluated with two transport approaches coupled to the same centrality-resolved 3+1D aHydroQP background: the QTRAJ-NLO open-quantum-system calculation, implemented with the QTraj code, and the TAMU-NP semiclassical rates, including primordial suppression and regeneration. The CNM effects give a moderate, state-independent suppression, dominated by the nPDF modification. The energy loss and transverse momentum broadening contribution remains at the few-percent level. Both transport approaches predict a sequential suppression pattern, $R_{AA}^{\Upsilon(1\rm{S})}>R_{AA}^{\Upsilon(2\rm{S})}>R_{AA}^{\Upsilon(3\rm{S})}$, with the strongest suppression around midrapidity in central collisions. The suppression of the ground state is similar in the two approaches but differs for the excited states. Since the CNM factor is common to all states, double ratios provide a direct measure of the relative hot-medium suppression. Our results support the conclusion that ${\rm O}+{\rm O}$ collisions at the LHC can produce a short-lived QGP capable of modifying bottomonium yields.

Upon transmission through an unpolarized target initially unpolarized nuclei with spin $S\ge1$ acquire tensor polarization due to spin dichroism effect. For nuclei passing several nuclear lengths in the target, the acquired component $p_{zz}$ can reach substantial values of ~0.2-0.8. The beam obtained in this way can be effectively used to study reactions with tensor-polarized nuclei.

A sufficiently strong hadron-to-quark first-order phase transition can give rise to a third family of stable compact stars that are commonly referred to as hybrid hadron-quark stars. Stable hybrid stars that have the same gravitational mass as neutron stars are referred to as twin stars. Although equilibrium twin stars may exist, whether they can be dynamically formed remains an open question. We investigate this problem by examining the gravitational binding energy of competing equilibrium configurations at fixed baryonic rest mass and by performing general relativistic hydrodynamical simulations of several possible transition channels. While twin stars are more gravitationally bound than neutron stars with the same rest mass, this energetic preference alone does not determine the dynamical outcome. Compression and shocks during the evolution generate thermal pressure that can prevent the system from settling on the cold twin star branch. Our simulations show that sufficiently rapid cooling can remove this thermal support and enable twin star formation, whereas slower or no cooling generally favors a neutron star remnant. Accessing the twin star branch through the formation channels considered here requires cooling on a timescale comparable to or shorter than the stellar dynamical timescale. Since realistic cooling mechanisms operate on much longer timescales, our results suggest that in channels that conserve the total rest-mass neutron stars may be dynamically favored even when a more gravitationally bound twin star configuration exists with the same rest mass. Our results demonstrate a point of principle, at least for equations of state where the quark deconfinement density does not change appreciably for temperatures up to $10-20\,\textrm{MeV}.$

Recent progress in collider physics has reformulated phenomenological questions in terms of detector correlation functions and advanced their theoretical understanding. These advances have primarily focused on correlators of the average null energy operator, $\mathcal{E}(\vec{n})$, known as energy correlators. However, colliders have access to a much broader class of detector operators, $\mathcal{E}^n_R(\vec{n})$, which measure powers of the energy on a subset of hadrons $R$, such as charged hadrons. These generalized detectors are generically not infrared and collinear safe, and their description requires nonperturbative matching between the hadronic detectors measured in the infrared and the partonic detectors used in ultraviolet calculations. We develop a framework for computing their multi-point correlation functions. We introduce universal nonperturbative matching coefficients, termed "detector functions", that implement this infrared-ultraviolet matching. For the $\mathcal{E}_R^n$ operators studied here, these coefficients are represented by energy-weighted moments of single- and multi-hadron fragmentation functions. We present their renormalization group structure, derive QCD factorization theorems for the projected correlators, and compute jet functions through next-to-leading order. In the fixed-coupling pure Yang-Mills limit, we derive the light-ray OPE of hadronic detectors and connect it to the QCD factorization framework. We also identify universal nonperturbative power corrections generated by soft radiation, which are enhanced in the collinear limit and can substantially modify the perturbative angular scaling. A parton shower study finds qualitative agreement with the predicted perturbative and nonperturbative scaling behaviors. Our work significantly broadens the space of detector operators under theoretical control, with potential phenomenological applications.

The neutron skin, defined by the difference between neutron and proton root-mean-square radii, is a characteristic manifestation of isospin asymmetry and an important probe of the isovector nuclear interaction. This focused review examines how neutron skins influence particle emission and collective dynamics in heavy-ion collisions, from the Fermi-energy regime to ultra-relativistic energies. By modifying the initial neutron and proton density profiles, the neutron skin affects the isospin composition and geometry of the participant region, pre-equilibrium emission, particle production, fragment formation, and collective flow. We review neutron-to-proton and $\rm{t}/^3\rm{He}$ yield ratios, light clusters, pion ratios, bremsstrahlung photons, isoscaling and fragment momentum distributions, and neutron-proton differential flow and momentum observables, emphasizing their interplay with the symmetry energy and transport dynamics. At high energies, neutron skins also modify the initial geometry, eccentricities, multiplicities, and anisotropic flows in isobar and heavy-nucleus collisions. We discuss the challenge of disentangling these effects from deformation, surface diffuseness, shell structure, clustering, and model dependence. Broader connections to parity-violating electron scattering, dipole responses, coherent elastic neutrino-nucleus scattering, SRC-induced proton skins in momentum space, and neutron-star observables are also explored. Finally, we highlight opportunities from radioactive beams, improved collision experiments, microscopic many-body and transport calculations, and Bayesian inference. Combining multiple reaction systems and observables with complementary nuclear-structure and astrophysical information will be essential for quantitatively constraining neutron skins and the density dependence of the symmetry energy.

We present an ab initio description of the emergence and collapse of enhanced quadrupole collectivity in nuclei near $N=Z=40$ using multi-shell valence-space Hamiltonians derived from chiral two- and three-nucleon forces with the in-medium similarity renormalization group. Projected generator-coordinate calculations with consistently evolved $E2$ operators capture the strong collectivity in $^{80}$Zr and its decrease toward $^{86}$Mo and $^{88}$Ru without empirical effective charges. While the $N,Z=40$ effective single-particle energy gaps remain open, the $1g_{9/2}$–$2d_{5/2}$ spacing is smallest near $^{76}$Sr and $^{80}$Zr, with its variation governed mainly by the proton-neutron monopole contribution. The associated occupancies are consistent with quadrupole correlations involving pseudo-SU(3) $pf$ holes and quasi-SU(3) particles. Excluding the occupation of the proton and neutron $2d_{5/2}$ from the variational space strongly suppresses the deformation and $B(E2;2_1^+\rightarrow0_1^+)$ in $^{80}$Zr. These results mark a steady step toward ab initio computations of heavy open-shell nuclei.