Check out this article by Max Tegmark:http://arxiv.org/pdf/0905.1283.pdf
Just sayin....this is how parallel universes and the multiverse are actually done in practice by theoretical physicists.
I found the fly in the ointment with this. The existence of other universes is irrelevant. The reason is that the other universes have no effect on our universe, and have never had any effect. The initial conditions in this universe are not determined or even related to the initial conditions of another universe, since the theory claims they are random. They cannot effect us and we cannot effect them, so their existence is irrelevant.
And I have a whole bunch of questions about that paper. Max's explanation of a level I multiverse begins AFTER the big bang. But, the possibility of a multiverse is based on the idea that before the big bang you had this empty space with random quantum fluctuations, and somehow some set of those fluctuations created the initial conditions of our universe, and initial conditions of the others. The BB didn't create more than one universe as it too was based on a single set of initial conditions. But it seems that Max is saying that a Level I MV is just our universe so I'm confused what a Level I MV is. And why would the I.C.'s be the same for all universes?
I think the multiverse theory is nothing more than starting with the concept of "we don't know" and then creating a theory that makes it ok that we don't know. Normally, a scientific theory as developed in order to explain, as yet unexplained, behavior. But the multiverse theory seems to be going in the reverse direction, trying to find behavior to match the completely imagined theory.
I'm not saying that I know for a fact that there is no multiverse but we must have a sound basis for theorizing such a thing. At the very least this is a not fully formed theory. And if there is a multiverse, so what? How does it relate to I.D.?