It is well known that nothing can escape a black hole, including gravitational radiation. Many questions have been asked here about this topic, such as:
- Can gravitational waves escape a black hole?
- Can we detect gravitational waves generated from inside the event horizon of a black hole?
- Can gravitational waves escape from inside of black holes?
- How does gravity escape a black hole?
and they all have the same answer. Gravitational radiation cannot propagate faster than the speed of light.
On the other hand, it also seems to be generally agreed that if an Alcubierre drive is physically possible, one can theoretically use one to escape a black hole. (Could a ship equipped with Alcubierre drive theoretically escape from a black hole?)
Now an Alcubierre drive is essentially just a particular spacetime metric. You don't even need negative energy density to make one. In particular, it was recently shown that one can construct a superluminal soliton solution in general relativity using only positive energy densities.
Connecting these ideas, it seems that it should be possible, in principle, to fall through the event horizon of a black hole; construct an Alcubierre spacetime by manipulating a collection of very massive objects; and escape the event horizon with information from inside the black hole. Then my question is: where is the line between gravitational waves and Alcubierre spacetimes? Could there be other Alcubierre-like metrics that do not contain a full warp bubble, but still allow information to escape from a black hole?