A black hole is a volume from which photons, or any matter, can not escape. More formally, the coordinate speed of light at the event horizon - the boundary of a black hole - is zero, as measured by a sufficiently separated observer.
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Is the Graveyard Really so Serious?
Calculations in relation to black holes are solely in consideration of spacetime curvature and its effects. They are in total alienation with respect to the action of inertial agents[external ...
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281 views
Do spacelike junctions in the Thin-Shell Formalism imply energy nonconservation and counterintuitive wormholes?
The Thin Shell Formalism (MTW 1973 p.551ff) is used to properly paste together different vacuum solutions to the Einstein equations. At the junction of the two solutions is a hypersurface of matter – ...
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106 views
Rotation of Spacetime => Change in orbit/path
Along the idea of frame-dragging;
Will the rotation of a black hole, which has some velocity v and angular momentum, influence its path in 3D space?
I've seen the fact that depending on the ...
3
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1answer
77 views
Will the black hole evaporate in finite time from external observer's perspective?
There is the problem that is bothering me with the black hole evaporation because of Hawking radiation.
According to Hawking theory the black hole will evaporate in finite time because of quantum ...
3
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1answer
267 views
Are black hole states completely mixed?
A completely mixed state is a statistical mixture with no interference terms, and (QMD, McMahon, pg 229):
$$\rho = \dfrac{1}{n}I$$
$$Tr(\rho^2) = \dfrac{1}{n}$$
Are black hole quantum states ...
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1answer
55 views
Relativistic Computation?
Is it possible to employ relativity to develop computational technology?
Here is a really basic example:
Build a Computer and Feed it the Problem (say the problem is projected to take 10 years to ...
2
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1answer
260 views
Gravitational Redshift around a Schwarzschild Black Hole
Let's say that I'm hovering in a rocket at constant spatial coordinates outside a Schwarzschild black hole.
I drop a bulb into the black hole, and it emits some light at a distance of $r_e$ from the ...
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199 views
Special relativity paradox and gravitation/acceleration equivalence
One of the features of the black hole complementarity is the following :
According to an external observer, the infinite time dilation at the horizon itself makes it appear as if it takes an ...
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1answer
103 views
Do all black holes spin in the same direction?
My question is as stated above, do all black holes spin the same direction?
To my knowledge, the spin in the direction of the spin of the matter that created them. Another similar question was asked ...
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99 views
How about destroying a black hole?
Can we destroy a black hole? I know it is pretty powerful and hardcore stuff but there should be a way even theoretically as we know know nothing is perfect in this universe as it exist due to ...
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147 views
How is the logarithmic correction to the entropy of a non extremal black hole derived?
I`ve just read, that for non extremal black holes, there exists a logarithmic (and other) correction(s) to the well known term proportional to the area of the horizon such that
$S = \frac{A}{4G} + K ...
6
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67 views
Is the Hawking radiation of a charged black hole thermal?
Suppose you have a Schwarzschild black hole of mass $M$ and angular parameter $a = 0$ (no rotation).
Question: is it possible to throw a charge $Q$ at a faster rate that it will be reradiated? Will ...
6
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0answers
87 views
Hawking radiation for closely orbiting black holes
Suppose we have two black holes of radius $R_b$ orbiting at a distance $R_r$. I believe semi-classical approximations describe correctly the case where $R_r$ is much larger than the average black body ...
5
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78 views
Do semiclassical GR and charge quantisation imply magnetic monopoles?
Assuming charge quantisation and semiclassical gravity, would the absence of magnetically charged black holes lead to a violation of locality, or some other inconsistency? If so, how?
(I am not ...
5
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0answers
51 views
paper about black branes and implications to 4d black holes
This paper makes a case for piezoelectric response (electric dipole moment under mechanical oscillations) of black branes. This paper does not make an implication of their results for 4D black holes ...
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98 views
Maximal kinetic energy due to gravitational attraction
Two related questions:
Small object of mass $m$ is falling into the supermassive black hole of mass $M$. What is the maximal kinetic energy can be acquired by the small object, from the point of ...
5
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88 views
Geometric entropy vs entanglement entropy (dependent on curvature coupling parameter)
I have a quick question. In hep-th/9506066, Larsen and Wilczek calculated the geometric entropy (which I believe is just another name for entanglement entropy) for a non-minimally coupled scalar field ...
4
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51 views
Gravitational redshift of Hawking radiation
How can Hawking radiation with a finite (greather than zero) temperature come from the event horizon of a black hole? A redshifted thermal radiation still has Planck spectrum but with the lower ...
4
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0answers
89 views
Alternate geodesic completions of a Schwarzschild black hole
The Kruskal-Szekeres solution extends the exterior Schwarzschild solution maximally, so that every geodesic not contacting a curvature singularity can be extended arbitrarily far in either direction.
...
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81 views
Can a nearly-extremal black hole be stable against Schwinger vacuum breakdown?
I was doing some basic algebra to estimate the range of possible masses $M$ and electric charge $Q$ for a nearly extremal Reissner-Noström black hole. I want to see if the logic is correct
the ...
4
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0answers
84 views
Information scrambling and Hawking non-thermal radiation states
Could a very small black hole where half of its entropy has been radiated, emit Hawking radiation that is macroscopically distinct from being thermal? i.e: not a black body radiator. Or would the ...
4
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0answers
45 views
Kerr solution for finite collapse time
The Kerr black hole solutions gives an analytic continuation that is asymptotically flat. Some people have argued that this is another universe, but others state that the analytic continuation ...
4
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0answers
170 views
What is a black hole?
Is there a definition of a black hole in a generic spacetime? In some books, for example Wald's, black holes are defined for asymptotically flat spacetime with strong asymptotic predictability, ...
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39 views
What is the physical meaning of fact, that Reissner-Nordstrom black hole is thermodynamically unstable?
It is known, that Reissner-Nordstrom black hole is thermodynamically unstable [1].
Does it mean, that there is no Reissner-Nordstrom black hole in physical world?
Does it mean, that there may be ...
3
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0answers
109 views
Going through a ring of black holes
Mathematician here with a speculative physical question -- feel free to boot me if the level isn't right.
Suppose one finds, or builds, a constellation of several black holes arranged in a circle. ...
3
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152 views
micro black hole forces
A black hole would radiate mass optimally for interstellar-travel applications in the range between $10^7$ and $10^8$ kilograms. Assuming a light-only radiation emission spectrum, with a parabolic ...
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53 views
Entanglement and Black holes
If you have two entangled quantum states, One state falls into a black hole and you measure the other state, What can you say about the state that has fallen into the black hole?
If you have billions ...
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89 views
Falling into a black hole emitter vs observer
Let's say we are working with the Schwarzschild metric and we have an emitter of light falling into a Schwarzschild black hole.
Suppose we define the quantity $$u=t- v$$ where $$dv/dr= ...
2
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167 views
Nonlinear refraction index of vacuum above Schwinger limit
This question is more about trying to feel the waters in our current abilities to compute (or roughly estimate) the refraction index of vacuum, specifically when high numbers of electromagnetic quanta ...
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15 views
Pair production intefering with gamma-ray laser black hole fabrication
A common "proposal" to make a micro black hole is to use on the order of 10^12 kg of gamma-ray lasing medium and focus all the light at a small point. However, intense light will interact with itself ...
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49 views
Singularities in Schwarzchild space-time
Can anyone explain when a co-ordinate and geometric singularity arise in Schwarzschild space-time with the element
$$ ...
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0answers
21 views
Magnetic field-pulsed microwave transmission line
Here's the reference:
The researchers showed that a magnetic field-pulsed microwave transmission line containing an array of superconducting quantum interference devices, or SQUIDs, not only ...
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0answers
67 views
Black hole entropy from collapsed entangled pure light
Consider the following scenario, very similar to the one proposed in this question, but this time, the pure quantum radiation used for the black hole collapse, is now being split with down-converter ...
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transition between extremal and nonextremal black hole states
Extremal black holes are at zero temperature, hence they do not radiate.
my question is twofold:
1) is extremality of micro black holes a stable property? electric charge is quickly emitted from ...
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98 views
Does black hole complementarity apply to white holes?
If physics is time reversal invariant, there ought to be white hole complimentarity as well. Imagine a white hole so enormous that it is possible for life to evolve entirely within it for billions of ...
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78 views
How complete is our understanding of general-relativistic solutions for extremal black holes?
Putting aside quantum mechanics (or at least putting aside the question of fermions), is our knowledge of extremal General-Relativity solutions good enough that we would be able to rule out a ...
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0answers
30 views
How connected thermodynamical stability and dynamical stability for black holes?
Criteria for thermodynamical stability is the convex of entropy. But for black hole entropy is non-additive.
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157 views
Spacetime around a Black Hole
If we consider the sun, then space-time is curve around it. My question is that what is the kind of curvature of space and time around the black hole. Is that space and time more curved around the ...
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Are quarks the limits? The end of the fundamental science. For collisions on more higher energies will lead to black holes after all?
Are quarks the limit and the Plank scale is believed to be the limit of distance when the very concept of space and length cease to exist (10^-19)
Any attempt to research the existence of shorter ...
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115 views
Is it mathematically possible or topologically allowable for cutouts, or cavities, to exist in a 3-manifold?
A few weeks back, I posted a related question, Could metric expansion create holes, or cavities in the fabric of spacetime?, asking if metric stretching could create cutouts in the spacetime manifold. ...
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66 views
How to calculate the mass of the Cygnus X-1 black hole?
I have received a question about how to calculate the mass of Cygnus x-1 (black star).
Since we are able to find the the mass through this Wikipedia page I know that we can find the mass through ...
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54 views
What is the physical mechanism for the subjective rapid vanishing of the firewall on such a short notice?
Suppose there is an astronomical sized black hole. There is an observer Alice. She jumps into the black hole after it has emitted 2/3 — or 3/4, the exact number doesn't matter — of all the ...
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36 views
Relation between maximum entropy thermodynamics and entropy bounds
Here is a question which I've been thinking about, I'm sorry if it's little too vague, maybe you could point me to some source to read, if there's no clear direct answer.
The whole concept of ...
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109 views
State of the entangled particles at the event horizon of black hole
Looking through the article of Samir Mathur http://arxiv.org/abs/0909.1038
he assumes that the entangled particles created at the event horizon have all the state ...
