Assumptions of the Bell theorem

[physika]

This reasoning is basically circular. If correlations require a common cause, and the common cause principle requires causality... then of course correlations require causality. But this is the quantum world! You can't make such sweeping assertions!

Simply put: There is no time ordering required by quantum predictions (I'm thinking of the various array of Bell tests). You can in fact entangle pairs *after* they are measured, by the same mechanism as you would entangle them before they are measured (swapping). Completely consistent with quantum theory are the various acausal/adynamical and time symmetric interpretations. In those, a future measurement setting is part of an overall context. No single component of the overall context can be considered to be the "cause" of the final correlated outcome(s). See for example:

Time Symmetric Quantum Mechanics:
https://arxiv.org/abs/0706.1232

Relational BlockWorld:
http://philsci-archive.pitt.edu/3247/1/RBW_FPP_2007.pdf

As far as anyone knows, these are not inconsistent with relativity. You can't assume classical causality, except by personal preference.

First, causality goes beyond classical thinking (false dichotomy) and second, correlations can't be arbitrary.

 

[Killtech]

First, causality goes beyond classical thinking (false dichotomy) and second, correlations can't be arbitrary.

But correlations can be quite arbitrary. Think of the most simple case of two random variables with some joint probability distribution $\rho(x_1,x_2)$. Expectation values (first order), variances and correlations (second order), skews and all higher order of that distribution are just a the coefficients of a series decomposition much like Taylor is. When the random variables live in a space-time, then there are also coordinates to play with, including time. Ah and yeah, simultaneity isn't well defined here as well.

What's the causality of that? I don't think that is makes sense to apply causality everywhere.

Causality implies a strict order. So it makes only sense where that is the case, i.e. systems with entropy that have a visible direction of time.

 

[RUTA]

This reasoning is basically circular. If correlations require a common cause, and the common cause principle requires causality... then of course correlations require causality. But this is the quantum world! You can't make such sweeping assertions!

Simply put: There is no time ordering required by quantum predictions (I'm thinking of the various array of Bell tests). You can in fact entangle pairs *after* they are measured, by the same mechanism as you would entangle them before they are measured (swapping). Completely consistent with quantum theory are the various acausal/adynamical and time symmetric interpretations. In those, a future measurement setting is part of an overall context. No single component of the overall context can be considered to be the "cause" of the final correlated outcome(s). See for example:

Time Symmetric Quantum Mechanics:
https://arxiv.org/abs/0706.1232

Relational BlockWorld:
http://philsci-archive.pitt.edu/3247/1/RBW_FPP_2007.pdf

As far as anyone knows, these are not inconsistent with relativity. You can't assume classical causality, except by personal preference.

Here is our book on acausal explanation resolving the mysteries of modern physics: Beyond the Dynamical Universe, and here is our most recent paper on it: Beyond Causal Explanation: Einstein's Principle Not Reichenbach's. Accordingly, explanation is fundamentally about 4D constraints and dynamical/causal explanation follows when appropriate. For example, Fermat's Principle is a 4D constraint and Snell's Law is the dynamical counterpart. Typically, people believe the converse is true and that's what causes so many mysteries in modern physics (origin of the universe, grandfather paradox for closed timelike curves, entanglement, measurement problem, ... ). What we argue in the book and paper is that sometimes there just isn't a reasonable dynamical/causal counterpart to the fundamental 4D constraint. Another one that we're all familiar with is the relativity principle applied to the measurement of the speed of light c. Today, we (most of us anyway) just accept that "principle explanation" of time dilation and length contraction without requiring a causal mechanism ("constructive counterpart") a la the luminiferous aether. If you apply the relativity principle to the measurement of Planck's constant h, you get the difference between quantum probability theory and classical probability theory to include Bell state entanglement. Here is a paper on that: Answering Mermin's Challenge with Conservation per No Preferred Reference Frame. Here is an argument using Information Invariance & Continuity per quantum information theory (still under review) that makes the point more generally: The Relativity Principle at the Foundation of Quantum Mechanics.

If someone later comes along with a "theory of the aether," it will not in anyway refute the already existing principle account (unless it changes Lorentz invariance or makes conflicting predictions). Likewise, for Bell state entanglement and the mysteries of quantum mechanics. It's been well over 100 years without seeing anything accepted along those lines for SR or QM, so we could be waiting a long time. In the meantime, we have the principle accounts based on empirical and mathematical facts :-)

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[Sunil]

This reasoning is basically circular. If correlations require a common cause, and the common cause principle requires causality... then of course correlations require causality. But this is the quantum world! You can't make such sweeping assertions!

?? Quantum theory is science. At least I hope so. Science has to follow scientific methodology. Once it is part of scientific methodology that correlations require causal explanations, causality is part of scientific methodology. Means, causality (the variant of it which includes the common cause principle) is part of scientific methodology. Means, quantum theory is obliged to follow the principles of causality. If some interpretation of quantum theory violates the principles of scientific methodology, it has to be rejected, that's all.

No circular reasoning here - except if you define scientific methodology as all what some scientists are doing. But this would be your personal [self-censored] decision, I do not support such [self-censored].

If you name this a "sweeping assertion" and add some ! this does not define an impressive argument. "Science" without the requirement to find causal explanations of observed correlations is not science, but something comparable with astrology.

Simply put: There is no time ordering required by quantum predictions (I'm thinking of the various array of Bell tests). You can in fact entangle pairs *after* they are measured, by the same mechanism as you would entangle them before they are measured (swapping).

Whatever, all those predictions are compatible with a particular choice of time ordering. Take any time coordinate, and consider the dBB version of such experiments, and you will always find a picture with FTL influences but nonetheless causal.

Completely consistent with quantum theory are the various acausal/adynamical and time symmetric interpretations.

I can name also other nonsense which is "completely consistent with quantum theory". I have recently seen a paper discussing the compatibility of Hindu mysticism with quantum theory. Once scientific methodology requires causal explanations for correlations, interpretations which reject causality should be rejected as violating scientific methodology.

If there would be no interpretation of QT at all which would be compatible with the common cause principle, you could reasonably argue that there is something wrong with the common cause principle. It would be nonetheless a hard job for you, given that you would either have to present some replacement sufficient to replace causal reasoning in everyday life about smoking and lung cancer, or to reject all the up to now scientific conclusions based on the application of the common cause principle.

But actually we have causal interpretations of QT, starting with dBB as the most famous one. So there is no base at all for doubt.

In those, a future measurement setting is part of an overall context. No single component of the overall context can be considered to be the "cause" of the final correlated outcome(s). See for example:

Time Symmetric Quantum Mechanics:
https://arxiv.org/abs/0706.1232

Relational BlockWorld:
http://philsci-archive.pitt.edu/3247/1/RBW_FPP_2007.pdf

As far as anyone knows, these are not inconsistent with relativity. You can't assume classical causality, except by personal preference.

Same point - compatibility with relativity does not mean compatibility with the scientific methodology. Anti-scientific mysticism may be compatible as with quantum mysticism, as with relativistic mysticism.

Relativistic causality itself (Einstein causality) is compatible with classical causality as well as what scientific methodology requires - it does not reject the common cause principle, or anything else, but makes the stronger claim that causal influences can happen only inside the light cone. This notion of Einstein causality allows to prove the Bell inequalities, thus, has been empirically falsified.

Weakening it to "signal causality" does not save relativistic causality because it is not really a notion of causality, given that it does not contain the common cause principle. If it is nonetheless compatible with some relativistic version of mysticism or not is irrelevant.

 

[PeterDonis]

Thread closed for moderation.