The era of precision ab initio nuclear theory has arrived, enabling uncertainty-quantified predictions for nuclear structure and for interactions with external probes directly from the underlying nuclear force and electroweak currents. This review highlights recent breakthroughs that extend ab initio calculations to the heavy nucleus $^{208}$Pb, to medium-mass systems with complex deformation, and to weakly-bound nuclei near the driplines. We also summarize ab initio calculations of nuclear responses for dark matter direct detection. Together, these advances demonstrate how ab initio methods can substantially reduce nuclear-physics uncertainties in searches for physics beyond the Standard Model, providing a more robust interpretation of current and forthcoming precision experiments.

We studied the level shifts in the $K^- p$ system caused by the interplay of strong nuclear and long range Coulomb potentials. We observed a level rearrangement in the system and found that the $1s$ shift of kaonic hydrogen is in fact ``attractive''. In addition, we demonstrated that absorption in the strong antikaon-nucleon interaction does not destroy the level rearrangement.

Hadronic stars and strange quark stars could coexist within the so-called two-families scenario. In this respect, hadronic matter and strange quark matter correspond to two distinct equilibrium phases described by two different equations of state. We perform here the first detailed Bayesian analysis that makes use of astrophysical and laboratory data in order to constrain the equations of state adopted within the two-families scenario for hadronic and strange quark matter. In particular, in hadronic matter we consider the possible formation of hyperons and delta resonances (beside nucleons) within a class of non linear relativistic mean field models and in quark matter we consider the possible formation of a color-superconducting phase within a bag-like model. Results of the analysis indicate that while at the moment both the one-family and the two-families scenarios are compatible with the data, by comparing the Bayes factors of both models, the two-families scenario is favored with respect to the one-family scenario. Specifically, the two-families framework naturally relieves the tension between the intermediate-density softness of the equation of state required by small-radius objects and the high-density stiffness needed to support massive pulsars. Ultimately, future detections of even more massive compact objects, very compact ordinary-mass objects, or precise measurements of two distinct masses with the same radius, will provide strong indications in favor of the two-families scenario.

The Fayans energy density functional (EDF), and in particular its pairing sector, have been claimed to be able to reproduce the experimental data of charge radii in many instances. A particularly intriguing case is that of the $ \mathrm{Ca} $ isotopes between $ A = 40 $ and $ 48 $, where charge radii exhibit a "bell shape". In our work, we examine the microscopic origin of this behaviour. We prepare in total $ 25 $ paramerizations of the Fayans-like pairing interaction, that are equivalent in fulfilling the same criteria for the reproduction of empirical pairing gaps. We find that both the density and the density-gradient dependence of the pairing interaction are important to reproduce the well-known enhancement of charge radii in the open-shell nuclei, leading to the "bell shape" behaviour of $ \mathrm{Ca} $ isotopes. In particular, this originates from the repulsive nature of the rearrangement potential, and cannot simply be mocked up by a refit of the pairing strength. At the same time, we notice some drawbacks of the Fayans standard EDFs, that may call for investigating a more general form of it.

We establish a short-range effective theory for deformed s-wave halos. The theory applies to a system in which neutrons are weakly bound to a core nucleus, and that core nucleus also exhibits a low-lying rotational band with a $0^+$ ground state and a first $2_1^+$ excited state. The effective theory then must have both halo degrees of freedom and degrees of freedom associated with rotation of the core. This leads to the particle plus rotor model of Bohr and Mottelson at leading order. We identify the relevant leading-order operators in the Hamiltonian that respect the symmetries of the system and the small parameters which define the effective theory's power counting. We carry out calculations for the $^{11}$Be and $^{17}$C systems in which we compute the low-lying positive-parity states of the core $+$ neutron systems up to the core$(2_1^+)$-neutron threshold. We do this for several different regulator parameters and establish that these energies can be renormalized using the leading-order set of operators. The spectrum is accurately described at leading order in both cases. Decay widths to d-wave core-neutron states have sizable cutoff dependence, but the Asymptotic Normalization Coefficients (ANCs) in $s$-wave channels exhibit regulator dependence of a size consistent with next-to-leading-order effects. We also compute Coulomb breakup observables and compare with experimental data, finding leading-order results in reasonable agreement with data for both ${}^{11}$Be and ${}^{17}$C. The addition of one next-to-leading-order operator renders the ANCs of all s-wave states stable with respect to the regulator. It consequently also removes most of the 30\% variation of the leading-order Coulomb dissociation cross section with the regulator.

How are the electric and magnetic distributions carried by protons and neutrons arranged inside an atomic nucleus? One of the most reliable ways to answer this question is to scatter electrons from nuclei. Because the electromagnetic interaction is well understood and electron beams can be prepared and detected with high precision, electron scattering acts as a microscope that probes nuclear structure across a wide range of length scales. In this chapter we discuss how electron-nucleus scattering measurements are related to the distribution of the electric charge and magnetization inside nuclei, and what these distributions reveal about nuclear structure. We present this discussion through modern theoretical tools based on ab initio approaches, which describe nuclei as interacting many-body quantum systems, with many-nucleon interactions and electroweak currents derived from first principles.

The symplectic no-core configuration interaction (SpNCCI) framework is an ab initio many-body method for nuclear structure which makes use of the approximate symplectic symmetry of nuclei by appropriate choice of many-body basis states. In this paper we derive recurrence relations allowing for calculation of one-body and two-body density matrix elements between the SpNCCI basis states. Availability of these matrix elements allows for integration of the SpNCCI framework with other modern many-body methods and for calculation of matrix elements of any one-body or two-body operator.

A systematic Bayesian inference study of the equation of state (EOS) of dense matter with strangeness is presented, extending five relativistic mean-field (RMF) models with both constant and density-dependent couplings to include the full baryon octet. The hyperon-nucleon couplings in the scalar channel are varied within ranges informed by hypernuclear data, while vector isoscalar couplings are fixed by the SU(6) symmetry quark model. Observational constraints from NICER (PSR J0030, J0437, J0740) and GW170817, theoretical constraints from chiral effective field theory ($\chi$EFT) and perturbative QCD (pQCD), and experimental constraints from nuclear saturation properties are imposed simultaneously. We find that the inclusion of hyperons systematically reduces the maximum neutron star mass by $0.05$-$0.10,M_\odot$ across all models while increasing the radius at $1.4,M_\odot$ by $0.5$-$0.8$ km. The speed of sound exhibits a characteristic softening at densities $2$-$3,\rho_{\rm sat}$ coinciding with hyperon onset. All hyperonic models remain consistent with the $2,M_\odot$ constraint. Models with a more flexible isovector channel span a larger proton fraction when only nucleons are included. However, the extra flexibility is visibly suppressed by hyperons, meaning that the average proton distribution is independent of model flexibility when hyperons are included. Less flexible models show comparable or slightly increased proton fractions due to EOS stiffening when hyperons are included. Only a residual number of hyperonic equations of state give rise to a mass-radius curve with a negative slope at low masses. A $1.8,M_\odot$ neutron star with a radius larger than or similar to the radius of a $1.2,M_\odot$ star would provide strong evidence that the star contains baryonic degrees of freedom beyond nucleons.

A microscopic description of nucleon-nucleon (NN) and nucleon-nucleus (NA) scattering is developed using chiral effective field theory (chiEFT) at next-to-next-to-next-to-leading order N3LO. The NN interaction is taken from the EGM formulation, which incorporates spectral function regularization Lambda-tilde to control short range components of the two pion exchange force, together with a Gaussian regulator Lambda to ensure convergence of the Lippmann-Schwinger (LS) equation. The regulator parameters (Lambda, Lambda-tilde) = (450, 500), (550, 600), (600, 600) MeV. The resulting chiEFT NN t-matrix is used to construct the first order optical potential, from which Wolfenstein amplitudes and elastic differential cross sections are calculated. The theoretical amplitudes (B) and (C) for pp and pn scattering at 100 and 200 MeV show good overall agreement with experimental data, with the largest discrepancies appearing in the small real component of the spin orbit amplitude. Calculations of p + 16O and p + 40Ca elastic scattering at 100 and 200 MeV reproduce the measured angular distributions with high accuracy, particularly at forward and intermediate angles. These results demonstrate that the EGM chiEFT potential provides a consistent and quantitatively reliable framework for describing NN observables and NA elastic scattering in the 100-200 MeV energy range, while highlighting the need for improved treatment of short range and spin dependent contributions at higher energies.

Relativistic heavy-ion collisions create deconfined QCD matter whose properties must be inferred from final-state observables through dynamical modeling. This contribution discusses recent progress and open issues in multistage simulations, with emphasis on the connection between bulk evolution, conserved charges, strangeness, and heavy flavor. At RHIC Beam Energy Scan energies, the breaking of longitudinal boost invariance makes charge stopping and rapidity-dependent observables essential for constraining the finite-density medium. Strange hadrons are sensitive to the local chemical environment and conserved-charge correlations, while heavy flavor probes microscopic transport and hadronization. Combining these observables within multi-sector inference frameworks provides a path toward more robust constraints on the equation of state and transport properties of QCD matter.

We introduce novel full configuration interaction quantum Monte Carlo (FCIQMC) as an accurate many-body solver for $\textit{ab initio}$ nuclear structure calculations. This stochastic approach directly samples the exact wave function in the full configuration space, enabling high-fidelity treatment of high-order many-body correlations in strongly interacting nuclear systems. Using interactions from chiral effective field theory, we have computed ground-state energies and charge radii of $^4$He, $^8$Be, $^{12}$C and $^{16}$O with sub-percent-level many-body uncertainties. These results establish FCIQMC as a stochastic full-configuration-space solver capable of treating systems beyond the reach of the conventional no-core shell model, and as an accurate benchmark for truncated many-body expansion methods.

We study O+O collisions at $\sqrt{s_\mathrm{NN}} = 5.36$ TeV within a fully three-dimensional $\text{McDipper}$+$\text{MUSIC}$ model, which allows us to describe the experimentally measured dependence of charged hadron multiplicity on centrality and pseudorapidity. We show that the initial elliptical eccentricity is mainly driven by the fluctuations of the energy deposition and thereby varies considerably event-by-event within a fixed centrality class. This also holds for elliptic flow $v_2$, whose origin in O+O thus differs from that in collisions of heavy nuclei. Using a decomposition of initial states in an average event and uncorrelated modes, we find that despite the large size of fluctuations we can reproduce the joint probability distribution of eccentricity and elliptic flow with a reasonable accuracy with only a small set of fluctuation modes.

Nuclei charge radii play an essential role in understanding the fundamental interactions of finite quantum fermion systems. In this work, input-driven Bayesian neural network based on the Monte Carlo dropout approach has been built to characterize the systematic evolution of charge radii of nuclei with proton number $Z\geq20$ and mass number A\geq40$. The motivated underlying mechanisms have been introduced into the input structures, which contain pairing effect, isospin asymmetry degree, the correlations between the valence nucleons and valence holes for neutron and proton, quadrupole deformation parameter $\beta_{20}$, and the local shape staggering phenomena of $^{181,183,185}$Hg this http URL addition, shell quenching effect is also taken into account by incorporating the modified Casten factor $P^{*}$ into the input structure. The quadrupole deformation parameters $\beta_{20}$ derived from finite-range droplet model (FRDM), relativistic mean field (RMF) theory and Weizsäcker-Skyrme (WS) approach are employed to analyze the local variations of nuclear charge this http URL hyperparameter is adjusted automatically in the constructed this http URL calibrated results give comparable root-mean-square deviations (RMSD) in the training and validation sets with various shape deformation inputs. The abrupt increase in charge radii around N=60 is well reproduced along Z=37-40 isotopic chains, but this trend is less pronounced along Z=36 and 41 chains. This provides a indicator to confirm the rapid shape-phase transition regions around N=60 from the perspective of finite nuclei size. Shell quenching effect of charge radii along the bismuth isotopes are reproduced well at N=126, but slight deviations can be encountered due to the absence of high-order octupole deformation around N=130 regions and shape-staggering phenomena toward neutron-deficient regions, respectively. This means that...

Pion exchange plays a fundamental role in nuclear structure and is responsible for tensor correlations and high-momentum components in nuclei. The $(p,p'\pi)$ reaction provides a unique opportunity to investigate pion dynamics under large-momentum-transfer conditions. Its three-body kinematics allows large momentum transfer to be achieved while keeping the excitation energy of the residual nucleus low. We investigate the kinematical properties of the $^{12}\mathrm{C}(p,p'\pi^+)^{12}\mathrm{B}$ reaction using Lorentz-invariant three-body phase-space calculations. The calculations were performed for a 392-MeV proton beam assuming a constant transition amplitude. The resulting momentum-transfer map and phase-space distribution identify experimentally accessible regions of large momentum transfer and provide guidance for optimizing a double-arm spectrometer experiment at RCNP. The present study establishes a model-independent kinematical foundation for future investigations of pion-induced correlations, high-momentum components, and pion dynamics in nuclei.

The Transition Density Amplitude (TDA) method of Griesshammer et al. is applied to compute scattering observables for Compton scattering, threshold neutral pion photoproduction, and elastic pion scattering on the light nuclei Hydrogen 3, Helium 3, Helium 4, and Lithium 6. In this formalism the amplitude factorizes into an irreducible few-body kernel, which encodes the interaction of the probe with the active nucleons, and a transition density amplitude, which carries the nuclear structure information. Because the densities are computed once per nucleus and momentum transfer and then convolved with any process-specific kernel, the same nuclear input is reused across reactions, yielding substantial computational savings over direct evaluation. This factorization is realized in the publicly available Fortran suite DensityScattering, developed as part of the present work; a researcher implementing a new reaction need only supply the corresponding kernel in a prescribed format, with infrastructure for density handling, integration, quantum-number summation, and output already provided. The TDAs are constructed from nuclear wave functions using the semilocal momentum-space regularized chiral potential of Reinert, Krebs, and Epelbaum at cutoffs of 450 and 500 MeV. For Lithium 6, no-core shell model wave functions are evolved under a Similarity Renormalization Group (SRG) transformation; a back-transformation scheme ("SRG-And-Back"), co-developed for the present work, returns the densities to the physical momentum scale and thereby preserves the original chiral ordering. The induced uncertainty is validated against exact Helium 4 results at the 2% level, and convergence studies for Lithium 6 Compton scattering bound the residual uncertainty below 6%.

Precise knowledge of nuclear structure is essential across fundamental physics, yet probing these structures is notoriously difficult. To address this challenge, ultra-peripheral collisions (UPCs) provide a femtoscopic tomography for imaging the atomic nucleus. UPCs offer a pristine electromagnetic pathway: coherent vector-meson photoproduction generates patterns of diffraction and two-source interference that directly encode the nuclear spatial density. Turning these patterns into quantitative constraints is, however, a challenging inverse problem, complicated by correlated sensitivities to deformation and neutron skin, phase smearing, and experimental backgrounds. Here we introduce an interpretable Multitask deep-learning framework that maps transverse momentum distributions to multiple nuclear-structure indicators simultaneously and identifies the kinematic regions driving each inference. We demonstrate the approach with coherent $J/\psi$ photoproduction in $^{96}_{40}\text{Zr} + ^{96}_{40}\text{Zr}$ collisions, showing that the learned features separate diffraction-dominated and interference-dominated information and provide analysis-ready observables for future high-luminosity data.

The ultra-high-energy cosmic ray (UHECR) puzzle is reviewed under the hints of a few basic results: clustering, anisotropy, asymmetry, bending, and composition changes with energies. We show how the lightest UHECR nuclei from the nearest AGN or Star-Burst sources, located inside a few Mpc Local Sheets, may explain, at best, the observed clustering of Hot Spots at tens EeV energy. Among the possible local extragalactic candidate sources, we derived the main contribution of very few galactic sources. These are located in the Local Sheet plane within a distance of a few Mpc, ejecting UHECR at a few tens of EeV energy. UHECR also shine at lower energies of several EeV, partially feeding the Auger dipole by LMC and possibly a few nearer galactic sources. For the very recent highest energy UHECR event, if a nucleon, it may be explained by a model based on the scattering of UHE ZeV neutrinos on low-mass relic neutrinos. Such scatterings are capable of correlating, via Z boson resonance, the most distant cosmic sources above the GZK bound with such an enigmatic UHECR event. Otherwise, these extreme events, if made by the heaviest composition, could originate from the largest bending trajectory of heaviest nuclei or from nearby sources, even galactic ones. In summary, the present lightest to heavy nuclei model UHECR from the Local Sheet could successfully correlate UHECR clustering with the nearest galaxies and AGN. Heavy UHECR may shine by being widely deflected from the Local Sheet or from past galactic, GRB, or SGR explosive ejection.

We present a variational approach to quantum field theory based on wavefunctions parameterized by neural networks. While variational methods have a celebrated history across many fields, their application to quantum field theory has been limited by well-known challenges. We show that neural-network wavefunctions, combined with modern machine-learning techniques, enable competitive variational calculations in nontrivial field theories. As a demonstration, we reproduce the essential features of the two-dimensional nonlinear $\sigma$-model: asymptotic freedom, dynamical mass generation and the model's step-scaling function.

We introduce and demonstrate an event-level analysis framework for quark-gluon imaging. For a first application we use it for the inference of parton distribution functions from synthetic deep inelastic scattering data. This framework removes the need for unfolding of detector effects and the binning of events, and therefore eliminates two key sources of information loss. We contrast this event-level framework with the traditional histogram approach by performing a closure test for parton distribution functions from event data obtained from a known ground truth. In this study we assume a perfect detector, which makes unfolding straightforward. The elimination of binning in the event-level framework is demonstrated to have important benefits over the traditional histogram approach, and performs better in the closure test, particularly for a smaller number of events. For example, defining a mean-squared error distance metric, we find that the event-level framework performs around $35\%$ better than the traditional approach for a moderate number of events. The benefits of an event-level framework should increase for inference associated with 3D quark-gluon imaging, because these differential cross sections are of higher dimension and the comparative number of measured events is significantly reduced.

Generalized transverse-momentum-dependent parton distributions (GTMDs) are the most complete two-parton correlation functions in QCD, encoding the joint spatial and momentum structure of hadrons. Through appropriate projections and limits they yield generalized parton distributions (GPDs), transverse-momentum-dependent distributions (TMDs), parton distribution functions (PDFs), and phase-space (Wigner) distributions. We construct conformal moments of unpolarized gluon GTMDs at strong coupling using gauge/string duality. For fixed even conformal spin $j$, we distinguish the local boundary limit at $b_T=0$ from the finite-separation regime $b_T>0$, where the planar semiclassical amplitude is governed by a minimal worldsheet. There the GTMD moment factorizes into a universal staple-worldsheet soft factor and a stripped spin-$j$ Witten amplitude carrying target dependence. The cusp of the renormalized minimal area generates the rapidity-logarithmic Collins-Soper structure. We derive universal ultraviolet and infrared endpoint reductions. As $b_T\to0^+$, the finite-separation sector matches onto the local conformal moment through a universal overlap kernel. At large $b_T$, after cusp/perimeter subtraction, it factorizes into target projections and infrared transfer kernels. The ultraviolet endpoint is universal within the leading saddle, whereas the infrared tail depends on the holographic completion: soft-wall, gap-matched hard-wall, and repulsive-wall backgrounds generate algebraic, exponential, and Gaussian falloffs, respectively. Analytic continuation in $j$ yields the low-$x$ Regge regime governed by the holographic Pomeron spectral curve. The framework describes hadron tomography, transverse structure, rapidity evolution, and Reggeization for GTMD moments and provides a unified starting point for holographic studies of observables relevant to the Electron-Ion Collider.

Understanding the structural properties of the pion is essential for elucidating the mechanisms of mass generation within the Standard Model and their role in the emergence and properties of the hadronic matter. Light-front wave functions encode extensive information about the internal structure of these systems and provide the link to measurable quantities such as generalized parton distributions and transverse-momentum-dependent distributions. Guided by recent progress in continuum Schwinger methods, we derive well-founded and practical representations of these quantities, enabling the exploration of several facets of the pion structure, including distribution amplitudes and distribution functions, elastic and gravitational form factors, and the associated momentum and spatial distributions. The results presented here are consistent with expectations and can be tested at modern experimental facilities, including the new generation of electron-ion colliders.

The positive-parity structure of 152Sm has been investigated through high-statistics {\gamma}-ray spectroscopy following the (150Nd({\alpha},2n)152Sm reaction at Elab = 26 MeV. Several collective structures built on excited 0+ states have been extended through the observation of new levels and {\gamma}-ray transitions, and spin-parity assignments have been established using directional-correlation and linear-polarization measurements. Electromagnetic transition strengths (B(E2)), deduced from measured branching ratios and known level lifetimes, reveal pronounced collectivity among the excited configurations. The resulting level scheme provides evidence for a sequence of excited collective bands extending beyond the well-known ground-state and first excited 0+ structures. The excitation energies and transition strengths are examined within the framework of the X(5) critical-point description of the first-order U(5)-SU(3) shape-phase transition. In addition to the established X(5)-like features of the low-lying spectrum, the observed systematics of the higher-lying bands are found to be consistent with excited collective structures exhibiting X(5)-like characteristics. The results provide new constraints on the realization of critical-point behavior in finite nuclei and on the evolution of collectivity in the N=90 region.

The dimensionless tidal deformability, $\Lambda$, of neutron stars (NSs), inferred from gravitational-wave (GW) observations, has thus far been used primarily to constrain the pressure of dense matter near twice nuclear saturation density, leaving the core equation of state (EOS) largely inaccessible to inspiral-phase GW observations. We show that the core EOS can be probed directly through $\Lambda$ using a perturbative analysis of the dimensionless stellar-structure and tidal-response equations formulated in terms of scaled intrinsic variables, without invoking any specific EOS model. We uncover a remarkable EOS-insensitive scaling relation between $\Lambda$ and the central EOS parameter $\mathrm{X}\equiv P_{\rm c}/\varepsilon_{\rm c}$, where $P_{\rm c}$ and $\varepsilon_{\rm c}$ denote the central pressure and energy density, respectively. The relation is validated against a broad ensemble of physically viable EOSs. Applying it to tidal deformabilities inferred from events such as GW170817 enables a direct determination of $\mathrm{X}$. We further derive a tight lower bound, $\Lambda_{\rm{TOV}}\gtrsim 9.2^{+1.2}_{-1.2}$, for maximum-mass NSs along stable mass-radius sequences, quantitatively demonstrating that even the most compact stable NSs remain distinctly separated from black holes, for which $\Lambda_{\rm{BH}}=0$. These findings reveal a previously unrecognized connection between inspiral-phase tidal deformability and the core EOS, establishing a direct link between GW observables and the microphysics of ultradense matter in the strong-gravity regime. The resulting scaling establishes inspiral-phase tidal deformability as a direct and largely model-insensitive probe of the EOS of NS cores.

We numerically calculate the shear viscosity of quark-gluon matter via the Green-Kubo relation with an improved ZPC model. We include all $2\leftrightarrow 2$ parton cross sections at finite temperature, which are based on perturbative QCD and screened with thermal masses, and consider massless quark-gluon systems with Boltzmann statistics in chemical equilibrium. We then compare the Green-Kubo results with the analytical results from the leading-order Chapman-Enskog method for the same parton cross sections over the temperature range $150-600$ MeV. We also examine the simpler case of isotropic and constant parton cross sections. Overall, we find that the two methods agree rather well. Specifically, the Green-Kubo results are greater than the Chapman-Enskog results by an average of $\sim 9\%$ for isotropic and constant cross sections and by an average of $\sim 3\%$ for finite-temperature pQCD cross sections, where the difference between the two methods is presumably due to higher-order corrections to the leading-order Chapman-Enskog results.

The proton's unpolarized $u(x)-d(x)$ parton distribution function (PDF) has been studied by a number of lattice QCD groups through large momentum expansion. However, due to lattice artifacts (excited state contaminations, unphysical pion masses, and discretization effects) and less-advanced theoretical analysis (renormalizations, large-distance extrapolations, and large-log resummations), the resulting PDFs cannot be compared strictly with experimental data. By using the state-of-the-art theoretical tools and mitigating the lattice artifacts empirically, we reanalyze the available datasets in the literature and find that the new PDF in the physical limits is consistent with global fittings within $\sim1\sigma$. This provides compelling evidence that large momentum expansion is capable of accurately predicting the $x$-dependence of the PDFs when ideal lattice data become available.

We present a quantum algorithm for simulating Generalized Parton Distributions (GPDs) in the Schwinger model. Unlike the staggered fermions widely utilized in current quantum simulations, we employ Wilson fermions for lattice discretization. This choice is critical for the quantum computation of GPDs due to their strict preservation of charge conjugation symmetry. We construct a comprehensive algorithmic framework that includes the preparation of hadronic states with non-zero momentum and the measurement of light-cone correlation functions incorporating Wilson lines. We provide a complexity analysis, demonstrating that the resources required for our algorithm scale polynomially with both the number of qubits and the desired precision $\varepsilon$. Finally, we benchmark our approach using exact diagonalization, extracting mass spectra and GPDs (also parton distribution functions) that are consistent with theoretical expectations and fundamental physical constraints.

Standard perturbative quantum field theory is persistently challenged by ultraviolet (UV) divergences and overlapping sub-divergences. In this work, we construct an absolutely UV-finite effective field theory (EFT) natively in four-dimensional spacetime. We embed the complete dynamical operator within a double-exponential capacity measure derived from quantized irreversible null-geometry. By analytically expanding the exact operator resolvent, we demonstrate that a universal macroscopic proper-time bound ($T \ge \tau_0$) natively emerges, structurally collapsing the high-order UV phase space via topological contraction. This mathematically defines the absolute UV boundary of the EFT. Consequently, overlapping subgraph divergences are rigorously identified as distributional pseudo-singularities caused by the continuous approximation analytically oversmoothing the discrete lattice bounds. These artifacts are systematically corrected by employing the Bogoliubov-Parasiuk-Hepp-Zimmermann (BPHZ) protocol strictly as an algebraic mapping operator. Evaluating Quantum Electrodynamics in 4D, we obtain a finite electron bare mass ($m_0 \approx 0.427$ MeV) and derive finite renormalization constants, analytically preserving the exact Ward-Takahashi identity ($Z_1=Z_2$). In Quantum Chromodynamics, the exact preservation of Slavnov-Taylor identities yields a calculable finite bare strong coupling ($\alpha_{s,0} \approx 0.0191$). Generating analytically closed non-perturbative Schwinger-Dyson Equations, this framework provides a consistent, anomaly-free mathematical foundation for finite effective field theories to address dynamic chiral symmetry breaking and mass generation.

Two particle momentum correlation functions provide a nontrivial tool for probing the strong interaction and/or extracting particle emission source information in relativistic nuclear collisions. Although transport models can describe the microscopic phase-space evolution of the collision system, calculating correlation functions within the framework of transport models remains challenging. In this paper, we employ the mixed-event technique to calculate two particle momentum correlation function as $C(k^*)= \mathcal{N} \xi(k^*)\frac{N_{\mathrm{same}}(k^*)}{N_{\mathrm{mixed}}(k^*)}$ based on the parton and hadron cascade model PACIAE simulated final hadronic state (FHS) with introducing a modification factor $\xi(k^*)$ to improve the treatment of final-state interactions and quantum statistics effects in the PACIAE model. The simulated results show good agreement with the ALICE data for $Kp$, $pp$, $p\Lambda$, and $\Lambda\Lambda$ momentum correlation functions in $pp$ collisions at $\sqrt{s}=7$ TeV. On the other hand, the particle emission source radius of the correlated pairs are also evaluated based on the simulated FHS self-consistently. Since the PACIAE model employs hadron-hadron cross sections derived from the additive quark model, the calculation of two-particle momentum correlation functions does not require prior assumptions about the interaction between the two correlated particles. This successful ``PACIAE + modification factor" approach may shed light on the future study of momentum correlation functions for dimesons, dibaryons, and even diexotic hadrons.

We present new constraints on the mass and radius of the neutron star in the neutron star low-mass X-ray binary EXO 0748$-$676 obtained from a joint analysis of 20 quiescent X-ray observations obtained between 2008 and 2025, including 14 Chandra and 6 XMM-Newton exposures. These data sample two quiescent episodes separated by the 2024$-$2025 outburst. We model the 0.5$-$10 keV spectra with a hydrogen-atmosphere model, assuming a source distance of 7.1 kpc. In a global Markov Chain Monte Carlo analysis in which the hydrogen column density, neutron star mass, and radius are tied across all observations, we obtain a neutron-star mass of $1.77^{+0.17}_{-0.22}\,M_\odot$ and a radius of $12.62^{+0.56}_{-0.74}$ km ($1\sigma$ credible intervals). We further perform independent fits to the first and second quiescent epochs and find that the combined data set significantly reduces the low-mass tail in the posterior distribution, leading to tighter lower bounds on the neutron-star mass. Incorporating the distance uncertainty of $7.1\pm1.2$ kpc, we conservatively constrain the neutron-star mass and radius to $M\simeq 1.41-2.11~M_{\odot}$ and $R\simeq 10.15-15.13$ km, favoring relatively stiff dense-matter equations of state. We also trace the thermal evolution across two quiescent epochs and find evidence for renewed crust cooling following the 2024$-$2025 outburst, providing a unique opportunity to compare the thermal relaxation behavior after two distinct accretion episodes.

The eta and eta' mesons are conventionally known to receive contribution from the anomalous breaking of axial U(1) symmetry, and they are considered to not be the Nambu-Goldstone (NG) bosons of the spontaneous chiral SU(3)_L x SU(3)_R symmetry breaking of QCD. However, it has recently been shown that this axial U(1) anomaly is not actually physical. In this contribution, we first review this statement and then propose a mechanism in which eta and eta' mesons are indeed NG bosons while being consistent with the axial U(1) problem.

The flavor diagonal CP violation of elementary particle physics contributes to the atomic, nuclear, and nucleon electric dipole moments (EDMs), T-violating neutron optics, and to the angular correlations of beta decay. In this contribution, we review the basics and the importance of CP violation in the search for new physics beyond the standard model, the recent progress in the quantification of the hadron level CP violation contributing to the aforementioned observables, and finally the current attempt to solve the strong CP problem without additional interactions and fields.

Low-energy vibrational excitations associated with the fluctuation of quadrupole deformed shapes are discussed within the frame of state-of-the-art Configuration Interaction calculations, actually performed via the Quasi-particle Vacua Shell Model version of the Monte Carlo Shell Model. Recently, low-lying $\gamma$ bands in heavy strongly deformed nuclei were shown to be rotational $K^P$ = 2$^+$ excitations of triaxially deformed states (see T. Otsuka \etal, Eur. Phys. J. A 61, 126 (2025)) rather than vibrational excitations as traditionally interpreted. In this context, it is important to identify possible low-lying vibrational excitations and to characterize the excitation energy at which they emerge. Focusing on two typical examples, $^{166}$Er and $^{162}$Dy, vibrational states are indeed identified above the $\gamma$ band using an extended version of the so-called T-plot. The phenomenon of shape coexistence is also shown to produce low-lying states below such vibrational band heads. These results suggest novel and rich structures in heavy deformed nuclei. While experimental counterparts are seen for some of such states, others are predictions opening doors to future dedicated experiments.

The Parity-Doublet Model (PDM) is a chirally invariant effective theory for strong-interaction matter involving nucleons and their opposite-parity partners in a parity-doubling framework. We introduce a multiplicatively renormalizable mean-field approach to include the baryonic vacuum contributions to the resulting grand-canonical potential in an explicitly renormalization-group invariant form. As an application, we evaluate the pertinent thermodynamics of two-flavor symmetric and asymmetric nuclear matter, focusing on the restoration of spontaneously broken chiral symmetry at baryon densities and temperatures relevant for the astrophysics of neutron stars. Special attention is paid to the effect of the baryonic vacuum fluctuations on the evolution of the chiral condensate with baryon density and temperature for specific choices of the chirally invariant baryon mass m0 to demonstrate the importance of consistently including these vacuum fluctuations in the PDM.

We present a framework for local quantum cooling that can be efficiently applied to large-scale Fermi systems. The method introduces local Hermitian operators as a cooling potential while strictly preserving the unitarity of time evolution. Our formulation scales favorably with system size and can be seamlessly integrated into time-dependent density-functional theory frameworks. We demonstrate that energy cooling arises from the damping of particle currents and pairing-field fluctuations. Furthermore, we develop a variant of the scheme that allows the particle number to vary in time, enabling controlled density scans. The method is generic and versatile, as illustrated by applications to spin-imbalanced unitary Fermi gases and to nuclear matter in the neutron-star crust. The framework can be naturally extended to include stochastic noise, providing a foundation for studying thermalization in strongly interacting Fermi superfluids.

Three-nucleon force (3NF) plays an important role in understanding the structure of finite nuclei and the saturation properties of infinite nuclear matter. More specifically, 3NF should be necessary for each two-nucleon force (2NF) to obtain more accurate description of nuclear systems. 3NF derived from the chiral effective field theory has been successful in $\textit{ab initio}$ calculations of atomic nuclei. Most of established chiral nuclear forces have a nonlocal form in the momentum space. In this work, we construct a companion chiral 3NF specifically tailored to the new Idaho local position-space 2NF, and calculate binding energies and radii of nuclei up to $^{132}$Sn. We find that a chiral 3NF with hybrid local and nonlocal regulators has advantages in improving the nuclear structure calculations of both binding energies and radii with the new Idaho 2NF. The two low-energy constants of 3NF are constrained by the ground-state energies of $^3$H and $^{16}$O as suggested in a recent work.

The unique resonance features in the $^{12}$C+$^{12}$C fusion reaction lead to significant fluctuations in the branching ratio $R_{p/\alpha}=\sigma_p/\sigma_\alpha$, making it difficult to determine the $R_{p/\alpha}$ at astrophysical energies. By combining Hauser--Feshbach statistical-model calculations with constraints from direct charged-particle and gamma-ray measurements, we investigate the energy dependence of the averaged $R_{p/\alpha}$ and predict its behavior within the Gamow window. Owing to the strong energy dependence of $R_{p/\alpha}$, the corresponding reaction-rate ratios, $\langle \sigma v \rangle_p / \langle \sigma v \rangle_\alpha$, during core and shell carbon burning are determined to be 0.29, 0.45, and 0.52 at $T_9 = 0.5$, 1.0, and 1.2, respectively, significantly lower than the widely adopted CF88 constant value of 0.79. The implications of the revised $\langle \sigma v \rangle_p / \langle \sigma v \rangle_\alpha$ ratio for stellar nucleosynthesis and white-dwarf evolution are also discussed.

To improve the prediction accuracy of $\alpha$-decay half-lives in heavy and superheavy nuclei, a physics-guided residual-correction framework combining the effective liquid drop model (ELDM) with machine-learning methods is proposed. The ELDM is first used as the macroscopic baseline for describing the barrier-penetration process, and XGBoost and TabPFN models are then employed to learn the residual deviations between ELDM predictions and experimental data. To incorporate microscopic nuclear-structure information, several physically motivated descriptors are constructed, including deformation-related quantities, Geiger--Nuttall-related features, and minimum orbital angular momentum. The results show that machine-learning residual correction significantly improves the predictive performance of the ELDM baseline. Among all models, TabPFN-term3 achieves the best accuracy, reducing the RMSE and MAE to 0.348 and 0.248, corresponding to improvements of 38.60\% and 40.46\%, respectively. Residual-distribution and feature-ablation analyses further indicate that the corrected predictions are closer to experimental values and that physically motivated descriptors play an important role in learning nonlinear residual structures. Overall, the proposed ELDM-based residual-correction framework can effectively compensate for missing microscopic nuclear-structure effects while preserving physical interpretability, providing a feasible strategy for high-precision $\alpha$-decay half-life prediction.

The scaling properties of the $\Delta\gamma$ correlator, guided by calculations from the Anomalous Viscous Fluid Dynamics (AVFD) model, are used to investigate charge separation in $p$+Au, $d$+Au, Ru+Ru, Zr+Zr, and Au+Au collisions at $\sqrt{s_{\mathrm{NN}}}=200$~GeV, and in $p$+Pb and Pb+Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ and $2.76$~TeV. The ratio $\Delta\gamma/v_2$, where $v_2$ is the elliptic-flow coefficient, exhibits a common approximate $1/N_{\rm ch}$ scaling behavior for $p$+Au, $d$+Au, $p$+Pb, and Pb+Pb collisions, establishing a common multiplicity-dilution baseline for background-driven charge correlations. In contrast, Ru+Ru, Zr+Zr, and Au+Au collisions show significant deviations from this scaling trend. These violations are qualitatively similar to those obtained in AVFD calculations with an input chiral magnetic effect (CME) signal and point to an additional charge-separation component beyond that expected from the observed background scaling. Quantitative estimates indicate that, in mid-central collisions, the corresponding CME-sensitive fraction of the measured $\Delta\gamma/v_2$ is approximately 27\% for Au+Au collisions and roughly a factor of two smaller for Ru+Ru and Zr+Zr collisions, which exhibit similar magnitudes within uncertainties. The extracted magnitudes imply an expected Ru+Ru--Zr+Zr signal difference of only $\sim1.3\%$, suggesting limited sensitivity of the $\Delta\gamma$ correlator to the small difference expected between the isobar signals.

Emergent macroscopic descriptions of matter, such as hydrodynamics, are central to our description of complex physical systems across a wide spectrum of energy scales. The conventional understanding of these many-body phenomena has recently been shaken by a number of experimental findings. Collective behavior of matter has been observed in \emph{mesoscopic} systems, such as high-energy hadron-hadron collisions, or ultra-cold gases with only few strongly interacting fermions. In such systems, the separation of scales between macroscopic and microscopic dynamics (at the heart of any effective theory) is inapplicable. To address the conceptual challenges that arise from these observations and explore the universality of emergent descriptions of matter, the EMMI Rapid Reaction Task Force was assembled. This document summarizes the RRTF discussions on recent theoretical and experimental advances in this rapidly developing field. Leveraging technological breakthroughs in the control of quantum systems, we can now quantitatively explore what it means for a system to exhibit behavior beyond the sum of its individual parts. In particular, the report highlights how the (in)applicability of hydrodynamics and other effective theories can be probed across three principal frontiers: the size frontier, the equilibrium frontier, and the interaction frontier.

We perform the first simultaneous global QCD analysis of pion and kaon parton distribution functions (PDFs), constrained by pion- and kaon-induced Drell-Yan (DY) and leading neutron electroproduction data, together with lattice QCD data on pion and kaon PDF moments. The analysis indicates a softer valence $\bar u$ distribution in the $K^-$ than in the $\pi^-$, and a significantly more peaked valence $s$-quark density in $K^-$ compared with the $\bar u$. The effective exponent governing the high-$x$ behavior of the PDF is found to be larger for $\bar u$ in the kaon, $\beta_{\bar u}^{K^-}\!= 1.6(2)$, than in the pion, $\beta_{\bar u}^{\pi^-}\!= 1.16(4)$, in the range $0.7 \leq x \leq 0.95$. From the gluon momentum fractions we find the pion's gluon content accounts for $\approx 1/3$ of the mass budget of the pion at $\mu=2~{\rm GeV}$, but only $\approx 1/4$ for the kaon.

In recent years, astrophysical observations have placed tight constraints on key properties of the nuclear equation of state (EoS). Using 93 two-dimensional simulations for three different EoS compatible with the current tight constraints, we show that the EoS remains a major uncertainty for the outcome of core-collapse supernovae. Whereas explosions are obtained in most cases for the SFHo and SFHx EoS, for the CMF EoS, which includes a crossover from nucleonic matter to a quark phase, explosions occur only for 2 out of 15 progenitors. Less favourable conditions for neutrino-driven explosions arise for the CMF EoS due to lower neutrino luminosities and mean energies and slightly weaker contraction of the warm proto-neutron star. Our results suggest that the explodability of massive stars cannot yet be predicted based on first principles without better knowledge of the nuclear EoS. Conversely, observational constraints on stellar explodability may help further constrain the EoS.

Using a hadronic framework, we derive an explicit expression for photon production from neutral pions in a weak background magnetic field. Our calculation is built on the proton triangle diagram with an effective Yukawa $\pi^0$-proton coupling, offering an alternative to quark-level descriptions that is advantageous when the magnetic length greatly exceeds the proton size. Corrections to the pion decay constant are computed up to second order in the magnetic-field strength, revealing that the field generally suppresses the decay rate. Quantitatively, however, the effect remains modest even for fields as strong as $|eB|\simeq m_\pi^2$. The differential photon emission rate exhibits anisotropy, with the strongest suppression occurring when the pion momentum is perpendicular to the magnetic field. Overall, the modification of the $\pi^0 \to \gamma\gamma$ rate is parametrically small, scaling as $|eB|^2/m_P^4$, where $m_P$ is the proton mass. While the magnetic-field-induced anisotropy is conceptually interesting in principle, it is likely too small to be resolved in present heavy-ion measurements.

We investigate the effects of anisotropy on dispersion relations and convergence in relativistic hydrodynamics. In particular, we show that for dispersion relations with a branch point at the origin (such as sound modes), there exists a continuum of collisions between hydrodynamic modes at complex wavevector. These collisions are then explicitly demonstrated to be present in a holographic plasma. We lay out a criterion for when the continuum of collisions affects the convergence of the hydrodynamic derivative expansion. Finally, the radius of convergence of hydrodynamic dispersion relations in anisotropic systems is bounded from above on the basis of compatibility with microscopic causality.

The hyperfine interaction in the ground state of a hydrogen atom of assumed radius $R$ is proportional to $-1/R^3$, raising the question of why the hyperfine interaction does not lead to collapse of hydrogen, or positronium. We approach the problem in terms of a minimax variational calculation based on the exact Gordon solution of the Dirac equation for the hydrogen atom ground state. The full Dirac treatment leads to the result that in an assumed variational state of size $R$, when $R$ minimizes the total energy the magnetic moment of the electron assumes its usual value, $e\hbar/2mc$, but when $R<\hbar/mc$, the effective electron magnetic moment becomes essentially $eR/2$, softening the hyperfine interaction and eliminating an energy minumum at small $R$. The magnetic moment of the proton is similarly suppressed, and the hyperfine interaction of a small size atom becomes bounded by the kinetic energy, thus assuring stability. We extend the Dirac variational calculation to positronium where we find simple results for the ground state energy and hyperfiine interaction, and then extend this variational calculation to Coulombic atoms of two fermions of arbitrary masses. This paper also lays out a framework for treating diquarks as relativistic Coulombic systems, in the presence of color electric and magnetic interactions.

We construct a hybrid equation of state (EoS) by smoothly interpolating the EoS in the hadron resonance gas at low temperatures to that in the ideal parton gas at high temperatures, and employ it to study the properties of the quantum chromodynamics (QCD) matter under finite magnetic field and nonzero chemical potential. In this work, we neglect the anomalous magnetic moment effects of both charged and neutral particles. Our results show that the thermodynamic observables such as the entropy density, the pressure, the energy density, the trace anomaly, and the specific heat at constant volume are sensitive to both finite magnetic field and chemical potential. As the chemical potential increases from zero, these quantities rise in both the hadronic and quark-gluon plasma phases. In contrast, introducing a magnetic field suppresses them at low temperatures but enhances them at high temperatures. Furthermore, nonzero chemical potential and magnetic field introduce nontrivial modifications to the squared speed of sound. Both effects increase its value near the critical temperature while reducing it at lower temperatures. When both the chemical potential and the magnetic field are present, their influences superimpose, leading to more intricate changes in the thermodynamic behavior. Finally, we compare our results with the lattice QCD data for the quadratic fluctuations of conserved charges and their correlations. The model successfully reproduces the temperature dependence of these observables at $eB=0$ and 0.04 GeV$^2$. However, at the stronger field strength $eB=0.14$ GeV$^2$, the model underestimates the magnitudes while still capturing the overall temperature trend.

It is well known that the diffusion equation, when treated as a stand-alone partial differential equation, exhibits exponential instabilities in boosted frames, which render the corresponding initial-value problem ill-posed. Recently, however, it was shown that Fick-type diffusion arises as the exact hydrodynamic sector of relativistic Fokker-Planck kinetic theory. In this work, we exploit this kinetic embedding to formulate a modified initial-value problem for one-dimensional Lorentz-boosted diffusion. We show that the resulting dynamics are well posed both forward and backward in time, provided the boosted density profiles admit a kinetic-theory realization. Such profiles form a space of band-limited functions, within which the evolution can be expressed as a discrete superposition of spatially sampled initial data, weighted by a Shannon-Whittaker-type Green function defined on the full Minkowski plane. The Green function is obtained in closed analytic form.

We study QED$_2$ in de Sitter space as a minimal interacting gauge theory in which cosmological expansion directly competes with quantum dynamics. In cosmic time, the hopping redshifts as $1/a(t)$ while the electric term grows as $g^2 a(t)$, sweeping the spectrum through a moving narrow-gap region in the $(\tau,m)$ plane. Exact diagonalization shows that this defines a pseudo-critical line governing the loss of adiabaticity, excitation growth, and redshifted response. Using matrix-product states at a fixed mass, we separate the fixed-cutoff thermodynamic limit from the continuum extrapolation. The late-time dip survives in the infinite physical box size limit, and shifts to later $\tau$ as the lattice spacing goes to zero, with current data favoring $\tau_* \approx 3.1$, while the dip depth remains less controlled. For Gibbs initial states, the same mechanism produces an irreversibility front in the relative entropy that tracks the pseudo-critical line and is detectable via LOCC-accessible observables. These results identify de Sitter QED$_2$ as a controlled setting for linking curved-space gauge dynamics, near-critical spectral structure, and operational irreversibility.

We present the TQ4Q2.0 fragmentation functions for the production of all-heavy (fully heavy) $S$-wave tetraquarks ($T_{4Q}$) with scalar ($0^{++}$), axial-vector ($1^{+-}$), and tensor ($2^{++}$) quantum numbers in high-energy hadronic collisions. This work extends the previous TQ4Q1.1 framework by incorporating nonconstituent heavy-quark contributions and introducing a replica-based uncertainty-quantification strategy derived from multi-scale variations (MHOUs). The construction follows a nonrelativistic QCD factorization approach, combining gluon- and heavy-quark-initiated fragmentation channels at leading power. Initial-scale inputs are modeled through updated potential-inspired wave functions, while the subsequent DGLAP evolution is performed via the threshold-aware HF-NRevo scheme. A comprehensive systematic analysis of uncertainties is carried out, with contributions from color-composite long-distance matrix elements (LDMEs) and perturbative multiscale inputs. The resulting TQ4Q2.0 grids, publicly released in LHAPDF6 format, provide the first complete phenomenological set for all-heavy exotics, enabling precise studies of all-charm tetraquark production and jet-associated observables within the JETHAD environment. This article completes the high-energy resummation-driven generation of the TQ4Q program and establishes a definitive baseline for future collider-oriented analyses of all-heavy multiquark dynamics.

The exclusive photoproduction of a pair of light mesons is studied within the framework of collinear factorisation. The amplitude factorises into a process-dependent perturbatively calculable hard part, a generalised parton distribution (GPD) and two distribution amplitudes (DAs). We focus on the production of any combination of $\rho$ and $\pi$ mesons (of any charge and polarisation) that do not involve neutral $C=+$ exchanges with the nucleon. This gives a total of 26 distinct channels, which are sensitive to quark GPDs only. We calculate the amplitude for this family of di-meson processes at leading order in the strong coupling constant $\alpha_s$ and at leading twist, in a fully-automated way. Depending on the choice of mesons in the final state, some of these processes are sensitive to chiral-odd (helicity-flip) GPDs. Particular attention is given to the treatment of poles in the 3-dimensional convolution integral of the momentum fractions connecting the hard part with the different non-perturbative components. These poles are regularised by the usual Feynman $i \epsilon$ factors, but lead to numerical instabilities if not dealt with properly. We also discuss in detail the construction of the phase space. Importantly, we propose a resolution for the inconsistency of the kinematics of the hard part of the process, where hadron masses and other soft scales are neglected, with the rest of the process. As a proof of concept, we explicitly evaluate the cross section, for a subset of processes whose amplitudes have been constructed, at energies typical of the CLAS12 experiment at JLab. Our results indicate that exclusive di-meson photoproduction processes have very good statistics, which can be a factor of up to a hundred more than the exclusive photon-meson photoproduction process. Therefore, the family of processes that we study here represents a great opportunity for GPD extraction.

We present a four-dimensional equation of state for strongly interacting matter at finite temperature and conserved charge densities, constructed using a deep neural network. It is designed for direct use in hybrid models of relativistic heavy-ion collisions: it reproduces hadron resonance gas thermodynamics at typical particlization scales, is consistent with lattice QCD at low baryon chemical potential, and extrapolates into the high-density region inaccessible to either approach, which is precisely the regime targeted by RHIC BES, FAIR, HADES, and CBM. Thermodynamic consistency throughout the full phase space is enforced via a physics-informed loss function. We demonstrate the developed equation of state by implementing it at zero net strangeness and fixed electric-to-baryon charge ratio within the integrated hydrokinetic model.