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.
A Universal Framework for Horizon-Scale Tests of Gravity with Black Hole Shadows
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abstract
In this Letter, we have developed a numerically efficient framework for evaluating parameters in metric theories of gravity, and applied it to constrain the horizon-scale magnetic field in the Kerr-Bertotti-Robinson (Kerr-BR) spacetime using the latest EHT observations. The method's adaptive ray-tracing strategy achieves near-linear computational efficiency without loss of numerical accuracy. Owing to this efficiency, the framework enables high precision shadow modeling at minimal computational cost and, for the first time, supports statistically robust inference of black hole parameters from horizon-scale observations for arbitrary stationary black holes. The above framework is applied to the recently obtained Kerr-BR black hole, an exact magnetized and rotating solution to the Einstein field equations. We have evaluated the horizon-scale magnetic fields of M87* and Sgr A*, with the latter showing a field strength of $93.3^{+14.7}_{-23.8}G$, consistent with the equipartition estimate of $71G$ from polarized ALMA observations, thereby supporting Einstein's gravity.
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gr-qc 5years
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Torn accretion disks around Kerr black holes erode the inner shadow and create bifurcated, crescent, and multi-ring shadow features driven by sub-disk discontinuities and outer tilt angle.
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.
The Ma-Lü background spacetime is an electrovacuum Kundt spacetime of type D with electric or magnetic charge, identified via algebraic classification and explicit coordinate transformations.
Entropy corrections to black holes produce modified metrics whose photon-sphere and shadow sizes can be constrained by Sgr A* observations.
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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Reshaping the inner shadow of a Kerr black hole by a torn accretion disk
Torn accretion disks around Kerr black holes erode the inner shadow and create bifurcated, crescent, and multi-ring shadow features driven by sub-disk discontinuities and outer tilt angle.
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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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Comment on the "New Rotating Black Hole in Electromagnetic Fields: Cosmological Horizon without Cosmological Constant''
The Ma-Lü background spacetime is an electrovacuum Kundt spacetime of type D with electric or magnetic charge, identified via algebraic classification and explicit coordinate transformations.
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Photon Spheres and shadow of modified black-hole entropies
Entropy corrections to black holes produce modified metrics whose photon-sphere and shadow sizes can be constrained by Sgr A* observations.