The Kerr metric describes the geometry of empty spacetime around a rotating uncharged axially-symmetric black hole.
Questions tagged [kerr-metric]
286 questions
39
votes
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Why does Roy Kerr claim that the Kerr black hole does not contain a singularity?
In a preprint posted on the arXiv, Roy Kerr claims that there is a widespread misunderstanding related to the singularity inside the black hole that bears his name.
Can anyone explain his argument in "simple terms"?
Are there any pitfalls in his…
noir1993
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votes
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Wouldn't Miller's planet be fried by blueshifted radiation?
In Interstellar, wouldn't Miller's planet be fried by blueshifted radiation? The 61,000x time dilation multiplier would make even cosmic background radiation photons into extreme UV photons.
I was told that this is off-topic for Science Fiction &…
blademan9999
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votes
2 answers
Do black holes have a moment of inertia?
My question is in the title: Do black holes have a moment of inertia?
I would say that it is: $$I ~\propto~ M R_S^2,$$ where $R_S$ is the Schwarzschild radius, but I cannot find anything in the literature.
mattiav27
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votes
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How does the Penrose diagram for a spinning black hole differ in realistic scenarios (formed by stellar collapse)?
The Penrose diagram for a non-spinning Schwarzschild black hole is
Notably, there is a second universe "on the other side" of the black hole. However, actual black holes form by stellar collapse, and the collapse process leads to a different…
user1379857
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Can a Kerr black hole become super-extremal?
Let's assume there is a large Kerr black hole, which is almost
extremal and would become extremal with the addition of a small
amount of mass $M$ with spin $J$ to make the final $J=M$.
What if this amount of mass $M$ with spin $J$ approached the…
Andrew
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What is the maximum time dilation factor when orbiting a rotating black hole?
Suppose one spaceship is stably orbiting a rotating black hole and another is far away from the black hole. What is the maximum time dilation factor between the two ships? Can it be made arbitrarily large, and if so does that require the black hole…
Mark Eichenlaub
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15
votes
5 answers
Surface gravity of Kerr black hole
I'm going through Kerr metric, and following the 'Relativist's toolkit' derivation of the surface gravity, I've come to a part that I don't understand.
Firstly, the metric is given…
dingo_d
- 1,873
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Massless Kerr black hole
Kerr metric has the following form:
$$
ds^2 = -\left(1 - \frac{2GMr}{r^2+a^2\cos^2(\theta)}\right) dt^2 +
\left(\frac{r^2+a^2\cos^2(\theta)}{r^2-2GMr+a^2}\right) dr^2 +
\left(r^2+a^2\cos(\theta)\right) d\theta^2
+…
Nikita
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Derivation of Kerr metric, is there any reference?
In studying general relativity, many text deals with the derivation of
Schwarzschild metric starting from generic metric form.
After that impose static, spherical symmetry and obtain the desired Schwarzschild metric.
But I haven't find any…
phy_math
- 3,782
14
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What do black holes spin relative to?
What do black holes spin relative to?In other words, what is black hole spin measured in relation to?
Spinning black holes are different from non-spinning black holes. For instance, they have smaller event horizons. But what are the spins of…
Joshiepillow
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Closed timelike curves in the region beyond the ring singularity in the maximal Kerr spacetime
The region beyond the ring singularity in the maximal Kerr spacetime is described as having closed timeline curves. Why and/or how is the question.
Now if you look a Kruskal-Szkeres Diagram (or a Penrose Diagram as above) you can see that the Kerr…
Timaeus
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11
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Why are complex coordinates outlawed in physics?
In the case of the Kerr metric, for a high enough angular velocity such that on transformation to Boyer-Lindquist coordinates yields complex coordinates for the event horizon, why is it assumed then that the coordinates "disappear"? are complex…
Dan
- 139
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3 answers
Physical motivation for mathematically extending solutions to Einstein's equations
Sorry if this question gets a little long; I want to explain why I'm asking it.
The usual Schwarzchild metric
$$ds^2 = -\left(1-\frac{2M}{r}\right) dt^2 + \left(1-\frac{2M}{r}\right)^{-1} dr^2 + r^2(d\theta^2+\sin^2\theta\ d\phi^2)$$
makes sense…
Javier
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votes
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What happens to a particle in the exact center of a Kerr black hole?
Kerr black holes (and Kerr-Newman black holes), instead of the "point" singularity theorized in spherically symmetric black holes, instead have a "ring" singularity, spread along the equatorial plane of rotation. any particle inside a spherically…
HDE 226868
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Does the twist of spacetime by a black hole increase over time?
From the Wikipedia page about Ergospheres:
As a black hole rotates, it twists spacetime in the direction of the rotation...
Does this "twisting up spacetime" add up over time in any measurable way? Or do I take a metaphor too literal?
What I mean…
Brotcrunsher
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