A question about black holes

[Equilibrium]

I recently read about the Information Theory and i think it said something about how information cannot be destroyed. But if matter falls into a black hole, doesn't it become wiped out from existance? Also black holes seem to be breaking the Law of Conservation too. I remember something about the string theory involved but i need some clarification here please.

[MRlogic]

well we dont know anything about a black hole except it large amount of gravity.

 

for all we know it does destroy everything from existance or it could be a passage to another part of the universe since there have been reports of white hole or it could lead to another dimension or even another universe

[ajb]

Your question is the black hole entropy problem.

 

So Hawking showed that black holes radiate and that this radiation is thermal. So it contains no information about what the black hole is made of or what fell in.

 

As black holes have a temperature, they should have an entropy. It is known that this entropy is given by one quarter the surface area of the black hole, in sensible units. (Note surface area and not volume.) Entropy from temperature is the thermodynamics or macroscopic view of black holes. So it is natural to think of states somehow being associated with the surface of a black hole, this is the statistical mechanics or microscopic view of black holes. However, the no-hair theorem does not give us any classical candidates for doing so.

 

The solution (or one solution) is string theory which does provide us with the necessary states, but if I recall this is not immediately very intuitive. Anyway, you can then calculate the entropy and temperature of a black holes using statistical mechanics.

 

The big question here is what happens to a black hole when ends its evaporation? Maybe information is truly lost, or maybe there is some remnant left behind or maybe the information get put back in the universe in one last flash or maybe something else? No one really knows.

 

well we dont know anything about a black hole except it large amount of gravity.

 

That statement can be refuted. Quite a lot is know about black hole solutions in general relativity. However, there are still plenty of open fundamental questions particularly relating to the nature of the singularity.

[imatfaal]

This question has taxed the greatest minds - Stephen Hawking and Kip Thorne had a long running and public bet with John Preskil on whether information was lost or maintained (hawking said lost, preskill maintained.) Hawking has paid up and he now believes that the information is retained within the universe. I don't believe the solution has been found yet; although a group claimed to have done so a few years back.

[between3and26characterslon]

I have just been watching something to do with this.

 

Hawking initially said that information was destroyed

 

Susskind (and others) said that the information was not lost, as it would violate a fundamental principle of physics, rather it was smeared over the surface of the event horizon

 

Hawking eventually admitted (after 30 years) that he was wrong, and the others were wrong too, but now believes that the information is retained in universes where the black hole does not exist. I don't think there is any proof for this yet though.

[imatfaal]

3-26,

I think Hawking originally said that the information was retained in new black holes in baby universes - but has retreated from that position and now believes that the information is retained within this universe. Susskind, I think, was responsible for the string theory development that AJB referred to.

[ajb]

Susskind, I think, was responsible for the string theory development that AJB referred to.

 

Some Speculations about Black Hole Entropy in String Theory, L. Susskind, arXiv:hep-th/9309145v2, 1993.

 

I think it was Strominger and Vafa who first understood the role of branes and the BPS condition here.

 

Microscopic Origin of the Bekenstein-Hawking Entropy, A. Strominger, C. Vafa, Phys.Lett.B379:99-104,1996 (also so available as arXiv:hep-th/9601029v2 )

 

When I find time I will have a look into it

[Equilibrium]

I know i watched something about this but i can't recall. I know this will sound rather dumb but i remember something about the information being "recorded" on a kind of "holographic film" on the edge of the universe, which seems stupid. Dont trust what i said though because there's a high percentage that it is wrong

[ajb]

I know i watched something about this but i can't recall. I know this will sound rather dumb but i remember something about the information being "recorded" on a kind of "holographic film" on the edge of the universe, which seems stupid. Dont trust what i said though because there's a high percentage that it is wrong

 

The holographic principle. It seems to be an important feature of quantum gravity.

 

For example, notice the information about a black hole is encoded in the surface area and not the volume. The physics of the black hole is described by physics on the surface.

 

Very much related to this is the AdS-CFT correspondence. Gravity in the bulk can be described by a conformal field theory on the boundary.

[pioneer]

The answer to the black hole information question only takes a little common sense. Say you had a cloud of hydrogen gas in space, that become a star due to gravity. The information in the original hydrogen gas cloud will change, since the material information will be compressed, heated, fused and mixed with new forming higher atom information. If we keep compressing due to gravity, we can get a neutron star. Now the information of the original hydrogen is totally gone, since all we have are neutrons. From those neutrons you can not tell the original composition (information) of that star, since any composition will end as run of the mill neutron density.

 

Where the confusion comes from, is gravity not only alters space-time, but gravity also creates pressure, with this pressure creating phase changes. If the laws of physics are the same in all reference, altering space-time alone will not cause phase changes. Only my watch will appear to slow down. It is the pressure aspect of gravity that causes phases and information changes. What we have in the contracted space-time reference in the center of a star is a pressure phase shift from the chemistry of hydrogen into nuclear physics. If we extrapolate from the neutron star to the blackhole, a point singularity means any form of information ends up as the same singular information bit. Hawkings was originally correct, but was swayed by lack of common sense.

Edited October 22, 2010 by pioneer

[lemur]

The answer to the black hole information question only takes a little common sense. Say you had a cloud of hydrogen gas in space, that become a star due to gravity. The information in the original hydrogen gas cloud will change, since the material information will be compressed, heated, fused and mixed with new forming higher atom information. If we keep compressing due to gravity, we can get a neutron star. Now the information of the original hydrogen is totally gone, since all we have are neutrons. From those neutrons you can not tell the original composition (information) of that star, since any composition will end as run of the mill neutron density.

Excuse me if this question is naive, but what basis is there to assume that neutrons cannot fuse further under certain conditions? I am very interested in what basis there is to assume such a thing as maximum mass-density exists. I could imagine that black-holes are able to convert matter into pure gravitation by reducing all particles into a volume-less center-point in a pure gravitational field. Is this impossible for some reason?