Undergrad Local, non-realistic description of the EPR-Bohm experiment

[ueit]

https://www.physicsforums.com/threa...entanglement-and-nonlocality-comments.864726/

See post @ # 12 by @vanhees71 It seems this could qualify for a local non realistic model :
Non realistic since particles at A or B, in superposition, do not have definite spin values until measured.

I agree this account is non-realistic but it is not local (or at least not obviously so) according to the way I defined the term. That post explains that no faster-than light communication is possible, but this is also true in Bohm's interpretation even if the theory is non-local.

In the post you linked it is accepted that A and B will get anti-correlated results but no cause is given for this fact. So, either vanhees believes there is no cause (in which case the theory is indeed local, but fine-tuned) - my option 1 or, if there is a cause, we are not told about it.

 

[ueit]

Your argument does not cover all logical possibilities, just all the scientific ones (the first one is called "coincidence").
There is possibility that measurement records are not factual i.e. they are somehow subjective. That's on the side of non scientific possibilities.

I think that most non-realists would disagree with you that this subjectivity is non-scientiffic. Some claim that this is in fact the deep implication of QM. Sure, I disagree with this.

But even if we accept this subjectivity, a theory still has to provide some sort of explanation (why some observer experiences a result and not some other result). So far I have not seen such a well-defined account.

 

[morrobay]

I agree this account is non-realistic but it is not local (or at least not obviously so) according to the way I defined the term. That post explains that no faster-than light communication is possible, but this is also true in Bohm's interpretation even if the theory is non-local.

In the post you linked it is accepted that A and B will get anti-correlated results but no cause is given for this fact. So, either vanhees believes there is no cause (in which case the theory is indeed local, but fine-tuned) - my option 1 or, if there is a cause, we are not told about it.

The cause is given in post #9 same reference, again by @vanhees71 partial quote:

There is no action at a distance related to entanglement, but it's described by states of systems that are not localized and thus observations of far distant parts of the system can be correlated, but this correlation is due to the preparation of the state long before any measurement on the partial systems is done." ...
https://www.physicsforums.com/threa...entanglement-and-nonlocality-comments.864726/

 

[ueit]

The cause is given in post #9 same reference, again by @vanhees71 partial quote:

There is no action at a distance related to entanglement, but it's described by states of systems that are not localized and thus observations of far distant parts of the system can be correlated, but this correlation is due to the preparation of the state long before any measurement on the partial systems is done." ...
https://www.physicsforums.com/threa...entanglement-and-nonlocality-comments.864726/

It seems to me that the system preparation being the cause of the correlations is just postulated. The theory does not provide any link between the system preparation and the actual results. The non-localized state does not contain enough information to determine the results. And if you cannot determine the results how can you determine a correlation between them?