Yes, and that’s why it made sense for us to make this abstraction.
With regards to bell’s theorem, the issue is that even in MWI, which is local, there’s still the whole thing that if you are randomly orienting a polariser, you either do it based on some quantum mechanical ‘randomness’, MWI style, or it was predetermined. You don’t have agents deciding with their immaterial souls which way to turn polarizer. It doesn’t work like decision theory where agent can decide to turn polarizer randomly, or to turn it at specific angle. There’s causes to agent’s decision. It is very difficult to reason about this stuff.
edit: to expand on that. What happens in the bell’s theorem experiment (the simplest one where you have two photons go into two polarizers and onto detectors) under MWI, is that distribution of photon angles get emitted, it hits the polarizers, resulting distribution of the detector states has the probability of agreement proportional to cosine of the angle between polarizers. Under MWI that happens as in the end when observers talk with each other they fork each other changing the perceived probabilities of events that ‘already happened’, resulting in a huge mess where it is very difficult to show how did the probabilities emerge (not sure there is a satisfactory account of that yet, even). While the MWI may be most compact, it surely is not most computationally efficient; it is much more computationally efficient to drop the belief in causality and accept the result that the agreement is proportional to cosine of angle between detectors, as a fact that you don’t derive from some causal explanation—you just observed it (and duly noted that angle of one detector has to affect results on the other detector for there to be such correlation). And indeed that is how most humans operate.
The causality is something we came up with to be able to reason easier; there’s no need to hold onto it when it doesn’t make problems easier.
The differential equations are time-reversible, but the boundary conditions (ridiculously low entropy in the past) aren’t.
Yes, and that’s why it made sense for us to make this abstraction.
With regards to bell’s theorem, the issue is that even in MWI, which is local, there’s still the whole thing that if you are randomly orienting a polariser, you either do it based on some quantum mechanical ‘randomness’, MWI style, or it was predetermined. You don’t have agents deciding with their immaterial souls which way to turn polarizer. It doesn’t work like decision theory where agent can decide to turn polarizer randomly, or to turn it at specific angle. There’s causes to agent’s decision. It is very difficult to reason about this stuff.
edit: to expand on that. What happens in the bell’s theorem experiment (the simplest one where you have two photons go into two polarizers and onto detectors) under MWI, is that distribution of photon angles get emitted, it hits the polarizers, resulting distribution of the detector states has the probability of agreement proportional to cosine of the angle between polarizers. Under MWI that happens as in the end when observers talk with each other they fork each other changing the perceived probabilities of events that ‘already happened’, resulting in a huge mess where it is very difficult to show how did the probabilities emerge (not sure there is a satisfactory account of that yet, even). While the MWI may be most compact, it surely is not most computationally efficient; it is much more computationally efficient to drop the belief in causality and accept the result that the agreement is proportional to cosine of angle between detectors, as a fact that you don’t derive from some causal explanation—you just observed it (and duly noted that angle of one detector has to affect results on the other detector for there to be such correlation). And indeed that is how most humans operate.
The causality is something we came up with to be able to reason easier; there’s no need to hold onto it when it doesn’t make problems easier.