Stellar-mass binary black holes (BBH) may form, evolve, and merge within the dense environments of active galactic nuclei (AGN) discs, thereby contributing to the BBH population detected by gravitational wave (GW) observatories. Mergers occurring in AGN discs may be gravitationally lensed by the central supermassive black hole. Such lensing presents a potential probe of BBH formation channels through its probability. In this work, we calculate the AGN lensing probability of LIGO sources embedded in an AGN disc by relating mismatch threshold to the signal-to-noise ratio. The AGN lensing probability of a GW190521-like event will be $\sim 3\%$ for the O3 power spectral density (PSD), $\sim 6\%$ for the Aplus PSD, and $\sim 33\%$ for the ET PSD. If AGNs are indeed the primary formation channel for BBHs, we could quantify the probability of detecting the lensed GW events in such a scenario. The nondetections, on the other hand, will place stricter constraints on the fraction of AGN disc BBHs and even the birthplaces of BBH mergers.

We study electromagnetic radiation from classical sources near a planar interface separating a topological and a trivial insulator, modeled within axion electrodynamics. The system features a piecewise constant $\theta$ term that encodes the magnetoelectric response of topological surface states. Treating this coupling perturbatively, we derive analytical corrections to the standard Liénard-Wiechert potentials and obtain modified radiation fields in the far zone. As applications, we analyze the emission from linear antennas and the bremsstrahlung radiation of accelerated charges near the interface. For antennas, the surface Hall response breaks axial symmetry and produces azimuthal modulations that grow with the electrical length, leading to distinct scaling behaviors in the total and angular radiated power. For accelerated charges, the emitted intensity is uniformly reduced by a factor $1-({\sigma }_{\text{Hall}}/2\epsilon v{)}^2$, which we interpret as a process-specific attenuation of the radiative strength due to interference with its image magnetic monopole inside the topological medium. These results reveal how topological surface states mediate measurable modifications to classical radiation, establishing a link between axion electrodynamics, topological phases, and field theories with spatially varying couplings.

The locality of field theories strongly constrains the possible behaviors of symmetry-twisted partition functions, and thus they serve as order parameters to detect low-energy realizations of global symmetries, such as spontaneous symmetry breaking (SSB). We demonstrate that the tensor renormalization group (TRG) offers an efficient framework to compute the symmetry-twisted partition functions, which enables us to detect the symmetry-breaking transition and also to study associated critical phenomena. As concrete examples of SSB, we investigate the two-dimensional (2D) classical Ising model and the three-dimensional (3D) classical $O(2)$ nonlinear sigma model, and we identify their critical points solely from the twisted partition function. By employing the finite-size scaling argument, we find the critical temperature $T_c=2.2017(2)$ with the critical exponent $\nu =0.663(33)$ for the 3D $O(2)$ model. In addition, we also study the Berezinskii–Kosterlitz–Thouless (BKT) criticality of the 2D classical $O(2)$ model by extracting the helicity modulus from the twisted partition functions, and we obtain the BKT transition temperature, $T_{\mathrm{BKT}}=0.8928(2)$.

We set the scale of $\mathrm{SU}(N)$ Yang-Mills theories for $N=3$, 5, 8 and in the large-$N$ limit via gradient flow, as a first step towards the computation of the large-$N$ $\mathrm{\Lambda }$-parameter using step scaling. We adopt twisted boundary conditions to achieve large-$N$ volume reduction and the Parallel Tempering on Boundary Conditions algorithm to tame topological freezing. This setup allows accurate determinations of the gradient-flow scales down to lattice spacings as fine as $\sim 0.025\mathrm{fm}$ for all the explored values of $N$, a regime that has never been reached with ergodic algorithms. Moreover, we are able to precisely estimate the finite-size systematics related to topological freezing, and to show the suppression of finite-volume effects expected by virtue of large-$N$ twisted volume reduction.

We present the nonrelativistic QCD (NRQCD) calculations at the next-to-leading order (NLO) of ${\alpha }_s$ for $B_c^{*}\to {\eta }_c$ vector, axial-vector, tensor, and axial-tensor form factors, and obtain complete analytical expressions for the form factors, along with their asymptotic forms in the hierarchical heavy quark limit. Our results show that the NLO corrections are both sizable and well behaved in the low squared transfer momentum $(q^2)$ region. Using the $\mathrm{NRQCD}+\text{lattice}+z$-series method, we further provide theoretical predictions for $B_c^{*}\to {\eta }_c$ form factors across the full physical $q^2$ range. Based on these predicted form factors, we finally compute the decay widths and branching fractions for the semileptonic decays $B_c^{*}\to {\eta }_c+l{\nu }_l$.

We systematically investigate the dibaryons ${\mathrm{\Xi }}_{cc}^{(*)}{\mathrm{\Xi }}_{cc}^{(*)}$ (di-${\mathrm{\Xi }}_{cc}$) and ${\mathrm{\Xi }}_{bb}^{(*)}{\mathrm{\Xi }}_{bb}^{(*)}$ (di-${\mathrm{\Xi }}_{bb}$), with various isospin-spin configurations $I(J^P)$ in a nonrelativistic quark model. For the di-${\mathrm{\Xi }}_{cc}$ system, only the single channels ${\mathrm{\Xi }}_{cc}{\mathrm{\Xi }}_{cc}^{*}$ and ${\mathrm{\Xi }}_{cc}^{*}{\mathrm{\Xi }}_{cc}^{*}$ with $0(1^{+})$ are capable of forming deuteronlike bound states, with the $\sigma$ meson exchange playing a decisive role. Those states have binding energies of approximately $-1.5\mathrm{MeV}$ and $-3.3\mathrm{MeV}$ and sizes of 2.37 fm and 1.87 fm, respectively. The coupled channel effect in the di-${\mathrm{\Xi }}_{cc}$ system with $0(1^{+})$ enhances the attraction. As a result, this di-${\mathrm{\Xi }}_{cc}$ system can establish a deuteronlike configuration, with the binding energy of $-7.5\mathrm{MeV}$ relative to the threshold ${\mathrm{\Xi }}_{cc}{\mathrm{\Xi }}_{cc}$ and the size of approximately 1.40 fm. For the di-${\mathrm{\Xi }}_{bb}$ system, the single channels with $0(1^{+})$, $0(2^{+})$, and $0(3^{+})$ can give rise to deuteronlike bound states with binding energies ranging from $-6.1\mathrm{MeV}$ to $-14.3\mathrm{MeV}$. Additionally, the di-${\mathrm{\Xi }}_{bb}$ system with $1(0^{+})$ and $1(2^{+})$ can also establish deuteronlike bound states with binding energies of around $-0.5\mathrm{MeV}$. When considering the coupled channel effect in the di-${\mathrm{\Xi }}_{bb}$ system with $0(1^{+})$, a compact hexaquark state is formed, exhibiting a binding energy of $-21.2\mathrm{MeV}$ relative to the threshold ${\mathrm{\Xi }}_{bb}{\mathrm{\Xi }}_{bb}$ and a size of 0.53 fm. In this state, the $\pi$ meson exchange provides a very powerful attractive force. The meson exchange interactions in the quark model is dispensable in the di-${\mathrm{\Xi }}_{bb}$ bound states, except for ${\mathrm{\Xi }}_{bb}^{*}{\mathrm{\Xi }}_{bb}^{*}$ with $1(0^{+})$.

A search for $K_{\mathrm{S}(\mathrm{L})}^0\to {\pi }^{+}{\pi }^{-}{\mu }^{+}{\mu }^{-}$ decays is performed using proton-proton collision data collected by the LHCb experiment at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of $5.4{\mathrm{fb}}^{-1}$. No $K_{\mathrm{S}(\mathrm{L})}^0\to {\pi }^{+}{\pi }^{-}{\mu }^{+}{\mu }^{-}$ signals are found and upper limits are set for the first time on the branching fractions $\mathcal{B}(K_{\mathrm{S}}^0\to {\pi }^{+}{\pi }^{-}{\mu }^{+}{\mu }^{-})<1.4\times {10}^{-9}$ and $\mathcal{B}(K_{\mathrm{L}}^0\to {\pi }^{+}{\pi }^{-}{\mu }^{+}{\mu }^{-})<6.6\times {10}^{-7}$, at the 90% confidence level.

We derive regular black hole solutions, including the Hayward metric, from four-dimensional action principles involving vector fields in addition to the metric. These black holes possess additional hair associated with the vector fields, manifesting as free integration constants that regularize the geometry. These constants can be chosen such that regular black holes of all masses are extremal. As a result, they have vanishing surface gravity and are not susceptible to mass-inflation instability. We also discover another regular black hole metric with these properties, which constitutes a gravastar for an appropriate choice of integration constant.

We explore an unusual symmetry in a field theory on a specific ($1+1$)-dimensional curved spacetime, which has an interesting interpretation as an approximate asymptotic Weyl symmetry. Unlike the conventional Weyl symmetry, the boundary term under the variation plays a crucial role in understanding for its anomaly. After converting a two-dimensional field theory on curved spacetime to an inhomogeneous field theory, we obtain the vacuum expectation value of the energy-momentum tensor. Then, we show the existence of an Unruh-like effect in the bubble wall expansion at the zero temperature.

We investigate covariant loop quantum black hole models in effective quantum gravity by using the orbital motion of the S2 star around Sagittarius ${\mathrm{A}}^{\star }$. Three representative covariant metrics that preserve general covariance while incorporating distinct quantum corrections are analyzed: two derived with relaxed gauge-fixing conditions and one nonsingular model with holonomy corrections. By investigating orbital motions from the geodesic equations and comparing with astrometric and spectroscopic observations from the GRAVITY Collaboration, we perform a Markov chain Monte Carlo analysis to search for loop quantum gravity signatures. No statistically significant evidence for quantum modifications is found. The 95% credible upper limits on the dimensionless deformation parameter are $\zeta \lesssim 0.723$ for model I, $\zeta \lesssim 88.622$ for model II, while no meaningful constraint can be placed on model III with the current data. A complementary analysis within the parametrized post-Newtonian framework likewise reveals no detectable deviations from general relativity. Such results imply that current data of the S2 star possess less ability of searching the signal beyond general relativity within the spherically symmetric spacetimes.

We present an analytical and numerical investigation of the quasinormal excitation factors of ultracompact horizonless objects. These systems possess long-lived quasinormal modes with extremely small imaginary parts, originating from the effective cavity between the photon sphere and the object’s interior. We show that the excitation of such modes is strongly suppressed, scaling with the imaginary part of their frequency, and therefore they contribute to the waveform only at very late times. This hierarchy naturally explains the structure of echo signals; the prompt ringdown is dominated by standard light-ring modes, the early echoes arise from moderately damped cavity modes, and only the latest echoes are governed by long-lived modes. Building on this, we propose a practical ringdown waveform model that combines ordinary black-hole quasinormal modes with cavity modes, capturing the complexity of the ringdown of horizonless ultracompact objects. We further demonstrate that the combination of small excitation factors and weak damping enhances the robustness of long-lived modes against localized perturbations, in contrast to the spectral instabilities affecting standard black-hole quasinormal modes. Finally, we extend the analysis of greybody factors to exotic compact objects and wormholes, showing that they remain stable under small deformations of the effective potential and thus represent robust observables. Our results provide a unified framework for understanding excitation, stability, and echoes in ultracompact horizonless objects, with direct implications for their spectral properties and gravitational-wave signatures.

An extremal Reissner-Nordström black hole can form in finite time in the gravitational collapse of a massless charged scalar field. The proof of this is based on the method of characteristic gluing, which involves making an Ansatz for the scalar field at the horizon. We perform a numerical investigation of the characteristic gluing procedure for several different Ansätze. In each case, gluing is possible only if the final black hole mass is large enough. We find that the minimum required mass varies significantly for different Ansätze. We also consider the effect of including a mass term for the scalar field. In this case, for each Ansatz we determine the maximum mass-to-charge ratio for the scalar field such that gluing is possible. Analogous results are obtained for a nonzero cosmological constant.

We present measurements of the temperature and E-mode polarization angular power spectra of the cosmic microwave background (CMB) from observations of 4% of the sky with SPT-3G, the current camera on the South Pole Telescope (SPT). The maps used in this analysis are the deepest used in a CMB $\mathrm{TT}/\mathrm{TE}/\mathrm{EE}$ analysis to date. The maps and resulting power spectra have been validated through blind and unblind tests. The measurements of the lensed EE and TE spectra are the most precise to date at $\ell =1800–4000$ and $\ell =2200–4000$, respectively. Combining our $\mathrm{TT}/\mathrm{TE}/\mathrm{EE}$ spectra with previously published SPT-3G CMB lensing results, we find parameters for the standard $\mathrm{\Lambda }$ cold dark matter ($\mathrm{\Lambda }\mathrm{CDM}$) model consistent with Planck and ACT DR6 with comparable constraining power. We report a Hubble constant of $H_0=66.66\pm 0.60\mathrm{km}{\mathrm{s}}^{-1}{\mathrm{Mpc}}^{-1}$ from SPT-3G alone, $6.2\sigma$ away from local measurements from SH0ES. For the first time, combined ground-based ($\mathrm{SPT}+\mathrm{ACT}$) CMB primary and lensing data have reached Planck’s constraining power on some parameters, a milestone for CMB cosmology. The combination of these three CMB experiments yields the tightest CMB constraints to date, with $H_0=67.19\pm 0.38\mathrm{km}{\mathrm{s}}^{-1}{\mathrm{Mpc}}^{-1}$, and the amplitude of clustering ${\sigma }_8=0.8137\pm 0.0037$. CMB data alone show no evidence for physics beyond $\mathrm{\Lambda }\mathrm{CDM}$, however, we observe a $2.8\sigma$ difference in $\mathrm{\Lambda }\mathrm{CDM}$ between CMB and baryon acoustic oscillation (BAO) results from DESI-DR2, which is relaxed in extended models. The combination of CMB and BAO yields $2-3\sigma$ shifts from $\mathrm{\Lambda }\mathrm{CDM}$ in the curvature of the Universe, the amplitude of CMB lensing, or the dark energy equation of state. It also drives mild preferences for models that address the Hubble tension through modified recombination or variations in the electron mass in a nonflat Universe. This work highlights the growing power of ground-based CMB experiments and lays a foundation for further cosmological analyses with SPT-3G.

The $w_{†}\mathrm{VCDM}$ (V-cold dark matter) framework provides a theoretically well-controlled extension of $\mathrm{\Lambda }\mathrm{CDM}$ within the class of minimally modified gravity theories, allowing for flexible cosmological background evolution and linear perturbation dynamics while remaining free of pathological instabilities. In this work, we have shown that this scenario remains robust when confronted with current cosmological observations, even in the presence of an extended neutrino sector. Combining Planck CMB data with the Dark Energy Spectroscopic Instrument Data Release 2 baryon acoustic oscillations (BAO) and PantheonPlus, we obtain stringent constraints on neutrino physics, including $\sum m_{\nu }<0.12\mathrm{eV}$ (95% confidence level) and $N_{\mathrm{eff}}=3.114_{-0.128}^{+0.139}$, fully consistent with Standard Model expectations within $1\sigma$. Crucially, the data exhibit a statistically significant preference for a late-time dark-energy transition, characterized by a robust quintessence-phantom crossing that remains stable across all dataset combinations and neutrino-sector extensions, including the presence of a sterile neutrino. The combined effects of modified late-time expansion and additional relativistic degrees of freedom systematically raise the inferred Hubble constant, substantially alleviating the $H_0$ tension without invoking early dark energy or introducing theoretical instabilities. Overall, the $w_{†}\mathrm{VCDM}$ scenario emerges as a compelling phenomenological framework that simultaneously accommodates current constraints on neutrino physics, provides an excellent fit to recent BAO and supernovae data, and offers a viable pathway toward resolving persistent tensions in the standard cosmological model.

Quantifying the imprints of freeze-in dark matter (DM) on cosmological structures requires knowledge of its phase-space distribution. We investigate how variations in the cosmological history before nucleosynthesis, the “weather” of that epoch, give rise to distinct “seasons” in the DM momentum distribution that governs its warmness. Studying decay-driven production across diverse cosmological histories, we map how these conditions shape DM phase-space properties. Our study quantifies how the early Universe composition plays a key role in determining the mass bound on freeze-in DM.

Data-driven approaches using deep learning are emerging as powerful techniques to extract non-Gaussian information from cosmological large-scale structure. This work presents the first simulation-based inference (SBI) pipeline that combines weak lensing and galaxy clustering maps in a realistic Dark Energy Survey Year 3 (DES Y3) configuration and serves as preparation for a forthcoming analysis of the survey data. We develop a scalable forward model based on the cosmogridv1 suite of $N$-body simulations to generate over one million self-consistent mock realizations of DES Y3 at the map level. Leveraging this large dataset, we train deep graph convolutional neural networks on the full survey footprint in spherical geometry to learn low-dimensional features that approximately maximize mutual information with target parameters. These learned compressions enable neural density estimation of the implicit likelihood via normalizing flows in a ten-dimensional parameter space spanning cosmological $w$CDM, intrinsic alignment, and linear galaxy bias parameters, while marginalizing over baryonic, photometric redshift, and shear bias nuisances. To ensure robustness, we extensively validate our inference pipeline using synthetic observations derived from both systematic contaminations in our forward model and independent buzzard galaxy catalogs. Our forecasts yield significant improvements in cosmological parameter constraints, achieving $2–3\times$ higher figures of merit in the ${\mathrm{\Omega }}_m\text{−}{S}_8$ plane relative to our implementation of baseline two-point statistics and effectively breaking parameter degeneracies through probe combination. These results demonstrate the potential of SBI analyses powered by deep learning for upcoming stage-IV wide-field imaging surveys.

Precise laser alignment in optical cavities is essential for high-precision laser interferometry. We report on a table-top optical experiment featuring two alignment sensing schemes: the conventional wavefront sensing (WFS) scheme which uses quadrant photodetectors (QPDs) to recover optical alignment, and the newly developed radio frequency jitter alignment sensing (RFJAS) scheme, which uses an electro-optic beam deflector (EOBD) to apply fast angular modulation. This work evaluates the performance of RFJAS through a direct, side-by-side comparison with WFS. We present a detailed noise budget for both techniques, with particular emphasis on limitations at low frequencies, below 30 Hz. Our results show that WFS performance is constrained by technical noise arising from beam spot motion (BSM), mainly due to beam miscentering on QPDs. In contrast, RFJAS is primarily limited by residual RF amplitude modulation. A blended scheme that combines both sensing methods may offer the most practical approach for use in gravitational wave detectors such as Advanced LIGO.

The GWTC-4.0 catalog of transient gravitational wave signals describes observations made in the first part of the fourth observing run of the LIGO-Virgo-KAGRA (LVK) gravitational wave detector network. Here we extend the LVK’s GWTC-4.0 analysis to elliptic orbits, and an improved description of spin precession in the frequency domain. For this study we use state-of-the-art waveforms from the IMRPhenom family (specifically XPNR, TPHM, and TEHM), and we consider the 84 confidently detected events that are consistent with binary-black-hole mergers. We present an extended catalog of updated posterior samples, quantify how incorporation of these waveform effects alters inferred source properties relative to previous analyses, and discuss waveform systematics.

The masses of exotic quantum-number $1^{-+}$ compact tetraquark states are calculated in a constituent quark model, where a Cornell-like potential is employed as the central potential, spin-spin and spin-orbit coupling derived from the Breit-Fermi interaction are treated as hyperfine corrections, and model parameters are taken from previous works. The ground state $1^{-+}$ P-wave tetraquarks are predicted at 1.9, 4.2, and 6.6 GeV for the light, charmoniumlike, and fully charm sectors, respectively. The decay width ratios of $1^{-+}$ tetraquark states are calculated for two-body strong decay channels within the rearrangement mechanism, including $\omega h_1$ and $\eta f_1$ for isospin $I=0$ light tetraquarks, $\rho h_1$ and $\pi f_1$ for isospin $I=1$ light tetraquarks, $\pi /\eta +{\chi }_{c1}$ and $\rho /\omega +h_c$ for charmoniumlike tetraquarks, and ${\eta }_c{\chi }_{c1}$ and $J/\psi h_c$ for fully charm tetraquarks. The theoretical results are compared with the observed exotic $1^{-+}$ states, and promising search channels for $1^{-+}$ tetraquarks are discussed. The work suggests that ${\eta }_1(1855)$ is unlikely to be a compact tetraquark state.

We present a comprehensive study of secluded dark matter (DM) $\chi$, where the relic abundance is set by annihilations into lighter dark mediators $\varphi$ that couple only feebly to the Standard Model (SM). In contrast to canonical weakly interacting massive particles (WIMPs), which are now strongly constrained by direct and indirect searches, secluded models still achieve the observed relic abundance via thermal freeze-out into hidden-sector mediators, while predicting highly suppressed present-day signals. We analyze three minimal models: (i) a $U(1{)}_X$ gauge boson ($A^{\prime }$) with kinetic mixing; (ii) a scalar DM candidate $S$ with a scalar mediator $K$ that has a trilinear vertex; and (iii) a Dirac fermion $\chi$ whose mass arises from a Higgs–mixed singlet $H_p$. For each model we derive annihilation and scattering rates in both WIMP-like and secluded regimes, and solve the Boltzmann equations: a single-species equation for the WIMP case and a coupled $\chi -\varphi$ system for the secluded case to account for possible early departure of the mediator from thermal equilibrium with the SM bath. In this regard, we provide explicit lower limits on the portal coupling $\epsilon$ required to keep the mediator in thermal equilibrium with the SM bath and to ensure mediator decay before big bang nucleosynthesis. We show that for portal couplings $\epsilon \ll {10}^{-3}$ the relic density is dominantly controlled by DM annihilation into mediator pairs, while spin-independent scattering lies well below current limits and remains viable even for future experiments approaching the irreducible neutrino background floor. Indirect constraints are typically weak due to $p$-wave suppression, off-resonance $s$-channels, and cascade spectra controlled by ${\epsilon }^2$. Finally, we highlight the most promising collider tests, which remain sensitive despite tiny portal couplings.