Thanks for noticing the pre-print version of the paper. Its only 5 pages and surprisingly not too terribly difficult to follow. From the article:
How does information get out of a black hole? My work with Hartle showed the radiation could be thought of as
tunnelling out from inside the black hole. It was therefore not unreasonable to suppose that it could carry information
out of the black hole. This explains how a black hole can form and then give out the information about what is inside
it while remaining topologically trivial. There is no baby universe branching off, as I once thought. The information
remains firmly in our universe. Iâ€™m sorry to disappoint science fiction fans, but if information is preserved, there is
no possibility of using black holes to travel to other universes. If you jump into a black hole, your mass energy will
be returned to our universe but in a mangled form which contains the information about what you were like but in a
state where it can not be easily recognized. It is like burning an encyclopedia. Information is not lost, if one keeps the
smoke and the ashes. But it is difficult to read. In practice, it would be too difficult to re-build a macroscopic object
like an encyclopedia that fell inside a black hole from information in the radiation, but the information preserving
result is important for microscopic processes involving virtual black holes. If these had not been unitary, there would
have been observable effects, like the decay of baryons.
I gave John an encyclopedia of baseball, but maybe I should just have given him the ashes.
i doubt that passing something through a singularity is a unitary process
Hawking basically states this is a unitary process by what isn’t observed in other quantum effects…i.e. the decay of baryons. I’m not sure if that is really proof or just a strong indication however.