We search for the reaction channel $e^{+}{e}^{-}\to \eta \eta J/\psi$ in a data sample with center-of-mass energies from 4.226 to 4.950 GeV that was collected by the BESIII detector operating at the Beijing Electron Positron Collider (BEPCII). The data analysis is performed with two different reconstruction methods, exclusive and semi-inclusive, enabling a comparison and combination of the results. Only at a few energy points is a nonzero cross section observed with a statistical significance of more than $3\sigma$ using one of the methods. Therefore, the corresponding upper limits of the cross section at the 90% confidence level are determined. The energy-dependent results show clear deviations from the line shape expected from three-body phase space alone. Since the statistical significance for almost all center-of-mass energies is low, the upper limits for the reaction channel $e^{+}{e}^{-}\to \eta \eta J/\psi$ also serve as limits for the existence of a possible isospin partner to the charmonium-like isospin triplet $Z_{\mathrm{c}}(3900)$ which decays to $J/\psi \eta$.

This work investigates dynamically generated hidden-charm baryon resonances arising from meson-baryon interactions. Using the local hidden gauge formalism, we model the interaction via t-channel vector meson exchange and unitarize the amplitude using the Bethe-Salpeter equation. To address regularization issues, we propose a novel “hybrid loop function” scheme that eliminates the unphysical poles—common artifacts in cutoff or dimensional regularization—while keeping the predictions of physical states. Consequently, the model successfully reproduces six experimentally known hidden-charm pentaquarks as well as earlier theoretical results, and predicts new states in the $S=-1,I=1$ sector.

We investigate saturation effects in exclusive vector meson production in deep inelastic scattering, where we model fluctuations within the target protons as localized color-charge hot spots. Based on the color glass condensate framework and the dipole picture for vector meson production, we examine the dependencies of coherent and incoherent scattering cross sections on the momentum transfer. We draw conclusions on the effectiveness of our hot spot model and the strength of the suppression of the scattering cross sections caused by saturation effects. We find that saturation has mild effects in the given energy and charge-density ranges, but can also show that suppression becomes more prominent as the color-charge density inside the proton increases.

The precise measurement of the $e^{+}{e}^{-}\to {\pi }^{+}{\pi }^{-}{\pi }^0$ cross section is performed in the center-of-mass energy range $E=560–1100\mathrm{MeV}$ using a data sample of $66{\mathrm{pb}}^{-1}$ collected in the experiment with the SND detector at the VEPP-$2000e^{+}{e}^{-}$ collider. The systematic uncertainty of the cross section measurement is 0.9% at the maximum of the $\omega$ resonance and 1.2% at the maximum of the $\varphi$ resonance. The leading-order hadronic contribution to the muon magnetic anomaly calculated using the $e^{+}{e}^{-}\to {\pi }^{+}{\pi }^{-}{\pi }^0$ cross section measured by SND from 0.62 to 1.975 GeV is $(45.95\pm 0.06\pm 0.47)\times {10}^{-10}$. From the fit to the cross section data with the vector meson dominance model, the parameters of the $\omega$, $\rho$, and $\varphi$ resonances are obtained. The obtained values of $\mathcal{B}(\omega \to e^{+}{e}^{-})\mathcal{B}(\omega \to 3\pi )$, mass and width of the $\omega$ meson, and $\mathcal{B}(\rho \to 3\pi )$ have accuracy better than the current world average values.

Using $e^{+}{e}^{-}$ collision data collected with the BESIII detector at the BEPCII collider corresponding to a total integrated luminosity of $44{\mathrm{fb}}^{-1}$, we present the first measurement of the Born cross sections for the process $e^{+}{e}^{-}\to K_S^0{\overline{\mathrm{\Xi }}}^{+}{\mathrm{\Sigma }}^{-}$ at 56 center-of-mass energies from 3.510 to 4.951 GeV. By fitting the dressed cross sections of $e^{+}{e}^{-}\to K_S^0{\overline{\mathrm{\Xi }}}^{+}{\mathrm{\Sigma }}^{-}$ with the assumption of a power-law function plus a charmonium(-like) resonance, i.e., $\psi (3770)$, $\psi (4040)$, $\psi (4160)$, $Y(4230)$, $Y(4360)$, $\psi (4415)$, $Y(4500)$, $Y(4660)$, and $Y(4710)$, no significant signal of any charmonium(-like) state decaying into the $K_S^0{\overline{\mathrm{\Xi }}}^{+}{\mathrm{\Sigma }}^{-}$ is observed. Upper limits on the product of the electronic width and branching fraction at the 90% confidence level are given for each resonance. Combining this result with the previous measurement of the isospin-symmetric process $e^{+}{e}^{-}\to K^{-}{\overline{\mathrm{\Xi }}}^{+}{\mathrm{\Sigma }}^0$, the ratio of the Born cross sections, $R={\sigma }^B(e^{+}{e}^{-}\to K_S^0{\overline{\mathrm{\Xi }}}^{+}{\mathrm{\Sigma }}^{-})/{\sigma }^B(e^{+}{e}^{-}\to K^{-}{\overline{\mathrm{\Xi }}}^{+}{\mathrm{\Sigma }}^0)$, is found to be consistent with unity.

We introduce equivariant localization as a method for computing the action of probe branes in supergravity backgrounds. We apply it to supersymmetric probe D3-branes in type IIB supersymmetric spacetimes obtained by uplifting the Kerr-Newman-anti-de ${\mathrm{Sitter}}_5$ black hole on a toric Sasaki-Einstein space. Depending on the cycles they wrap, such branes represent nonperturbative corrections to or defect operator insertions in the superconformal index of a large family of four-dimensional $\mathcal{N}=1$ quiver superconformal field theories. The resulting action reduces to equivariant integrals and can be evaluated entirely from toric data.

We study the real-time quantum dynamics of a matrix model consisting two bosonic fields on the fuzzy sphere $S_F^2$ using the Gaussian state approximation. Starting from the Hamiltonian formulation and using Wick’s theorem, we derive a closed set of coupled nonlinear differential equations governing the time evolution of the one- and two-point correlation functions. The thermal equation of state is found by maximizing the von Neumann entropy over Gaussian states and solving the algebraic self-consistency equation(s) leading to a complete determination of the symplectic spectrum of the covariance matrix. We identify near-thermal initial conditions and use them to solve the equations of motion and employ our findings to probe chaos by calculating the largest Lyapunov exponent at various temperatures. Our results demonstrate that the latter tends to zero at a finite temperature indicating that the quantum dynamics respect the Maldacena-Shenker-Stanford bound across all temperatures, while approaching toward the classically chaotic regime at high temperatures. Finally, we examine the entanglement dynamics of the model in real-time by considering a sequence of bipartitions of the Hilbert space and computing the entanglement entropy and clearly exhibit the fast scrambling features that emerge in due detail.

Understanding the properties of strongly interacting matter at extreme densities is a central problem in fundamental physics, with neutron star mergers offering a natural laboratory to probe this regime. However, the complexity of the merger process complicates the interpretation of the associated gravitational-wave and electromagnetic signals. This picture becomes even more complex in the potential scenario in which dark matter accumulates around and in neutron stars, altering their structure and the associated observables. In this work, we study synthetic gravitational-wave observations of binary neutron star mergers with next-generation detectors, investigating their potential to extract both nuclear physics and dark matter constraints. We also examine how the potential presence of fermionic, non-self-interacting dark matter inside neutron stars affects the inference of nuclear empirical parameters. We find that combining observations can tighten constraints on nuclear empirical parameters. However, the inferred values remain sensitive to systematic modeling biases and intrinsic degeneracies among the parameters. Conversely, our analysis reveals that for non-self-interacting fermionic dark matter at mass fractions below one percent, it will be unlikely to find decisive evidence for dark matter when analyzing gravitational-wave signals. Consequently, systematic biases in nuclear empirical parameter inference potentially resulting from such a dark matter component are expected to be negligible even for observations with next-generation gravitational-wave detectors.

We observe that a large class of well-behaved stationary and axisymmetric black hole solutions in general relativity and in the Einstein-Maxwell theory can be classified according to the properties of their backgrounds. Indeed, all these backgrounds belong to a unique family, which includes simultaneously all the known axisymmetric and regular backgrounds: the swirling, the Bertotti-Robinson, the Bonnor-Melvin universe, Witten’s expanding bubble, and also other novel, regular, rotating gravitational or electromagnetic environments. All these can be, fundamentally, traced back to the double Wick rotation of the topological generalization of the (accelerating) Kerr-Newman-NUT metric. We present a black hole embedded in an unexplored sector of the general background: Schwarzschild inside a generalized rotating (and possibly electromagnetic) universe. These results indicate that basically all the known analytical and exact single black hole solutions in the four-dimensional Einstein-Maxwell theory belong to the (accelerating) Kerr-Newman-NUT family embedded into backgrounds that are a subcase of the conjugated Kerr-Newman-NUT spacetime with an angular manifold of arbitrary topology.

In an ideal world, the measurement noise in gravitational wave data would be stationary and Gaussian. In reality, neither of these conditions holds. Here a general framework is introduced that can be used to model nonstationary noise in an easily interpretable way, using a dynamic power spectrum $S(f,t)$. The construction is a Gram-factor model for the noise covariance matrix that is positive semidefinite by construction. This construction generalizes the familiar stationary power spectrum $S(f)$. The dynamic spectrum encodes the properties of the noise covariance matrix in any basis, including the frequency domain, time domain, and time-frequency wavelet domain. Closed form expressions are given for discrete Fourier representations of the data, and for discrete Wilson-Daubechies wavelet representations of the data. Both take the form of Gramian matrices. Examples are provided, including the nonstationarity caused by window functions, the modulated response to galactic binary signals for space-based detectors, and other, more general types of nonstationarity.

We examine analytically the restricted 3-body problem in general relativity for a set of extremally charged black holes. We apply the method of Ferrell and Eardley, which consists in perturbing the Majumdar-Papapetrou solution that describes a static set of such black holes. We extend the method from a pair of black holes to a triplet. We compare the motion of a test particle and a small black hole in the field of a rotating black hole binary and discover a repulsive self-force acting upon the third black hole.

Single-field ultra-slow-roll (USR) inflation is among the most studied mechanisms for primordial black hole (PBH) formation. When a nonstationary inflection point close to cosmic microwave background (CMB) scales is present, these models predict a negative spectral running (${\alpha }_s<0$), whose magnitude increases with the PBH mass. This is in tension with recent hints for positive running from Atacama Cosmology Telescope (ACT) CMB data. However, inflationary parameters inferred from CMB data are sensitive to the assumed prerecombination expansion history, which is precisely where new physics motivated by the Hubble tension should operate. Focusing on axionlike early dark energy (EDE) as a benchmark, we investigate the effect of such prerecombination new physics on ${\alpha }_s$, and hence on the viability of USR PBH models, in light of state-of-the-art CMB data from Planck, ACT, and the South Pole Telescope, together with baryon acoustic oscillation data from the Dark Energy Spectroscopic Instrument Data Release 2. Our analysis, therefore, provides an updated set of constraints on ${\alpha }_s$ and the running of the running ${\beta }_s$. For most dataset combinations, moving from $\mathrm{\Lambda }$ cold dark matter to EDE increases the inferred ${\alpha }_s$: once the acoustic angular scale ${\theta }_s$ is fixed, EDE increases the diffusion-to-acoustic angular scale ratio ${\theta }_d/{\theta }_s$, and the shift in ${\alpha }_s$ compensates this extra damping by increasing small-scale power. In this sense, tension calls for tension: taking the Hubble tension seriously as an indication for new physics strengthens the challenges faced by USR PBH models. More broadly, our analysis stresses that inflationary model selection using CMB-inferred inflationary parameters such as $n_s$ and ${\alpha }_s$ may be premature, especially until the Hubble tension, and more generally the prerecombination expansion history, is understood.

Axionlike particles (ALPs) coupled to nucleons can be efficiently produced in core-collapse supernovae (SNe) and then, if they couple to photons, convert into gamma rays in cosmic magnetic fields, generating short gamma-ray bursts. Though ALPs from a Galactic SN would induce an intense and easily detectable gamma-ray signal, such events are exceedingly rare. In contrast, a few SNe per year are expected in nearby galaxies within $\sim \mathcal{O}(10)\mathrm{Mpc}$, where strong magnetic fields can enable more efficient ALP-photon conversions than in the Milky Way, offering a promising extragalactic target. This circumstance motivates full-sky gamma-ray monitoring, ideally combined with decihertz gravitational-wave detectors to enable time-triggered searches from nearby galaxies. We show that, under realistic conditions, a decade of coverage could reach sensitivities to the product of the ALP-proton and ALP-photon couplings $g_{ap}\times g_{a\gamma }\gtrsim {10}^{-24}{\mathrm{GeV}}^{-1}$ for ALP masses $m_a\lesssim {10}^{-9}\mathrm{eV}$. This sensitivity would allow one to probe a large, currently unexplored region of the parameter space below the long-standing SN 1987A bound.

Quasiperiodic eruptions (QPEs) are repeated x-ray bursts originating in galactic nuclei. Of the many proposed models, the favored model is the disk-collision model, in which a stellar mass orbiter collides with a disk formed from a tidal disruption event, generating flares twice per orbit. In this model QPEs are tracers of circular extreme mass ratio inspirals (EMRIs) and can be used to infer the EMRI formation rate and estimate their contribution to the stochastic gravitational wave background (SGWB) in the Laser Interferometer Space Antenna (LISA) band. Whether the secondary is a stellar mass black hole or a main-sequence star is still debated and leads to different results for the EMRI rate and SGWB. We obtain fiducial rates—subject to systematic uncertainties—of $R_{\mathrm{SE}}=2.88\times {10}^{-6}$ per galaxy per year for stellar EMRIs and $R_{\mathrm{BHE}}=6.07\times {10}^{-6}$ per galaxy per year for black hole EMRIs, then estimate their contribution to the SGWB. We find that only black hole EMRIs contribute to the 1–10 mHz band resolvable by LISA and, depending on the secondary mass and formation radius, can contribute from just below the LISA sensitivity curve to roughly 2 orders of magnitude above it. Stellar EMRIs, being tidally disrupted before reaching the 1–10 mHz band, only contribute to submillihertz frequencies and remain below the LISA sensitivity curve.

Constructing spacetime solutions that describe black holes embedded in dark matter environments is a crucial step toward probing the properties of dark matter in the strong-field regime of gravity. At present, however, there is no unique or systematic framework to model such configurations, and several commonly adopted approaches raise methodological ambiguities. Motivated by these challenges, we build upon a perturbative framework to describe deformations of static, spherically symmetric black holes induced by a surrounding dark matter distribution. Within this framework, we compute the leading-order corrections to both the photon-sphere radius and the radius of the black hole shadow, assuming a generic dark matter halo profile. We then apply the formalism to physically motivated density profiles, including the Hernquist and Navarro-Frenk-White models, obtaining closed-form analytical expressions for the perturbed metric functions and for the critical impact parameter in the Schwarzschild background. Using these results, we obtain quantitative estimates for the corresponding shadow deviations and find that they lie well beyond the current observational bounds set by Keck and very large telescope interferometer measurements. As a consistency check, we further estimate the total dark matter mass enclosed within the orbital radius of the S2 star and show that it remains well below the 0.1% upper limit reported by the GRAVITY Collaboration. Overall, this approach offers a systematic avenue to investigate perturbative effects of dark matter on black hole phenomenology, including potential implications for gravitational wave observations.

One of the key tests of the quantum nature of gravity is to test whether the virtual mediator of gravity between matter and photon gives rise to the quantum light-bending phenomenon. The off-shell degrees of freedom, involving the spin-2 and spin-0 components of graviton, reproduce the classical deviation of light rays, as well as have been predicted to generate entanglement between matter and photon. This paper explores the generation of entanglement due to the quantum gravitational interaction in an optomechanical setup with a quantum rotor and photon. The virtual exchange of a graviton provides entanglement between the photon degrees of freedom and the spatial position of the quantum rotor, with the rotational state affecting its magnitude. We analyze the case of a high spinning rotor, in an approximately classical state of angular momentum, and quantify its effect on the gravitationally induced entanglement between the photon and the position of the quantum rotor. We show that the difference in the linear entanglement entropies, of prograde-and-retrograde motion of the photon with respect to the quantum rotor, provide tangible observable consequences.

We derive compact analytical formulas for the spectrum of nonlinear Compton scattering in a finite plane-wave pulse with a smooth temporal envelope. The strong-field QED probability is reduced to finite-pulse phase integrals, which are evaluated asymptotically for multicycle pulses with a broad class of smooth envelopes. We use the uniform approximation to remove the caustic divergences that appear at the nonlinear edges of broadened harmonics. Away from the caustics, it reduces to the standard saddle-point result. The behavior near the linear edge is further improved by an envelope-corrected saddle-point approximation. The approach retains the harmonic substructure in the spectral-angular region carrying the dominant part of the emitted radiation. The locally monochromatic approximation is recovered by averaging the finite-pulse interference. Within their asymptotic domain of applicability, the resulting formulas agree with direct numerical calculations and can be used to evaluate spectra from an electron beam.

We investigate the arrival time and the Faraday rotation of extragalactic electromagnetic signals coming from fast radio bursts (FRBs) and propagating through chiral cosmic media within the framework of the Maxwell-Carroll-Field-Jackiw (MCFJ) electrodynamics. By treating the interstellar medium as a cold, ionized chiral plasma, we derive the time delay between two traveling signals and express it in terms of modified dispersion measures (DMs) containing chiral contributions. The Faraday rotation angle is written in terms of modified rotation measures (RMs). By combining the DMs and redshift data from a set of FRBs, we achieve constraints on the chiral parameter magnitude at the order of ${10}^{-26}-{10}^{-24}\mathrm{GeV}$. The Faraday rotation formulae and RM measurements yield upper bounds as stringent as ${10}^{-43}\mathrm{GeV}$ on the MCFJ parameters.

The Standard Model (SM) cannot explain the observed baryon asymmetry of the Universe (BAU), thus driving the need for physics beyond the SM, which can generate the electroweak baryogenesis through a strong first-order electroweak phase transition (SFOPT). We extend the SM with a complex singlet scalar (cxSM) and examine the phase transition dynamics using a fully general renormalizable scalar potential that permits a complex vacuum expectation value for the singlet scalar and coupled dynamics among multiple scalar fields. Employing the full one-loop thermal effective potential, we conduct an extensive parameter space scan, enforcing both theoretical and experimental constraints on the scalar sector. To efficiently capture the highly nonlinear structure of model parameter space, we embark on a classifier based machine learning approach to identify regions manifesting SFOPT while revealing key signatures of model parameters. From these regions, we select a few representative benchmark scenarios that show multistage transitions followed by the production of stochastic gravitational wave signals from bubble nucleation dynamics. The resulting spectra fall within the projected sensitivities of future space-based detectors such as LISA, BBO, DECIGO, and U-DECIGO. Thus, the cxSM offers a compelling setting for the electroweak baryogenesis, enriched by correlated gravitational wave and collider phenomenology.

We revisit the renormalization of models with two U(1) gauge symmetries, in a formulation with noncanonical gauge kinetic terms which is covariant under field reparametrizations among the two gauge bosons. This approach is convenient to study the appearance of kinetic mixing in scale evolution because a coupling matrix is attributed to the gauge kinetic terms. We obtain simple $\overline{\mathrm{MS}}$ renormalization group equations up to two-loop, which can be solved to give effective millicharges at low energy which depend on the running couplings and heavy mass scales of the model. This formulation allows one to construct “invariants” out of running Lagrangian parameters, which are invariant under generic gauge field reparametrizations, including rescalings, and which can be related directly to observables such as the millicharge.