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If no singularity, what’s inside a big black hole?

by jimgraber
Tags: black, hole, inside, singularity, what’s
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Bernie G
#19
Aug28-11, 09:22 AM
P: 136
That sounds too weird. I think simply a radiation ball exists inside the Schwarzchild Radius, with a density profile similar to that of a conventional star (denser closer to the core). I think this because neutrons can not exist at these high pressures and energies. Radiation pressure would be the supporting mechanism. This might be confirmed by observation within 20 years by observing the merger of 2 typical 8 solar mass black holes in other galaxies. (Roughly perhaps 100 mergers of neutron stars and black holes occur annually, so about one black hole - black hole merger should occur annually.) If the radiation ball size is ≥ 70% of the Schwarzchild radius, a large observable burst of radiation will occur, but if the black holes are a point singularity nothing will be ejected of course. I hope to have a good estimate soon for the size of this theoretical radiation ball, but have to get a formula for the radiation pressure P first. P should be equal to (1/3)pc^2 or (2/3)pc^2 or pc^2, where p is the radiation density.
tom.stoer
#20
Aug28-11, 01:28 PM
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There are several proposals from ceratin theories of quantum gravity, i.e. the fuzzball proposal in string theory and a 'huge intertwiner' in loop quantum gravity. In both cases the singularity is resolved by quantum effects.
tanzanos
#21
Sep2-11, 07:58 AM
P: 63
If the mass that makes it past the event horizon end up in an infinite spiral then how can we account for the massive gravitational force of a black hole? On the other hand if there is no singularity and no infinite spiral then again where does the gravity emanate from?

Does this mean that there is no limit to the mass that a black hole can "ingest"?
Surely mass cannot be infinitely compressed?

What if information remains on the event horizon but the mass disappears either in an endless spiral or ends up elsewhere then would it be wrong to claim that the G forces are emanating not from the core of the black hole but the event horizon where information remains?

Pardon my ignorance but although I am not a physicist I am still fascinated by these glorious beasts.
phinds
#22
Sep2-11, 08:05 AM
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Quote Quote by tanzanos View Post
Does this mean that there is no limit to the mass that a black hole can "ingest"?
Surely mass cannot be infinitely compressed?
.
I can't see that infinite compression follows from more and more mass. Why do you think it should? "Infinite" is a word you need to use with great care.
tanzanos
#23
Sep2-11, 08:32 AM
P: 63
Quote Quote by phinds View Post
I can't see that infinite compression follows from more and more mass. Why do you think it should? "Infinite" is a word you need to use with great care.
Ok I see what you mean so let me put it differently: is there a limit where mass cannot be compressed more? If yes then black holes cannot contain a singularity and continue to feed indefinitely. Perhaps you may shed some light on this?

Thanks!
med17k
#24
Sep2-11, 11:30 AM
P: 46
I thought that superstring theory considers a black hole to be a p brane vibrating at a very high frequency .
phinds
#25
Sep2-11, 02:12 PM
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Quote Quote by tanzanos View Post
Ok I see what you mean so let me put it differently: is there a limit where mass cannot be compressed more? If yes then black holes cannot contain a singularity and continue to feed indefinitely. Perhaps you may shed some light on this?

Thanks!
No, as far as I am aware, there is absolutely no reason why black holes cannot contintue to accrete matter. I don't believer there is an upper limit on mass or any reason why there should be. Mass just won't compress beyond a certain point, but that doesn't mean you can't add more.

Also, there are theories that the mass-singularity at the heart of a black hole is NOT actually what's there and that it becomes a dense soup of radiation. That may or may not be, but in any case do NOT let it lead you off into crackpot land where the singularity that started out universe was a black hole. Black holes don't have THAT much mass.
tanzanos
#26
Sep2-11, 03:01 PM
P: 63
Quote Quote by phinds View Post
That may or may not be, but in any case do NOT let it lead you off into crackpot land where the singularity that started out universe was a black hole. Black holes don't have THAT much mass.
True but if the universe were to experience a "Big Crunch" then suffice it to say a super impossibly dense black hole would arise. For as you say there is no limit on how much mass can be compressed then all the mass of the universe can be compressed into a singularity? Of course we are not sure in what way the end of the universe will be but were it to contract back then it is possible and upon evaporation a point will be reached where the singularity will release the mass in a "Big bang" thus repeating a cycle?

Just asking!
phinds
#27
Sep2-11, 06:52 PM
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Quote Quote by tanzanos View Post
True but if the universe were to experience a "Big Crunch" then suffice it to say a super impossibly dense black hole would arise ...
Well the original singularity was a dense soup of radiation with no mass at all, so why would a big crunch necessarily be any different?

EDIT: actually that's not a correct statement. What I should say is that no more than one Plank time AFTER the singularity, the universe was a ... (we don't know WHAT the singularlity was or was like --- maybe if we ever get a viable theory of quantum gravity ... )
Naveen123
#28
Sep4-11, 02:13 AM
P: 4
Does science offer any explanation or conjecture as to why the initial 'singularity' exploded.
Thanks.
tom.stoer
#29
Sep4-11, 03:25 AM
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As of today there is no explanation, but there are some research directions indicating what could happen.

For example in LQC which is a "symmetry reduced" "approximation" to LQG one finds something like a "cyclic universe" where the big bang singularity is replaced by a big bounce. That means that a collapsing universe is bouncing back due to repulsive quantum gravity near Planck scale. It is problemativ to described this classically as the bounce itself is a quantum effect where notions like space and time do no longer apply.

(We should be rather careful as this is work in progress and by no means a well-established fact)
Bernie G
#30
Sep7-11, 12:33 PM
P: 136
To continue on the size of the theoretical radiation ball inside a black hole: The radiation will generate a pressure proportional to density and therefore should have the same density profile as a conventional gas star, varying about as 1/(r^2). The gravitation potentional energy of this density profile is about (2GM^2)/R.

If the results of the viral theorem can be used here (and maybe the viral therom can’t be used here because the supporting energy is always constant here regardless of size), the supporting energy would equal half the gravitational potential energy, or (2GM^2)/2R = (GM^2)/R. If the supporting energy is (1/3)Mc^2, R would equal (3GM)/(c^2), which doesn’t work because R then would be larger than the Schwarzchild radius. I think the most likely value for supporting energy would be (2/3)Mc^2 since the measured value of reflected radiation pressure is (2/3)Mc^2 from laboratory measurements. If the supporting energy is (2/3)Mc^2 and half the gravitational energy is (GM^2)/R, then the radius R of the radiation ball would equal (3GM)/(2c^2).

Note that (3GM)/(2c^2) is 75% of the Schwarzchild radius, which means a large observable burst of radiation should occur when 2 typical 8 solar mass black holes merge. I hope this is confirmed by observation in the future.
Bernie G
#31
Sep8-11, 09:34 PM
P: 136
I'm not terribly happy about the possible calculation above for the size of a theoretical radiation ball inside the Schwarzchild radius. Does anyone have a better simple non-relativistic formula for the radius of a gravitationally formed sphere of Mass M, with a density profile of 1/r^2, and a supporting pressure of (1/3)pc^2 or (2/3)pc^2 or pc^2, where p is the radiation density?
Bernie G
#32
Sep9-11, 12:48 PM
P: 136
Maybe the maximum fraction of energy that can exerted by a neutron to generate pressure is (1/3)Mc^2 or (2/3)Mc^2, and above that a neutron disintegrates.
mjacobsca
#33
Sep9-11, 03:05 PM
P: 98
There are theories for quark stars and preon stars, so why not further degenerate states such as photon-degenerate stars, string-degenerate, etc...? I suppose a photon-degenerate star would technically be a radiation soup as suggested above. But my gut says that the actual center of a black hole is going to be no more interesting than the center of any other degenerate star. No infinity. No wormholes. No baby universes. Just plain old photons/other tiny particle stuck together by gravity with a big old beware-of-danger sign on their front porch. I'm no expert, but it seems a degenerate state of matter beyond from which light cannot escape is simple, logical, and plausible without blowing up physics as we know it.
tom.stoer
#34
Sep9-11, 05:50 PM
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Quote Quote by mjacobsca View Post
There are theories for quark stars and preon stars, so why not further degenerate states such as photon-degenerate stars, string-degenerate, etc...?
There are such theories, i.e. fuzzballs in string theory.

Quote Quote by mjacobsca View Post
Just plain old photons/other tiny particle stuck together by gravity ... but it seems a degenerate state of matter beyond from which light cannot escape is simple, logical, and plausible without blowing up physics as we know it.
The problem is that we do not know any force in nature that is able to stabilize this state. There are indications coming from quantized gravity (strings, loops) that gravity itself could do the job, but this is still work in progress.
Bernie G
#35
Sep10-11, 07:49 AM
P: 136
Yes, the "relativists" say that inside the Schwarzchild radius a photon must have energy greater than mc^2 if it is not to proceed inexorably towards the center. My experience is they do not accept that other forces (such as radiation pressure) can overcome or balance the force of gravity inside the Schwarzchild radius. One possible error in this way of thinking is that just inside the Schwarzchild radius of a large black hole, the gravitational force is much weaker than that just inside the Schwarzchild radius of a small black hole. This might be settled someday if and when the effects of the merger of 2 roughly equal size black holes are observed. If there is a large radiation burst the relativists will not be able to explain it. In the meantime they will give each other praise and awards.
phinds
#36
Sep10-11, 08:10 AM
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Quote Quote by Bernie G View Post
... In the meantime they will give each other praise and awards.
This point of view seems to me to demonstrate a totally unwarrented distain for scientists and the scientific method. Is that in fact how you feel or am I misinterpreting you?


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