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.
On the number of light rings in curved spacetimes of ultra-compact objects
5 Pith papers cite this work. Polarity classification is still indexing.
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Pith papers citing it
abstract
In a very interesting paper, Cunha, Berti, and Herdeiro have recently claimed that ultra-compact objects, self-gravitating horizonless solutions of the Einstein field equations which have a light ring, must possess at least {\it two} (and, in general, an even number of) light rings, of which the inner one is {\it stable}. In the present compact paper we explicitly prove that, while this intriguing theorem is generally true, there is an important exception in the presence of degenerate light rings which, in the spherically symmetric static case, are characterized by the simple dimensionless relation $8\pi r^2_{\gamma}(\rho+p_{\text{T}})=1$ [here $r_{\gamma}$ is the radius of the light ring and $\{\rho,p_{\text{T}}\}$ are respectively the energy density and tangential pressure of the matter fields]. Ultra-compact objects which belong to this unique family can have an {\it odd} number of light rings. As a concrete example, we show that spherically symmetric constant density stars with dimensionless compactness $M/R=1/3$ possess only {\it one} light ring which, interestingly, is shown to be {\it unstable}.
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UNVERDICTED 5roles
background 2representative citing papers
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.
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.
Presents classical GR solutions for black holes enveloped by ultra-relativistic orbiting particle shells that extend the photon sphere to arbitrary depth while remaining optically indistinguishable from standard black holes.
A necessary and sufficient condition for thermodynamic mimicry of Schwarzschild black holes is satisfied by a one-parameter family of self-similar systems including hillingar black holes, stiffest stars, and frozen stars, derived from photon-sphere control of junction conditions and the TOV equation
citing papers explorer
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On Black Holes Surrounded by Radiation: I. Classical Considerations
Presents classical GR solutions for black holes enveloped by ultra-relativistic orbiting particle shells that extend the photon sphere to arbitrary depth while remaining optically indistinguishable from standard black holes.
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As Cold as a Black Hole: Extended Photon Spheres
A necessary and sufficient condition for thermodynamic mimicry of Schwarzschild black holes is satisfied by a one-parameter family of self-similar systems including hillingar black holes, stiffest stars, and frozen stars, derived from photon-sphere control of junction conditions and the TOV equation