A classification of admissible energy density profiles with bounded Kretschmann scalar yields a unified framework for regular static spherically symmetric spacetimes satisfying the weak energy condition, recovering known models and producing new families with hypergeometric and other closed forms.
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Horizon-scale tests of gravity theories and fundamental physics from the Event Horizon Telescope image of Sagittarius A$^*$
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abstract
Horizon-scale images of black holes (BHs) and their shadows have opened an unprecedented window onto tests of gravity and fundamental physics in the strong-field regime. We consider a wide range of well-motivated deviations from classical General Relativity (GR) BH solutions, and constrain them using the Event Horizon Telescope (EHT) observations of Sagittarius A$^*$ (Sgr A$^*$), connecting the size of the bright ring of emission to that of the underlying BH shadow and exploiting high-precision measurements of Sgr A$^*$'s mass-to-distance ratio. The scenarios we consider, and whose fundamental parameters we constrain, include various regular BHs, string-inspired space-times, violations of the no-hair theorem driven by additional fields, alternative theories of gravity, novel fundamental physics frameworks, and BH mimickers including well-motivated wormhole and naked singularity space-times. We demonstrate that the EHT image of Sgr A$^*$ places particularly stringent constraints on models predicting a shadow size larger than that of a Schwarzschild BH of a given mass, with the resulting limits in some cases surpassing cosmological ones. Our results are among the first tests of fundamental physics from the shadow of Sgr A$^*$ and, while the latter appears to be in excellent agreement with the predictions of GR, we have shown that a number of well motivated alternative scenarios, including BH mimickers, are far from being ruled out at present.
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3D GRMHD simulations of accretion onto a JMN-1 horizonless singularity produce a magnetically arrested disk with an accretion rate of ~3e-6 Eddington matching M87* observations and EHT-consistent images, plus central brightness inside the shadow as a discriminant from black holes.
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.
An analytical traversable wormhole solution with positive cosmological constant is obtained via gravitational decoupling on the Ellis-Bronnikov metric, featuring a cosmological throat, verified flare-out conditions, null energy condition violation, and traversability constraints, though not yielding
CosmicDancePro integrates multimodal datasets to reveal that solar storms cause significant Starlink orbital decay and network degradation, and explains a 'W'-shaped altitude variation pattern via day-night atmospheric density differences.
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.
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.
The LQG parameter ξ enlarges equatorial bound orbit energy ranges, confines off-equatorial trajectories, and produces larger deviations from Kerr waveforms in EMRI models for two rotating LQG black holes, though signals fall below detector sensitivities.
Quintessence black holes produce observer-dependent shadow angular sizes, with infalling observers seeing smaller shadows than static ones, yielding stronger equation-of-state constraints from M87* observations.
The graviscalar quasinormal mode spectrum and late-time power-law tails of a Rastall thick brane are computed numerically, showing that the Rastall parameter λ controls mode lifetimes and tail exponents.
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.
Derives spin-dependent bounds on NED deformation g/M from Sgr A* shadow, eikonal QNMs, and Comisso-Asenjo reconnection power in rotating geometries.
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.
Rotation enhances Breit-Wigner resonances in scalar wave transmission through Teo wormholes by trapping modes in the throat potential well.
Bardeen's definition of black hole critical curves deviates from de Vries and Grenzebach definitions in homogeneous plasma by contracting with increasing density, contrary to prior expectations.
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.
A constructive algorithm yields NEC-obeying static spherical metrics with g_tt g_rr = -1, including a log-corrected Schwarzschild geometry that can mimic black holes.
Multiple black-hole and naked-singularity spacetimes are tested against S2 star astrometric and spectroscopic data, showing statistical degeneracy among several models under current observations.
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.
Numerical construction of Hayward boson stars shows that frozen states produce Schwarzschild-like shadows with no extra photon rings while non-frozen states show multiple photon rings inside the shadow.
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.
Higher-curvature corrections induce polarization-dependent effective metrics for photons that shift photon spheres, alter eikonal quasinormal modes, and modify deflection angles in static spherically symmetric backgrounds.
Simulations of accreting black holes in standard and complex spacetimes indicate that magnetic geometry, quantum corrections, and binary dynamics influence flares, precession, photon rings, and multi-wavelength variability, with potential EHT constraints.
Bayesian fitting to mock GRAVITY data shows robust detection of secondary images from Sgr A* flares requires both an order-of-magnitude larger sample and astrometric uncertainties reduced to 40% of current levels for |ΔBIC| > 7.9.
citing papers explorer
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Families of regular spacetimes and energy conditions
A classification of admissible energy density profiles with bounded Kretschmann scalar yields a unified framework for regular static spherically symmetric spacetimes satisfying the weak energy condition, recovering known models and producing new families with hypergeometric and other closed forms.
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GRMHD accretion beyond the black hole paradigm: Light from within the shadow
3D GRMHD simulations of accretion onto a JMN-1 horizonless singularity produce a magnetically arrested disk with an accretion rate of ~3e-6 Eddington matching M87* observations and EHT-consistent images, plus central brightness inside the shadow as a discriminant from black holes.
-
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.
-
Analytical solution of traversable wormholes in the presence of positive cosmological constant
An analytical traversable wormhole solution with positive cosmological constant is obtained via gravitational decoupling on the Ellis-Bronnikov metric, featuring a cosmological throat, verified flare-out conditions, null energy condition violation, and traversability constraints, though not yielding
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Breaking Parameter Degeneracies in a Magnetically Charged Black Hole Embedded in a Hernquist Dark-Matter Halo: A Multi-Observable Analysis
CosmicDancePro integrates multimodal datasets to reveal that solar storms cause significant Starlink orbital decay and network degradation, and explains a 'W'-shaped altitude variation pattern via day-night atmospheric density differences.
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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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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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Particle motions and gravitational waveforms in rotating black hole spacetimes of loop quantum gravity
The LQG parameter ξ enlarges equatorial bound orbit energy ranges, confines off-equatorial trajectories, and produces larger deviations from Kerr waveforms in EMRI models for two rotating LQG black holes, though signals fall below detector sensitivities.
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Shadows of quintessence black holes: spherical accretion, photon trajectories, and geodesic observers
Quintessence black holes produce observer-dependent shadow angular sizes, with infalling observers seeing smaller shadows than static ones, yielding stronger equation-of-state constraints from M87* observations.
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Quasinormal modes of scalar perturbations in Rastall thick brane
The graviscalar quasinormal mode spectrum and late-time power-law tails of a Rastall thick brane are computed numerically, showing that the Rastall parameter λ controls mode lifetimes and tail exponents.
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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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Energy extraction from NED-deformed rotating black holes via the Comisso-Asenjo reconnection process
Derives spin-dependent bounds on NED deformation g/M from Sgr A* shadow, eikonal QNMs, and Comisso-Asenjo reconnection power in rotating geometries.
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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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Resonant transmission of scalar waves through rotating traversable wormhole
Rotation enhances Breit-Wigner resonances in scalar wave transmission through Teo wormholes by trapping modes in the throat potential well.
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A note on methods for computing the critical curve of Kerr-like black holes
Bardeen's definition of black hole critical curves deviates from de Vries and Grenzebach definitions in homogeneous plasma by contracting with increasing density, contrary to prior expectations.
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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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Energy conditions in static, spherically symmetric spacetimes and effective geometries
A constructive algorithm yields NEC-obeying static spherical metrics with g_tt g_rr = -1, including a log-corrected Schwarzschild geometry that can mimic black holes.
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Testing the Spacetime Geometry of Sgr A* with the Relativistic Orbit of S2 star
Multiple black-hole and naked-singularity spacetimes are tested against S2 star astrometric and spectroscopic data, showing statistical degeneracy among several models under current observations.
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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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Light Rings, Accretion Disks and Shadows of Hayward Boson Stars
Numerical construction of Hayward boson stars shows that frozen states produce Schwarzschild-like shadows with no extra photon rings while non-frozen states show multiple photon rings inside the shadow.
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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.
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Polarization-Dependent Photon Propagation, Quasinormal Modes, and Gravitational Lensing in Higher-Curvature Effective Theories
Higher-curvature corrections induce polarization-dependent effective metrics for photons that shift photon spheres, alter eikonal quasinormal modes, and modify deflection angles in static spherically symmetric backgrounds.
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GRMHD and GRRT Simulations of Black Hole Accretion: Flares, Precession, and Complex Spacetimes
Simulations of accreting black holes in standard and complex spacetimes indicate that magnetic geometry, quantum corrections, and binary dynamics influence flares, precession, photon rings, and multi-wavelength variability, with potential EHT constraints.
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Detectability of secondary images from flares near Sgr A* with mock GRAVITY data
Bayesian fitting to mock GRAVITY data shows robust detection of secondary images from Sgr A* flares requires both an order-of-magnitude larger sample and astrometric uncertainties reduced to 40% of current levels for |ΔBIC| > 7.9.
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Scalar-Electromagnetic Couplings as Source of Deformed Black Hole: From Shadows to Thermodynamic Topology
A scalar-NED coupled black hole metric is reconstructed from an effective geometry, yielding EHT bounds on magnetic charge, Hawking-Page transition, and topological equivalence to the Reissner-Nordström solution.
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Photon Propagation and Black Hole Imaging in Kruglov Nonlinear Electrodynamics
In Kruglov NED, small positive q can create stable photon orbits and reshape black-hole shadows and accretion images even when the metric stays close to Reissner–Nordström.
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Shadow of the Scalar Hairy Black Hole with Inverted Higgs Potential
Hairy black hole shadows and disks grow with horizon scalar value but can mimic Schwarzschild by adjusting horizon radius, with the potential parameter Lambda constrained by supermassive black hole observations.
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Astrophysical environment around a black hole in the braneworld and its optical signatures
Braneworld quadratic and nonlocal corrections weaken gravity in anisotropic Einstein-cluster environments around black holes, blocking horizon formation and shifting Einstein-ring and shadow radii in ways that may constrain brane tension for sub-stellar-mass objects.
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Probing Kalb-Ramond gravity with charged rotating black holes: constraints from EHT observations
EHT shadow observations constrain the Lorentz-violating parameter ℓ in Kalb-Ramond gravity for charged rotating black holes to roughly |ℓ| ≲ 0.1-0.2, with an upper bound ℓ ≲ 0.19 from Sgr A*.
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Testing black hole metrics with binary black hole inspirals
Constraints on deviations from Kerr black hole metrics are derived from binary black hole inspiral waveforms modeled with effective one-body methods and analyzed via the parameterized post-Einsteinian framework.
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Quantum-Corrected Thermodynamics of Conformal Weyl Gravity Black Holes: GUP Effects and Phase Transitions
Quantum-corrected thermodynamics of conformal Weyl gravity black holes via GUP and exponential entropy reveals parameter-dependent divergences in heat capacity and shifts in Joule-Thomson inversion points indicating phase transitions.
- Higher-Derivative Corrections to Reissner--Nordstr\"om Black Holes from Worldline QFT
- Probing Effective Field Theory Corrections with Quasinormal Modes and Gravitational Lensing in Reissner-Nordstr\"om Black Holes
- Can finite-density QCD matter support a regular black hole core?
- Perturbations in the parametrized wormhole spacetime and their related quasinormal modes
- Photon Spheres and Shadows of Black Holes with Modified Entropy-Inspired Metrics