Measuring the tau-lepton ($\tau$) anomalous magnetic moment $a_{\tau }=(g_{\tau }-2)/2$ in photon fusion production ($\gamma \gamma \to \tau \tau$) tests foundational Standard Model principles. However, $\gamma \gamma \to \tau \tau$ eludes observation in LHC proton collisions (pp) despite enhanced new physics sensitivity from higher-mass reach than existing probes. We propose a strategy to measure $\mathrm{pp}\to \mathrm{p}(\gamma \gamma \to \tau \tau )\mathrm{p}$ by introducing the overlooked electron-muon signature with vertex isolation for signal extraction. Applying the effective field theory of dipole moments, we estimate 95% confidence level sensitivity of $-0.0092<a_{\tau }<0.011$ assuming $300{\mathrm{fb}}^{-1}$ luminosity and 5% systematics. This fourfold improvement beyond existing constraints opens a crucial path to unveiling new physics imprinted in tau-lepton dipoles.

True muonium (${\mu }^{+}{\mu }^{-}$) is one of the heaviest and smallest electromagnetic bound states not containing hadrons, and has never been observed so far. In this work we show that the spin-1 TM state (ortho-TM) can be observed at a discovery level of significance in three months at the CERN SPS North-Area H4A beam line, using 43.7 GeV secondary positrons. In this way, by impinging the positrons on multiple thin low-Z targets, ortho-TM, which decays predominantly to $e^{+}{e}^{-}$, can be produced from $e^{+}{e}^{-}\to \mathrm{TM}$ interaction on resonance ($\sqrt{s}\sim 2m_{\mu }$).

Given a bipartite quantum system in an energy eigenstate, the dynamical description for one component can be derived via entanglement using the other component as a clock. This is the essence of the Page and Wootters mechanism. Moreover, if the clock is subject to a gravitational-like interaction, relative time evolution is then described by a time-dilated Schrödinger equation, in which the so-called redshift operator describes a purely quantum effect, analog to gravitational time-dilation. Here we adopt a nonperturbative approach and present a finite-dimensional generalization of this mechanism, expressing the quantum time-dilation effect as an effective interaction involving previously noninteracting system components. We name this a time-dilation induced interaction transfer (TiDIT) mechanism and discuss an example using two coupled spins as a quantum clock model. Our approach is suitable for implementations in current quantum technology and provides a new tool for exploring gravity at the intersection with quantum physics.

This work provides evidence for the existence of supersymmetric and scale-separated ${\mathrm{AdS}}_4$ vacua in M-theory of the Freund-Rubin type. The internal space has weak $G_2$-holonomy, which is obtained from the lift of AdS (anti–de Sitter) vacua in massless type IIA on a specific SU(3) structure with O6-planes. Such lifts require a local treatment of the O6-planes, therefore going beyond the usual smeared approximation. The setup is analyzed by solving the pure spinor equations and the Bianchi identities perturbatively in a small backreaction parameter, preserving supersymmetry manifestly and therefore extending on previous work. This approach is applicable to lifts of other type IIA vacua on half-flat SU(3) structures, including those with D6-brane sources. The resulting 7D manifold presented here exhibits singularities originating from the O6-planes loci in type IIA theory. Additionally, scale separation in M-theory arises from a decoupling between the Ricci curvature and the first eigenvalue of the Laplacian of the proposed 7D manifold, thereby challenging certain conjectures in the swampland program.

The Einstein Telescope faces a critical data analysis challenge with correlated noise, often overlooked in current parameter estimation analyses. We address this issue by presenting the statistical formulation of the likelihood that includes correlated noise for the Einstein Telescope or any detector network. By considering varying degrees of correlation, we probe the impact of noise correlations on the parameter estimation analysis of a GW150914-like event. We show that neglecting these correlations may significantly reduce the accuracy of the chirp mass reconstruction. This emphasizes how critical a proper treatment of correlated noise is, as presented in this work, to unlocking the wealth of results promised by the Einstein Telescope.

In this paper, we examine gravitational collapse of matter fields in $n$-dimensional general relativity. The matter energy-momentum tensor under consideration includes dust, perfect fluids with equations of state and matter admitting bulk and shear viscosity. By adjusting various parameters of the matter energy-momentum tensor, we determine the trapped region and spherical marginally trapped surfaces in homogeneous and inhomogeneous models of collapse. We show that, as expected, the time development of marginally trapped tube is intricately related to the initial velocity and density profiles of the collapsing matter configuration. This study clarifies the role of initial data in the formation of spacetime singularity during gravitational collapse and implies that, under generic conditions on the matter profiles, the central spacetime singularity is always covered by a horizon.

It was reported that the optical field fluctuations in self-defocusing media can be described by sound waves propagating in a two-dimensional photon fluid which is controlled by the driving laser beam. The photon fluid can be regarded as the background where the sound waves propagate in the way of a scalar field propagating in curved spacetime, thus providing a platform to study physics in analog gravity. In this analog gravity model, to be more specific, in the analog rotating black hole background, we study the quasinormal modes (QNMs) of massive scalar field perturbations, as a natural extension of the recent work on the massless QNMs in photon fluid. We analyze the properties of the spectrum of fundamental QNMs which are calculated by the continued fraction method and WKB approximation method. We also investigate the quasiresonance and find that it may exist in this analog gravity model. The existence of quasiresonance is important to study the QNMs in analog gravity apparatus due to its slow damping rate and longevity which give us better opportunity to probe and study it in laboratory.

Recently, theoretical studies on the bumblebee gravity model, a nonminimally coupled vector-tensor theory that violates the Lorentz symmetry, have flourished, with a simultaneous increase in the utilization of observations to impose constraints. The static spherical solutions of neutron stars (NSs) in the bumblebee theory are calculated comprehensively in this work. These solutions with different coupling constants reveal a rich theoretical landscape for NSs, including vectorized NSs and NSs with finite radii but divergent masses. With these solutions, preliminary constraints on the asymptotic vector field values are obtained through restrictions on the stellar radius.

We present a rapid stellar core-collapse waveform emulator built using a deep convolutional generative adversarial network (DCGAN). The DCGAN was trained on the Richers et al. [Phys. Rev. D 95, 063019 (2017)] waveform catalog to learn the structure of rotating stellar core-collapse gravitational-wave signals and generate realistic waveforms. We show that the DCGAN learns the distribution of the training data reasonably well, and that the waveform emulator produces signals that appear to have the key features of core-collapse, bounce, early postbounce, and ringdown oscillations of the early protoneutron star. The pretrained DCGAN can therefore be used as a phenomenological model for rotating stellar core-collapse gravitational-waves.

We investigate the evolution of cosmological scalar perturbations in the case where the background radiation is weakly coupled to a light scalar field $\varphi$. The light scalar $\varphi$ is a homogeneous background field with a large initial value. In the radiation-dominated Universe, the coupling term introduces an effective mass to $\varphi$ and the background ultrarelativistic particles. The oscillations of $\varphi$ result in the periodic change of the equation-of-state parameter and the sound speed, which provides a novel mechanism to amplify subhorizon scalar perturbations through parametric resonance. The amplification of scalar perturbations leads to a stochastic gravitational-wave background (SGWB) expected to be observed by multiband gravitational-wave observers. The observation of the SGWB helps to determine the initial value of $\varphi$ and the coupling strength of the interaction. This mechanism is generally applicable to the interactions that introduce an effective mass, and we take the interaction between $\varphi$ and electrons as a concrete example to illustrate the result. We find that under the condition that the coupling coefficient $\lambda ={10}^{-16}$ and the initial value ${\varphi }_i={10}^{18}\mathrm{GeV}$, the resulting SGWB spectrum is expected to be observed by the future observers including LISA, Taiji, DECIGO, and BBO.

In this paper, we show that the initial clustering of supermassive primordial black holes (SMPBHs) beyond a Poisson distribution can efficiently enhance the matter power spectrum, and thus the halo mass function. As a result, the population of initially clustered SMPBHs with $M_{\mathrm{PBH}}\sim {10}^9{M}_{\odot }$ and the fraction of energy density $f_{\mathrm{PBH}}\sim {10}^{-3}$ (consistent with current constraints on SMPBHs) has the potential to naturally explain high-redshift massive galaxies observed by the James Webb Space Telescope.

Baryonic feedback is a major systematic in weak lensing cosmology. Its most studied effect is the suppression of the lensing power spectrum, a second-order statistic, on small scales. Motivated by the growing interest in statistics beyond the second order, we investigate the effect of baryons on lensing non-Gaussian statistics and the resulting biases in the matter clustering amplitude $S_8={\sigma }_8\sqrt{{\mathrm{\Omega }}_m/0.3}$. We focus on the Subaru Hyper Suprime-Cam Year 1 (HSC-Y1) data which, with its high source number density, closely resembles those expected from the upcoming Euclid and Rubin Legacy Survey of Space and Time. We study four non-Gaussian statistics of convergence maps—peak counts, minimum counts, the probability distribution function, and the scattering transform coefficients—in addition to the usual power spectrum. We first estimate the biases in $S_8$ using mock observations built from the IllustrisTNG and BAHAMAS hydrodynamical simulations and theoretical models built from dark-matter-only simulations. We find up to $1\sigma$ bias in $S_8$ when the smallest scales (2 arcmin) and the highest feedback level are considered. We then analyze the HSC-Y1 data and compare the $S_8$ obtained for each statistic with different smoothing scales or scale cuts. As we expect that baryons mostly affect the small scales, comparing the results obtained from including and excluding small scales can indicate the level of impact from baryons. With HSC data, we find only minor ($\le 0.5\sigma$) differences in $S_8$ for all statistics, even when considering very small scales (2 arcmin). Our results suggest that the effect of baryons is insignificant at the level of HSC-Y1 down to 2 arcmin for all statistics examined here, or it is canceled by other scale-dependent systematics.

In this study, we explore the reconstruction of the lensing convergence $\kappa$ map using the cosmic magnification effect in DECaLS galaxies from the DESI imaging surveys DR9. This complementary approach provides valuable insights into the large scale structure of the Universe alongside traditional cosmic shear measurements. It is achieved by linearly weighing 12 maps of galaxy number overdensity in different magnitude bins of $grz$ photometry bands. The weight is designed to eliminate the mean galaxy deterministic bias, minimize galaxy shot noise while maintaining the lensing convergence signal. We also perform corrections of imaging systematics in the galaxy number overdensity. The $\widehat{\kappa }$ map has $8365{\mathrm{deg}}^2$ sky coverage. Given the low number density of DECaLS galaxies, the $\widehat{\kappa }$ map is overwhelmed by shot noise, and the map quality is difficult to evaluate using the lensing autocorrelation. Alternatively, we measure its cross-correlation with the cosmic shear catalogs of DECaLS galaxies of DESI imaging surveys DR8, which have a sky area that fully covers the reconstructed $\widehat{\kappa }$ map. Since the $\widehat{\kappa }$ map is contaminated by residual galaxy clustering, we model it as $\widehat{\kappa }=A\kappa +\epsilon {\delta }_{\mathrm{m}}+\cdots$. Under this assumption, we detect a convergence-shear cross-correlation signal with $S/N\simeq 22$. The analysis also shows that the galaxy intrinsic clustering is suppressed by a factor $\mathcal{O}(10)$. Various tests with different galaxy and shear samples, as well as the Akaike information criterion analysis, all support the lensing detection. In addition, the imaging systematics corrections enhance the lensing signal detection by $\sim 30\%$. We discuss various issues for further improvement of the measurements.

Low-redshift probes, such as baryon acoustic oscillations (BAO) and supernovae Ia luminosity distances, have been shown to be crucial for improving the bounds on the total neutrino mass from cosmological observations, due to their ability to break degeneracies among the different parameters. Here, we expand background observations to include $H(z)$ measurements from cosmic chronometers, distance moduli from gamma ray bursts (GRBs), and angular diameter distances from galaxy clusters. For the first time, using the physically motivated assumption of positive neutrino mass, we find that neutrino mass limits could be at 95% CL below the minimal expectations from neutrino oscillation probes, suggesting possible nonstandard neutrino and/or cosmological scenarios. Interestingly, it is not only the combination of the three background probes that is responsible for the $\sum m_{\nu }<0.06\mathrm{eV}$ limits, but also each of them independently. The tightest bound we find here is $\sum m_{\nu }<0.043\mathrm{eV}$ at 95% CL after combining cosmic microwave background Planck data with DESI BAO, supernovae Ia, GRBs, cosmic chronometers, and galaxy clusters, showing a clear tension between neutrino oscillation results and cosmological analyses. In general, removing each one of three background probes still provides a limit $\sum m_{\nu }\lesssim 0.06\mathrm{eV}$, reassuring the enormous potential of these low-redshift observations in constraining the neutrino mass.

The early inspiral from stellar-mass binary black hole(sBBHs) can emit milli-Hertz gravitational wave signals, making them detectable sources for space-borne gravitational wave missions like TianQin. However, the traditional matched filtering technique poses a significant challenge for analyzing this kind of signals, as it requires an impractically high number of templates ranging from ${10}^{31}$ to ${10}^{40}$. We propose a search strategy that involves two main parts: initially, we reduce the dimensionality of the simulated signals using incremental principal component analysis (IPCA). Subsequently we train the convolutional neural networks (CNNs) based on the compressed TianQin data obtained from IPCA, aiming to develop both a detection model and a point parameter estimation model. The compression efficiency for the trained IPCA model achieves a cumulative variance ratio of 95.6% when applied to ${10}^6$ simulated signals. To evaluate the performance of CNN we generate the receiver operating characteristic curve for the detection model which is applied to the test data with varying signal-to-noise ratios. At a false alarm probability of 5% the corresponding true alarm probability for signals with a signal-to-noise ratio of 50 is 86.5%. Subsequently, we introduce the point estimation model to evaluate the value of the chirp mass of corresponding sBBH signals with an error. For signals with a signal-to-noise ratio of 50, the trained point estimation CNN model can estimate the chirp mass of most test events, with a standard deviation error of $2.49M_{\odot }$ and a relative error precision of 0.13.

If dark matter (DM) accumulates inside neutron stars (NS), it changes their internal structure and causes a shift of the tidal deformability from the value predicted by the dense-matter equation of state (EOS). In principle, this shift could be observable in the gravitational-wave (GW) signal of binary neutron star (BNS) mergers. We investigate the effect of fermionic, noninteracting DM when observing a large number of GW events from DM-admixed BNSs with the precision of the proposed Einstein telescope (ET). Specifically, we study the impact on the recovery of the baryonic EOS and whether DM properties can be constrained. For this purpose, we create event catalogs of BNS mock events with DM fraction up to 1%, from which we reconstruct the posterior uncertainties with the Fisher matrix approach. Using this data, we perform joint Bayesian inference on the baryonic EOS, DM particle mass, and DM particle fraction in each event. Our results reveal that when falsely ignoring DM effects, the EOS posterior is biased toward softer EOSs, though the offset is rather small. Further, we find that within our assumptions of our DM model and population, ET will likely not be able to test the presence of DM in BNSs, even when combining many events and adding Cosmic Explorer (CE) to the next-generation detector network. Likewise, the potential constraints on the DM particle mass will remain weak because of degeneracies with the fraction and EOS.

The isotropic gamma-ray background (IGRB), measured by the Fermi Large Area Telescope, is the result of several classes of extragalactic astrophysical sources. Those sources include blazars, start-forming galaxies and radio galaxies. Also, ultrahigh-energy cosmic rays interacting with the infrared background contribute to the isotropic background. Using information from Fermi’s gamma-ray sources catalog and the results of dedicated studies of these classes of sources, from observations at the infrared and radio, we model their contribution to the IGRB. In addition to conventional astrophysical sources, dark matter may be a component of the IGRB. We combine our model of conventional astrophysical sources and of dark matter annihilation in distant galaxies, marginalizing over relevant uncertainties, to derive constraints on the dark matter annihilation cross section, from the measured IGRB. In calculating the contribution from dark matter we include the flux from extragalactic halos and their substructure and also the subdominant contribution from the Milky Way’s halo at high galactic latitudes. The resulting constraints are competitive with the strongest current constraints from the dwarf spheroidal galaxies. Under certain dark matter assumptions, we also find an indication for a small excess flux in the isotropic background. Our results are consistent with the gamma-ray excess at GeV energies toward the galactic center.

In the one-photon exchange approximation, we analyze polarization effects in the elastic $\overrightarrow{e}\overrightarrow{p}\to ep$ and $e\overrightarrow{p}\to \overrightarrow{e}p$ processes in the case when the spin quantization axes of a target proton at rest and an incident or scattered electron are parallel. To do this, in the kinematics of the SANE Collaboration experiment [A. Liyanage et al., Phys. Rev. C 101, 035206 (2020)] using the J. Kelly [Phys. Rev. C 70, 068202 (2004)] and I. Qattan et al. [Phys. Rev. C 91, 065203 (2015)] parametrizations for the Sachs form-factor ratio $R\equiv {\mu }_p{G}_E/G_M$, a numerical analysis was carried out of the dependence of the longitudinal polarization degree transferred to the scattered electron in the $e\overrightarrow{p}\to \overrightarrow{e}p$ process and double-spin asymmetry in the $\overrightarrow{e}\overrightarrow{p}\to ep$ process on the square of the momentum transferred to the proton, as well as on the scattering angle of the electron. It is established that the difference in the longitudinal polarization degree of the scattered electron in the $e\overrightarrow{p}\to \overrightarrow{e}p$ process in the cases of conservation and violation of the scaling of the Sachs form factors can reach 70%. This fact can be used to set up polarization experiments of a new type to measure the ratio $R$. For double-spin asymmetry in the $\overrightarrow{e}\overrightarrow{p}\to ep$ process, the corresponding difference does not exceed 2.32%. This fact means that it is not sensitive to the effects of the Sachs form-factor scaling violation and could be used as a test for the $R\approx 1$ equality.

Our goal is to investigate the charged Higgs phenomenology in the framework of 2HDM at the upcoming $e^{+}{e}^{-}$ and muon colliders. We are primarily concerned with the associated production processes with a fermion pair: ${\ell }^{+}{\ell }^{-}\to {\tau }^{+}{\nu }_{\tau }{H}^{-}$ and ${\ell }^{+}{\ell }^{-}\to t\overline{b}{H}^{-}$, as well as with the W boson and a neutral Higgs boson: ${\ell }^{+}{\ell }^{-}\to W^{\pm }{H}^{\mp }S$ ($S=h$, $H$, $A$) and ${\ell }^{+}{\ell }^{-}\to W^{\pm }{H}^{\mp }Z$. We first update the results for $e^{+}{e}^{-}\to \{{\tau }^{+}{\nu }_{\tau }{H}^{-},t\overline{b}{H}^{-}\}$ and then discuss our findings for $e^{+}{e}^{-}\to \{W^{\pm }{H}^{\mp }S\}$ for various center-of-mass energies 500 GeV, 1 TeV, 1.5 TeV, and 3 TeV. In the case of muon collider, we show that the new s-channel and t-channel diagrams can increase the cross sections by virtue of their Yukawa couplings. We systematically compare our results for the muon collider with those obtained at the International Linear and Compact Linear colliders. We select benchmark points and conduct signal-background analyses, incorporating detector simulations. For a 3 TeV muon collider, our results show an exclusion region at the $2\sigma$ level and a discovery region at the $5\sigma$ level.

We calculate the amplitudes of the axion photoproduction off the nucleon, i.e., $\gamma N\to aN$, within the framework of chiral effective field theory. Several different types of contributions are simultaneously included in our calculation, namely, the nucleon exchanges up to next-to-leading order, the $a\gamma \gamma$ vertex, and the vector-meson exchanges in the $t$ channel. We utilize the existing hadronic inputs as much as possible to fix the unknown couplings. A comprehensive study of the phenomenological discussions is then provided in this work. Different mechanisms in the $\gamma N\to aN$ processes manifest distinct behaviors in the total and differential cross sections, which could provide useful quantities to distinguish different axion models.