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entropy1
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Does the definition of locality in the QM sense include the prohibition of retrocausality?
Can you give a yes/no answer?Given that this is B-level, I have to ask if you know what those words mean. For example, how do you express locality mathematically? And if you don't, how can we provide a B-level answer?
In any proper journal article the authors will define what they mean by words of this sort, precisely because there is no single universally understood definition. Unless and until you do that, the answer to this question is going to be some variant of "It depends".Does the definition of locality in the QM sense include the prohibition of retrocausality?
The proof of the Bell theorem contains an assumption that there is no retrocausality. The transactional interpretation of QM assumes that it is precisely retrocausality that resolves the associated quantum puzzles.Does the definition of locality in the QM sense include the prohibition of retrocausality?
You apparently haven't grasped the fact that it is the fuzziness that makes it impossible to give a definite answer to your question. That's not going to change no matter how many times you rephrase it.Sorry if I'm a bit fuzzy in my formulation.
Well, maybe if I put it this way:You apparently haven't grasped the fact that it is the fuzziness that makes it impossible to give a definite answer to your question. That's not going to change no matter how many times you rephrase it.
For that purpose you need to read an actual proof of the Bell theorem, because such a proof contains a precise formal definition of locality.Well, maybe if I put it this way:
Bell showed that "Local Realism" can not be maintained as part of QM. So what does the term "local" mean in this context? It is often explained as: "Spooky action at a distance", but I don't know what is ment by that.
Have you read Bell's paper? He gives an explicit definition of his concept of "locality".Bell showed that "Local Realism" can not be maintained as part of QM. So what does the term "local" mean in this context?
Is that what you mean? Or need I do the math?that the result of a measurement on one system be unaffected by operations on a distant system with which it has interacted in the past
Then you obviously aren't looking at Bell's actual paper. Please do so. Our own @DrChinese has provided links to key papers on this topic:I can only find this definition
In this paper, the locality assumption is "the vital assumption" after Eq. (1).@PeterDonis I used this text, which is searchable. I think it is the same one. I searched for "local" and got four matches.
It's called the Reichenbach's common cause principle.If ##A## is correlated with ##B##, then it must be the case that one of the following is true:
If you make this assumption (@Demystifier probably knows the philosophical term for it),
- ##A## influences ##B##
- ##B## influences ##A##
- There is some common cause ##C## that influences both.
But if there was such a law, I don't see how can see such a law be considered a local law.But there is nothing logically inconsistent about assuming that the radios are just emitting random noise, and one of the laws of the universe is that the random noise produced on one radio is always the same as that produced on the other.
What is the punishment for treason against the scientific method?For that treason, some defenders of local interpretation of QM go a step further, by denying the existence of correlation before the observation of correlation. For instance, if Alice measures spin of one particle in New york and, at the same time, Bob measures spin of the other particle in London, there is no correlation until someone (say Charlie) looks at both measurement results.
Yes, I agree. But it's not logically necessary to posit a FTL mechanism for the correlations. You could just say that that's the way the universe works.But if there was such a law, I don't see how can see such a law be considered a local law.
To add to this, I think that if you propose a FTL mechanism, you need to show, at least in principle, a scenario where there can be FTL transmission.Yes, I agree. But it's not logically necessary to posit a FTL mechanism for the correlations. You could just say that that's the way the universe works.