Revisiting Vaidya Horizons

Nielsen, A. B.

doi:10.3390/galaxies2010062

Cited by 18 publications

(13 citation statements)

References 21 publications

(23 reference statements)

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“…The apparent horizon is located by the root of the equation ∇ c r∇ c r = g rr = 0, which yields r AH = 2m(v). The apparent horizon is distinct from the event horizon, which is given approximately by the expression [10,20,15,97,137]…”

Section: Event Horizonsmentioning

confidence: 99%

“…where ṁ ≡ dm/dv. The phenomenology of the event horizons is reported in several studies (e.g., [10,20,15,97,137] and we will not repeat the analysis here. To summarize the situation, an event horizon forms and grows starting from the centre and an observer can cross it and be unaware of it even though his or her causal past consists entirely of a portion of Minkowski space.…”

Section: Event Horizonsmentioning

confidence: 99%

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Embedding Black Holes and Other Inhomogeneities in the Universe in Various Theories of Gravity: A Short Review

Faraoni

2018

Universe

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The classic black hole mechanics and thermodynamics are formulated for stationary black holes with event horizons. Alternative theories of gravity of interest for cosmology contain a built-in time-dependent cosmological "constant" and black holes are not stationary. Realistic black holes are anyway dynamical because they interact with astrophysical environments or, at a more fundamental level, because of backreaction by Hawking radiation. In these situations the teleological concept of event horizon fails and apparent or trapping horizons are used instead. Even as toy models, black holes embedded in cosmological "backgrounds" and other inhomogeneous universes constitute an interesting class of solutions of various theories of gravity. We discuss the known phenomenology of apparent and trapping horizons in these geometries, focusing on spherically symmetric inhomogeneous universes.

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Section: Event Horizonsmentioning

confidence: 99%

Section: Event Horizonsmentioning

confidence: 99%

Embedding Black Holes and Other Inhomogeneities in the Universe in Various Theories of Gravity: A Short Review

Faraoni

2018

Universe

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“…Let us now consider an example of conformally static, ingoing Vaidya space-time with D = 4 illustrating the location of a conformal Killing horizon. The spacetime metric reads [25][26][27]…”

Section: An Example In Linear Vaidya Spacetimementioning

confidence: 99%

Conformal Killing horizons and their thermodynamics

Nielsen¹,

Shoom²

2018

Class. Quantum Grav.

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Certain dynamical black hole solutions can be mapped to static spacetimes by conformal metric transformations. This mapping provides a physical link between the conformal Killing horizon of the dynamical black hole and a Killing horizon of the static spacetime. We show how this conformal relation can be used to derive thermodynamic properties for the dynamical black holes. Although these horizons are defined quasi-locally and can be located by local experiments, they are distinct from other popular notions of quasi-local horizons such as apparent horizons. Thus in the dynamical Vaidya spacetime describing constant accretion of null dust, the conformal Killing horizon, which is null by construction, is the natural horizon to describe the black hole.

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“…The apparent horizon (AP) is given by r = 2m(v) [21] and does not coincide with the future event horizon…”

Section: Photon Sphere Of Dynamical Eternal Black Holementioning

confidence: 99%

Dynamical photon sphere and time evolving shadow around black holes with temporal accretion

Koga,

Asaka,

Kimura

et al. 2022

Preprint

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A photon sphere is known as the geometrical structure shaping a black hole shadow. The mechanism is well understood for static or stationary black hole spacetimes such as the Schwarzschild and the Kerr spacetimes. In this paper, we investigate and explicitly specify a photon sphere that shapes a black hole shadow in a dynamical spacetime while taking the global structure of the spacetime into account. We consider dynamical and eternal black hole cases of the Vaidya spacetime, which represents a spherically symmetric black hole with accreting null dust. First, we numerically show that there are the dynamical photon sphere and photon orbits corresponding to the shadow edge in a moderate accretion case. Second, the photon spheres are derived analytically in special cases. Finally, we discuss the relation between our photon sphere and the several notions defined as a photon sphere generalization.

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Revisiting Vaidya Horizons

Cited by 18 publications

References 21 publications

Embedding Black Holes and Other Inhomogeneities in the Universe in Various Theories of Gravity: A Short Review

Embedding Black Holes and Other Inhomogeneities in the Universe in Various Theories of Gravity: A Short Review

Conformal Killing horizons and their thermodynamics

Dynamical photon sphere and time evolving shadow around black holes with temporal accretion

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