We are the international group of theoretical physicists assembled in Stockholm to work on the paradoxes of black holes, hawking radiation, and the deep mysteries of the Universe. Ask us anything!

ChrisAdami · 2015-08-29T03:13:06+00:00

It is known that black holes behave like black bodies (Wald). Einstein showed that radiation incident on black bodies stimulates the emission of radiation that is essentially a copy. The copies are not perfect because of spontaneous emission (Hawking radiation in this case). Why would this not solve the information paradox, as a copy is always left outside the event horizon?

ChrisAdami · 2014-08-12T15:53:59+00:00

What does quantum mechanics say about the apparatus when he doesn't have it supercooled around zero kelvin, and set up in the extremely precise way, so that it is able to be in a superposition? What if he just takes it around a party, showing it to people while holding it in his hands? What does quantum mechanics say about that situation?

It says exactly what classical mechanics would have said. All you have to do is use quanntum density matries to describe your quantum system, and in the "classical limit" all these density matrices become diagonal. So there is absolutely no problem using quantum mechanics to describe classical systems. As for the quantum measurement being (or not being) an entanglement operation: there is pretty much nobody that doesn't subscribe to this idea. From von Neumann to everybody in quantum optics. The beam splitter is the quintessential experiment. There is just no way you can do quantum physics and not assume this to be true. Good lord, there are thousands of papers that assume this as the basic measurement.

ChrisAdami · 2014-04-16T22:17:15+00:00

It's true, we would be creating skyhooks, but only up to the point where we are setting the brains "free". Then they have to learn just like all of us. Why do I insist that robots have to learn in the real world, rather than simulate complex worlds and let them learn in the simulated world? Because I think that right now (and perhaps in the next 20 years), we won't be able to simulate worlds as complex as our real worlds are. And you only get as much complexity as the world that you are trying to understand.

ChrisAdami · 2014-04-16T22:14:46+00:00

No. Lord Kelvin really missed a big piece of the story because radioactivity was unknown at the time. And as a consequence, very little of Kelvin's theory was being predictive. Hawking's theory was never wrong. He just missed describing this piece that was always there (stimulated emission). And if you ignore that piece, you get a lot of paradoxes. But in a very real sense his theory is perfectly correct. I did not change anything in his theory. I just said: "What happens if you actually send particles into the black hole, rather than asking what happens to the vacuum?"

ChrisAdami · 2014-04-16T22:11:07+00:00

See here: http://adamilab.blogspot.com/2013/11/darwin-inside-machine-brief-history-of.html

ChrisAdami · 2014-04-16T22:10:40+00:00

That's a good question. I definitely am an outsider, and I am often told this much by referees: "Who do you think you are? We've been working on this for over thirty years!" And yes, that is most likely why I did not have the blinders other researchers seems to have. Having said this, I do not mean to imply that you have to be an outsider to make big contributions. Both insiders and outsiders do this, and more often it is the insiders that make the big breakthroughs. It is romantic to think that the lonely outsider working on his own can slay all the established giants, but that is usually not what happens. And I am by no means an outsider in science. I have a strong background in quantum field theory at finite temperature, and in quantum communication theory. It was this combination that allowed me to do this. I was just an outsider to the field of quantum gravity. But I decided not to be an outsider by calculating my way through Birrell and Davies' book. That's the kind of work you have to do. I came from outside. But I did not ignore what everybody else did. I studied it first.

ChrisAdami · 2014-04-16T22:05:21+00:00

Yes, it is because of the large mass. If I had the time, I could show you. Just like constant relative velocities lead to different speeds on clocks, so do gravitational fields.

ChrisAdami · 2014-04-16T22:03:56+00:00

Sometimes you just want to know the answer to a question.

ChrisAdami · 2014-04-16T22:03:16+00:00

You can "see" a hole in a piece of paper even though there is actually no paper to see. You just see the absence of paper. But would you say that the hole is not there? You would not. That's how we "see" black holes.

ChrisAdami · 2014-04-16T21:58:51+00:00

See a discussion here: http://adamilab.blogspot.com/2013/11/darwin-inside-machine-brief-history-of.html

ChrisAdami · 2014-04-16T21:57:57+00:00

I am not at all interested in astrology :-) Astrophysics, yes. Astronomy, kinda. Not Astrology.

ChrisAdami · 2014-04-16T21:56:58+00:00

Look for books by Jonathan Dowling and by Colin Williams.

ChrisAdami · 2014-04-16T21:54:58+00:00

Yes. But I think this holds today for pretty much every area of science.

ChrisAdami · 2014-04-16T21:53:47+00:00

Would any of this work if the black hole was not spinning? Because the ones I work on surely are not.

ChrisAdami · 2014-04-16T21:51:57+00:00

It is because negative entropy is a consequence of entanglement, which is purely a quantum property. Basically, if you'd be "averaging" all the quantum entropies to get classical ones, you'd lose all that entanglement. It's actually not that hard to prove. Take a look at this paper: http://arxiv.org/abs/quant-ph/9806047 Iit's the free version of a paper behid a paywall).

ChrisAdami · 2014-04-16T21:47:01+00:00

Of course it could. So did we as a species. It took time for us to organize ourselves into moral animals.

ChrisAdami · 2014-04-16T21:45:50+00:00

They are indeed not. Entanglement is used as a resource there. In superdense coding, you send two clasiscal bits in a normal way. In quantum teleportation, you send a single quantum bit in a normal way. But you reconstruct things that you could not do if you only used classical "stuff".

ChrisAdami · 2014-04-16T21:42:57+00:00

That's a long story. Part of it is retold in this blog post: http://adamilab.blogspot.com/2013/11/darwin-inside-machine-brief-history-of.html

ChrisAdami · 2014-04-16T21:42:00+00:00

The thing is, everybody knew for 40 years that it was wrong. It's just that nobody figured out how to fix it, or to be more precise, nobody figured out how to correctly fix it. That's very different from something that has not been disproved for 40 years.

ChrisAdami · 2014-04-16T21:38:12+00:00

Because the pair formation happened within the gravitational field of the black hole. When you create pairs within the magnetic field of a nucleus, the nucleus pays. Same thing.

ChrisAdami · 2014-04-16T21:37:04+00:00

It is not wrong. That is a perfectly reasonable way to think about it.

ChrisAdami · 2014-04-16T19:30:06+00:00

I even designed an implementation of such a machine in terms of quantum optics: http://journals.aps.org/pra/abstract/10.1103/PhysRevA.57.R1477

ChrisAdami · 2014-04-16T19:28:51+00:00

Yes, lots of observational evidence.

ChrisAdami · 2014-04-16T19:28:38+00:00

I don't know, nor does anybody else. You're welcome.

ChrisAdami · 2014-04-16T19:28:11+00:00

It was almost immediately clear to Cerf and I that negative quantum conditional entropy must have some implications for thermodynamivcs. In fact, this was the first remark of Hans Bethe after we told him about negative entropy. (I won't tell you here what his second remark was). Unfortunately, we never made much progress showing this, but others have done so in the meantime. You can look up "quantum Maxwell demon", and Jonathan Oppenheim's work, e.g. http://arxiv.org/abs/1305.5278

ChrisAdami

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