Here one has to be very careful with the proof of such a multiverse picture, because, as usual, we replace the observed averaging of outcomes of experiments repeated in time in our world by the squared modulus of the (normalized) amplitude interpreted as the probability of our world which effectively means averaging over an ensemble of parallel worlds, whose number since the birth of the universe may be infinite.
The explanatory idea is there, but even in the 2025 paper it still looks underdeveloped. I don’t understand this very well, so I can’t give more details.
If you only have unitary evolution, you end up with superpositions of the form
|system state 1> |pointer state 1> + |systems state 2> |pointer state 2> + … + small cross-terms
Are you proposing that we ignore all but one branch of this superposition?
My favorite point origins of Born’s rule of view is the following. The final state is a superposition, but we are all inside it.
And since these two states are orthogonal, state 1⟩ does not see 2⟩, and vice versa; God only knows.
The works by Zurek (https://arxiv.org/pdf/1807.02092) and the more recent one (https://arxiv.org/html/2209.08621v6) shed more light on this.
Here one has to be very careful with the proof of such a multiverse picture, because, as usual, we replace the observed averaging of outcomes of experiments repeated in time in our world by the squared modulus of the (normalized) amplitude interpreted as the probability of our world which effectively means averaging over an ensemble of parallel worlds, whose number since the birth of the universe may be infinite.
The explanatory idea is there, but even in the 2025 paper it still looks underdeveloped. I don’t understand this very well, so I can’t give more details.