Papers

The effect of deflection of a light signal that propagates through the gravitational field of a solar system body at rest is considered in the case that the source and the observer are at a finite distance from the body. The observer is assumed to be located somewhere nearby the Earth, for instance at Lagrange point L2 of the Sun-Earth system, while the spatial position of the celestial light source is arbitrary. The gravitational fields in the exterior of the bodies are described by the full set of time-dependent mass-multipoles and spin-multipoles of these bodies. So the gravitating bodies can be of arbitrary shape, inner structure and rotational motion. The unit tangent vector of the light trajectory at the position of the observer is determined in the 1PN and 1.5PN approximation of the post-Newtonian (PN) scheme. A simplified expression for the unit tangent vector is obtained, where all terms are neglected that together contribute less than 10 nano-arcseconds in light deflection for all astrometric configurations between source, body and observer. It is shown that in the case of an axi-symmetric body the unit tangent vector of the light ray as well as the light deflection are given in terms of Chebyshev polynomials. This fact allows for determining the effect of light deflection in the gravitational fields of the bodies up to any order of the mass-multipoles and spin-multipoles. It is shown that the total light deflection, that is the angle of light deflection where source and observer are located at infinite spatial distance from the body, represents an upper limit of the effect of light deflection. These investigations are aiming at astrometric measurements on the sub-micro-arcsecond level of accuracy.

We investigate the thermalization process of two-level probes in de Sitter spacetime from a quantum-metrological perspective. For a static probe separated by a finite distance from a freely falling observer, both the intrinsic Gibbons–Hawking temperature and the position-dependent Unruh temperature are encoded in the probe state. The mutual influence between the encoding rate of the Gibbons–Hawking temperature and that of the Unruh temperature is studied. Results show that the thermalization rate is equal to the sum of the encoding rates of the Gibbons–Hawking temperature and that of the Unruh temperature. Interestingly, a nonzero inherent acceleration induced by the separation between the probe and a freely falling observer does not necessarily suppress the encoding of the Gibbons–Hawking temperature. Instead, there exists an optimal inherent acceleration at which the encoding rate of the Gibbons–Hawking temperature is maximized. Furthermore, the required total probe time of estimating the thermal effect with sufficient precision is shown in relation with the thermalization rate. The required total probe time and the corresponding number of probes remain experimentally feasible when the position-dependent inherent acceleration satisfies $\frac{a}{2\pi\omega_0}\rightarrow0.1$.

We study the quantum interference of two paths that enclose a slowly rotating, infinitely long, and infinitely thin cylindrical shell, using the spacetime metric induced by the gravitational source. We show that the rotation of the shell affects the interference pattern even though it does not contribute to the classical motion of particles propagating outside the shell. Furthermore, we find that the gravitomagnetic field is non-vanishing only in the region inside the shell, yet it contributes to the interference taking place entirely in the exterior region. This phenomenon is therefore a gravitational analogue of the Aharonov-Bohm effect, in which a field confined to an inaccessible region influences the quantum phase of particles propagating in a field-free region.

In February 2016 the LIGO and Virgo collaborations reported the discovery of gravitational waves in merging black holes, with the conclusion that their observational data did not show any violation of general relativity. The joint LIGO and Virgo team presented an upper limit on the graviton mass, using tests of modified gravitational dynamics. Yukawa-type gravitational potential corrections are often used as generic finite-range parametrisation in modified gravity contexts, including massive-gravity inspired models. Yukawa corrections are derived by semi-empirical approach, in the framework of f(R) gravity, a type of modified gravity which generalises Einsteins general relativity. Contrary to this approach, we use a classical Newtonian gravitational potential corrected by nonlinear effects in order to obtain a characteristic wavelength of the nonlinear density wave. This wavelength is then phenomenologically identified with an effective graviton Compton wavelength, leading to a model-dependent estimate of an effective graviton mass within the galaxy scale. The presented approach is independent from other methods published until now.

The presence of hyperons in the cores of neutron stars opens fast strangeness equilibration channels that can produce bulk-viscous dissipation during binary inspiral. Because these reactions coexist with electron $\beta$-equilibration, tidal compression can drive the two coupled chemical imbalances far beyond linear response. We construct the first reaction network that self-consistently evolves the electron and strangeness fractions with a four-dimensional strangeness-dependent chiral mean-field (CMF) equation of state, including nucleonic and hyperonic Urca processes and non-leptonic hyperon reactions. For periodic density perturbations, representative of inspiral oscillations, we find that rapid strangeness conversion can generate a large $\beta$-imbalance, after which slow $\beta$-equilibration bottlenecks strangeness relaxation. Rather than decaying exponentially, the coupled system consequently exhibits dynamically important algebraic decay in a far-from-equilibrium regime. At the $\rm keV$ temperatures expected during inspiral, this nonlinear response produces a broad enhancement of the effective bulk viscosity, reaching $\sim10^{31}\,\mathrm{g\,cm^{-1}\,s^{-1}}$ for $320$ Hz oscillations. A phenomenological estimate of continuous inspiral dissipation yields gravitational-wave phase shifts up to $\sim0.14$ rad for neutron stars with hyperonic cores. Self-consistent, far-from-equilibrium strangeness transport may therefore provide a dynamical probe of hyperons in neutron-star interiors.

Black holes embedded in a dark matter background represent an important candidate model that extends the standard vacuum case, characterizing the strong gravitational environments at galactic centers and the gravitational influence of dark matter. This study focuses on dark matter halo-modified Kerr black holes and systematically investigates the observational characteristics of their surrounding thin accretion disks. The dark matter halo is modeled by a general double power-law density profile, whose integrated mass $M_D(r)$ modifies the radial mass function of Kerr metric to $m(r) = M + M_D(r)$. Based on this spacetime, we analyze the observational properties of their thin accretion disk, including the radiative flux, temperature, differential luminosity, and spectral luminosity as a function of radius, with respect to the black hole spin and dark matter halo parameters. Furthermore, by combining ray-tracing methods, we simulate the bolometric image of the thin accretion disk under different black hole spins, dark matter halo parameters, and viewing inclinations. The dark matter halo enhances the gravitational potential, shifting the innermost stable circular orbit (ISCO) of the accretion disk outward, suppressing the peak radiative flux, and producing a fainter image, thereby generating signatures that are possibly observational distinguishable from standard vacuum Kerr black holes.

The static tidal Love numbers (TLNs) of $4$-dimensional black holes vanish for bosonic perturbations but are generically nonzero for fermions, with rare exceptions. In this paper, we show that for static, spherically symmetric black holes, fermionic TLNs vanish if and only if the black hole is extremal, in the sense that its horizon is degenerate. This follows from a closed formula for the static fermionic TLN of any asymptotically flat black hole, obtained by solving the static massless Dirac equation exactly on an arbitrary such spacetime and imposing regularity at the horizon. As applications, we analyze the Culetu–Simpson–Visser regular black hole and the loop-quantum-gravity remnant black holes, whose extremal configurations lead to vanishing fermionic yet nonvanishing bosonic TLNs.

We study how composition order becomes operationally distinguishable when a phase-sensitive Gaussian control is applied before or after black-hole greybody scattering. The scattering process is formulated on calibrated asymptotic mode ports as a bosonic attenuation channel, and the control is a calibrated squeezing transformation. For finite-dimensional faithful families near a common faithful output, the local symmetrized Umegaki response is governed by the Bogoliubov-Kubo-Mori norm of the channel-composition defect; the corresponding bosonic problem is solved exactly at the Gaussian-state level. The exact attenuation-squeezing response yields an infrared exponent-transfer law relating greybody transmission and occupation scalings to distinguishability. For a massless scalar on Schwarzschild, matched low-frequency scattering gives an explicit fixed-partial-wave logarithmic coefficient and a locally integrable packet response. At finite squeezing, the infrared outputs approach distinct pure Gaussian supports, producing finite sandwiched Rényi divergence below unit order, logarithmic Umegaki growth at unit order, and divergence above unit order. Schwarzschild-de Sitter boundary prescriptions generate controlled source-isolated and product-horizon crossover sectors. The results apply to calibrated asymptotic-port compositions and to the reduced finite-band selected-mode realization under the stated narrowband and channel assumptions.

We study Schwarzschild–AdS black holes in conformal Killing gravity with non-perturbative entropy corrections within the extended phase-space formalism. By deriving the quantum-corrected heat capacity, Helmholtz free energy, internal energy, and Gibbs free energy, we show that quantum corrections modify phase transition points and thermal stability mainly at small horizon radii, while classical behavior is recovered for large black holes. Critical behavior of van der Waals type appears exclusively for positive values of the conformal Killing parameter $a$. Applying the island prescription, we find that the entanglement entropy of Hawking radiation saturates after the Page time at $S_{\text{sat}} = 2(\pi r_H^2 + \eta e^{-\pi r_H^2})$, thereby restoring unitarity. Stronger quantum corrections increase the entropy threshold and delay information recovery. Furthermore, we examine the universal thermodynamic relation in the extremal limit under a minimal perturbation of the AdS curvature radius. We prove that the quantum correction parameter $\eta$ cancels out completely, yielding the robust universal combination $U = -r_{\text{ext}}^3 / l^3$. This demonstrates that the universal relation remains stable against non-perturbative quantum corrections to the entropy.

We characterize the gravitational radiation present in the general Plebański-Demiański type~D solution with cosmological constant $\Lambda$ of any sign. We show that radiation escapes towards infinity if and only if the acceleration parameter is non-zero. We calculate the Cotton-York tensor and the boundary stress-energy tensor at infinity for negative $\Lambda$, and for positive $\Lambda$ the $D$ tensor that complements initial or final data at $\mathscr{J}$. In addition, we recast a recent parametrization of this family of metrics into a new form by a simple homothety, correctly identifying $\Lambda$, and study the existence and regularity of the possible axes of symmetry, searching for a relation between deficit angles and radiation. We also identify the branch of general non-radiating solutions with non-vanishing Cotton-York tensor at $ \mathscr{J} $.

We investigate the sensitivity of IndIGO-D, a proposed space-based decihertz gravitational-wave interferometer, to different classes of ultralight dark matter. IndIGO-D will probe the $\sim0.01$–$10~\mathrm{Hz}$ frequency band between those accessible to current ground- and future space-based gravitational-wave interferometers, providing access to ultralight dark-matter masses beyond the reach of existing instruments. We consider two complementary signatures: interferometric displacements induced by coherently oscillating scalar (dilaton), vector (dark-photon, $U(1)_B$ and $U(1)_{B-L}$ gauge groups), and tensor fields with masses $m_{\rm DM}\sim10^{-17}$–$10^{-14}~\mathrm{eV}$; and changes in laser polarization induced by pseudoscalar axion dark matter at higher masses, around $m_a\sim10^{-12}~\mathrm{eV}$. For the dilatons, dark photons and tensors, we compute the expected sensitivities using two pipelines – cross-correlation and BSD excess-power – assuming L-shaped and triangular interferometer layouts and three representative noise power spectral densities (S1, S2, S3), each for two years of continuous observation. We find that the projected sensitivities agree to within a factor of order unity across the search pipelines and interferometer geometries. In particular, we show that IndIGO-D could open previously unconstrained coupling parameter space for vector and tensor dark matter across $m_{\rm DM}\sim10^{-16}$–$10^{-14}~\mathrm{eV}$, bridging the sensitivity of space- and ground-based experiments. For axion dark matter, we demonstrate that a complementary detection for laser light polarization shifts, limited primarily by photon shot noise, could probe the axion-photon coupling $g_{a\gamma}$ at masses around $m_a\sim10^{-12}~\mathrm{eV}$ at a level potentially better than that of other future experiments without degrading sensitivity to gravitational waves.

We investigate the fluid interpretation, Hawking–Ellis classification, and energy conditions of the proper kinetic gravity braiding contribution to the stress tensor of minimally coupled scalar fields for timelike, spacelike, and open-region null scalar gradients. Using a $2+1+1$ decomposition adapted to the gradient, we derive the associated effective fluid variables. Unlike k-essence, braiding generates heat fluxes and pressure anisotropies: radial and tangential heat fluxes for timelike gradients, and a radial heat flux plus mixed radial–tangential anisotropies for spacelike gradients. These quantities depend only on the normal fundamental scalars and the two-dimensional accelerations, despite the larger set of variables appearing at intermediate stages. For open-region null gradients, the proper-braiding stress tensor has null-dust form. We obtain the complete Hawking–Ellis classification: the timelike sector is Type I for positive discriminant, Type II on the nontrivial discriminant hypersurface, and Type IV for negative discriminant; the spacelike sector has the same generic branches and additional Type II and Type III degeneracies when the squared radial heat flux equals the squared mixed anisotropy. The open-region null sector is Type II for nonzero null-dust density and vanishes in the zero-density case. Finally, the standard energy conditions further restrict the Type I and generic Type II sectors. The null energy condition excludes Types III and IV and, for spacelike gradients, every nonzero radial heat flux or mixed anisotropy. Thus admissible spacelike proper braiding is diagonal, whereas in the timelike sector the energy conditions bound the total heat flux.

In this paper, we investigate static magnetic brane solutions in (n+1)-dimensional quartic quasi-topological gravity coupled to power-law Maxwell nonlinear electrodynamics. We derive the corresponding solutions and analyze their geometric and physical properties. We observe that the solutions are horizonless and free of curvature singularities in the physically accessible region, while the spacetime generally exhibits a conical singularity with a nonzero angular deficit at the lower radial endpoint. We demonstrate that the endpoint is independent of the higher-curvature couplings lambda, mu, and c, whereas the near-endpoint geometry is mainly controlled by the magnetic parameter q and the nonlinear parameter s. At large radial distances, we find that the higher-curvature couplings govern the asymptotic behavior of the metric. We also establish that finite asymptotic solutions require 1/2 < s <= 2 and analyze the dependence of the angular deficit on q, s, and the endpoint parameter rho_+. Using the counterterm method, we calculate the conserved mass density and show that the static magnetic brane carries no net electric charge. Finally, we verify that the power-law Maxwell theory recovers linear Maxwell electrodynamics at s=1 and Einstein gravity when lambda=mu=c=0.

We investigate the spatial geometry of the Universe within the framework of a sign-switch dark energy scenario by extending the recently proposed $\Lambda_{\rm s}$CDM model to include a free curvature parameter $\Omega_k$.In this framework, the effective cosmological constant undergoes a transition from a negative to a positive value at a characteristic redshift $z_{\dagger}$. Using the latest Planck 2018 cosmic microwave background (CMB) data, DESI DR2 baryon acoustic oscillation (BAO) measurements, and the PantheonPlus&SH0ES Type Ia supernova sample, we derive joint constraints on the spatial curvature parameter $\Omega_k$ and other cosmological parameters. We find that Planck data itself slightly favors a closed universe within both the $\Lambda_{\rm s}$CDM$+\Omega_k$ and $\Lambda$CDM$+\Omega_k$ frameworks, although spatial flatness remains well within the allowed uncertainties. When low-redshift probes were included, the curvature constraints were significantly tightened. In particular, the full Pk18+DR2+PP&SH0ES dataset yields $\Omega_k = 0.0001 \pm 0.0014$ for the $\Lambda_{\rm s}$CDM model, indicating a universe that is remarkably consistent with spatial flatness. We further analyzed the correlations between $\Omega_k$, $H_0$, and $S_8$, finding that the inclusion of curvature and a sign-switch dark energy component helps stabilize cosmological parameter estimates while remaining compatible with current observational constraints. Model comparison using AIC and Bayesian evidence shows that the $\Lambda_{\rm s}$CDM model receives inconclusive/weak observational support relative to $\Lambda$CDM.

This sixth version of the Domain-Adaptive Network for Transient Evaluation (DANTE) preprint stress-tests an unsupervised transient-noise pipeline under representation mismatch and observing-run adaptation. We reanalyse 10,429 detector-time strain candidates from 42 LIGO O4a sessions using frozen DINOv2 patch embeddings and a Top-k multiple-instance score. Candidate and native-background Q-transforms share Q in [4,64], and detector-specific thresholds are calibrated from 5,000 run-native windows by temporal-block bootstrap. The coherent analysis yields 6,365 ROBUST, 1,275 AMBIGUOUS, and 2,789 BACKGROUND statistical dispositions; 4,676 of 10,372 paired historical dispositions differ from the cross-representation v5 analysis. Direct controls resolve an O3b-O4a score shift and reduction after native adaptation for H1, but not L1, while known-glitch separation is detector- and morphology-dependent. Replicated studies quantify population-dependent sensitivity to background draw, clustering seed, dictionary size, and whitening, demonstrate native-index absorption, and identify conditional low-Q blindness. A conservative H1-L1 max-shift screen yields 13/8,806 values above threshold, but its on-source values and pooled per-event null maxima are not exchangeable. The primary two-null PEM endpoint shows no resolved ROBUST-BACKGROUND enrichment (p=1.000), and two catalogue overlaps are consistent with a circular-shift coverage proxy (p=0.651). Simulation-only compact-binary controls show detector- and distance-dependent disagreement between novelty, native disposition, and physical coincidence. We withdraw the v5 discovery, rate-limit, catalogue-recall, and survey-wide stability interpretations. The supported result is a measured set of failure modes and validity conditions for unsupervised detector characterization, not a new glitch class or an astrophysical search.

Magnetic reconnection has been widely recognized as an important mechanism for extracting energy from rapidly rotating black holes. We find that magnetic reconnection can also efficiently extract energy from slowly rotating ModMax black holes. In this paper, we investigate the magnetic reconnection process of ModMax black holes in both circular and plunging orbits. First, we analyze the fundamental characteristic quantities of the ModMax black hole, including the event horizon, ergosphere radius, and circular photon orbits. The results indicate that the charge parameter $Q$ and screening factor $\gamma$ exhibit a competing effect on the fundamental characteristic quantities of the ModMax black hole. Furthermore, for the extremal ModMax black hole, a larger $Q$ and a smaller $\gamma$ lower the minimum allowed spin parameter $a$. Subsequently, we analyze the parameter space $(r,a)$ for energy extraction in circular and plunging orbits. A larger $Q$ and a smaller $\gamma$ reduce the region for energy extraction and decrease the minimum spin parameter $a$ required for energy extraction. For circular orbits, the minimum allowed spin parameter is $a\simeq 0.50071$, while for plunging orbits, this threshold further decreases to $a\simeq0.22407$. This proves that energy extraction from lower spin ModMax black holes is theoretically feasible. Finally, we compare the energy extraction region, power, and efficiency between circular and plunging orbits. It is found that these quantities in plunging orbits are always higher than those in circular orbits, indicating that energy extraction from plunging orbits via magnetic reconnection may be more efficient.

In the present study, we analyze the power and efficiency of energy extraction via magnetic reconnection in the rotating Einstein-AdS-SU($N$)-NLSM black hole, both in the circular-orbit regime and in the plunging region. Initially, we define the background properties of this spacetime, and then analyze the physical quantities such as the size of the ergoregion, the event horizon, and the boundaries of the ergosphere. We analyze the magnetic reconnection process within circular orbits. We plot energy-extraction parameter diagrams and analyze the power and efficiency of energy extraction. Our results indicate that energy extraction remains feasible even at a spin parameter as low as $0.7$, significantly below previously reported thresholds, and the extracted power can exceed that of the Blandford-Znajek mechanism with specific constraints. The coupling constant $K$, AdS radius $l$ and the flavors number $N$, collectively participate in lowering the spin threshold for energy extraction. Consequently, we further investigate the permissible energy extraction region for the energy extraction mechanism in the plunging region, as well as the corresponding power output and efficiency. We observe that the energy extraction is possible even at a spin as low as $0.2$. Importantly, the parameters $N,~K$ and $l$ mainly contribute to lowering the energy extraction spin threshold. This behavior is similar to that in circular orbits. Finally, comparing the plunging region with the circular orbits, we observe that the energy extraction power in the plunging region is higher than in the circular orbits.

Recently, Comisso and Asenjo introduced a new energy extraction mechanism based on magnetic reconnection. In this paper, we investigate the power and efficiency of magnetic reconnection energy extraction in a rotating black hole surrounded by a cold dark matter halo. We first examine the properties of the underlying spacetime and its physical quantities, including the event horizon, photon sphere, and ergosphere. We then analyze the allowed energy extraction region and the corresponding energy extraction efficiency for circular orbits. Our results show that energy extraction is feasible for black holes with a spin parameter.

We investigate the quasinormal modes (QNMs) and greybody factors of dilaton-Euler-Heisenberg (dEH) de Sitter (dS) black holes in string-inspired Euler-Heisenberg gravity. Since the axial gravitational and electromagnetic perturbations decouple, we treat them independently. By applying the asymptotic iteration method (AIM) alongside a sixth-order WKB approximation, we compute the quasinormal frequencies and find excellent agreement between the two approaches. We also find that the QNM spectra depend sensitively on the magnetic charge $Q_{\text{m}}$, cosmological constant $\Lambda$, and nonlinear coupling $\epsilon$, with a notable topological anomaly appearing in the electromagnetic frequency trajectories. Additionally, larger values of $Q_{\text{m}}$ or the multipole number $l$ generally suppress wave transmission, while the electromagnetic sector with $\epsilon=1$ exhibits an anomalous response.

We develop a novel analytical framework for constructing axisymmetric black hole spacetimes sourced by dark matter (DM) halos. Applying this to extreme mass ratio inspirals (EMRIs), we find that the DM induces a detectable gravitational-wave dephasing, scaling monotonically with the halo's compactness. Notably, BH spin significantly suppresses this dephasing, indicating that analyses neglecting rotation would overestimate DM signatures. Faithfulness calculations confirm that future space-borne detectors can robustly distinguish such DM environments, establishing EMRIs as a novel probe for galactic DM distributions.

We present an exact static and spherically symmetric traversable wormhole solution in 5D Einstein-Gauss-Bonnet (EGB) gravity supported by a Letelier cloud of strings. The physically admissible parameter space is determined by imposing the flare-out condition together with the positivity of the string-cloud density, and the resulting spacetime is shown to be asymptotically flat. An analysis of the Ricci scalar, Ricci tensor squared, and Kretschmann scalar confirms that the geometry is free from curvature singularities. The effective null, weak, strong and dominant energy conditions are either satisfied or saturated at the throat. The generalized TOV equation demonstrates that the wormhole remains in mechanical equilibrium. We further investigate its traversability by studying the proper radial distance, embedding diagrams, traversal time, proper acceleration, and tidal accelerations, showing that the solution satisfies the Morris-Thorne criteria for traversable wormholes. The optical properties of the spacetime are explored through null geodesics, unstable photon circular orbits, and the corresponding shadow, revealing the influence of both the Gauss-Bonnet coupling and the string-cloud density. Finally, scalar perturbations are analyzed using the sixth-order WKB approximation method together with time-domain evolution. The quasinormal mode spectra exhibit negative imaginary frequencies throughout the considered parameter space, indicating linear stability, while the close agreement between the WKB, time-domain, and eikonal results provides additional consistency for the analysis. These results demonstrate that higher-curvature effects in 5D EGB gravity can support a regular, traversable and dynamically stable wormhole sustained by a physically motivated string-cloud matter source.

We analyze a sharply delimited comparison problem for a static spherical hollow core: an empty, flat cavity surrounded by a positive matter wall. In the unit-lapse, flat-slice radial Painleve–Gullstrand (PG) class the Type-I source obeys $p_r=-\rho$ and $p_\perp=-\rho-r\rho'/2$. A regular nonnegative density that rises out of the cavity must therefore violate the transverse null and weak energy conditions. We quantify this boundary obstruction by an exact weighted onset budget and a depth–width bound, and show that the sharp limit has the same negative tangential pressure as its symmetry-invariant regularized Israel layer. We then close the adjacent unit-lapse, curved-slice route under a monotone areal-radius hypothesis. Finally, when only the lapse is released, an incomplete-beta family gives regular hollow shells with flat cavities, Schwarzschild exteriors, no thin shells, and NEC/WEC/SEC/DEC on an explicit compactness interval. The family is conditionally characterized in the minimum-degree and $p_r=0$ sectors and admits a fixed-ADM-mass cavity redshift benchmark. The result is a static boundary theorem and construction, not a general hollow-shell existence theorem, a transport result, or an experimental feasibility claim.

We present a relativistic framework for computing corrections to the eigenfrequency spectrum of a massive scalar field in perturbed black-hole spacetimes, including first-order shifts to decay rates and second-order mode-mixing effects. We also clarify the regime of validity of non-relativistic treatments and show that the accuracy of completeness-based descriptions is limited, highlighting the non-Hermitian nature of the spectrum. Using galactic halos and accretion disks as physically motivated perturbations, we benchmark the relativistic perturbative predictions to the eigenfrequency shifts against non-perturbative numerical solutions. We also present first-order relativistic eigenfrequency shifts induced by binary companions, whose potentially stronger impact on superradiant dynamics of massive scalar fields around spinning black holes motivates future dedicated analyses. Our results suggest that previous estimates of the termination of superradiance due to binary companions and disks should be revisited within a relativistic framework.

Black-hole entropy and multi-horizon area-product relations represent two apparently distinct manifestations of universality, arising respectively from microscopic statistics and classical geometry. We show that these structures are unexpectedly connected. Extending a minimum-assumptions statistical discretization to multiple Killing horizons, with distinct horizon sectors treated as statistically independent, we derive a general area-product rule. In particular, while the leading Bekenstein-Hawking entropy probes the sum of the horizon areas, the logarithmic correction probes their product. Consequently, whenever the classical area product is mass independent, the logarithmic entropy automatically inherits this universality. We demonstrate this for Reissner-Nordström and, under an area-based extension to rotating horizons, Kerr-Newman black holes. However, Reissner-Nordström-de Sitter provides a crucial three-horizon counterexample, for which the area-product rule survives while mass independence is generically lost for the physical horizons. Thus, statistical area-product selection and classical universality are distinct properties. Our results uncover a structural connection between microscopic entropy counting and classical multi-horizon geometry that is invisible at the level of the leading area law, suggesting that logarithmic corrections encode distinctive information about the global horizon structure.

We study a mirror Standard Model world which contains a high scale duplicate of the Standard Model, and includes a singlet mirror scalar extension coupled to the mirror Higgs particle. Among the interactions of the mirror Higgs to the mirror singlet scalar, we include dimension-six non-renormalizable operators. We examine the electroweak phase transition of this mirror singlet extended world and we show that the phase transition is a strong first order phase transition, the bubble collision of which can be detectable by LISA, the BBO and the DECIGO gravitational wave experiments. We also provide a rough estimate of the abundance of the mirror singlet and we show that the whole dark matter in the Universe may be comprised by mirror particles and atoms.

The radial acceleration relation (RAR) is a tight correlation between the distribution of baryonic matter in galaxies and their observed dynamics, even in systems where dark matter dominates. This suggests a universal acceleration scale exists in galaxies, which appears to challenge the $\Lambda$CDM standard cosmological model and favor Modified Newtonian dynamics (MOND). However, MOND also deviates from the RAR, so these deviations are not fully explained by the $\Lambda$CDM model or MOND. A theory that explains gravity and the dark sector geometrically, and treats dark matter as a spin-1 particle, is required, such as Modified General Relativity (MGR). It is the only metric-compatible theory of gravity that describes local gravitational energy-momentum by the connection-independent symmetric tensor $\varPhi_{\alpha\beta}$, which completes the total energy-momentum tensor of the Einstein equation. Dark energy is explained by the energy-related component $\varPhi_{00}$, and dark matter by the stress components $\varPhi_{ij}$. Dark matter is extremely difficult to observe because it is fundamentally related to the Lorentzian metric of spacetime itself. The physical origin of the RAR follows directly from the equilibrium between the dark energy and Newtonian forces in the outer part of the rotation curve of galaxies or galaxy clusters, and that between the dark sector forces in the inner part of the rotation curve. It is shown that MGR subsumes MOND, accounts for the gravitational anomaly observed in wide binaries, and exhibits the observed Newtonian behavior of gravity at large scales.

Hawking radiation away from stationarity is governed, at the ray tracing level, by the retarded time evolution of the null mapping. We consider an extracted massless conformal channel whose outgoing directions are labelled on a fixed reference horizon slice. Balanced uniformisation, after fixing a nondegenerate balanced branch, defines an induced antipodal involution on this slice. We prove that creation and erasure of centred antipodal odd structure in the channel labelled peeling field enforce a lower bound on the time integrated spatial norm of the conformal channel defect. The forcing scale depends only on the largest intermediate mismatch and the intrinsic Jacobian distortion of the induced antipode, while greybody filtering, angular and frequency mixing, mass effects, spin dependence, and residual propagation or extraction corrections enter through a remainder whose integrated norm must be controlled independently. Round sphere odd scalar harmonics provide analytic calibrations, with the compact dipole pulse saturating the geometric and temporal estimates. A time-averaged form identifies a transient conformal channel scale proportional to the antipodal peeling amplitude divided by the episode duration.

The treatment of the stellar surface in binary neutron star simulations is crucial for the accuracy of the numerical evolution and the physical reliability of the predicted observables. Numerical artifacts associated with the treatment of steep gradients near the stellar surface can produce spurious heating during the inspiral, leading to an artificial increase of the internal energy and an unphysical expansion of the neutron star. In this work, we investigate the effectiveness of the entropy-based flux-limiting (EFL) scheme in mitigating these numerical effects within the finite-difference code BAM. We perform simulations of both isolated neutron stars and binary neutron star inspirals employing a representative set of hybrid equations of state. We show that the EFL scheme significantly reduces artificial surface heating. This reduction is observed consistently across all stellar models and binary configurations considered, demonstrating that the reduction of numerical heating is a robust feature of the EFL method.

We apply a convenient parametrization of all Plebanski-Demianski black holes of algebraic type D with the Kerr rotation, NUT twist, acceleration, electric and magnetic charges, and any value of the cosmological constant $\Lambda$, recently found by Astorino. This represents a complete class of exact solutions to the Einstein-Maxwell-$\Lambda$ equations such that the (non-null) electromagnetic field is aligned with both the (geodesic, shear-free, double) principal null directions of the Weyl tensor. We derive a novel appropriate metric form and the corresponding canonical frames naturally adapted to both the de~Sitter-like ($\Lambda>0$) and the anti-de~Sitter-like ($\Lambda<0$) conformal infinity, and we demonstrate that these geometric objects are useful for investigation of radiation properties. In particular, using the Fernandez-Alvarez-Senovilla criterion, it confirms that the gravitational radiation is present if, and only if, these black holes are accelerating.

At a black-hole exceptional point (EP), two quasinormal modes coalesce and their separate residues become ill-conditioned. Rather than postulating a near-degenerate modal fit, we derive the response constructively from the complex-scaled Regge–Wheeler–Zerilli resolvent, treating the modes as one isolated rank-two Riesz cluster. Its zeroth and first contour moments determine an exact pair resolvent on both sides of, and at, the EP, without labeling the individual modes or constructing a normalized Jordan chain. At a second-order EP, these moments determine the simple- and double-pole Laurent operators. Although the modal decomposition is singular, fixed-real-frequency transmission and the greybody factor remain real-analytic through the EP, provided that the cluster remains isolated, the complementary resolvent is regular, and no pole reaches the physical axis. Source–observer matrix elements of the Laurent operators define finite, normalization-independent amplitudes and fix both the constant and linear-in-time terms in the causal ringdown. Their equality with the coefficients from the Jost double-zero expansion shows that they are operator-defined coefficients of the specified physical response, rather than fitting parameters. Thus two cluster moments provide mode-label-free data from which both scattering and driven responses follow.