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Ok Eric, since the proof that the above listed assumptions lead to predeterminability of outcomes is straightforward, I will be glad to find which of the above assumptions the 2 theories you linked reject. But this will take me some time.
Thanks for the discussion.
Hi Eric, maybe we are not understanding each other, but if you read my paper you will clearly see that the EPR-Bell’s version that I have re-examined do not need neither “outcome independence” nor “factorization of probabilities”. They only (implicitly) need these two assumptions (implicit in the common scientific way of thinking):
1) If there are correlations, then you need a causal explanation, that is to say or one caused the other (there is a physical influence of one on the other, so one is in the past light cone of the other) or they interacted appropriately in their common past, which I think you would call “Common Cause as such”.
2) “intersubjective reality of S,a,b,A,B events in a definite space-time causal structure” which I think is what you would call “macrorealism”.
At this point, if you assure to me that there exist some models that accept all these hypothesis and still explain EPR correlations without rejecting Einstein locality (which implies parameter independence) and S.I.+ “free will”, then I’m glad to find where the errors in their claims could be, otherwise I’m not interested in loosing my time, since 1) and 2) in my opinion are both necessary to do science.
P.s. five years ago Rovelli told me that relational quantum mechanics reject Einstein locality and that it’s not a (multi) solipsistic interpretation (whatever this could mean), so let me think that he is confused more than at least one of us.
“I see no fundamental difficulty of understanding it from the perspective of a theory in which Macroreality is false, like Everett, relational quantum theory, or QBism”
Hi Eric, since I see many difficulties to give an operational notion of speed of influences in physical space without taking S,a,b,A,B as real events occurring in space, could you give me some references where these interpretation account for that? Thanks.
# “the measurement outcomes happen to be correlated in the appropriate way, but it is not that one of the outcomes causes the other, or objectively collapses the state of the distant system. They just happen to occur spontaneously, undetermined, but correlated, even if at a distance”
This is not a way out, this is purely nonsense, with all the due respect for Shimony. The assumptions of EPR are clear, so if you want to reject predetermination you need to reject or “locality” or “free will” or the correctness of quantum mechanics, since rejecting the reality of S,a,b,A,B preclude an operational definition of speed of influences in space (if you need a proof of this statement I can write something, but it seems obvious from my point of view).
# “Bell’s and EPR’s notion of locality, or more precisely, of Local Causality”
No, from my understanding EPR notion of locality only implies what you call “parameter independence”.
# “to give up the classical principle of causality encapsulated in Reichenbach’s principle of common cause.”
If you reject this principle (and I think that it would be even worse than the solipsism option) you would invalidate all the scientific knowledge we have. At this stage it would be useless to talk about locality or everything else. The hypothesis that causes are in the past and that correlations need an explanation in my opinion is necessary to do science.
Hi Eric, thanks for the comment.
#) “Note also that 1-3 are not the assumptions made by EPR at all”
They are. Maybe the presentation of the argument written by Podolski in 1935 it’s not so clear, so I’m referring actually to the later presentation of the argument in Einstein 1948 (thanks for the implicit reminder, I need to add the reference in my paper), but the real assumptions are nevertheless present in the 1935 paper (if you don’t find them in the paper I can quote the relevant parts for you). They are:
1) Psi is a complete description of the system (there exists only psi and it evolves according to the Schrödinger equation)
2) Quantum mechanical predictions (collapse + Born’s rule) are exactly valid in every experimental situation (every possible physical context).
3) “free will”: Alice and Bob can choose independently the kind of measurement and the instant to do it.
4) “locality”: actions/physical influences cannot propagate in any frame at a speed faster than the speed of light.
From these assumptions you can deduce with a simple counterfactual reasoning that there must exist the local information to calculate the outcomes of every possible measurement. At this point you can start with Bell’s theorem, as explained in my paper and I emphasise that I DON’T need the Outcome independence assumption.P.s. You can add as an implicit assumption the fact that S,a,b,A,B are real events occurring in space-time, as I noticed in the parallel discussion. This is true because otherwise you cannot even talk meaningfully about speed of real physical influences from Bob, Alice and the Source.
Hi Eric, thanks for the reply.
#) “I gather that what you mean is that if Charlie’s observations are real, then they must be (real) hidden variables (for Alice). That may be true, but again, we do not need to make that assumption”
Independently by the fact that you explicitly make that assumption, it’s nevertheless surely true.
#) “If you object to the idea that one can maintain Parameter Independence while abandoning Macroreality, I’m happy to discuss. “
I’m objecting exactly that, because the reality of the spatiotemporal events S, a, b, A, B (S is the process of emission of particles in the source) is a necessary condition to define speed of influences and so locality in physical space. In fact this is an implicit assumption of EPR-Bell argument/theorem.
So if your theory reject this kind of “reality” assumption you cannot say neither that it’s local neither that it’s non-local (as in the many-world/mind interpretation). It’s pretty the same for retrocausal models. If you admit the possibility that the future can influence the past, then it’s not clear what’s the meaning of locality in physical space. For this reason I personally like to interpret this kind of models as superdeterministic models (conspiracy on global initial conditions).
“However, we emphasise once more that those correspond to observed events, and note that we make no assumption
about hidden variables predetermining all measurement outcomes.”Regarding the first part of the quoted sentence, I would like to note that from Alice’s perspective those events observed by Charlie are not more real than hidden variables (or than Bob’s measurement choices and outcomes) until Alice become conscious of them. So it seems to me that it’s not a thing particularly interesting to emphasise.
Regarding the second part of the quoted sentence, I think that this is not a step beyond Bell’s theorem, but it’s a step back, since the existence of the information for predetermining all measurement outcomes is a consequence of EPR argument, from which Bell’s theorem starts, as remembered in my paper for this workshop. This fact suggests that abandoning “macroreality” is not a valid option for saving locality.
New version of the paper, feedback are welcome:
