Questions tagged [kerr-newman-metric]

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2
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1answer
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Area of Kerr-Newman event horizon

I want to calculate the area of event horizon for a Kerr-Newman black hole by using boyer's coordinates. I searched a lot from web, but I could not find any information about calculating event ...
2
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1answer
86 views

Metric diameter of a ring singularity

In the Kerr metric the ring singularity is located at the coordinate radius $r=0$, which corresponds to a ring with the cartesian radius $R=a$. So the center of the ring singularity in cartesian ...
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0answers
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Would naked singularities have a complex irreducible mass?

The formula for the irreducible mass, also known as the Christodoulou and Ruffini equation, is $$M_{\rm irr} = \frac{\sqrt{2 M^2-Q^2+2 M \sqrt{M^2-Q^2-a^2}}}{2}$$ where M is the mass equivalent of ...
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0answers
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Coordinate transformation from Boyer-Lindquist to rotating frame

The Kerr-Newman metric in Boyer-Lindquist coordinates $ x^{\mu} = (t,r,\theta,\phi) $ is of the form $$ ds^2 = g_{tt}dt^2 + 2g_{t\phi}dt d\phi + g_{rr}dr^2 + g_{\theta \theta} d\theta^2 + g_{\phi \phi}...
4
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2answers
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Equation of motion for a charged particle

To compute the equations of motion of a neutral testparticle in the graviational field, one needs the metric tensor $g_{\mu \nu}$ and $g^{\mu \nu}$ to compute the Christoffel-symbols $${\Gamma^{\rm ...
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0answers
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Near Horizon Vector Field

I am studying this paper https://arxiv.org/pdf/0811.4393.pdf. I find a probem to find the near horizon form of the vector (2.17) and electromagnetic (2.18) field. I have tried to use the near horizon ...
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2answers
258 views

Are electrons points or Kerr naked ring singularities?

I have heard contradictory descriptions of electrons as both points and kerr naked ring singularities, with that said which is it? Are they rings or are they points? Are they somehow both?
1
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1answer
84 views

Gravitation Acceleration in General of Kerr-Newman Black Hole

The surface gravity (acceleration at event horizon, as measured by an observer at infinity, since the proper acceleration is infinite) of a Kerr-Newman black hole is given (e.g. here) as:$$ \kappa ...
3
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1answer
154 views

Gravitational and electromagnetic radiation from collision of Kerr-Newman black holes

When black holes collide, they produce a gravitational wave, as has been recently established by LIGO. When a charge is accelerated, it creates an electromagnetic wave. Does an accelerated massive ...
1
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2answers
277 views

Explain Kerr-Newmann Black Hole Spins in SI Units

I'm trying to run some calculations on Kerr-Newman black holes, but I'm having two major difficulties. First, most equations I've been able to find are only for Kerr black holes. Second, essentially ...
7
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2answers
461 views

Escape velocity from a rotating black hole

Under Newton, the escape velocity is $$v_{esc} = \rm c \ \sqrt{r_s/r}$$ where $\rm r_s=2 \ GM/c^2$. In the nonrotating relativistic case (the Schwarzschild case) the radial escape velocity is the ...
0
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1answer
107 views

Why doesn't the Kerr-Newman metric reduce to the Schwarzschild metric?

I hope this is not just an algebra mistake (and I'm very sorry if it is). Also, note I use the convention that the time argument is negative. Setting $G=M=c=1$ for the Schwarzschild metric, it ...
3
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0answers
160 views

Does the event horizon of a black hole need to be an oblate sphere?

Suppose two black holes where rotating around each other, perhaps spinning into each other, at a distance such that their event horizons merge into one event horizon. It seems to me that the event ...
4
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0answers
327 views

How to find the Hawking temperature for this metric?

I am reading this paper about "Hawking radiation of Kerr-Newman-de Sitter black hole", where the authors find Hawking temperature of this metric The authors state that hawking temperature is given by ...
2
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1answer
75 views

GR Verification for a Charged Black Hole

For a charged ($Q$) rotating ($L$) mass ($M$), the Kerr-Newman equations give the angular deflection of light. Has there been observational verification (I would prefer to use only the angular ...
1
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1answer
253 views

Electromagnetic four-potential for Kerr-Newman solution

Any textbook or paper on the Kerr-Newman metric I found contains the solution for the electromagnetic tensor $ F^{\mu}_{\phantom{\mu} \nu}$. Can you provide a (reliable) reference for the solution ...
6
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1answer
248 views

Charged versus rotating black holes as different kinds of wormholes

I've heard that a maximally extended charged black hole can be a traversable wormhole to the same universe whereas a maximally extended uncharged rotating black hole can only be a wormhole to ...
2
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1answer
171 views

Generalized Bekenstein-Hawking temperature for Kerr-Newmann-dS black holes

What is the formula for the Bekenstein-Hawking temperature in a Kerr-Newmann-de Sitter spacetime, i.e., the temperature for a black hole with Mass (M), angular momentum (J), electric charge (Q) and ...
1
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1answer
370 views

Surface gravity for a rotating charged black hole

I have that the surface gravity (at the outer event horizon) for a Kerr-Newman black hole is $$ K_+ = \frac{r_+-r_-}{2(r_+^2+(J/M)^2)} = \frac{\sqrt{M^2-Q^2-J^2/M^2}}{2M^2-Q^2+2M\sqrt{M^2-Q^2-J^2/M^2}}...
2
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1answer
1k views

is this generalized Hawking radiation formula right?

Look at equation 11.2.17 in this page. The expression is: $$ T = 10^{-5} \text{K m} \frac{\xi}{\frac{GM}{c^2} \lbrace \frac{GM}{c^2} + \xi \rbrace - e^2 }$$ where $$ \xi = (r_s^2 - a^2 - e^2)^{1/2}$...
2
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1answer
184 views

Kerr-Newman black holes and infinite charge

Recall the first law of BH thermodynamics $ dM=\frac{\kappa}{8\pi} dA + \Omega dJ + \Phi dQ $ Now, let's consider the Reissner-Nordstrom solution $J=0$ such that $m>Q$ but only slightly greater. ...
16
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2answers
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If a Kerr-Newman black hole is like a charged, spinning, heavy magnet, what kind of magnet is it like?

I was reading up on De Sitter spaces, which states that the gravitational effects from a black hole is indistinguishable from any other spherically symmetric mass distribution. This makes a lot of ...