Haggard and Rovelli against the Eddington principle

[Demystifier]

In a new paper
http://lanl.arxiv.org/abs/1407.0989
Haggar and Rovelli offer a new solution to the black-hole information paradox, by proposing a time-symmetric scenario in which black hole tunnels into a white hole.

I think the main problem with this proposal is violation of the second law of thermodynamics. Of course, to resolve the information paradox, it is very likely that we should violate some of the otherwise well-accepted physical laws. But whatever this law-to-be-violated might be, the Eddington principle tells that it shouldn't be the second law.

What is the Eddington principle? Let me quote:
"If someone points out to you that your pet theory of the universe is in disagreement with Maxwell's equations—then so much the worse for Maxwell's equations. If it is found to be contradicted by observation—well these experimentalists do bungle things sometimes. But if your theory is found to be against the second law of thermodynamics I can give you no hope; there is nothing for it but to collapse in deepest humiliation."
Sir Arthur Stanley Eddington

 

[Haelfix]

There are a lot of problems with this sequence of papers and I believe they are more appropriate for something from the 1980s.

The remnant models they consider generically violate the equivalence principle at the horizon. That would be ok, there are many models that do this in some sense or the other, but they do need to do some work at trying to alleviate the concerns of relativists about how to solve the violence done to the causal structure of spacetime as a whole.

They unfortunately don't bother to address any of the historical concerns with remnants (and there are many of them). Like the quantum nucleation and renormalization problems, the thermodynamic instabilities and ultimately the apparent loss of unitarity that seems to occur b/c the thermal radiation still ends up in a mixed state.

They presumably don't believe in the explicit examples of matrix models or ads/cft and more generally holography is violated in such a remnant scenario (violation of various entropy bounds)..

I think the biggest problem I have is the complete lack of a semiclassical treatment and the failure to really address the central lesson of the recent firewall papers and ensuing discussion. Namely, I want to know where effective field theory fails, I want to know how it fails. I want a careful microphysics explanation about Alice and Bob and their entanglement entropy, I want to see the evolution of their descriptions throughout every stage of the black holes lifetime and eventual bounce and I want to see an explicit construction of the operators involved as well as to see the source of Hawking area formula. Which cherished principle of physics are we giving up if any (this paper seems to suggest that we need to abandon GR, locality, quantum mechanics and stat mech)

 

[marcus]

In a new paper
http://lanl.arxiv.org/abs/1407.0989
Haggar and Rovelli offer a new solution to the black-hole information paradox, by proposing a time-symmetric scenario in which black hole tunnels into a white hole.
...

Thanks for pointing to the paper! They essentially present a toy model sketch of an idea here, which could be worked out in more detail.

I don't see that it has enough structure to allow one to talk, at this point, about entropy. They explicitly say they are not including features like that in the toy model. As a first approximation to make it easy to calculate, they assume everything is time-reversible.

So your thread title is kind of ridiculous, isn't it Demy? To validate it you yourself would have to develop their idea, include more detail, make it more complete and realistic, and THEN see if it was incompatible with 2nd Law. In their toy model they don't even have matter. They don't have anything with mass, falling in. Just a shell of LIGHT going in and then expanding out, or something slightly more general than such a shell.

 

[Chronos]

I'm tempted to raise the Fermi objection here [where are they?], but, like a Planck star, the answer appears to be the universe is still too young for any white holes to emerge. This work is, of course, little more than a mathematical curiosity until a testable prediction emerges. On the other hand, it is fair to note that you have to start somewhere. GR did not just fall out of the sky. Einstein had to toy with and assemble it piece by piece. And it still had some subtle defects in its original form. It is not unreasonable to expect a working theory of quantum gravity will suffer similar birthing pains. Figuring out which of the 'mathematical curiosities' that have emerged from quantum gravity research will prove vital is quite the challenge. Will some obscure post doc be the one to solve the puzzle? That would be ironic.

 

[MTd2]

In a new paper
I think the main problem with this ...e universe heats more with the output energy.

 

[Demystifier]

Thanks for pointing to the paper! They essentially present a toy model sketch of an idea here, which could be worked out in more detail.

I don't see that it has enough structure to allow one to talk, at this point, about entropy. They explicitly say they are not including features like that in the toy model. As a first approximation to make it easy to calculate, they assume everything is time-reversible.

So your thread title is kind of ridiculous, isn't it Demy? To validate it you yourself would have to develop their idea, include more detail, make it more complete and realistic, and THEN see if it was incompatible with 2nd Law. In their toy model they don't even have matter. They don't have anything with mass, falling in. Just a shell of LIGHT going in and then expanding out, or something slightly more general than such a shell.

But if we are dealing with an open system, the 2nd law doesn't necessarily apply. It's like the the white hole is a fridge but the universe heats more with the output energy.

You are making good points, perhaps my objection was too hasty. But still, the question of the second law in a realistic scenario of this type is certainly a potential problem that needs to be explored.