Is many-worlds a local theory?
The simplest way to see that the many-worlds metatheory is a local theory is to note that it requires that the wavefunction obey some relativistic wave equation, the exact form of which is currently unknown, but which is presumed to be locally Lorentz invariant at all times and everywhere. This is equivalent to imposing the requirement that locality is enforced at all times and everywhere. Ergo many-worlds is a local theory. Another way of seeing this is examine how macrostates evolve. Macrostates descriptions of objects evolve in a local fashion. Worlds split as the macrostate description divides inside the light cone of the triggering event. Thus the splitting is a local process, transmitted causally at light or sub-light speeds. (See “Does the EPR experiment prohibit locality?” and “When do worlds split?
