Below is the first paragraph of a blog post by Zeeya Merali about a recent paper by Alexander Vilenkin about the possibility of black holes containing inflating universes.
It’s hard to say what’s the most exciting element of this
new paper on parallel universes, the inflationary multiverse, and black holes, by Tufts cosmologist (and FQXi member) Alex Vilenkin and colleagues. Is it the idea that black holes hide baby universes inside them — inflating their own spacetimes — connected to our universe by wormholes? Could it be that, according to the authors, astronomers may soon be able to find evidence to confirm this crazy notion? Perhaps it’s the fact that this paper could be presenting the first way to find definitive evidence that an inflationary multiverse of parallel worlds exists. Oh yes, and the authors also say that such black holes could have seeded supermassive black holes — the origin of which remains a mystery — *and*, in some of the scenarios they’ve looked at, they could comprise dark matter, the invisible stuff that makes up most of the matter in the universe.
Phew! No wonder the paper by Vilenkin along with Jaume Garriga, at the University of Barcelona, and Jun Zhang also at Tufts, is almost 50 pages long! (”Black Holes and the Multiverse”
arXiv:1512.01819v2.)