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I get a bit confused seeing where Feynman's many paths fits into the Many-worlds interpretation. Both start off with the fact that there are many possible paths for a particle to take. Then, crudely paraphrasing Feynman's schema, each path will be given a probability amplitude according to the action associated with the path, the amplitudes essentially add up (interfere) until there is one path left, which is the one the particle takes. Yet with the many-worlds interpretation, the path it takes is the one which our world chooses, and in other worlds it may take another path. The two schemata don't seem equivalent to me, so I would enjoy being enlightened. For instance, if, in another "world", the possible paths are the same, and the actions and interference are the same, then if it takes another path than the one prescribed by the minimum action, this would seem to mean that in that other world, the principle of least action does not apply. But I thought the assumption was that in the other worlds the same physical principles apply. The only way out that I can see is that there are several paths who all share the same minimum of the action, and the worlds "choose" amongst them.