Looks like Stephen Hawking has left us a great paper to ponder … Are there traces of other universes to be found in cosmic background radiation?
“The usual theory of inflation breaks down in eternal inflation. We derive a dual description of eternal inflation in terms of a deformed CFT located at the threshold of eternal inflation. The partition function gives the amplitude of different geometries of the threshold surface in the HartleHawking state. Its local and global behavior in dual toy models shows that the amplitude is low for surfaces which are not nearly conformal to the round three-sphere and essentially zero for surfaces with negative curvature. Based on this we conjecture that the exit from eternal inflation does not produce an infinite fractal-like multiverse, but is finite and reasonably smooth.”
If you understand German, here’s a recap.
If you are intersted in the holographic principle, read this.