Black Holes & Firewalls: Recent Papers

[PAllen]

As I understand it, the time dimension inside a black hole is alway pointed directly to the singularity. So objects that fall inside a BH can only travel with some component of their velocity pointing towards the center. In other words, you can non travel in any direction with a component pointing outwards, you must always have some component inward. I think this means that no object can travel tangentially to the center. So you will ever see objects coming from the side, only from the rear.

Some of this is just peculiarities of the way Schwarzschild coordinates label things. Geometrically, you can say that all forward going timelike curves reach the singularity (in more complex black holes than the spherically symmetric, this is not necessarily true - some can escape to other 'sheets' of the manifold). It is true that you cannot have a time like path remaining on a 2-sphere of constant area around the singularity [ take this a definition of pure tangential motion]. However, you can have tangential components, such that infallers can collide before reaching the singularity.

As for seeing, if you have luminous dust falling in from all radial directions, an ifnaller will see light from all spatial directions until they reach the singularity. What is unusual is that light seen from toward the singularity was actually emitted from a dust particle as of when it was further from the singularity than you are now. You receive it from the direction of the singularity because you 'bump' into the light as it slowly moves inwards, though emitted in an outward direction. Despite this, all looks normal (sufficiently locally). A key point to keep in mind: no matter how extreme the near singular region, a sufficiently small chunk of spacetime behaves just like Minkowski spacetime - this is part of the fundamental definition of a pseudo-riemannian manifold.

 

[audioloop]

Just had a thought about that. An infalling observer to outsiders appears to and "" at the . But compared to the radiation at the , this may seem like a burning fire. Or am I missing something?

Hence the term...


-----
Guest Post: Joe Polchinski on Black Holes, Complementarity, and Firewalls
http://blogs.discovermagazine.com/c...on-black-holes-complementarity-and-firewalls/
...The idea is that an observer falling into a black hole, contrary to everything you would read in a general relativity textbook, really would notice something when they crossed the event horizon. In fact, they would notice that they are being incinerated by a blast of Hawking radiation: the firewall...



-----
...or the information is lost
(or the unitarity is lost, option gaining attention now)

This is what I thought. To for the time compression in relation to the infinity, the hawking radiation should go to infinite, that is, it would burn fast. So, isn't it an argument supporting fast scramble interpretation?

right

Almheiri, Marolf, Polchinski, Sully, arXiv:1207.3123: You hit
a firewall at the horizon if t > O(R log R) (scrambling time)

 

[PAllen]

It doesn't seem to have been pointed out that you can say that this new physics at the horizon does not apply to our universe until heat death. All existing black holes (stellar or galactic) are 'new' in the sense of the firewall papers until CMB radiation has fallen far closer to absolute zero; only then do the BH's even start losing mass to Hawking radiation. Then they must lose some significant amount of mass before proposed firewalls occur. This would be orders of magnitude times the age where all stars have burned out.

Note, this observation is related to 'old' being the Page time. This is what is most strongly argued in the Polchinski et.al. paper. However, they argue that very likely the criterion is the scrambling time. The above observation does not apply if this is true.

 

[sshai45]

Note, this observation is related to 'old' being the Page time. This is what is most strongly argued in the Polchinski et.al. paper. However, they argue that very likely the criterion is the scrambling time. The above observation does not apply if this is true.

So does this mean that any black hole existing now would have a firewall? I find this intriguing, since it seems to be suggesting that general relativity starts to fail even sooner than one may think, in that it starts to fail right at the event horizon, well before the singularity.

 

[PAllen]

So does this mean that any black hole existing now would have a firewall? I find this intriguing, since it seems to be suggesting that general relativity starts to fail even sooner than one may think, in that it starts to fail right at the event horizon, well before the singularity.

Yes, that would be the consequence if Polchinski et.al. are right about firewalls forming in scramble time.

 

[S.Daedalus]

Actually I prefer Bousso's statement that the cloning paradox and entanglement paradox don't exist at all(http://arxiv.org/abs/1207.5192). No observer can see both of the qubits, so it does not contradict no cloning principle. This is the 'observer complementarity'.

Continuing what is apparently en vogue for this topic, Bousso has 'completely rewritten' his paper, from "Observer Complementarity Upholds the Equivalence Principle" to now "Complementarity Is Not Enough", apparently now considering his earlier argument 'naive'.

 

[S.Daedalus]

Hm, there's a new paper by Andrew Hamilton -- "Illusory horizons, thermodynamics, and holography inside black holes" -- which does not address the firewall issue directly, but might nevertheless be relevant: he argues for an 'illusory horizon', which is the horizon an infalling observer continues to see 'below' himself, even after crossing the 'true' horizon. This horizon is the one where the infalling observer sees the Hawking radiation being emitted. He only 'reaches' this horizon upon reaching the singularity. This seems to suggest that either there is no necessity for a firewall, or, if there still is, the infalling observer only encounters it at the singularity. But I haven't really thought about this much (and it's not my field at any rate).

 

[Sourabh N]

It seems a popular assumption -- "Consider a black hole that forms from collapse of some pure state" (quoted from the AMPS paper). I don't see an obvious reason for this though. Can someone explain this or direct me to one?

 

[audioloop]

http://www.nature.com/news/astrophysics-fire-in-the-hole-1.12726

"Polchinski admits that he thought they could have made a silly mistake. So he turned to Susskind, one of the fathers of holography, to find it. “My first reaction was that they were wrong,” says Susskind. He posted a paper stating as much8, before quickly retracting it, after further thought. “My second reaction was that they were right, my third was that they were wrong again, my fourth was that they were right,” he laughs. “It’s earned me the nickname, ‘the yo-yo,’ but my reaction is pretty much the same as most physicists’.”

Since then, more than 40 papers have been posted on the topic in arXiv, but as yet, nobody has found a flaw in the team’s logic. “It’s a really beautiful argument proving that there’s something inconsistent in our thinking about black holes,” says Don Page, a collaborator of Hawking’s during the 1970s who is now at the University of Alberta in Edmonton, Canada."

"here is another option that would save the equivalence principle, but it is so controversial that few dare to champion it: maybe Hawking was right all those years ago and information is lost in black holes. Ironically, it is Preskill, the man who bet against Hawking’s claim, who raised this alternative, at a workshop on firewalls at Stanford at the end of last year. “It’s surprising that people are not seriously thinking about this possibility because it doesn’t seem any crazier than firewalls,” he says"

 

[Ben Niehoff]

As someone who works on fuzzballs, I have to point out that being incinerated at the horizon does NOT necessarily violate unitarity. It just means that one's degrees of freedom are being violently reorganized.

 

[audioloop]

Black hole horizons and Quantum information
21-29 March 2013. CERN.
http://indico.cern.ch/conferenceOtherViews.py?view=standard&confId=222307

An Apology for Firewalls
Speaker: Joseph Polchinski (KITP)
http://indico.cern.ch/getFile.py/access?contribId=10&resId=1&materialId=slides&confId=222307

Comments on black hole interiors
Speaker: Juan Maldacena (IAS Princeton)
http://indico.cern.ch/getFile.py/access?contribId=11&resId=0&materialId=slides&confId=222307

Quantum Mechanics vs. the Equivalence Principle
Speaker: Raphael Bousso (LBL Berkeley)

...

 

[jacophile]

Hi, can someone help me understand the firewall idea?

I have a heuristic understanding that the firewall is created due to breaking entanglement between particles (virtual particles?) inside the EH and old Hawking radiation that emanated from the BH previously.

I don't understand how the entanglement problem arises. They seem to be saying that all particles "in" the BH are entangled with previous Hawking radiation. They then say that a recent Hawking radiated particle must be entangled with its anti-pair that falls inside the EH.

So far so good...

The problem seems to be that the new particle is also entangled with previous radiation. Why?

The new particle is generated outside the EH not inside it where the previously entangled particles are.

So why is the newly created particle entangled with old radiation?

I know that the particle pair explanation is a heuristic analogy but whatever is going on, it's outside the EH and therefore not associated with previous radiation surely?

Judging from the previous post this is a very trivial and huristic view of the postulated system but can someone explain it to me in these terms?

 

[tade]

I believe the answer lies in entanglement.

 

[jacophile]

Care to elaborate?
My question is about entanglement so yep, I'm sure the answer is too...

 

[tade]

Care to elaborate?
My question is about entanglement so yep, I'm sure the answer is too...

At first I thought the photons due to Hawking radiation were entangling with one another through some kind of holographic manifestation. Though now that I think about it, it sounds highly unlikely.

 

[audioloop]

http://www.scientificamerican.com/article.cfm?id=black-hole-firewall-paradox

“To me it’s the best thing that’s happened in awhile,” says University of California, Berkeley, physicist Raphael Bousso of the so-called “black hole firewall paradox,”

Polchinski and his colleagues conclude that not only is space not smooth at a black hole horizon—at that point the laws of physics completely break down. Instead of an unobtrusive boundary, the scientists argue that there must actually be a sharp division they call a firewall. “The firewall is kind of a wall of energy—it could be the end of spacetime itself,” Polchinski says. “Anything hitting it would break up into its fundamental bits and effectively dissolve.”

But physicists have also assumed that information can never be destroyed. The new work says those two ideas are mutually incompatible. “It’s a paradox because several things we believed were true can’t all be true,” -----
SPOTLIGHT LIVE: FALLING INTO A BLACK HOLE
http://www.kavlifoundation.org/science-spotlights/spotlight-live-falling-into-black-holes.

 

[PAllen]

We should note in this thread the latest two papers by a pair of (string) theorists who have been consistently arguing against BH firewalls:

http://arxiv.org/abs/1310.6334
http://arxiv.org/abs/1310.6335

Not sure why this line of papers (these are latest in a series going back to shortly after the AMPS paper) has gotten little attention. These arguments seem broadly consistent with the recent Maldacena/Susskind questioning of firewalls.

 

[atyy]

Andreas Karch's What’s Inside a Black Hole’s Horizon (which I came across via Lubos Motl's blog post) includes favourable comments on the first in the series of papers by Papadodimas and Raju which PAllen linked to.

 

[Haelfix]

We should note in this thread the latest two papers by a pair of (string) theorists who have been consistently arguing against BH firewalls:

http://arxiv.org/abs/1310.6334
http://arxiv.org/abs/1310.6335

Not sure why this line of papers (these are latest in a series going back to shortly after the AMPS paper) has gotten little attention. These arguments seem broadly consistent with the recent Maldacena/Susskind questioning of firewalls.

They are well known in the field, and are taken very seriously. The current state of confusion involves dissecting exactly what is or is not generic. Currently ER=EPR and the A in Rb ideas (like the above) seem to involve special counterexamples, but whether the situation always holds in general is still murky.

 

[bcrowell]

Andreas Karch's What’s Inside a Black Hole’s Horizon (which I came across via Lubos Motl's blog post) includes favourable comments on the first in the series of papers by Papadodimas and Raju which PAllen linked to.

Can anyone explain more about the content of this article? It seems to be an attempt to water down Marolf and Polchinski's recent paper http://arxiv.org/abs/1307.4706 for nonspecialists, but it doesn't seem watered down enough for me to understand. He loses me in the first paragraph:

Marolf and Polchinski presented arguments, now reported in Physical Review Letters [1], suggesting that there is no well-defined quantum mechanical calculation that could predict the outcome of the in-falling observer’s measurement.

Why would we expect to have a calculation that could predict the outcome of this measurement? Don't we expect it to be random?

 

[Haelfix]

I think he means that it would be inconsistent to write down the state vector as |Alive> + |Dead> as seen by an infalling observer which the equivalence principle would naively seems to suggest. Instead it would be some horrible mix with all the scrambled degrees of freedom from the black hole and there is no quantum mechanical framework that would accurately predict the state vector for that type of experiment..

In a sense, a firewall is the complete excision of region II in a Kruskal diagram, the singularity is essentially moved right to the horizon..

 

[Demystifier]

A quote from the conclusion of the Marolf-and-Polchinski PRL paper:
"One may feel that all of these arguments are indirect,
based on logical deduction from general principles rather
than a concrete realization of quantum gravity in the bulk;
the same can be said of most of the literature arguing for or
against the firewall. Thus, we believe that a central lesson
is that, while gauge-gravity duality is a powerful tool, it is
not as complete a description as might have been believed,
and there is a gap to fill in the current understanding of
quantum gravity, even in anti–de Sitter spacetime."

 

[PAllen]

Can anyone explain more about the content of this article? It seems to be an attempt to water down Marolf and Polchinski's recent paper http://arxiv.org/abs/1307.4706 for nonspecialists, but it doesn't seem watered down enough for me to understand. He loses me in the first paragraph:



Why would we expect to have a calculation that could predict the outcome of this measurement? Don't we expect it to be random?

Note that the second of the two links I posted above claims to refute this paper's conclusions.

 

[MTd2]

Note that the second of the two links I posted above claims to refute this paper's conclusions.

But as Haelfix said, it is dificult to figure out what is general or not. For exmple, they suppose the existence of a superobserver which can both see inside or outside the black hole. They state it in the conclusion. And in the introduction, they say they give up background independence for local operators.

With this thing, they can build state dependent Operators, such that one inside and other outside can commute.

I am not sure if this is a fair approximation for the problem in hand. It sounds like there is a kind of operator that somehow is godlike and can trample GR.

 

[atyy]

But as Haelfix said, it is dificult to figure out what is general or not. For exmple, they suppose the existence of a superobserver which can both see inside or outside the black hole. They state it in the conclusion. And in the introduction, they say they give up background independence for local operators.

With this thing, they can build state dependent Operators, such that one inside and other outside can commute.

I am not sure if this is a fair approximation for the problem in hand. It sounds like there is a kind of operator that somehow is godlike and can trample GR.

I don't think that's the generalizability issue of the Papadodimas and Raju papers. In their first paper, their construction was used on the eternal AdS black hole. The ER=EPR paper was also similarly special.

There should be a godlike view of the situation, which is different from the low energy experiments the infalling observer can do. That seems reasonable. The surprising thing is that the infalling operators may have to be state dependent. In Mathur's viewpoint, he has long proposed the the fuzzball structure shouldn't be seen by "macroscopic" observer. I think the technical questions are how to construct the interaction of the macroscopic observer, and also what is the fuzzball picture for an evaporating black hole?

Also, couldn't giving up background independence for local operators be more background independent in the GR sense? If the local operators depend on the background, it is analogous to how in GR you cannot specifiy the matter configuration independently of the background.

 

[audioloop]

I think he means that it would be inconsistent to write down the state vector as |Alive> + |Dead> as seen by an infalling observer which the equivalence principle would naively seems to suggest. Instead it would be some horrible mix with all the scrambled degrees of freedom from the black hole and there is no quantum mechanical framework that would accurately predict the state vector for that type of experiment...

fully concur.




.

 

[audioloop]

Maldacena-Susskind, any entangled state is just an Einstein-Rosen brigde, Locality saved then.and:

http://physics.aps.org/articles/v6/115
"As Maldacena and Susskind recently explained, nonlocality issues could also be reconciled [5]. They postulate that thermal Hawking radiation, as it is emitted from the black hole, remains connected to the inside of the black hole by microscopic wormholes. These wormholes allow signals from the outside observer to immediately pop up inside the black hole, but not vice versa. While Marolf and Polchinski argue against this scenario, they admit that it may be consistent if one allows for a state-dependent identification between observers. And as we’ve seen, this state-dependent identification seems to be inevitable if one wants to avoid firewalls via complementarity anyway.

It is my view that state dependence is much easier to accept than the ad hoc introduction of firewalls. But the work of Marolf and Polchinski delivers a key message: one will have to accept either state dependence or firewalls as an integral part of quantum mechanics in the presence of black holes.".

 

[Haelfix]

Yet another characteristically beautiful paper on black hole Firewalls by Susskind. This reads as somewhat of a review of recent arguments, but it really sharpens a lot of the confusion and argumentation from the firewall conference at KITP in August. I find the sections on precursor states and its generalizations really satisfying.

http://arxiv.org/abs/1311.3335

 

[audioloop]

Yet another characteristically beautiful paper on black hole Firewalls by Susskind. This reads as somewhat of a review of recent arguments, but it really sharpens a lot of the confusion and argumentation from the firewall conference at KITP in August. I find the sections on precursor states and its generalizations really satisfying.

http://arxiv.org/abs/1311.3335

thanks for the paper.

read this

http://news.sciencemag.org/physics/2013/12/link-between-wormholes-and-quantum-entanglement



.

 

[audioloop]

Cool horizons for entangled black holes
http://arxiv.org/abs/1306.0533


then firewalls or cool horizons ?


http://data1.whicdn.com/images/32508178/broken-doll-fire-horror-terror-Favim.com-231939_large.gif

 

[PAllen]

When you've done all you want with your life, you can go and find out. You will have no trouble keeping the answer secret.

 

[audioloop]

very deep secret...


...lol...

 

[PAllen]

I guess the horizon firewall concept is slowly evaporating...

 

[Demystifier]

I guess the horizon firewall concept is slowly evaporating...

If the BH horizon evaporates, there is no doubt that it does so very slowly. But how slowly? As argued in
http://lanl.arxiv.org/abs/1311.4363
perhaps even slower than usually thought.