Ordinary quantum mechanics does not predict that the world splits, no more than does ordinary probability theory.
The zigzag interpretations are entirely relativistic, since the essence of a zigzag interpretation is that you have ordinary space-time with local causality, but you have causal chains that run backwards as well as forwards in time, and a zigzag in time is what gives you unusual spacelike correlation.
A “quantum causal history” (see previous link) is something like a cellular automaton with no fixed grid structure, no universal time, and locally evolving Hilbert spaces which fuse and join.
These three ideas—many worlds, zigzag, QCH—all define research programs rather than completed theories. The latter two are single-world theories and they even approximate locality in spacetime (and not just “in configuration space”). You should think about them some time.
Ordinary quantum mechanics does not predict that the world splits, no more than does ordinary probability theory.
The zigzag interpretations are entirely relativistic, since the essence of a zigzag interpretation is that you have ordinary space-time with local causality, but you have causal chains that run backwards as well as forwards in time, and a zigzag in time is what gives you unusual spacelike correlation.
A “quantum causal history” (see previous link) is something like a cellular automaton with no fixed grid structure, no universal time, and locally evolving Hilbert spaces which fuse and join.
These three ideas—many worlds, zigzag, QCH—all define research programs rather than completed theories. The latter two are single-world theories and they even approximate locality in spacetime (and not just “in configuration space”). You should think about them some time.