We introduce a novel extension of the volume-averaged correlation function (VACF) framework by replacing the traditional spherical smoothing kernels with anisotropic, ellipsoidal windows. This generalized approach enables the study of shape-dependent clustering statistics and captures directional information encoded in large-scale structure, particularly in redshift space where galaxy distribution is distorted by peculiar velocities. We define and compute ellipsoidal VACFs ${\overline{\xi }}_J(r_{\parallel },r_{\perp })$ and the corresponding reduced cumulants $s_J(r_{\parallel },r_{\perp })$, allowing for joint sensitivity to both scale and anisotropy across arbitrary statistical order $J$. Using a suite of comoving Lagrangian acceleration $N$-body simulations spanning a grid of cosmologies with varying ${\mathrm{\Omega }}_M$ and ${\sigma }_8$, we analyze the behavior of ellipsoidal VACFs and cumulants in both real and redshift space. We find that the shape of the smoothing kernel that maximizes the clustering signal depends strongly on the redshift-space distortion regime: spherical in real space, prolate in the fingers-of-god-dominated regime, and oblate in the Kaiser squashing-dominated regime. While the standard VACF amplitude is mainly sensitive to ${\sigma }_8$, the shape-dependence of redshift-space skewness shows a coherent response to the combined growth parameter $f{\sigma }_8$, with a typical sensitivity at the $1-3\sigma$ level between neighboring models. Our results demonstrate that ellipsoidal VACFs offer a computationally efficient and information-rich generalization of counts-in-cells analysis, with promising applications to galaxy survey data, halo catalogs, and cosmological tests of gravity beyond $\mathrm{\Lambda }$ cold dark matter.

In a previous paper, we proposed a new approach to the beginning of inflation—a lingering universe [Melcher et al. Phys. Rev. D 110, 063517 (2024).]—that is a quasistatic phase prior to inflation. The Universe begins in a lingering state with a nearly vanishing Hubble parameter. This calls into question the absolute age of the Universe, as the Hubble time can be nearly infinite. It also provides promise for addressing the initial singularity of inflation and issues with quantum field theory in de Sitter spacetime. Such models arise in classical cosmologies with nonvanishing spatial curvature (inspired by PLANCK 2018 data) and independently by models that arise in string cosmology. In this paper, we consider the importance of cosmological perturbations for the stability of the lingering phase and how this influences cosmological observations. Our goal is to establish observables in this new paradigm for the origin of inflation, which is in contrast to eternal inflation and cyclic cosmologies. We also address questions of stability and the transition to inflation.

A protoneutron star (PNS) gets formed after a successful supernova when the stellar remnant decouples from the ejecta. In this study, we explore a relativistic framework for the finite-temperature $\beta$-equilibrium limit of equation of state (EOS), constrained via a Bayesian inference methodology. The EOS is obtained using a minimal number of constraints, including a few nuclear saturation properties, low-density pure neutron matter constraints from chiral effective field theory, and a neutron star (NS) maximum mass greater than $2.0M_{\odot }$. Two sets of EOS derived from the relativistic mean-field model for nucleonic and hyperonic matter constrained by a Bayesian inference calculation at the zero temperature limit are used. The thermal adiabatic index (${\mathrm{\Gamma }}_{\mathrm{Th}}$) is calculated as a function of the baryonic density across several temperatures for both the sets. Our results suggest that the maximum NS mass is of the order of $2.15M_{\odot }$ if hyperons are present. In addition, the present study suggests that an observation of NS with mass larger than $2.2M_{\odot }$ can indirectly indicate the absence of hyperons in its core. The deleptonization of hyperonic PNS reduces the stellar maximum mass rendering the PNS exceeding the zero temperature maximum stellar (baryonic) mass limit becomes metastable which is prone to collapse into a black hole while PNSs below such a mass threshold evolve to a stable NS.

Instrumental artifacts, such as glitches, can significantly compromise the scientific output of the Laser Interferometer Space Antenna (LISA). Our methodology employs advanced Bayesian techniques, including reversible jump Markov chain Monte Carlo and parallel tempering to find and characterize glitches and astrophysical signals. The robustness of the pipeline is demonstrated through its ability to simultaneously handle diverse glitch morphologies and it is validated with a “Spritz”-type dataset from the LISA Data Challenge. Our approach enables accurate inference on massive black hole binaries, while simultaneously characterizing both instrumental artifacts and noise. These results present a significant development in strategies for differentiating between instrumental noise and astrophysical signals, which will ultimately improve the accuracy and reliability of source population analyses with LISA.

We use hierarchical Bayesian inference with nonparametric Gaussian process models to investigate the effective inspiral spin parameter, ${\chi }_{\mathrm{eff}}$, as a function of primary black hole mass in the third gravitational-wave transient catalog (GWTC-3). Our analysis reveals a transition in the population at a primary mass of ${46}_{-5}^{+7}{M}_{\odot }$. Beyond this mass, the ${\chi }_{\mathrm{eff}}$ distribution broadens, becomes consistent with being symmetric around zero, and has a median of $-0.03_{-0.59}^{+0.36}$ (90% credibility). These results are consistent with the presence of a pair-instability mass gap that is repopulated by black holes that are the remnant of a previous merger, formed in dense star clusters. However, asymmetric distributions skewed toward positive ${\chi }_{\mathrm{eff}}$ are not excluded by current data. Below the inferred transition mass, we constrain the fraction of second-generation black holes to be $\lesssim 10\%$. These results provide model-independent support for a high-mass and high-spin population of black holes in the data, consistent with earlier work using parametric models. Imminent gravitational-wave data releases will be essential to sharpen constraints on spin symmetry and clarify the origin of the black holes.

We explore the effects of the neutrino collisional flavor instability (CFI) based on 1D and 2D core-collapse supernova (CCSN) simulations done using the sophisticated radiation-hydrodynamic code fornax. We compare the growth rates of homogeneous CFI (hCFI) modes calculated by numerically solving the multigroup dispersion relation to those calculated using the monochromatic approximation. We find that the widely used monochromatic approximation leads to incorrect growth rates when applied in multigroup scenarios. As opposed to the $\sim {10}^5{\mathrm{s}}^{-1}$ values given by the monochromatic approximation, the actual growth rates of nonresonance multigroup hCFI are at most $\sim 200{\mathrm{s}}^{-1}$ in all our models and they are too slow to affect CCSN outcomes. We adopt a Bhatnagar–Gross–Krook flavor conversion scheme in the simulations to include the effects of resonancelike hCFI. We find that the CCSN dynamics and neutrino emission properties are only weakly influenced, and the intrinsic stochasticity due to convection and neutrino-driven turbulence can naturally lead to comparable effects. Hence, our analysis of the nonresonance and resonancelike hCFI into CCSN simulations suggests that the effects of neutrino flavor conversion triggered by hCFI modes are in general small.

Relativistic hydrodynamics provides a solid framework for evolving matter and energy in a wide variety of phenomena. Nevertheless, the inclusion of dissipative effects in realistic scenarios through causal, stable, and well-posed theories still constitutes an open problem. In this paper, we study the evolution of the algebraic and differential constraints stemmed from the first-order reduction proposed by Bemfica, Disconzi, Noronha and Kovtun (BDNK), for proving the local well-posedness of conformally invariant viscous fluids in Sobolev spaces. First, we show analytically that the whole set of constraints satisfies a homogeneous, strongly hyperbolic system of equations, ensuring a correct propagation as a consequence of the fluid equations. Motivated by this result, we explore their numerical stability by performing simulations of the BDNK reduction restricted to plane-symmetric configurations, in flat spacetime. We report on different initial datasets initially satisfying the constraints, and whose evolution leads to stable configurations. This result suggests that the proposed reduction by BDNK is suitable for numerical evolutions, keeping the constraints accurate under small numerical errors.

In this work, we investigate the behavior of Regge trajectories in the context of quantum field theory at finite temperature. For this purpose, we employ the $\lambda {\varphi }^3$ model. We first compute the Regge trajectories at zero temperature, establishing a baseline for comparison. As a key novelty, we extend our analysis to finite temperature and derive an analytical expression for the Regge trajectories in this regime. We explore how temperature modifies the structure of the Regge trajectories and analyze the physical implications of these modifications, which arise from the resummation of thermal ladder diagrams. As an interesting consequence, we find the thermal evolution of masses belonging to different Regge trajectories.

We introduce a physics-informed neural network (PINNs) framework for modeling the spatial distribution of chromodynamic fields induced by quark-antiquark pairs, based on lattice Monte Carlo simulations. In contrast to conventional neural networks, PINNs incorporate physical laws—expressed here as differential equations governing type-II superconductivity—directly into the training objective. By embedding these equations into the loss function, we guide the network to learn physically consistent solutions. Adopting an inverse problem approach, we extract the parameters of the superconducting equations from lattice QCD data and subsequently solve them. To accommodate physical boundary conditions, we recast the system into an integrodifferential form and extend the analysis within the fractional PINNs framework. The accuracy of the reconstructed field distribution is assessed via relative $L_2$-error norms. We further extract physical observables such as the string tension and the mean width of the flux tube, offering quantitative insight into the confinement mechanism. This method enables the reconstruction of color field profiles as functions of quark-antiquark separation without recourse to predefined parametric models. Our results illuminate aspects of the dual Meissner effect and highlight the promise of data-driven strategies in addressing nonperturbative challenges in quantum chromodynamics.

In this work, we investigate the mass spectra of excited charmonia employing a nonrelativistic potential model with screening effect and analyze their two-body strong decays, two-photon decays, leptonic decays, and hadronic transitions. Especially, we find that the newly observed resonances $X(4160)$, $Y(4500)$, and $Y(4710)$ can be identified as $3^3{P}_0$, $3^3{D}_1$, and $4^3{D}_1$ states, respectively. We also predict the masses and the widths of higher excited states in the charmonia family.

The independent quark model, formulated for a three-body system within a relativistic framework, is applied to singly heavy baryons ${\mathrm{\Omega }}_c^0$ and ${\mathrm{\Omega }}_b^{-}$ to investigate their spectroscopic properties. A Martin-like potential with an equal mixture of scalar and vector components is employed, with potential parameters fitted using ground-state experimental data. The resulting mass spectra include both radial and orbital excitations. The spin-parity for the recently observed states ${\mathrm{\Omega }}_c^0(3000)$, ${\mathrm{\Omega }}_c^0(3050)$, ${\mathrm{\Omega }}_c^0(3067)$, ${\mathrm{\Omega }}_c^0(3120)$, and ${\mathrm{\Omega }}_c^0(3185)$, as well as possible spin assignments for the four newly observed excited states of ${\mathrm{\Omega }}_b^{-}$ (${\mathrm{\Omega }}_b^{-}(6316)$, ${\mathrm{\Omega }}_b^{-}(6330)$, ${\mathrm{\Omega }}_b^{-}(6340)$, and ${\mathrm{\Omega }}_b^{-}(6350)$, are proposed. The magnetic moments of the ground and first excited states are also calculated, along with radiative decay widths and transition magnetic moments. The nonleptonic weak decays of ${\mathrm{\Omega }}_c^0$ are analyzed, with decay widths and branching ratios computed and compared with experimental data to validate the predictive power of the model. The branching ratios for the nonleptonic decays of ${\mathrm{\Omega }}_b^{-}$ are also predicted for future observations.

We consider a class of theories with a $\mathrm{U}(1{)}_X$ gauge symmetry associated with leptonic chiral currents. The low-energy effective field theory includes a light spin-1 boson coupled to the electroweak gauge sector via a Wess-Zumino term, which ensures anomaly cancellation in the infrared. As a concrete application, we show that a light vector boson with mass $m_X\simeq 2.1\mathrm{GeV}$, coupled to a $\tau$-lepton chiral current, can readily account for the recent $3\sigma$ excess observed in $B\to K^{(*)}{E}_{\mathrm{miss}}$ at Belle II, while remaining consistent with existing constraints from $Z\to \gamma E_{\mathrm{miss}}$ and direct searches for anomalon fields responsible for anomaly cancellation in the ultraviolet. After classifying phenomenologically viable models, we explore in greater detail two concrete realizations which give rise to distinctive phenomenological signatures, potentially accessible at future experiments at the high-energy and intensity frontiers.

Quarkonia, which are bound states of a heavy quark and antiquark, play a key role in probing the quark-gluon plasma (QGP). The dynamics of quarkonia in the QGP are encoded in their finite-temperature spectral functions. In this work, we estimate the quarkonium spectral functions in the pseudoscalar channel using ($2+1$)-flavor lattice QCD with a pion mass of 320 MeV, at temperatures of $220\mathrm{MeV}(1.2T_{pc})$, $251\mathrm{MeV}(1.4T_{pc})$, and $293\mathrm{MeV}(1.6T_{pc})$. Reconstructing the spectral function from the Euclidean lattice correlator is a well-known ill-posed problem, requiring additional physics-motivated input. We address this by smoothly matching contributions from different frequency regions of the spectral function, using appropriate physics valid for each region. The spectral function around $\omega \sim 2M_q$ is obtained using a nonperturbative complex potential, while for $\omega \gg 2M_q$ it is modeled using results from vacuum perturbation theory. Since the pseudoscalar channel does not receive a transport contribution near $\omega \sim 0$, we find that the combination of these two regions already provides a good description of the relativistic lattice pseudoscalar correlator. We observe a substantial thermal width in the ${\eta }_c(1S)$ state, indicating that pseudoscalar charmonium (${\eta }_c$) is nearing dissolution at the studied temperatures. In comparison, the ${\eta }_b$ ground state exhibits little change and remains well defined.

The unitarity of the 4D lattice theory of gravity in the case of the Minkowski signature is proved. The proof is valid only for lattices that conserve the number of degrees of freedom during time evolution. The Euclidean signature and the Minkowski signature are related by the deformation of the integration contours of dynamic variables in a discrete lattice functional integral. It is important that the result is obtained directly on the lattice. Since the studied lattice theory of gravity in the long-wave limit transforms into the well-known Einstein-Cartan-Palatini theory, the obtained result means that this lattice theory of gravity has the right to be considered as a discrete regularization of the generally accepted continuous physical theory of gravity.

We discuss the M1 radiative transitions $D^{*}\to D\gamma$, $D_s^{*}\to D_s\gamma$, $B^{*}\to B\gamma$, and $B_s^{*}\to B_s\gamma$. A relativistic potential model is proposed. The corresponding Hamiltonian, when expanded to terms of the order of $v^2/c^2$, where $v$ are the quark velocities, coincides with the Breit Hamiltonian. This model allows making predictions for the widths of radiative transitions of mesons with one light quark. Taking into account relativistic effects is especially important for the transitions $D_s^{*+}\to D_s^{+}\gamma$ and $D^{*+}\to D^{+}\gamma$, where there is a large compensation in the magnitude of the magnetic moment of these mesons. Our results are consistent with known experimental data.

We phenomenologically constrain the small-$x$ and small-$\xi$ gluon generalized parton distributions (GPDs) with the deeply virtual $J/\psi$ production ($\mathrm{DV}J/\psi \mathrm{P}$) in the framework of GPDs through universal moment parameterization (GUMP). We use a hybrid cross-section formula combining collinear factorization to the next-to-leading order (NLO) accuracy of the strong coupling ${\alpha }_s$, with corrections from nonrelativistic QCD to account for the power corrections due to the heavy $J/\psi$ mass. We reach reasonable fit to the measured differential cross sections of $\mathrm{DV}J/\psi \mathrm{P}$ by H1 at the Hadron-Electron Ring Accelerator as well as forward gluon parton distribution functions (PDFs) from JAM22 global analysis. We find that both NLO and nonrelativistic corrections are significant for heavy vector meson productions. Of course, the gluon GPD we obtain still contains considerable freedom in need of inputs from other constraints, particularly in the distribution-amplitude-like region.

In this work, we have investigated the valence quark structure through chiral-even vector quark generalized parton distributions (GPDs) of light $\rho$ and heavy $J/\psi$ vector mesons using the light-cone quark model. By solving the quark-quark correlator, we have represented the quark GPDs in the light-front wave function (LFWFs) form. The charge, magnetic, and quadrupole form factors of these particles have been derived from the vector quark GPDs and compared with available theoretical predictions and lattice simulation data. The structure functions corresponding to the Rosenbluth scattering cross section of these mesons have also been calculated and compared with available NJL model predictions. All the results of our calculations are found to follow a similar trend to other model results. We have also calculated the parton distribution functions (PDFs) of these particles in the forward limit of GPDs. The calculated PDFs have also been evolved to $5{\mathrm{GeV}}^2$ through next to next to leading order Dokshitzer-Gribov-Lipatov-Altarelli-Parisi (DGLAP) evolutions.

The observation of collectivity and strangeness enhancement in small collision systems, such as proton-proton (pp) and proton-lead (p-Pb) collisions, challenges traditional assumptions regarding thermalization and particle production mechanisms. In this study, we investigate particle yields and transverse momentum distributions in pp and p-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02\mathrm{TeV}$ using the EPOS4 event generator, which employs a core-corona framework to model particle production across a variety of system sizes. EPOS4 successfully reproduces many qualitative trends observed in experimental data, including the hardening of $p_{\mathrm{T}}$ spectra with multiplicity, the hierarchical strangeness enhancement in strange-to-pion ratios, and characteristic modifications of particle yield ratios as a function of $p_{\mathrm{T}}$ and multiplicity. The microcanonical approach to core hadronization used in EPOS4 seems to provide a more realistic description of small systems compared to grand-canonical treatments. Nonetheless, quantitative discrepancies still persist in describing several physical observables. Future model refinements, including improved core-corona balancing, differential freeze-out conditions for multistrange hadrons, and incorporation of finite strangeness correlation volumes, may be taken into account for enhancing EPOS4’s predictive power and deepening our understanding of the complex dynamics governing the particle production in high-energy collisions.

In this paper we found the nucleus-nucleus scattering amplitude at high energies by summing large Pomeron loops. It turns out that the energy dependence of this amplitude is the same for dipole-dipole scattering. This happens since the evolution of one dipole cascade contributes to this scattering.

We present a quantitative assessment of the anticipated impact of future Electron-Ion Collider (EIC) measurements on the extraction of parton-to-pion fragmentation functions (FFs). Our analysis combines simulated semi-inclusive deep-inelastic scattering (SIDIS) pseudo-data at EIC energies of 45 GeV and 140 GeV with existing single-inclusive electron-positron annihilation (SIA) and SIDIS experimental data. The pion fragmentation functions are determined at next-to-leading-order (NLO) accuracy using a perturbative quantum chromodynamics framework and a neural network parametrization. Uncertainties are rigorously estimated through Monte Carlo sampling, accounting for both experimental errors and variations in input parton distribution functions. Our results demonstrate that incorporating EIC pseudo-data reduces their uncertainties, especially at medium- to-large momentum fractions ($z$). This improvement is particularly pronounced for the gluon and selected quark FFs, highlighting the substantial role that EIC measurements will play in achieving high-precision extractions of FFs and informing future experimental and theoretical developments in collider physics.