Max Tegmark has put these ideas into a hierarchy of multiverses, where universes outside of the boundary of the observable Universe are a Type I multiverse, and

Max Tegmark has put these ideas into a hierarchy of multiverses, where universes outside of the boundary of the observable Universe are a Type I multiverse, and the many-worlds of the relative-state formulation form a Type III multiverse. http://space.mit.edu/home/tegmark/crazy.html http://space.mit.edu/home/tegmark/crazy.html