wavefunction collapse? My (layman's) understanding is that the Many Worlds theory is just an explanation for why quantum mechanics appear non-deterministic, (that they actually are deterministic, just that branching universes are created for each outcome and our experiential continuum is in only one of them) rather than the assertion that they are non-deterministic.
But "wavefunction collapse" is an ill-defined, non mathematical concept that will not stand the test of bigger and bigger quantum systems. See my more elaborate comment above.
