According to Transhumanist Terminology
, this is akin to a Basement Universe
, which, briefly, means it's an artificially created universe
linked to another with a wormhole
The uses for these are amazing, anything from controlling overpopulation, escape from a dying universe, hiding from your ex-wife, whatever.
The theory seems to have came from some thoughts w/r/t black holes.
Stephen Hawking had a book called Black Holes and Baby Universes.