Radiation that comes from pair production quantum effects in close vicinity to an event horizon, leading to the potential for eventual evaporation of black holes. Two mirror particles are created with one falling behind the horizon, becoming casually lost to the rest of the universe, including its ...
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2answers
576 views
Analog Hawking radiation
I am confused by most discussions of analog
Hawking radiation in fluids (see, for example,
the recent experimental result of Weinfurtner et
al. Phys. Rev. Lett. 106, 021302 (2011), ...
20
votes
3answers
798 views
From where (in space-time) does Hawking radiation originate?
According to my understanding of black hole thermodynamics, if I observe a black hole from a safe distance I should observe black body radiation emanating from it, with a temperature determined by its ...
11
votes
6answers
761 views
Do all massive bodies emit Hawking radiation?
It is known that any accelerated observer is subject to a heat bath due to Unruh radiation. The principle of equivalence suggests that any stationary observer on the surface of a massive body should ...
11
votes
2answers
400 views
Extremal black hole with no angular momentum and no electric charge
A black hole will have a temperature that is a function of the mass, the angular momentum and the electric charge. For a fixed mass, Angular momentum and electric charge are bounded by the extremality ...
10
votes
3answers
434 views
Hawking radiation and quark confinement
The simple picture of Hawking radiation is that a pair-antiparticle pair is produced near the event horizon, then one falls into the black hole while the other escapes. Suppose the particles are ...
10
votes
3answers
330 views
Hawking radiation and reversibility
It's often said that, as long as the information that fell into a black hole comes out eventually in the Hawking radiation (by whatever means), pure states remain pure rather than evolving into mixed ...
10
votes
3answers
360 views
Why is there a flux of radiation in the Hawking effect but not in the Unruh effect? (and other questions)
This question is slightly related to this one Do all massive bodies emit Hawking radiation?, which I think was poorly posed and so didn't get very useful answers. There are several questions in this ...
8
votes
1answer
123 views
Multipolar expansion profile of Hawking radiation on Kerr black holes
I would be very curious if Kerr black holes emit Hawking radiation at the same temperature in the equatorial bulges and in their polar regions. I've been looking some reference for this for a couple ...
8
votes
1answer
340 views
How do we know that black holes evaporate?
This has been bugging me for some time.
As I understand it, Hawking radiation is the result of the mismatch between the vacuum state of a quantum field as seen by a free falling observer (falling ...
8
votes
3answers
323 views
Thermodynamically reversed black holes, firewalls, Casimir effect, null energy condition violations
Scott Aaronson asked a very deep question at Hawking radiation and reversibility about what happens if black hole evolution is reversed thermodynamically. Most of the commenters missed his point ...
8
votes
1answer
86 views
Hawking Radiation as Tunneling
Firstly, I'm aware that Hawking radiation can be derived in the "normal" way using the Bogoliubov transformation. However, I was intrigued by the heuristic explanation in terms of tunneling. The ...
7
votes
2answers
416 views
Do apparent event horizons have Hawking radiation?
As I understand it, black holes have an absolute event horizon and an apparent horizon specific an observer. In addition to black holes, an apparent horizon can come from any sustained acceleration. ...
6
votes
2answers
246 views
How can one reconcile the temperature of a black hole with asymptotic flatness?
A stationary observer very close to the horizon of a black hole is immersed in a thermal bath of temperature that diverges as the horizon is approached. $$T^{-1} = 4\pi \sqrt{2M(r-2M)}$$ The ...
6
votes
1answer
62 views
does the background spacetime of a black hole affects its thermodynamic properties?
The question is this: will the thermodynamic properties of a black hole (Hawking radiation spectra and temperature, entropy, area, etc.) depend if the black hole sits in a DeSitter or an Anti-DeSitter ...
6
votes
4answers
450 views
de sitter cosmologic limit
It has been said that our universe is going to eventually become a de sitter universe. Expansion will accelerate until their relative speed become higher than the speed of light.
So i want to ...
6
votes
0answers
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
votes
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 ...
4
votes
8answers
608 views
Flat space limit of the Schwarzschild metric and Hawking temperature
The Schwarzschild metric reduces to the Minkowski metric in the limit of vanishing $M$, but the Hawking temperature which is proportional to $1/M$ diverges in the same limit. This would imply that ...
4
votes
1answer
494 views
On black holes, Hawking radiation and gravitational atoms
Over the past hour or so I've been following one of my standard physics-based, wanders-through-the-internet. Specifically, I began by reviewing some details of dark energy theory but soon found myself ...
4
votes
3answers
631 views
Black holes and positive/negative-energy particles
I was reading Brian Greene's "Hidden Reality" and came to the part about Hawking Radiation. Quantum jitters that occur near the event horizon of a black hole, which create both positive-energy ...
4
votes
1answer
108 views
Hawking radiation: direct matter -> energy conversion?
When a black hole evaporates, does it turn all the matter that has fallen in directly to energy, or will it somehow throw back out the same kind of matter (normal or anti) that went in?
4
votes
2answers
205 views
How does the evaporation of a black hole look for a distant observer?
Let's assume an observer looking at a distant black hole that is created by collapsing star.
In observer frame of reference time near black hole horizon asymptotically slows down and he never see ...
4
votes
1answer
180 views
What is a virtual photon pair?
When describing a black hole evaporation in the hawking black body radiation it is usually said that is due to a virtual photon pair, is it this what happens? And what is virtual photon pair, does the ...
4
votes
1answer
370 views
Why isn't black hole information loss this easy (am I missing something basic)?
Ok, so on Science channel was a special about Hawking/Susskind debating black holes, which can somehow remove information from the universe.
A) In stars, fusion converts 4 hydrogen into 1 helium, ...
4
votes
1answer
130 views
Hawking Radiation from the WKB Approximation
Reading this paper which is itself an exposition of Parikh and Wilczek's paper, I get to a point where I fail to be able to follow the calculation. Now this is undoubtably because my calculational ...
4
votes
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 ...
3
votes
2answers
103 views
Is there something like Hawking radiation that makes protons emit component quarks?
If Hawking radiation can escape from black holes, could quarks perhaps become separated from protons despite it being "impossible" for that to happen?
3
votes
1answer
145 views
Hawking Radiation: how does a particle ever cross the event horizon?
The heuristic argument for Hawking Radiation is, that a virtual pair-production happens just at the event horizon. One particle goes into the black hole, while the other can be observed as radiation.
...
3
votes
1answer
222 views
Wasn't the Hawking Paradox solved by Einstein?
I just watched a BBC Horizon episode where they talked about the Hawking Paradox. They mentioned a controversy about information being lost but I couldn't get my head around this.
Black hole ...
3
votes
1answer
112 views
How would you detect Hawking radiation?
Hawking theorized that a black hole must radiate and therefore lose mass (Hawking radiation). According to classical relativity though, nothing can escape a black hole, the hawking radiation would ...
3
votes
1answer
137 views
Does cosmological horizon grow or decrease as it radiates?
Ron Maimon in many posts claimed that cosmological horizon is like a big black hole.
Black holes decrease as they evaporate and their radius decreases as well.
So what is with a cosmological ...
3
votes
1answer
134 views
Formation of a black hole and Hawking radiation
From the perspective of an outside observer it takes infinitely long for the black hole to form.
But if the black hole is no extremal black hole, it emits Hawking radiation.
So the outside observer ...
3
votes
2answers
227 views
Why isn't Hawking radiation frozen on the boundary, like in-falling matter?
From the perspective of a far-away observer, matter falling into a black hole never crosses the boundary. Why doesn't a basic symmetry argument prove that Hawking radiation is therefore also frozen on ...
3
votes
1answer
125 views
Intensity of Hawking radiation for different observers relative to a black hole
Consider three observers in different states of motion relative to a black hole:
Observer A is far away from the black hole and stationary relative to it;
Observer B is suspended some distance ...
3
votes
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
votes
0answers
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 ...
2
votes
4answers
203 views
Time inside a Black hole
If time stops inside a black hole, due to gravitational time dilation, how can it's life end after a very long time? If time doesn't pass inside a black hole, then an event to occur inside a black ...
2
votes
5answers
434 views
Black Hole Singularities
If two black holes collide and then evaporate, do they leave behind two naked sigularities ore? If there are two, can we know how they interact?
2
votes
2answers
287 views
Theoretical basis for black hole evaporation
What is the basis for black hole evaporation?
I understand that Hawking-radiation is emitted at the event horizon, a theoretical result originating in General Relativity and Quantum Field Theory, but ...
2
votes
1answer
94 views
Reconstruction of the initial state from Hawking radiation?
I hear that unitary evolution and information conservation must imply that information about information content that defines the initial state of matter used to create a black hole can be inferred ...
2
votes
2answers
259 views
Hawking radiation from point of view of a falling observer
This paper tells that Hawking claimed that the falling to a black hole observer will not detect any radiation. But only because the frequency of the Hawking radiation will be of the order $1/R_s$ so ...
2
votes
1answer
59 views
An infalling object in a black hole looks “paused” for a far away observer, for how long?
As I understand, to an observer well outside a black hole, anything going towards it will appear to slow down, and eventually come to a halt, never even touching the event horizon.
What happens if ...
2
votes
1answer
139 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 - ...
2
votes
1answer
199 views
black hole event horizon
Given gravitational time dilation, under what conditions will a test particle cross an event horizon before the black hole evaporates? Assume zero background radiation.
2
votes
2answers
133 views
event horizons are untraversable by observers far from the collapse?
Consider this a followup question of this one
In the classical schwarszchild solution with an eternal black hole, the user falls through the event horizon in finite local time, but this event does ...
1
vote
5answers
279 views
Theoretical physics and education: Does it really matter a great deal about what happens inside a black hole, or about Hawking radiation? [closed]
I stumbled across this article http://blogs.scientificamerican.com/cross-check/2010/12/21/science-faction-is-theoretical-physics-becoming-softer-than-anthropology/
It got me thinking. Why do we ...
1
vote
3answers
228 views
Why can't light escape from inside event horizon of Black Holes?
The simple answer: Its because Gravity of Black Hole there doesn't allow it. See also this and this Phys.SE posts.
Isn't it a classical answer? When we're unable to connect Gravity with Quantum ...
1
vote
2answers
163 views
Is a black hole a perfect black body?
A black body absorbs all light/radiation in its reach. According to basic laws of physics, the more energy a body absorbs the more it can emit. Therefore, a black body absorbs all energy directed at ...
1
vote
2answers
463 views
Are information conservation and energy conservation related?
as evident from the title, are both, conservation of energy and conservation of information two sides of the same coin??
Is there something more to the hypothesis of hawking's radiation other than ...
1
vote
2answers
519 views
How do we determine the temperature of a Black Hole?
How do we determine the temperature of a Black Hole?
Since we cannot see a Black Hole, which I presume, is because it absorbs light, would it not also prevent radiation from escaping, making ...
