Take the tour ×  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?
share|improve this question Well, with topology change in
classical general relativity, a lot of wacky stuff happens. See
arxiv.org/abs/gr-qc/9406053 for example. –  Alex Nelson Jul 29
'12 at 15:46 In what sense do you mean "valid"? They would