Can the firewall be viewed as the holographic boundary? Naively a hologram 3d image can not cross the hologram 2d surface that produces that image. According to the metaphor the boundary - 2d field quantum theory without gravity - could act as a firewall for the enclosed space - 3d string theory with gravity and black holes. Yet information won't be lost by the presence of the firewall, because the digital bits would be just the pixels of that firewall/boundary. Doesn't this settle the paradox of entanglements non-locality with quantum gravity? " we must carefully impose the laws of thermodynamics and/or statistical physics to Maxwell's Demon himself and when we do so, his miraculous abilities to create a paradox evaporate." In the same way I'm asking to impose the boundary S matrix unitarity to the firewall ;-) The entangled partner behind the firewall is then a kind of fictitious hologram according to the Wheeler DeWitt diffeomorphism of quantum gravity, isn't it?

  • $\begingroup$ I'm not one of the downvoters, but I do think the question shows a lack of effort. There is lots of stuff around about firewalls, and if you spent some time working through it you would answer your own question. Much of it is hard of course, but for example Joe Polchinski's talk at youtube.com/watch?v=tEtt4A7WsDg would be a start. $\endgroup$ Oct 29, 2013 at 6:52
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    $\begingroup$ I disagree that someone could answer this question just by studying what experts say about firewalls. It requires some understanding of the holographic principle, maybe the membrane paradigm for black hole event horizons, and other concepts. I will answer if I can think of a reasonable thing to say. $\endgroup$ Oct 31, 2013 at 11:14
  • $\begingroup$ @MitchellPorter: Maybe, but what is the question even asking? The firewall supposedly is at the event horizon, isn't it? $\endgroup$ Nov 1, 2013 at 16:08
  • $\begingroup$ The question is assuming that the firewall is at the event horizon (as an hypothesis) and is asking if one can consider the event horizon as a boundary of the universe. If the answer is no, how can anything cross the firewall? If the answer is yes, so does it mean that a dual theory can describe the GR equivalence in terms of an 'on shell' string theory? $\endgroup$
    – user31807
    Nov 1, 2013 at 16:43
  • $\begingroup$ To be more specific about my last sentence you can refer to the "general covariance" requirement for the Dual Representations in the "DeSitter Entropy,..." as presented by Hawking $\endgroup$
    – user31807
    Nov 1, 2013 at 18:25

1 Answer 1


First we need to discuss what is meant by a boundary.

Consider a rectangular sheet of paper. The boundary of the whole sheet is a rectangle, the edge of the paper. It's where the paper ends.

Now draw a circle on the sheet of paper. The circle is the boundary of a disk-shaped region of paper inside the circle, but the paper doesn't stop there. This boundary has an outside as well as an inside.

The firewall, if it existed, would be like the boundary of the circle. But holographic duality involves the edge of the paper. The dual field theory describes everything on the sheet of paper, not just what happens inside the circle.

  • $\begingroup$ Hmm. I believe the original idea of black hole complementarity was that everything behind the event horizon is dual to degrees of freedom which pile up just outside the horizon, and then get re-radiated. So in the second picture, the Hawking radiation doesn't come from the other side... $\endgroup$ Nov 2, 2013 at 21:14
  • $\begingroup$ If such a picture were true, rather than being an addendum to holographic duality on the boundary, I think it would be just a possible redescription of the "bulk" theory. That is, you wouldn't have a new boundary theory which was defined on "rectangle+circle" (edge of space but event horizon)... $\endgroup$ Nov 2, 2013 at 21:16
  • $\begingroup$ However, I am somewhat skeptical of this picture (original BHC), and very skeptical of firewalls. The recent papers by Papadodimas and Raju look more plausible to me - no firewall, the AMPS paradox is avoided by a nuance of how the boundary theory describes the black hole interior... $\endgroup$ Nov 2, 2013 at 21:20
  • $\begingroup$ But I also liked Mathur's fuzzball concept, which could imply that the black hole is generically an extended object reaching out to the horizon - that even with a giant black hole, the event horizon isn't just homogeneous empty space on either side... $\endgroup$ Nov 2, 2013 at 21:31
  • $\begingroup$ It might be best if we created a room on chat.physics.SE or otherwise had a dialogue about these topics. $\endgroup$ Nov 2, 2013 at 21:38