Black hole final state

If you're more interested in the illusion of Intelligent Design, you can read this interview with Lenny Susskind who has his predecessor on his T-shirt. ;-) As the reviewer of the Cosmic Landscape at amazon.com wrote, this book has certainly energized God.

Eva Silverstein and Gary Horowitz have submitted an interesting paper that extends the research of the tachyons in cosmology and their impact on topology of spacetime. We talked about these things in the article about the theory of nothing.

One of the potentially far-reaching consequences of Eva's and Gary's paper is that they seem to have found some stringy realization of the black hole final state by Horowitz and Maldacena. Recall that Horowitz and Maldacena try to explain the information loss paradox semiclassically by saying that the information is not lost in the Schwarzschild singularity because all matter converges to a unique state near the singularity - the black hole final state. This is why no information really "crosses" the spacelike singularity inside the Schwarzschild.

In some sense, the matter propagates outside the black hole before it falls in. Then it continues inside the black hole to the singularity, bounces off the singularity because the unique black hole final state translates the incoming states into outgoing states. Then the matter propagates backward in time inside the black hole before it reaches the horizon and transforms into Hawking radiation that escapes to infinity. As you can see, the arrow of time is heavily violated near the singularity because normally we are only allowed to define initial states, not final states. Unitarity is preserved in the picture above because everything evolves with "time" in a unitary way except that this "time" goes back and forth in the real time, in some sense.

Preskill and Gottesman argued that once the interactions are taken into account, unitarity will be lost in the Horowitz-Maldacena picture anyway because the two Hilbert spaces of matter inside the black hole - that are used for the incoming and reflected matter, respectively - are no longer decoupled. These interpretations of the picture are due to your humble correspondent, but I believe that they capture the points of both papers.

Horowitz and Silverstein now argue that in perturbative CFTs with some tachyons, the black hole final state can be given quite an explicit form.

Because we talked about the information loss issues, I should also mention that tonight, David Lowe and Larus Thorlacius propose a plausible description of non-local effects in gravity that are small enough not to violate causality measurably but sufficient to preserve the information.