The Born Rule in Many-Worlds

  • #151
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That's where Bell enters to tell you there is indeed problem with locality so in the end you need nonlocality.
Not if everything is predetermined/superdeterministic. Bell himself commented on this loophole several times.
 
  • #152
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Not if everything is predetermined/superdeterministic. Bell himself commented on this loophole several times.
Right, let me clarify, I didn't mean that kind of hard determinism when I used the example of a common cause. Common causation doesn't even necesarilly always imply determinism.
In any case it was the first example that came to mind, I wasn't implying that it was the explanation of nonlocality.
 
  • #153
gill1109
Gold Member
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That's where Bell enters to tell you there is indeed problem with locality so in the end you need nonlocality.
Bell told us in "Bertlmann's socks" that there were four possible *alternative* diagnoses of the "problem" and only one of them was "locality". Moreover his list wasn't even exhaustive. There is also "Bell's fifth position" namely that no-one will ever be able to create the initial conditions to create a successful loophole-free Bell-CHSH type experiment - because of quantum uncertainty principles ie because of QM.
http://arxiv.org/abs/quant-ph/0301059
OK other people have other opinions. I am just reporting John Bell's own logical analysis. He made clear that from a logical point of view, all options were wide open.

He had his own personal preference or opinion - ie he wanted a local hidden variables theory, he did accept QM predictions as being pretty damn near the truth, he did not buy into conspiracy (super-determinism) and he therefore went for non-locality, but he freely admitted that that was just a matter of taste.
BTW my personal preference, today, is to reject *realism*. But my opinion can change if I see new evidence e.g. experimental, mathematical, pointing in other ways. Or if someone explains that I was seeing things which I already thought I knew in a wrong way. It's wise (scientific?) to keep an open mind. Have an opinion, to be sure, but be prepared for it to be changed. Distinguish facts from opinions. Don't believe everything you read just because famous or respectable people wrote it.
 
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  • #154
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BTW my personal preference, today, is to reject *realism*.
Mine is to reject both, but as you mentioned in another thread locality is dependant on your definition of locality. My definition is the cluster decomposition property - locality applies only to uncorrelated systems.

Have an opinion, to be sure, but be prepared for it to be changed. Distinguish facts from opinions. Don't believe everything you read just because famous or respectable people wrote it.
If you are interested in the foundations of QM, in my experience its vital to think through it yourself and reach your own conclusions. There is a lot of misinformation out there, as, answering questions on the forum has taught me only too well.

My view has changed considerably over time. Perhaps the biggest shift was simply realising an observation doesn't have to involve a concious organic observer.

Thanks
Bill
 
  • #155
gill1109
Gold Member
262
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My view has changed considerably over time.
Mine too! I believe that there are not any easy answers and people who tell you it is all very simple, have over-simplified or misunderstood or are fooling themselves.

BTW (discovered from the thread https://www.physicsforums.com/showthread.php?t=758324 on Bell's theorem) Bell says "I cannot say action at a distance is needed. I can say that you can't say it is not needed". This is like Buddha talking about self. He is actually saying that our usual categories of thought are *wrong*. Because of the words in our vocabulary and our narrow interpretation of what they mean, we ask stupid questions, and hence get stupid answers.


"The one place where the Buddha was asked point-blank whether or not there was a self, he refused to answer. When later asked why, he said that to hold either that there is a self or that there is no self is to fall into extreme forms of wrong view that make the path of Buddhist practice impossible. Thus the question should be put aside." http://www.accesstoinsight.org/lib/authors/thanissaro/notself2.html
Sorry for bringing esoteric philosophy to this forum, but it is pretty clear to me that John Bell himself was referring to exactly this same famous question. We know that Schrödinger, Bohr and other founding fathers of QM were drawn to Eastern philosophy - precisely because it emphasizes that usual categories of thinking may be a straight-jacket.
 
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