are bubbles of spacetime pinching-off allowed solutions to general relativity? With "pinch-off bubble" i really mean a finite 3D volume of space whose 2D boundary decreases until it reaches zero and it disconnects from the mother spacetime, becoming a compact "child" spacetime
I've read this as a way in eternal cosmologies to produce new universes, but i don't know if that is something something allowed in general relativity or is something from a more advanced theory (i.e: string theory)
In particular, unlike unitary black holes, this does not seem to conserve information, unless someone believes that complementarity can do strange things as clone the information (including the quantum one). Does that automatically make this an unphysical solution?