Famous Hawking Black Hole Bet Resolved?

Mick Ohrberg writes "In 1997 the three cosmologists Stephen Hawking, Kip Thorne and John Preskill made a famous bet as to whether information that enters a black hole ceases to exist -- that is, whether the interior of a black hole is changed at all by the characteristics of particles that enter it. It now looks like Stephen Hawking and Kip Thorne may owe John Preskill a set of encyclopedias of his choice, since physicists at Ohio State University 'have 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.'"

Comments

Hawking radiation

[Space cowboy]

Steven had posited in the 70's that the black holes leak (Hawking radiation), but the paradox is that they radiate a 'black-body' spectrum (entirely thermal radiation) in inverse proportion to their mass (so as they get smaller, the radiation increases). The problem here is that all the information went in, but it's very difficult to infer information from a black-body radiated spectrum (!). Steven therefore thinks that information is lost forever.

The article though is a bit hand-wavy over why the information is preserved in this new theory... (I guess Nth dimensional maths doesn't appeal to the reporter :-). I don't think the fact that the string-theory radius matches the black-hole radius is sufficient to prove the case, though it's an interesting pointer, a curious coincidence if indeed it is such ...

Effectively this is a conjecture - if the strings continue to exist, then they'd have the same size as the black hole appears to have. The throwaway statement " That means a black hole can be traced back to its original conditions, and information survives." seems a bit of a stretch though :-)

Simon

Re:Hawking radiation

[CAlworth1]

IANATP (theoretical physicist), but I think I may be able to shed a bit of light on the last question.

As I understand it, the idea is that the particle and the anti-particle come into being at the same place, moving in different dirrectsion, and the anti-particle is more prone to being pulled in somehow due it its being the opposite of the other mass in the black hole. The particle escapes, generating the black-body radiation, and the anti-particle enters the black whole and collides with a corresponding particle, leaving existance as the original particles came into existance - messed up I know.

If anyone is curious, (stolen from The Universe in a Nutshell by Stephen Hawking, the temp of a black hole is

Temp = (h * c^3)/(8 * pi * k * G * M)

where h is planck's constant, c is the speed of light, G is Newton's gravitational constant, k is Boltzman's costant,T is temp, and M is the mass of the black hole.

Re:Hawking radiation

[nihilogos]

The article though is a bit hand-wavy over why the information is preserved in this new theory...

The abstract from the NPB article is

• 
  It has been found that the states of the 2-charge extremal D1-D5 system are given by smooth geometries that have no singularity and no horizon individually, but a `horizon' does arise after `coarse-graining'. To see how this concept extends to the 3-charge extremal system, we construct a perturbation on the D1-D5 geometry that carries one unit of momentum charge P. The perturbation is found to be regular everywhere and normalizable, so we conclude that at least this state of the 3-charge system behaves like the 2-charge states. The solution is constructed by matching (to several orders) solutions in the inner and outer regions of the geometry. We conjecture the general form of `hair' expected for the 3-charge system, and the nature of the interior of black holes in general.
  

If your institution is a subscriber you can get the full text from here

Re:Hawking radiation

[ralphclark]

Because the escapeing particle was never in the event horizon to begin with, it can contain no information from within the black hole.

Except that the pair of virtual particles are an entangled pair and if one catches the escaped one and measures its quantum state, one then knows the quantum state of the one that fell in. Catch enough of them and you know about an appreciable fraction of the black hole (in theory!)

Now, how the black hole doesn't gain mass from the anti-particle I'm not quite sure

The energy that was used to create the virtual pair came from the black hole's gravitational field, thus robbing the hole temporarily of mass. For each "virtual" particle that escapes as Hawking radiation, that mass is lost permanently so the mass of the hole goes down, over time. Now remember that this loss can only happen at the event horizon; if the black hole is very large, the tidal force (the gravity gradient) at the event horizon will be weak and thus the rate of particle loss will be very low. For very small black holes the tidal force at the event horizon will be enormous and almost all virtual pairs close to the boundary will separate in this way.

So large black holes will simmer coldly, shrinking only with glacial slowness if at all, and small ones will be hot and shrink very rapidly indeed - finally disappearing altogether in an brief, intense burst of radiation, according to Hawking's theory.

Re:Hawking radiation

[krlynch]

Now, how the black hole doesn't gain mass from the anti-particle I'm not quite sure...

The black hole doesn't gain mass, because the particle that fell in has negative energy. Remember, you can't create energy from nowhere, but you can "borrow" some from the vacuum temporarily ... that's where the virtual pairs come from. They borrow energy from the vacuum, which they have to give back after a time (roughly) Delta T < hbar/E, where E is the energy of the particle pair.

Now, if one half of the pair falls across the event horizon, it isn't coming back. The particle that escapes the hole becomes "real" because it has no one to annihilate with, so it carries off energy E/2. But since you can't yank energy out of the vacuum indefinitely, the particle that fell in had to be carrying energy -E/2 ... which isn't a problem, because it isn't a "real" particle, so it's energy need not be consistent with your expectations from freshman physics.

So, where does that energy E/2 that goes into the escaping particle come from? The only place it can: the black hole. Remember, a negative amount of energy fell in. So the hole has to lose some mass in the process. Which is why we say that the black hole "emits" particles.

The mathematical details are, of course, much nastier than that, but that's the gist of things...

Re:Hawking radiation

[rpresser]

You misunderstand.

A particle and an antiparticle both have a positive mass. The "virtual particle" mechanism means that for periods of times short enough, the measurement of the space right outside the hole is uncertain enough that there "might" be a pair of antiparticles there. So they are there. While they're there, one of them falls into the hole - it doesn't matter which one - while the other gains potential energy from its mate falling in, and escapes. Yaay.

But you can't get something from nothing. Some mass escaped from the vicinity of the hole, so some mass has to disappear from the vicinity of the hole. So the hole loses mass.

How's that for handwavy?

Re:Simple question maybe

[benna]

Why not consult Official String Theory Web site :)

Re:status of string theory

[Anonymous Coward]

Responding as I am taking a string theory course from Prof. Zwiebach here at MIT ...

String theory certainly does predict a number of things that are easily testable ... just not right now. For instance, compactified extra dimensions (as SR includes) introduce additional energy terms to simple quantum problems (i.e. "particle in a box" problems, and SHOs). The problem is that these effects are very large; ergo, the energies necessitated to test these theories are somewhat higher than we can accomplish.

Yes, it's a theory, yes it's kinda off-the-wall and feels a bit contrived, but, studying it, I gotta say that it's pretty if nothing else. It's elegant enough and compelling enough - in terms of what it promises to explain - that it's worth following until it's found to actually be wrong.

A quantum theory of gravity might not be so motivating to you, but if you're a physicist, it's worth trying something wonky to get to it. (Speaking of which, Quantum Loop Gravity - also very wonky - is awesome).

And, as for "quite a few people" finding it too philosophical ... well, quite a few people aren't physicists. *shrugs*

Re:Is it me

[wass]

ike they're so determined to make something make sense, they blindly look for something that'll fit the problem, even if it's obvious that it's probably not right

I actually recently responded to a similar accusation against physicsists, and you can read my reply here . That response has more examples listed of 'kludges' in physics, but I'll talk about a few in more depth in this post.

What you've just described is known as phenomenology. In other words, trying to come up with some sort of basic theory to match the given data. Examples include Planck's original quantizing of radiation into discrete quanta, which turned out to be right. Another example is the Landau theory of 2nd-order phase transitions, where one builds a power-series expansion of the free energy in powers of something called the 'order parameter'. This is a total hack, but in many cases can adequately describe phase transitions (including superconductivity).

In fact, there are many kinds of physics theories, some termed 'macroscopic' in which case they're phenomonoligical, and describe what's going on, but don't adequately describe the 'physics' of the system. Then there's the microscopic theories that talk specifically about particle interactions, and follow directly from quantum mechanics, statistical mechanics, E&M, etc. The goal is to make these two approaches mesh.

For example, superconductivity could be described fairly well using the Ginzberg-Landau expansion, where the order parameter described above is complex, instead of real. Many things can be described this way, including Josephson Junctions and fluxoid quantization of superconducting loops. (Ginzberg just won the Nobel Prize in physics in 2003. Landau, if he were still alive, would have probably won it too, and it would have been his 2nd physics nobel prize). This approach worked fairly well, but physicists weren't sure why that was.

But then in 1957 Bardeen/Cooper/Schrieffer came up with the BCS theory of superconductivity, which explicitly describes how the electrons can pair up into Cooper pairs. Electrons want to repel, but in the right crystal lattice an electron-phonon-electron interaction (ie, a local distortion of the lattice) can produce an attractive interaction. BCS describe how this attraction comes about, how the energy gap forms, and how the electron pairs can carry a resistanceless supercurrent. BCS won the Nobel Prize in Physics in 1972.

This was microscopic vs macroscopic development of superconductivity. Two years later, physicist Gor'kov was able to show that the Ginzberg-Landau theory comes as a limiting case of the BCS theory. Hence, microscopic meets macroscopic, and everybody's happy.

So yes, physicists do look for something to fit the problem, but they don't just stop there. They also try to make those hacks or kludges match up directly from physical laws of the universe. That's what physics is about.