On Mon, Apr 11, 2022 at 4:23 PM smitra <smi...@zonnet.nl> wrote: > On 10-04-2022 06:53, Bruce Kellett wrote: > > On Sun, Apr 10, 2022 at 2:13 PM smitra <smi...@zonnet.nl> wrote: > > > > The simplest way to counter your assertions is to provide a simple > > counterexample. Consider the standard Alice/Bob setup, with up/down > > results coded as 1/0. According to MWI, on each trial, Alice splits, > > one copy recoding |1> and the other copy recording |0>. After N > > trials, there are 2^N copies of Alice, with records consisting of all > > possible binary sequences of length N. If Bob is spacelike separated > > and independent, he also splits into 2^N copie, consisting of all > > possible binary sequences of length N. > > > > When Alice and Bob meet (or exchange trial results), each copy of each > > splits into 2^N copies, one for each copy of the other party. So for > > Alice, each copy of Aice with some binary sequence of results, splits > > into 2^N copies, one for each of Bob's sequences. Now say, for > > example, that Alice and Bob both happen to have the same polarizer > > setting for the 10th trial, so that for trial 10, their polarizers are > > parallel. Since there are copies of Alice for all possible results for > > trial 10, there is an Alice with result |1> for this trial, and a > > different Alice with result |0>. Now each Alice splits according to > > all possible copies of Bob. So the Alice with result |1> meets a Bob > > with result |0> for the same trial. That is OK according to quantum > > mechanics. But by the rules of MWI, there is also a copy of Alice with > > result |1> who meets a Bob who recorded |1> for the 10th trial. > > No, there is no such copy. MWI = QM without collapse, and it's known > that MWI yields the same predictions as QM with collapse. >
You have a very unusual understanding of MWI. Look at a good textbook on the subject, such as David Wallace's "The Emergent Multiverse". He certainly states that there are four copies of each observer on each trial in this situation. When a measurement of spin is made, each observer splits, and the rest of the universe splits with them (including the other observer when they become included in the forward light cone of the event). So when Alice measures her particle, she splits into "Alice saw up" and "Alice saw down". Bob splits in the same way when he makes his independent measurement. When their future light cones overlap, each independently gets caught up in the splitting caused by the measurement made by the other. The result is four branches (copies), namely: "up-up" up-down' "down-up" and "down-down". The challenge is that only the "up-down" and "down-up" branches agree with QM when the polarizers are parallel. This is simple logic applied to the rules of MWI, so the QM-violating "up-up" and "down-down" branches certainly exist in strictly local MWI. The only way you are going to get rid of them (since they are unphysical and not observed) is by invoking a non-local interaction at the source of the measurement. Bob's measurement depends non-locally on the result of Alice's measurement (or vice versa for a different time order). The only alternative is a messy elimination of these branches at the time of light cone overlap. And there is no such interaction known to physics, or the experiments. In fact, if all that is exchanged is the actual numerical results, the permanent local records still exist, so changing the results at the time of overlap doesn't actually solve the problem. > > This > > contradicts QM, in fact it violates angular momentum conservation, so > > no such Alice/Bob coupling is possible. But, by following the rules of > > local MWI, such a pairing is inevitable. What is more, there will be > > many more pairings that conflict with the predictions of QM than there > > will be pairings that comply. > > > > The challenge for the local account of the Bell correlations in MWI > > is: What happens to all these incorrect couplings? There is clearly > > one correct matching for each Alice copy. She is bound to meet this > > since she meets all possible Bob sequences. But there are 2^N of > > these, and only one is strictly correct (though, since correlations > > are probabilistic, there will probably be some additional number of > > near misses). In general, this leaves 2^N-1 bad couplings for each > > copy of Alice -- (2^N)*(2^N -1) bad pairings that have to be got rid > > of somehow. MWI offers no mechanism for removing these bad pairings. > > > > Those incorrect couplings never arise in the first place. They are an > artifact of using your Straw Man version of the MWI. > There is no straw man version of MWI here, except that of your making. If you believe in your version of MWI, tell me what prevents the formation of these incorrect couplings in your (local) model. You always duck this and related questions, so I know that you are fraudulent in this matter. Bruce -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/everything-list/CAFxXSLSg1uumpL%3DuksmKnBJ-zeKjtmB6DVJJ%2BrpoqUPyM8s7Cw%40mail.gmail.com.
