Originally posted by finneganA lot of those possibilities are to all intents and purposes the same. The genuinely different ones are:
If we live in a multiverse, then we still cannot interact with any other universe than our own. Without interaction, arguably we do not live in a multiverse. We live only in our own universe.
A lot depends of course on which type of multiverse you refer to here.Summary of Various Versions of Parallel Universeshttps://www.goodreads.com/review/show/223950966?book_show_action=true&page=1
1. Quilted Multiverse: Conditio ...[text shortened]... l equations.
A) Inflationary driven cosmological life-death-rebirth (1, 2, 5) (1) just has the universe big to start with which the evidence seems to be against.
B) Brane-world scenarios where there's more than one brane (3, 4, 7) - the holographic variant is the same idea in different setting.
C) (6) is Everett's many universe interpretation for quantum theory, there are problems with the idea such as why something we think of as discrete (a universe) should have a measure associated with it.
D) (8) Simulated universes are basically out of the question. What the people who invent these things quietly ignore is that to simulate a physical system faithfully one needs a Qubit for each particle, so the computer simulating our universe would have to be in a universe significantly bigger than our one as it would need to contain a computer as big as our one.
E) (9) Maybe, we can't really rule this one out, but it's of no interest since it doesn't affect this universe. There's no reason the number of disconnected universes shouldn't be infinite.
A and B are the most reasonable, it depends on physics beyond the standard model. C depends on an interpretation of quantum theory which I personally don't believe. D is just bunk. E is metaphysics.