Three observables on a standardized segment of the Kerr critical curve uniquely fix spin a/M, inclination i, and segment location r_nl within the considered domain.
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First Sagittarius A* Event Horizon Telescope Results. I. The Shadow of the Supermassive Black Hole in the Center of the Milky Way
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abstract
We present the first Event Horizon Telescope (EHT) observations of Sagittarius A* (Sgr A$^*$), the Galactic center source associated with a supermassive black hole. These observations were conducted in 2017 using a global interferometric array of eight telescopes operating at a wavelength of $\lambda=1.3\,{\rm mm}$. The EHT data resolve a compact emission region with intrahour variability. A variety of imaging and modeling analyses all support an image that is dominated by a bright, thick ring with a diameter of $51.8 \pm 2.3$\,\uas (68\% credible interval). The ring has modest azimuthal brightness asymmetry and a comparatively dim interior. Using a large suite of numerical simulations, we demonstrate that the EHT images of Sgr A$^*$ are consistent with the expected appearance of a Kerr black hole with mass ${\sim}4 \times 10^6\,{\rm M}_\odot$, which is inferred to exist at this location based on previous infrared observations of individual stellar orbits as well as maser proper motion studies. Our model comparisons disfavor scenarios where the black hole is viewed at high inclination ($i > 50^\circ$), as well as non-spinning black holes and those with retrograde accretion disks. Our results provide direct evidence for the presence of a supermassive black hole at the center of the Milky Way galaxy, and for the first time we connect the predictions from dynamical measurements of stellar orbits on scales of $10^3-10^5$ gravitational radii to event horizon-scale images and variability. Furthermore, a comparison with the EHT results for the supermassive black hole M87$^*$ shows consistency with the predictions of general relativity spanning over three orders of magnitude in central mass.
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representative citing papers
In the rotating García-Díaz NLED black hole the Fresnel quartic factorizes into two optical metrics whose critical families project to distinct contours Γ+ and Γ- whose angular separation is generated by the constitutive response and redistributed by spin.
A covariant framework is developed for photon surfaces in dynamical spherical spacetimes, recovering static limits and applied to collapse and accretion/evaporation models.
Kerr black holes in an EsGB model without linear instability undergo nonlinear scalarization above spin 0.5, existing in a finite low-mass high-spin wedge rather than a narrow band.
Surface-gravity waves in shallow water can be configured with central and graded drainage to analogize regular black holes and mimickers, enabling lab study of their instabilities.
In massive self-gravitating black hole disks, magnetic turbulence damps the m=1 instability and gravitational waves when aligned with the spin, but strongly enhances both when the disk is antialigned.
Derives a factorized leading term for the strong deflection angle near degenerate photon spheres using local expansion of the effective potential and Weyl tensor measures.
In the Gravity from Entropy framework, spherically symmetric black holes acquire r^{-4} corrections to Schwarzschild geometry, with large-mass evaporation at constant rate -β/24 and intermediate-mass loss following the classical Hawking M^{-2} scaling.
Self-force theory is extended to compute merger and ringdown waveforms in beyond-GR black hole binaries under the extreme mass-ratio approximation, with first calculations of self-force corrections to the merger waveform.
In dRGT massive gravity, static spherically symmetric black holes exhibit zero, one, or two photon spheres whose topological charges and stability patterns differ from Einstein gravity and from horizonless compact objects.
A hierarchical analysis of 69 GWTC-3 black-hole merger candidates yields an effective compactness consistent with C=0.5 and no evidence for a low-compactness exotic population.
Exact Schwarzschild and Kerr geometries in a disformally related frame yield secondary disformal scalar hair on black holes in a projectively invariant scalar-torsion theory.
Presents an observability framework for solar gravitational lens astronomy and reports SSIM values of 0.993, 0.918, 0.973, and 0.923 for scalar reconstructions of four analytic scenes under stated assumptions.
Numerical computation of absorption cross sections for massive Proca fields on Schwarzschild black holes, revealing mass-induced longitudinal modes and breaking of even-odd parity degeneracy in transmission spectra.
The Breitenlohner-Freedman bound restricts Gauss-Bonnet scalarization of RN-AdS black holes to a single fundamental branch for 0<η<2.25, with a separate single branch for η<0.
Black-bounce solutions are obtained from a self-interacting 3-form field in GR plus scalar, producing two families that are globally regular with asymmetric horizons and different scalar behaviors.
Spinning test particles around rotating hairy black holes show finite-time instability in localized regions of the (spin, hair-parameter) plane that reorganize the strong-field phase space compared to Kerr.
A rotating black-hole metric with a dark-matter halo is derived, but the proposed halo profiles do not make the spacetime asymptotically flat as claimed.
Two new regular black-hole solutions with de Sitter cores, supported by magnetic nonlinear electrodynamics, are constrained by Sgr A* shadows and shown to be linearly stable under scalar perturbations.
Three distinct non-minimal curvature-EM couplings produce different enlargements or reductions of black hole shadows and alter photon ring separations in characteristic ways.
Corotating point sources on accretion disks near black holes distort the relative magnification factor distribution, modulating caustics and encoding accretion flow kinematics via time-delayed images.
Cuspy black hole shadows correspond to swallowtail thermodynamic free energy, with boundary self-intersections marking geometric phase transitions whose critical exponents fall in the mean-field class.
Superradiant amplification of charged scalar fields around rotating charged de Sitter black holes is suppressed in conformal Weyl gravity relative to general relativity, with strong exponential suppression for massive fields in the cosmological region.
Derives an exact solution for a black hole in anisotropic dark sector FLRW background with mass co-evolving via radius-dependent coupling governed by the dark halo profile.
citing papers explorer
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Determining Kerr black hole spin and inclination from a segment of the critical curve in black hole images
Three observables on a standardized segment of the Kerr critical curve uniquely fix spin a/M, inclination i, and segment location r_nl within the considered domain.
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Constitutive birefringence and critical curves in the rotating Garc\'ia--D\'iaz black hole
In the rotating García-Díaz NLED black hole the Fresnel quartic factorizes into two optical metrics whose critical families project to distinct contours Γ+ and Γ- whose angular separation is generated by the constitutive response and redistributed by spin.
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Photon spheres in dynamical space-times
A covariant framework is developed for photon surfaces in dynamical spherical spacetimes, recovering static limits and applied to collapse and accretion/evaporation models.
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Spin-Induced Nonlinear Scalarization of Kerr Black Holes in Einstein-scalar-Gauss-Bonnet Gravity
Kerr black holes in an EsGB model without linear instability undergo nonlinear scalarization above spin 0.5, existing in a finite low-mass high-spin wedge rather than a narrow band.
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Analog regular black holes and black hole mimickers for surface-gravity waves in fluids
Surface-gravity waves in shallow water can be configured with central and graded drainage to analogize regular black holes and mimickers, enabling lab study of their instabilities.
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Multimessenger Signatures of Tilted, Self-Gravitating, Black Hole Disks
In massive self-gravitating black hole disks, magnetic turbulence damps the m=1 instability and gravitational waves when aligned with the spin, but strongly enhances both when the disk is antialigned.
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Strong-deflection expansion of the deflection angle near a degenerate photon sphere
Derives a factorized leading term for the strong deflection angle near degenerate photon spheres using local expansion of the effective potential and Weyl tensor measures.
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Spherically symmetric black holes in Gravity from Entropy and spontaneous emission
In the Gravity from Entropy framework, spherically symmetric black holes acquire r^{-4} corrections to Schwarzschild geometry, with large-mass evaporation at constant rate -β/24 and intermediate-mass loss following the classical Hawking M^{-2} scaling.
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Black hole mergers beyond general relativity: a self-force approach
Self-force theory is extended to compute merger and ringdown waveforms in beyond-GR black hole binaries under the extreme mass-ratio approximation, with first calculations of self-force corrections to the merger waveform.
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Topological charge and black hole photon spheres in massive gravity
In dRGT massive gravity, static spherically symmetric black holes exhibit zero, one, or two photon spheres whose topological charges and stability patterns differ from Einstein gravity and from horizonless compact objects.
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Establishing Compactness as a Population Observable in Gravitational-Wave Astronomy
A hierarchical analysis of 69 GWTC-3 black-hole merger candidates yields an effective compactness consistent with C=0.5 and no evidence for a low-compactness exotic population.
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Nonrotating and rotating black holes with secondary disformal hair in a ghost-free metric-affine parity-violating scalar-torsion theory
Exact Schwarzschild and Kerr geometries in a disformally related frame yield secondary disformal scalar hair on black holes in a projectively invariant scalar-torsion theory.
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Ultra-High-Resolution Astronomy with the Solar Gravitational Lens
Presents an observability framework for solar gravitational lens astronomy and reports SSIM values of 0.993, 0.918, 0.973, and 0.923 for scalar reconstructions of four analytic scenes under stated assumptions.
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Absorption cross section of a Schwarzschild black hole for a massive vector field
Numerical computation of absorption cross sections for massive Proca fields on Schwarzschild black holes, revealing mass-induced longitudinal modes and breaking of even-odd parity degeneracy in transmission spectra.
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Curvature-induced scalarization of charged AdS black holes
The Breitenlohner-Freedman bound restricts Gauss-Bonnet scalarization of RN-AdS black holes to a single fundamental branch for 0<η<2.25, with a separate single branch for η<0.
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Black Bounce Solutions from a Self-Interacting 3-Form Field in General Relativity
Black-bounce solutions are obtained from a self-interacting 3-form field in GR plus scalar, producing two families that are globally regular with asymmetric horizons and different scalar behaviors.
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Spin-Hair Induced Chaos of Spinning Test Particles in Rotating Hairy Black Holes
Spinning test particles around rotating hairy black holes show finite-time instability in localized regions of the (spin, hair-parameter) plane that reorganize the strong-field phase space compared to Kerr.
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A metric solution for rotating black holes embedded in dark matter halos with central spikes
A rotating black-hole metric with a dark-matter halo is derived, but the proposed halo profiles do not make the spacetime asymptotically flat as claimed.
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Regular Black Holes in General Relativity from Nonlinear Electrodynamics with de Sitter Cores
Two new regular black-hole solutions with de Sitter cores, supported by magnetic nonlinear electrodynamics, are constrained by Sgr A* shadows and shown to be linearly stable under scalar perturbations.
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Photon rings and shadows of black holes with non-minimal couplings between curvature and electromagnetic field
Three distinct non-minimal curvature-EM couplings produce different enlargements or reductions of black hole shadows and alter photon ring separations in characteristic ways.
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Relative Magnification Factor of Point Sources on Accretion Disks
Corotating point sources on accretion disks near black holes distort the relative magnification factor distribution, modulating caustics and encoding accretion flow kinematics via time-delayed images.
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Gravity/thermodynamics correspondence via black hole shadows
Cuspy black hole shadows correspond to swallowtail thermodynamic free energy, with boundary self-intersections marking geometric phase transitions whose critical exponents fall in the mean-field class.
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Superradiant Suppression of Non-minimally Coupled Scalar fields for a Rotating Charged dS Black Hole in Conformal Weyl Gravity
Superradiant amplification of charged scalar fields around rotating charged de Sitter black holes is suppressed in conformal Weyl gravity relative to general relativity, with strong exponential suppression for massive fields in the cosmological region.
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Cosmological coupled black holes immersed in dark sector
Derives an exact solution for a black hole in anisotropic dark sector FLRW background with mass co-evolving via radius-dependent coupling governed by the dark halo profile.
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On the Cuspy Structure of Rotating Wormhole Shadows
Rotating wormhole shadows develop cusps above a universal critical redshift value λ_c, yielding four morphologies: smooth, cuspy, ears touching, and throat drowning.
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Bounds on the photon sphere radius for spherically symmetric black holes in n-dimensional Einstein gravity
Upper bound r_γ ≤ [(n-1)M]^{1/(n-3)} and lower bound r_γ ≥ ((n-1)/2)^{1/(n-3)} r_H on the photon sphere for nD black holes with anisotropic matter obeying the weak energy condition and non-positive trace.
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Particle dynamics around an electrically charged Kiselev black hole embedded in quintessence
Derives an electrically charged generalization of the Kiselev black hole metric and studies charged particle orbits, finding prograde periapsis shifts for uncharged particles but possible retrograde shifts for charged ones.
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An analytic model for a total process of gravitational collapse: From star to Schwarzschild black hole
An exact spherically symmetric analytic collapse model grows an apparent horizon H(t) from zero to 2M while hiding an integrable central singularity and preserving weak cosmic censorship without exotic matter.
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Observational Limits on Einasto Dark Matter Parameters from Event Horizon Telescope Images of Sgr A$^{*}$ and M87$^{*}$
EHT dimensionless shadow diameters plus stellar-dynamical mass priors constrain Einasto central density to ρ₀ ≲ 10^{-11} M⊙/pc³ (1σ) for Sgr A*, with weaker bounds for M87*.
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Bounds on the radius of outermost photon sphere and black hole shadow in $n$-dimensional Einstein gravity
For n-dimensional Einstein-gravity black holes with matter satisfying the weak and strong energy conditions, the shadow radius is bounded below by a function of the horizon radius and above by a function of the ADM mass, both saturated by the vacuum solution.
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Constraining Kerr supermassive black hole properties using gravitational waves from inspiraling stellar-mass binary black holes
LISA observations of inspiraling stellar-mass BBHs around SMBHs can achieve relative uncertainties of 10^{-5} for SMBH mass and a few percent for spin in high-SNR cases.
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A perturbative geometric approach for photon spheres, massive particle surfaces and black hole shadows with mass variations
Presents a curvature-based perturbative method for photon spheres, massive particle surfaces, and black hole shadows that handles mass variations and claims new results for the time-like case.
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Distorting Kerr Images with Parity-Odd Scalar Hair
Numerical study of thin accretion disk images shows that increasing parity-odd scalar hair on Kerr black holes shrinks and distorts the photon ring and shadow, producing multiple disconnected shadows and chaotic lensing features in strong-hair regimes.
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Periodic orbits and gravitational waveforms around a Schwarzschild black hole with a cloud of strings embedded in perfect fluid dark matter
Analysis of how string cloud parameter a and dark matter parameter α alter MBO, ISCO, periodic orbits indexed by q, and the gravitational waveforms generated by those orbits in a modified Schwarzschild spacetime.
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Chaotic motion of particles around a Schwarzschild black hole in a swirling electromagnetic background
Numerical chaos indicators applied to the Schwarzschild-Bertotti-Robinson-Bonnor-Melvin family show that chaos occurs without swirling and that electromagnetic field strengths and directions tightly restrict bound orbits.
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Observational signatures of negative mass wormholes through their shadows
Positive/negative-mass binaries would emit gravitational waves with decreasing frequency and amplitude, and a negative-mass wormhole would cast an asymmetric shadow with richer photon-ring substructure than a black hole.
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Photon Surfaces in Higher-Curvature Gravity: Implications for Quasinormal Modes and Gravitational Lensing
For a cubic-plus-quartic curvature EFT, photon-sphere and strong-lensing observables shift at first order in the couplings, but the impact-parameter formula is dimensionally wrong and the gravitational-wave QNM prediction is unproven.
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Macroscopic Optical Nonreciprocity: A Black Hole as an Optical Diode
Rotating black holes with a nonminimally coupled Lorentz-violating background act as optical diodes by producing direction-dependent shadows that morph from quasi-symmetric to teardrop upon path reversal.
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Scalarizations of magnetized Reissner-Nordstr\"om black holes induced by parity-violating and parity-preserving interactions
Magnetic fields lower the scalarization threshold for electromagnetic and gravitational Chern-Simons couplings but produce opposite trends on the two Gauss-Bonnet branches, with nonlinear terms converting exponential growth into bounded oscillations.
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Observational constraints on nonlocal black holes via gravitational lensing
Nonlocal black holes remain consistent with general relativity at the 1.13-sigma level after joint lensing and quasinormal-mode constraints.
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Spectroscopy of analogue black holes using simulation-based inference
Simulation-based inference reliably extracts physical parameters from noisy spectra of analogue black holes.
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Black Hole-Boson Star Binaries: Gravitational Wave Signals and Tidal Disruption
Numerical simulations of black hole-boson star binaries show that scalar self-interactions can suppress tidal disruption while radiative efficiency depends on the chosen potential.
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Long-lived quasinormal modes, shadows and particle motion in four-dimensional quasi-topological gravity
Massive scalar quasinormal modes in quasi-topological black holes become long-lived as scalar mass grows, while photon-sphere radius, shadow size, and ISCO exhibit moderate deviations from Schwarzschild.
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Roche limit and stellar disruption in the Simpson--Visser spacetime
Tidal forces in the Simpson-Visser spacetime produce Roche radii for stars that depend on observer type and regularization, with some disruptions occurring outside the event horizon for supermassive black holes.
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Shadow signatures and energy accumulation in Lorentzian-Euclidean black holes
Lorentzian-Euclidean black holes produce excess inner-shadow intensity and accumulate energy at the horizon with backreaction unlike stable light rings.
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Leading effective field theory corrections to the Kerr metric at all spins
Numerical solutions show that leading effective-field-theory corrections to the Kerr metric grow with spin and are largest near extremality.
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Periodic orbits and their gravitational wave radiations in $\gamma$-metric
Deviations from γ=1 in the Zipoy-Voorhees metric shift the (z,w,v) classification of periodic orbits and induce phase shifts plus amplitude modulations in their gravitational-wave signals.
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Observational Tests of Regular Black Holes with Scalar Hair and their Stability
Regular black holes with phantom scalar hair are constrained by Solar System and EHT observations, with exact relations linking photon sphere Lyapunov exponent to shadow size and impact parameter.
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GW250114: testing Hawking's area law and the Kerr nature of black holes
GW250114 data confirm the remnant black hole ringdown frequencies lie within 30% of Kerr predictions and that the final horizon area is larger than the sum of the progenitors' areas to high credibility.
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Scalar and Electromagnetic Perturbations around a Black Hole with a Topological Defect: Quasinormal Modes and Quasi-bound States in a Plasma Medium
Plasma and topological defect k suppress scalar QNM frequencies and allow axial EM quasi-bound states only for homogeneous plasma below a k- and l-dependent critical frequency.