What theorem would be violated if there is communication between the different branches? I read branches could be just possibilities.. so it's not hard for there to be communications between the possibilities. It is when you try to imagine the branches as worlds that you would find it hard to imagine for there to be communications. but it seems more of a category error... It's just like saying part of the cpu processing in your computer (the pipeline) are located in different worlds and so there is huge barrier between them. But if you think of them as possibilities like many do.. then it's no problem. But what theorem forbids the communications between branches...do you see it as like engenstates already formed and so there should be no communcations between the eigenstates? But what if the eigenstates have not yet formed.. it is because you assume the branches are eigenstates of the global superposition that you think they are separate already but if the eigenstates are like possibilities then they could still intermingle.