Recently, the IceCube Collaboration reported evidence for TeV neutrino emission from several nearby Seyfert galaxies, with the highest significance found for NGC 1068. Assuming stochastic proton acceleration in magnetized turbulence inside the corona, we model the neutrino emission of Seyfert galaxies as a function of their x-ray luminosity. Applying our model to NGC 1068, we obtain a good fit to the public IceCube data and constrain the coronal radius to $\lesssim 5R_S$ by comparing our MeV $\gamma$-ray predictions to Fermi-LAT observations. Extending to the full Seyfert population, we estimate their diffuse neutrino contribution and find that they can explain a significant fraction of the observed flux below 10 TeV. However, scenarios with highly turbulent coronae and high cosmic-ray pressure across the population are ruled out. In particular, if all sources shared the best-fit parameters obtained for NGC 1068, their cumulative neutrino emission would exceed current upper limits at TeV energies by $3.8\sigma$. Our results, informed by both neutrino and $\gamma$-ray data, show that those Seyfert galaxies that emerge as neutrino point sources must be exceptionally efficient neutrino emitters and are not representative of the broader population.

Relations between stellar properties independent of the nuclear equation of state offer profound insights into neutron star physics and have practical applications in data analysis by breaking the degeneracy between the parameters of interest. Commonly, these relations are derived from utilizing various realistic nuclear cold hadronic, hyperonic, and hybrid equation of state models, each of which should obey the current multimessenger constraints and cover a wide range of stiffnesses. Concurrently, the field of multimessenger astronomy has been significantly enhanced by the advent of gravitational wave astronomy, which increasingly incorporates deep learning techniques and algorithms. At the same time, x-ray spectral data from NICER based on known pulsars are available, and additional observations are expected from upcoming missions. Therefore, in the coming years, a wealth of information on neutron stars is expected to be gathered from multiple observational channels. In this study, we revisit established universal relations, introduce new ones, and reassess them using a feedforward neural network as a regression model. More specifically, we mainly propose “deep” EoS-insensitive hypersurface relations for rapidly rotating compact objects between several of the star’s global parameters, such as the moment of inertia, the reciprocal of the moment of inertia, the rotational frequency, mass and current multipole moments and the equatorial radius, which achieve an accuracy of within 1% in most cases, with only a small fraction of investigated models exceeding this threshold. While analytical expressions can be used to represent some of these relations, the neural network approach demonstrates superior performance, particularly in complex regions of the parameter space. Furthermore, we use the SHapley Additive exPlanations (SHAP) method to interpret the predictions of the suggested feedforward network, as SHAP is grounded in a robust theoretical framework inspired by the field of cooperative game theory. Most importantly, these highly accurate universal relations, empowered with the interpretability description, could be used in efforts to constrain the high-density equation of state in neutron stars, with the potential to enhance our understanding as new observables emerge.

We investigate the sensitivity of proposed circular electron positron collider (CEPC) and future circular collider in its electron–positron mode (FCC-ee) with a center-of-mass energy of 240 GeV to long-lived dark photons heavier than 2 GeV that are pair produced via the prompt decays of a light scalar mixed with the Standard-Model Higgs boson. We compute the production and decay rates of both the light scalar and the dark photon, and develop two search strategies targeting displaced vertices within the inner tracker of the main detectors. Using Monte Carlo simulations, we evaluate the signal acceptance and projected sensitivity for each strategy. Our results show that, for the scalar-Higgs mixing angle set at ${10}^{-2}$ just below the current upper limit, the proposed searches at CEPC and FCC-ee can probe a dark-photon kinetic-mixing parameter several orders of magnitude below existing bounds, for dark photons lighter than half the dark-scalar mass.

The dynamical chromoelectric color conductivity of a chiral plasma has been extracted from one loop gluon self energy by using linear response theory at finite temperature and density. It is shown that due to the $P$ and $CP$ violation the conductivity tensor has an anomalous contribution in addition to the longitudinal and transverse components. We identify this anomalous conductivity as chiral chromomagnetic conductivity. The spectral representations of real and imaginary parts of the longitudinal and transverse conductivities show marginal variations in chiral plasma as compared to the nonchiral plasma. The static limit of chiral chromomagnetic conductivity is found to be independent of medium properties reflecting its topological nature.

Effective interaction models of quantum chromodynamics, based on quark degrees of freedom, have been successfully employed to compute the properties of a large array of ground and excited meson and baryon states, along with their electromagnetic form factors, distribution functions, and thermal behavior. Amongst them, the contact-interaction model, while nonrenormalizable, implements confinement, satisfies Lorentz covariance, and correctly describes chiral symmetry and its dynamical breaking pattern. Original studies focused on the light hadron sector in the isospin limit and were thereafter extended to heavy mesons and baryons. The strong effective couplings, as well as infrared and ultraviolet regulators, are flavor-dependent model parameters adjusted to reproduce hadronic observables. In contrast, in this study we combine SU(4) flavor-symmetry breaking couplings, obtained from one-loop vacuum polarization amplitudes in the presence of background constituent quark currents, with the contact-interaction model. This allows us to reduce the number of mass-dimensioned parameters and to consistently relate all flavored couplings to a single mass scale, while the masses and weak decay constants of the pions, kaons, $D$ and $D_s$ mesons are in good agreement with average reference values. Allowing for realistic isospin breaking, $m_d/m_u=1.7$, in conjunction with the effect of the flavored couplings, leads to a mass splitting, $m_{{\pi }^{+}}-m_{{\pi }^0}\approx 0.3\mathrm{MeV}$, that agrees with lattice QCD values. For the kaons, the mass difference is $m_{K^0}-m_{K^{\pm }}\approx 2.3\mathrm{MeV}$, whereas $m_{D^{\pm }}-m_{D^0}\approx 0.5\mathrm{MeV}$ and the ${\eta }_c$ is 6% lighter than the experimental mass.

Utilizing $2712.4\pm 14.3\mathrm{million}$ $\psi (3686)$ events accumulated by the BESIII experiment, we perform a partial wave analysis of $\psi (3686)\to \gamma {\chi }_{cJ}\to \gamma \mathrm{\Lambda }\overline{\mathrm{\Lambda }}$ decay ($J=0$, 1, 2). The ratio of the helicity amplitudes with same (++) and opposite (+-) helicity for ${\chi }_{c2}\to \mathrm{\Lambda }\overline{\mathrm{\Lambda }}$ decay is determined for the first time to be $R_{{\chi }_{c2}}=0.575\pm 0.048\pm 0.018$, with a relative phase angle $\mathrm{\Delta }{\mathrm{\Phi }}_{{\chi }_{c2}}=0.37\pm 0.15\pm 0.05\mathrm{rad}$. The parameters of the angular distribution of ${\chi }_{c2}$ are determined to be ${\alpha }_{{\chi }_{c2}}=-0.211\pm 0.100\pm 0.050$ and ${\beta }_{{\chi }_{c2}}=-0.039\pm 0.089\pm 0.033$, based on the distribution $dN/d\cos \theta =1+{\alpha }_{{\chi }_{c2}}{\cos }^2\theta +{\beta }_{{\chi }_{c2}}{\cos }^4\theta$. The width of ${\chi }_{c0}$ is determined to be $12.31\pm 0.26\pm 0.12\mathrm{MeV}$. Additionally, the branching fractions for ${\chi }_{cJ}\to \mathrm{\Lambda }\overline{\mathrm{\Lambda }}$ are measured to be $(3.662\pm 0.048\pm 0.111)\times {10}^{-4}$, $(1.182\pm 0.026\pm 0.042)\times {10}^{-4}$, and $(1.704\pm 0.035\pm 0.057)\times {10}^{-4}$ for ${\chi }_{c0}$, ${\chi }_{c1}$ and ${\chi }_{c2}$, respectively, where the first uncertainty is statistical and the second systematic.

High statistical precision is critical for Monte Carlo (MC) samples in high energy physics and is degraded by negatively weighted events. This paper investigates a procedure to learn the relationship between the negative and positive weight distributions of any sample, allowing the reduction of statistical uncertainty by reweighting kinematically equivalent events with the same sign. A robust uncertainty quantification method is required for the practical application of such method. Two methods for the estimation of the reweighting uncertainty are developed: one at the event and another one at the final observable level. The latter method is strongly favored. The gains in statistical precision are then quantified. The method is demonstrated on Sherpa vector boson plus jets samples when using all generated events and when restricted to the signal region of a mock analysis. It is demonstrated to significantly reduce stochastic behavior in sparse MC samples while decreasing the overall uncertainty with a sufficiently well-known reweighting function.

We study the properties of the $X(1880)$, the structure around the $\overline{p}p$ threshold that appears in the $3({\pi }^{+}{\pi }^{-})$ invariant mass spectrum in the decay process of $J/\psi \to \gamma 3({\pi }^{+}{\pi }^{-})$. Nucleon-antinucleon rescattering is taken into account in our analysis, and the decay amplitude of $J/\psi \to \gamma 3({\pi }^{+}{\pi }^{-})$ can be obtained by the distorted wave Born approximation. With these amplitudes, we analyze the contributions to the $X(1880)$ from different partial waves. Our analysis suggests that the $X(1880)$ should be isoscalar $0^{-+}$, and it is generated by the threshold behavior.

The imaginary part of the effective action encodes vacuum instability and particle production in the background field. Two standard approaches are commonly used to derive it: the Bogoliubov method and the Green’s function method, which are usually expected to agree. However, in de Sitter spacetime they yield different results. We revisit this problem by introducing explicit time and momentum cutoffs in the Green’s function representation of the effective action. The apparent discrepancy is found to be due to the different limiting procedures in regularization, which reproduces the Bogoliubov result and the Green’s function result, respectively. Therefore, the two approaches are understood to be different regularization limits of the same expression, which clarifies the origin of their disagreement.

Flexible and accurate noise characterization is crucial for the precise estimation of gravitational-wave parameters. We introduce a Bayesian method for estimating the power spectral density (PSD) of long, stationary time series, explicitly tailored for Laser Interferometer Space Antenna (LISA) data analysis. Our approach models the PSD as the geometric mean of a parametric and a nonparametric component, combining the knowledge from parametric models with the flexibility to capture deviations from theoretical expectations. The nonparametric component is expressed by a mixture of penalized B splines. Adaptive, data-driven knot placement, performed once at initialization, removes the need for a reversible-jump Markov chain Monte Carlo, while hierarchical roughness-penalty priors prevent overfitting. Validation on simulated autoregressive (AR) data of order 4 [AR(4)] demonstrates estimator consistency and shows that well-matched parametric components reduce the integrated absolute error compared to an uninformative baseline, requiring fewer spline knots to achieve comparable accuracy. Applied to one year of simulated LISA $X$-channel (univariate) noise, our method achieves relative integrated absolute errors of $\mathcal{O}({10}^{-2})$, making it suitable for iterative analysis pipelines and multiyear mission data sets.

In this work, we use the weak cosmic censorship conjecture (WCC) to constrain black hole solutions in modified gravity theories. While Wald showed that extremal Kerr–Newman black holes in general relativity cannot be overcharged by test charged particles, this protection may fail in theories beyond general relativity. We have considered generic rotating black hole solutions beyond the Kerr-Newman family and examined particle absorption processes that could lead to overcharging and the emergence of naked singularities. Identifying regions of parameter space where WCC is violated allows us to place direct, physically motivated bounds on deviations from general relativity.

We present a numerical investigation of primordial black hole (PBH) formation from superhorizon curvature perturbations and the subsequent generation and propagation of sound waves, which can serve as a new source of stochastic gravitational-wave backgrounds presented in a companion letter. Using the Misner-Sharp formalism with an excision technique, our simulations extend to significantly later times than previous work and indicate that the near-critical perturbations produce a distinct compression wave featuring both over- and underdense shells, while significantly supercritical perturbations yield only an underdense shell. We also show that a softer equation of state suppresses the formation of compression waves. Furthermore, the comoving thickness of sound shells remains nearly constant during propagation and scales with the Hubble radius at horizon reentry, thereby serving as a key link between the gravitational-wave peak frequency and PBH mass in the companion letter. These results offer new insights into the dynamics of PBH formation and suggest potential observational signatures of PBHs in the gravitational-wave spectrum from associated sound waves.

We construct four-dimensional gravity theories that resolve the Schwarzschild singularity and enable dynamical studies of nonsingular gravitational collapse. The construction employs a class of nonpolynomial curvature invariants that produce actions with (i) second-order equations of motion in spherical symmetry and (ii) a Birkhoff theorem, ensuring uniqueness of the spherically symmetric solution. Upon spherical reduction to two dimensions, these theories map to a particular subclass of Horndeski scalar-tensor models, which we use to explicitly verify the formation of regular black holes as the by-product of the collapse of pressureless stars and thin shells. We also show that linear perturbations on top of maximally symmetric backgrounds are governed by second-order equations.

We investigate the scenario of interacting dark energy through a detailed confrontation with various observational datasets. We quantify the interaction in a general way, through the deviation from the standard scaling of the dark matter energy density. We use the cosmic microwave background data from Planck 2018, data from baryon acoustic oscillations from the recently released Data Release 2 of the Dark Energy Spectroscopic Instrument, observational Hubble data from cosmic chronometers, and finally various Supernova Type Ia datasets (PantheonPlus, Union3, and DESY5). For the basic and simplest interacting model we find a mild preference of the interaction at slightly more than $1\sigma$ however still within $2\sigma$, and thus no strong evidence of interaction is found. However, comparison with the $\mathrm{\Lambda }$ cold dark matter ($\mathrm{\Lambda }\mathrm{CDM}$) scenario through $\mathrm{\Delta }{\chi }_{\min }^2$, Akaike information criterion, and Bayesian analysis, reveals a mixed picture, namely according to $\mathrm{\Delta }{\chi }_{\min }^2$ the interaction is mildly favored by most of the datasets, while the remaining statistical measures are inclined toward $\mathrm{\Lambda }\mathrm{CDM}$.

We investigate a cosmological model inspired by hybrid inflation, where two scalar fields representing dark energy (DE) and dark matter (DM) interact through a coupling that is proportional to the DE scalar field $1/\varphi$. The strength of the coupling is governed solely by the initial condition of the scalar field, ${\varphi }_i$, which parametrizes deviations from the standard $\mathrm{\Lambda }$ cold dark matter ($\mathrm{\Lambda }\mathrm{CDM}$) model. In this model, the scalar field tracks the behavior of DM during matter domination until it transitions to DE while the DM component decays quicker than standard CDM during matter domination, and is therefore different from some interacting DM-DE models which behave like phantom dark energy. Using Planck 2018 CMB data, Dark Energy Spectroscopic Instrument baryonic acoustic oscillations measurements and $\mathrm{Pantheon}+\mathrm{supernova}$ observations, we find that the model allows for an increase in $H_0$ that can help reduce the Hubble tension. In addition, we find that higher values of the coupling parameter are correlated with lower values of ${\omega }_m$, and a mild decrease of the weak-lensing parameter $S_8$, potentially relevant to address the $S_8$ tension. Bayesian model comparison, however, reveals inconclusive results for most datasets, unless $\mathrm{S}{H}_0\mathrm{ES}$ data are included, in which case a moderate evidence in favor of the hybrid model is found.

Recent observations from the Dark Energy Spectroscopic Instrument (DESI) raise doubts about the standard cosmological model, $\mathrm{\Lambda }\mathrm{CDM}$, suggesting a preference for an inherently dynamical dark energy component. The Chevallier-Polarski-Linder (CPL) parametrization—a widely used two-parameter model for the dark energy equation of state—displays marked early-time phantom behavior and a recent crossing of the phantom divide. These features suggest the convenience to check observationally the robustness of such evolution. To address this, we design two alternative families of two-parameter dark energy parametrizations which remain close to the original CPL but aim to soften its phantom character. Specifically, these models reproduce CPL-like behavior at low redshift but mitigate early phantom behavior through the use of smooth sigmoid transitions, yielding a more gradual evolution. By combining recent DESI data with constraints from the cosmic microwave background and Type Ia supernovae, we assess the viability of these models. Our analysis shows that CPL remains a strong and competitive parametrization, with the proposed alternatives only marginally favored or disfavored. We conclude that current observational data lack the statistical precision to decisively distinguish between CPL and similarly constructed parametrizations across the redshift range probed by late-time observables.

We present measurements of the radial profile of mass and galaxy number density around x-ray selected ROSAT All Sky Survey-Multi-Component Matched Filter galaxy clusters using Year 3 data from the Dark Energy Survey. We measure the projected cross-correlation signal of the RedMaGiC “high density” galaxies around an approximately volume-limited sample of 255 galaxy clusters at a median redshift of $z=0.4$ and an x-ray luminosity $L_X>{10}^{44}\mathrm{ergs}{\mathrm{s}}^{-1}{\mathrm{h}}^{-2}$. This cross-correlation signal measured with a signal-to-noise ratio of 16.41 allows us to infer a 3D number density profile, which shows a significant steepening at the edges of these galaxy clusters, namely the splashback radius of $r_{\mathrm{sp}}/h^{-1}\mathrm{Mpc}=2.19_{-0.43}^{+0.50}$. We present the dependence of the splashback radius value over a range of absolute galaxy magnitude cuts to look for any evidence of dynamical friction affecting these results. The weak lensing signal around our galaxy clusters measured with a signal-to-noise ratio of 32.19 allows us to infer a halo mass $\log (M_{200\mathrm{m}}/h^{-1}{M}_{\odot })=14.68_{-0.04}^{+0.04}$. Comparison of the location of the splashback radius with the spherical overdensity boundary $r_{200\mathrm{m}}$ shows consistency with the $\mathrm{\Lambda }$ cold dark matter predictions. We present the first inference of the average mass accretion rate of galaxy clusters using our measurements of the splashback radius.

A long-range force acting only in the dark sector can displace the stellar component of satellite galaxies relative to their dark matter (DM) halos, thereby breaking the weak equivalence principle (WEP) between DM and baryons. We investigate observational signatures of such WEP breaking using $N$-body simulations of a Fornax-like Milky Way (MW) satellite, implementing a fifth force between DM particles of amplitude $\beta$ relative to Newtonian gravity (with a screening length much larger than the MW halo size). We find that $\beta \gtrsim 0.6$ strips and unbinds the bulk of the stellar component, leaving at most a negligible bound remnant that fails to match the observed stellar content, surface-brightness, and line-of-sight velocity-dispersion profiles of Fornax. By contrast, $\beta \lesssim 0.2$ yields only mild stellar stripping and remains broadly consistent with current photometric and kinematic constraints within our modeling assumptions.

In this work, we analyze the Higgs boson decay channels, specifically, $h\to \gamma \gamma$, $h\to V{V}^{*}$ (with $V=Z$, $W$), and $h\to f\overline{f}$ (for $f=b$, $c$, $\tau$) within the flavor-dependent $U(1{)}_F$ model (FDM). We also investigate processes induced by flavor-changing neutral currents, including the decays $\overline{B}\to X_s\gamma$ and $B_s^0\to {\mu }^{+}{\mu }^{-}$, the top quark decays $t\to ch$ and $t\to uh$, and the lepton flavor-violating decays $\tau \to 3e$, $\tau \to 3\mu$, and $\mu \to 3e$. Furthermore, we incorporate the electroweak precision observables constraints via the S, T, and U parameters. Compared to the Standard Model, the scalar sector of the FDM is extended by two Higgs doublets and one Higgs singlet, which affects the 125 GeV Higgs properties significantly. Meanwhile, the decays $h\to Z\gamma$, $h\to MZ$, and $h\to M\gamma$ [where $M$ is a vector meson $(\rho ,\omega ,\varphi ,J/\mathrm{\Psi },\mathrm{\Upsilon })$] of the Standard-Model-like Higgs are studied, and we illustrate how changes in the scalar sector and the Yukawa coupling influence the signal strengths for the 125 GeV Higgs decay channels and the Higgs mass in the FDM.

Through symmetry of the action under global spacetime translations, Noether’s first theorem infamously entails an energy-momentum tensor (EMT) that is neither symmetric nor gauge-invariant. In a prior work [Phys. Rev. D 106, 125012 (2022)], I had obtained a symmetric and gauge-invariant EMT by using Noether’s second theorem instead, with local spacetime translations as the symmetry group. However, the derivation therein was flawed, containing a faulty assumption about the transformation rule for spinor fields. In this work, I revisit the derivation of the previous work, both correcting the faulty step and simplifying the derivation for broader accessibility. The end result is an EMT for quantum chromodynamics that is gauge-invariant, but not symmetric.