A conformal isothermal reformulation of optical geometry converts the Gauss-Bonnet area term for weak deflection into boundary integrals evaluated on a flat reference ray, reproducing known finite-distance results for Schwarzschild, Reissner-Nordström, and Kottler spacetimes.
Time delay and magnification centroid due to gravitational lensing by black holes and naked singularities
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abstract
We model the massive dark object at the center of the Galaxy as a Schwarzschild black hole as well as Janis-Newman-Winicour naked singularities, characterized by the mass and scalar charge parameters, and study gravitational lensing (particularly time delay, magnification centroid, and total magnification) by them. We find that the lensing features are qualitatively similar (though quantitatively different) for the Schwarzschild black holes, weakly naked, and marginally strongly naked singularities. However, the lensing characteristics of strongly naked singularities are qualitatively very different from those due the Schwarzschild black holes. The images produced by Schwarzschild black hole lenses and weakly naked and marginally strongly naked singularity lenses always have positive time delays. On the other hand, the strongly naked singularity lenses can give rise to images with positive, zero, or negative time delays. In particular, for a large angular source position the direct image (the outermost image on the same side as the source) due to strongly naked singularity lensing always has negative time delay. We also found that the scalar field decreases the time delay and increases the magnitude of magnifications of images; this result could have important implications for cosmology. As the Janis-Newman-Winicour metric also describes the exterior gravitational field of a scalar star, naked singularities as well as scalar star lenses, if these exist in nature, will serve as more efficient cosmic telescopes than regular gravitational lenses.
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Semiclassical one-loop analysis of solvable near-critical collapse solutions shows quantum corrections selecting a Boulware-like state and producing a growing mode that yields a finite mass gap and a transition to Type I behavior, enforcing weak cosmic censorship.
New exact solutions to d-dimensional Einstein-scalar gravity are generated in Weyl form that incorporate multipolar scalars and magnetic fields, with limits matching scalar versions of Schwarzschild-Melvin and Fisher-Janis-Newman-Winicour spacetimes.
citing papers explorer
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Boundary-only weak deflection angles from isothermal optical geometry
A conformal isothermal reformulation of optical geometry converts the Gauss-Bonnet area term for weak deflection into boundary integrals evaluated on a flat reference ray, reproducing known finite-distance results for Schwarzschild, Reissner-Nordström, and Kottler spacetimes.
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Unveiling horizons in quantum critical collapse
Semiclassical one-loop analysis of solvable near-critical collapse solutions shows quantum corrections selecting a Boulware-like state and producing a growing mode that yields a finite mass gap and a transition to Type I behavior, enforcing weak cosmic censorship.
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Weyl-type solutions with multipolar scalar fields
New exact solutions to d-dimensional Einstein-scalar gravity are generated in Weyl form that incorporate multipolar scalars and magnetic fields, with limits matching scalar versions of Schwarzschild-Melvin and Fisher-Janis-Newman-Winicour spacetimes.