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Results tagged with black-holes
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user 311860
A black hole is a region of spacetime from which nothing can escape. More formally, the future light cone of any observer within the black hole is completely contained in the black hole, and the black hole region is not within the past light cone of any observer that goes to spatial infinity in an infinite amount of time.
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Shear on the event horizon of the black hole
In terms of spin coefficients, shear is defined as
$$\sigma=(m_a)(m_b)(\nabla_al^b)$$
where $m,l$ denotes null tetrad vectors. I came across the following paragraph from one of Stephen Hawking's paper …
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Null tetrad for a metric with most of the metric components non zero
I am working on a metric which is basically $g = g_0 + h_{\mu \nu}$ where $g_0$ is the Kerr metric up to order a (taking $a^2 = 0$) and $h_{\mu \nu}$ denotes perturbed metric. Hence the complete metri …
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Regarding Quasi-normal modes of black holes
I am a Ph.D. student working on quasinormal modes of black holes. I am following the paper
https://ui.adsabs.harvard.edu/abs/1985ApJ...291L..33S/abstract which is perhaps the first paper on calculatin …
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What is the difference between dynamical horizon and apparent horizon?
The condition for both the dynamical horizon and an apparent horizon is that expansion of outgoing null normal $\theta_l$ = 0 and expansion of ingoing null normal $\theta_n$ < 0. Then what is the dif …
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Understanding Haywards trapping gravity
In the paper General Laws of Black hole Dynamics, Hayward has proposed a formula for trapping gravity of an outer trapping horizon given by
$\kappa$ = $\frac{1}{2}$ $\sqrt{-e^f \mathcal{L}_- \Theta_+} …
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Stationary perturbations
What do we mean by "stationary" perturbations? I know that black hole perturbations are related to gravitational waves and stationary means there should be no flow of energy. But this is vague. I am l …
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How quasinormal modes of black holes related to black hole temperature?
I have heard that quasinormal modes of black holes are related to black hole temperature. QNMs describe how a black hole reacts to perturbation. Forex, when a black hole is perturbed, it will emit gra …
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Are mass and charge of a black hole related to each other? [duplicate]
While scrolling through an online document, I came across the statement, "If charges carried by the black hole are large, the curvature at the horizon is small." How is this so?
I tried to think of an …
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How increase in area of the horizon implies that the horizon in spacelike using Raychaudhuri...
In a talk The enigma of black hole horizons, (at 24:37), it is said that
"Raychaudhuri equation implies, if the flux into H is positive, area increases and horizon is spacelike".
How increase in are …
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