false to stable vacuum transition [closed]

if the universe transitioned from a meta-stable vacuum to a stable vacuum we assume a universal death scenario. However since it cannot propagate faster than the speed of light, from any particular starting point, the universal expansion has crossed an intrinsic "event horizon" so how can this actually happen in any conceivable time scale?

also - cheeky extra question - could energy rich galaxies dislocate in some way from energy poor regions of spacetime

• Since what cannot propagate faster than light? Also, what is an "energy rich galaxy", and what does it mean to dislocate from a region of spacetime?
– pela
Nov 23 '17 at 15:01

In an accelerating expanding universe like our current $\Lambda$CDM cosmology future lightcones actually have a finite radius as measured by co-moving coordinates (e.g. from the perspective of matter moving passively with the expansion of the universe). Beyond a certain (current) distance there are galaxies that will never be reached by a light signal we send now - when it gets to the distance they currently have they will have moved much further away, and it never manages to close the gap. Same thing for vacuum decay: the front will always expand outward at lightspeed, but large parts of the observable universe will expand away so fast that it will never catch up with them.