Hawking resolves black hole information paradox

Source:
- http://in.rediff.com/news/2004/jul/15hawking.htm

[size=+1]Hawking resolves black hole riddle[/size]

July 15, 2004 15:34 IST

After nearly 30 years of arguing that a black hole destroys everything that falls into it, Stephen Hawking is saying he was wrong.

In an announcement that has sent waves of excitement through the rarefied world of astrophysics, Prof Stephen Hawking claims to have solved one of the greatest mysteries of black holes, reports the Telegraph, London.

The new theory, which solves a major paradox about the most mysterious objects in the universe, has generated a flurry of excitement among his Cambridge colleagues, the Telegraph said.

'Black holes are regions of space where the gravitational force is so strong that nothing, not even light, can escape. Once thought to be purely destructive forces, they are now thought to play a crucial role in galaxy formation. Cosmologists believe that there are many types of black hole, ranging from mini holes with the mass of a small mountain to super-massive holes that lie at the centre of galaxies,' it said.

Their gravitational force is so powerful that everything is sucked inside. It was traditionally thought that once matter and light pass a black hole's "event horizon", then it can never escape.

'In 1975, Prof Hawking made his most important contribution to cosmology by proposing that black holes emit tiny amounts of radiation - known as "Hawking radiation". Eventually, all black holes will evaporate. He also claimed that his radiation contained no "information" about the matter sucked into the black hole,' said the article.

Once the black hole evaporates, all information about the black hole is lost. But under the laws of quantum mechanics describing the behaviour of the universe at the scale of individual particles, such information cannot simply disappear, the Telegraph said.

'For 30 years Prof Hawking tried to get around the paradox by suggesting that the rules of quantum physics were different inside black holes - a solution that many colleagues were unhappy with,' the article said.

Now, it seems that Hawking has an answer to the conundrum and the physics community is abuzz with the news. Hawking requested at the last minute that he be allowed to present his findings at the 17th International Conference on General Relativity and Gravitation in Dublin, Ireland on Wednesday, said the New Scientist.

"He sent a note saying 'I have solved the black hole information paradox and I want to talk about it'," New Scientist quotes Curt Cutler, a physicist at the Albert Einstein Institute in Golm, Germany, who is chairing the conference's scientific committee, as saying.

"I haven't seen a preprint [of the paper]. To be quite honest, I went on Hawking's reputation."

 

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Great. Hawking finally finds a problem in his own thought experiment (that that few ever really thought would have physical consequences). And that amounts to news.

 

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Black holes have so far been information killers. If Hawking can reverse this we might get a law of conservation of information..

 

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gj, Hawking.

 

I don't like that this is getting pre-publication press.
Even wheelchair-bound popular-author physicists should go through publication and peer review before doing press releases.

Shades of Pons and Fleischmann...

 

The thing is Pete, the Internet is classed as Publication and Peer review can actually now be performed online (like banking, Auctions and pretty much most things nowadays)

 

The thing is, it hasn't been published or peer reviewed.

 

Hehe,
and another solution to the problem of information loss has already been formulated...

Remember the `fuzzyblackhole theory` a few months ago?

An elegant theory that uses `superstrings` to conserve the information...

Oh well...

 

I agree. I'm not an expert on peer review or anything, but I see no reason why Hawking should be allowed any leeway in the process. He has become the darling of the press and this could easily cause problems. Science is science. Sell books on your own time, Mr. Hawking.

 

The problem has been known for a while, and it had unsavory consequences. It's a good thing it's finally resolved.

Hmm, good point. Strange I didn't even think of that.

Got a link?

I might point out that the Internet allows for a greater number of peers to review ones work...

 

Hum,
can`t find the link ...


A proposed solution is to use string theory, a theory that holds that all particles in the universe are made of tiny vibrating strings. Latest research has derived an extensive set of equations that strongly suggest that the information continues to exist -- bound up in a giant tangle of strings that fills a black hole from its core to its surface. The finding suggests that black holes are not smooth, featureless entities as scientists have long thought.

Instead, black-holes are stringy “fuzz balls.”
This won’t particularly surprise hawking and Thorne.
In their wager, Hawking, professor of mathematics and Thorne, professor of theoretical physics, bet that information that enters a black hole is destroyed, while Preskill -- also a professor of theoretical physics at Caltech -- took the opposite view. The stakes were a set of encyclopaedias.

“<i>I think that most people gave up on the idea that information was destroyed once the idea of string theory rose to prominence in 1995, It’s just that nobody has been able to prove that the information survives before now.</i>”

In the classical model of how black holes form, a super massive object, such as a giant star, collapses to form a very small point of infinite gravity, called a singularity. A special region in space surrounds the singularity, and any object that crosses the region’s border, known as the event horizon, is pulled into the black hole, never to return. In theory, not even light can escape from a black hole.

(hehe, basically it so small that all the information is squeezed out)

The diameter of the event horizon depends on the mass of the object that formed it. For instance, if the sun collapsed into a singularity, its event horizon would measure approximately 3 kilometres (1.9 miles) across. If Earth followed suit, its event horizon would only measure 1 centimetre (0.4 inches). As to what lies in the region between a singularity and its event horizon, physicists have always drawn a blank, literally. No matter what type of material formed the singularity, the area inside the event horizon was supposed to be <b>devoid</b> of any structure or measurable characteristics. And therein lies the problem.
The problem with the classical theory is that you could use any combination of particles to make the black hole -- protons, electrons, stars, planets, whatever -- and it would make no difference. There must be billions of ways to make a black hole, yet with the classical model the final state of the system is always the same. That kind of uniformity violates the quantum mechanical law of reversibility. Physicists must be able to trace the end product of any process, including the process that makes a black hole, back to the conditions that created it. If all black holes are the same, then no black hole can be traced back to its unique beginning, and any information about the particles that created it is lost forever at the moment the hole forms. Nobody really believes that now, but nobody could ever find anything wrong with the classical argument, either. We can now propose what went wrong.
In 2000, string theorists named the information paradox number eight on their top-ten list of physics problems to be solved during the next millennium. That list included questions such as “what is the lifetime of a proton?” and “how can quantum gravity help explain the origin of the universe?”

When you compute the structure of objects that lie in-between simple string states and large classical black holes. Instead of being tiny objects, they turned out to be large. The picture of a “fuzz ball” continued to hold true for objects more closely resembling a classic black hole.
According to string theory, all the fundamental particles of the universe -- protons, neutrons, and electrons -- are made of different combinations of strings. But even as tiny as strings are, they can form large black holes through a phenomenon called <b>fractional tension</b>. Strings are <i>stretchable</i>, but each carries a certain amount of tension, as does a guitar string. With fractional tension, the tension decreases as the string gets longer.
Just as a long guitar string is easier to pluck than a short guitar string, a long strand of quantum mechanical strings joined together is easier to stretch than a single string. So when great many strings join together, as they would in order to form the many particles necessary for a very massive object like a black hole, the combined ball of string is very stretchy, and expands to a wide diameter. The derived formula for the diameter of a fuzzy black hole made of strings is found to <b>match</b> the diameter of the black hole event horizon suggested by the classical model.
The conjecture suggests that strings continue to exist inside the black hole, and the nature of the strings depends on the particles that made up the original source material, then each black hole is as unique as are the stars, planets, or galaxy that formed it.
<i>The strings from any subsequent material that enters the black hole would remain traceable as well</i>.
That means a black hole can be traced back to its original conditions, and information survives... !

which i suppose is the same as what hawkings is about to announce...that an object falling into a black-hole somehow `changes` the singularity so that the information is `recorded` and eventually radiated away with "Hawking radiation"...er, but without the strings...

<b>OR</b>

A recent idea provides an <b>alternative</b> to black hole singularities is that matter is transformed into a spherical void surrounded by "an extremely durable form of matter known as a `<b>gravastars</b>`...

This would also get around the problem of the tremendous entropy, or information, that a black hole would hold .
So, theory holds that a black hole should have a billion, billion times more entropy sometimes referred to as states, than the star it formed from. Gravastars do not have this problem, as their entropy is very low, and basically <i>sidestep</i> to contradiction known as the “information paradox.”
The matter inside a gravastar would be akin to the <b>Bose-Einstein condensate</b>. It would exist in a vacuum, surrounded by an ultra-thin, ultra-cold, ultra-dark bubble, hence the name gra (vitational) va (cuum) star, or gravastar.

Decisions, decisions, decisions....

 

I think the first theory sounds more plausible. I'd like to see what Hawking thinks though.

 

Err .. just a note. If the laws of conservation (of information or whatever else) does not exist why can we point to black holes. I believe Hawkings has come to the same conclusion.

 

blobrana

If Heat cannot escape a BH then what will be its average temperature and at what temperature will it explode if it can.

 

Sry,
i should have said what `Hawkings radiation` was (it BTW has never been seen)...

Basically, `Virtual particle pairs` are constantly being created in `empty` space....and if they happen to be created near the horizon of the black hole, then one of them can fall in...
Normally, they are created as a <b>particle-antiparticle pair</b> and they quickly annihilate/cancel each other out; so obviously, if one fell into the BH then it's not possible for the other one to `cancel out` , in which case the other one manages to escapes as Hawking radiation.

The particle that fell into the BH is still virtual and must restore its `conservation of energy` by giving itself a <i>negative</i> mass-energy.
The black-hole cancels this negative mass-energy and loses some of it's total Mass and shrinks...
(well that's the simple version anyway)

The black-hole Mass (solar masses) radiates like a `blackbody` with a temperature of
(6 x 10^-8/Mass) Kelvin,
with the total lifetime of a black hole Mass of about:
10⁷¹ Mass³ seconds

< added >
Whoops, sry , my suspect maths...
http://en.wikipedia.org/wiki/Hawking_radiation
For a better answer...
< /added >


Perhaps Hawking will suggest, at the Dublin meeting on the 22^nd, that the virtual particle inside the BH can affect it's `partner particle` (er, with some spooky action at a distance/quantum-entanglement) to transfer the `information` (conserve) back to the rest of the universe...

 

That's a brilliant idea!
Someone should have thought of that sooner... like me.

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Hum,
well i can only speculate...for now...

Sounds a bit of a simple a solution to me as well, (if it is) ; anything that smears out the event horizon with superpositional/entangled particles to extract the `information` shouldn`t have taken him 30 years to figure out....

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Anyone else with other possible solutions?

 

The escape of information from a black hole by quantum entanglement of the Hawking
Radiation was proposed by Gary Horowitz and Juan Maldaccana in a paper entitled
'The Black Hole Final State' published in 2003. Here is a comment on the paper by
Gottesman & Preskill published earlier this year:
http://arxiv.org/PS_cache/hep-th/pdf/0311/0311269.pdf

I am not sure Hawking's proposal is going to reflect this same mechanism though. An
excerpt that is beyond my level of understanding:
" The information paradox for black holes

The Euclidean path integral over all topologically trivial metrics can be done by time slicing and so is unitary when analytically continued to the Lorentzian. On the other hand, the path integral over all topologically non-trivial metrics is asymptotically independent of the initial state. Thus the total path integral is unitary and information is not lost in the formation and evaporation of black holes. The way the information gets out seems to be that a true event horizon never forms, just an apparent horizon.
http://www.dcu.ie/~nolanb/gr17.htm

 

Hum,
tnx for that link, i was unaware of that paper...
I'll peruse that one later.

And yes, i suppose that it's difficult to imagine that Hawking would go over the same ground again...Hum...but how many other ways are there to retrieve the information?

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< Back to square one.... >



< added >
Ahh, found the pdf !
http://ernie.ecs.soton.ac.uk/opcit/cgi-bin/pdf?id=oai:arXiv.org:hep-th/0310281
< /added >

 

blobrana,
thanks for the explanation. but still, the information coming out of the black hole must maintain the information that entered. In other words, there must be a mechanism which attaches what comes out to what goes in. Regardless, I'm still perplexed by the problems created by assuming all physical processes can be run in reverse.

Quote:
" One of the great paradoxes is modern physics which often gets swept under the rug is the "collapse" postulate in quantum mechanics, where a quantum wavefunction "collapses" when it is observed by an outside observer. But the collapse postulate is not reversible like all the rest of physics! This is one clue that this particular interpretation of Quantum needs an overhaul, but cosmologists often avoid thinking about it by taking the entire universe as their quantum wavefunction. That way, they figure, there's no "outside" observer to collapse anything, and everything stays reversible. (This is somewhat sketchy, because I think it's evident that something HAS collapsed the universe or it would look very different than it does. But this is getting off-subject...) "

Ref: http://www.madsci.org/posts/archives/jun99/930428671.As.r.html

The concept of the conservation of information assumes we can reverse all physical processes including wavefunction collapses. But can we? Does Hawkings need to address this also? Or is he simply going to show one can reverse the process of black hole evaporation to obtain the information that entered the black hole?