Superdeterminism

[Joy Christian]

The experimenter is made of the same atoms, governed by the same physics - I just don't understand what is so special about him or his "free will"?

It is not a question of the experimenter or her "free will" being special. It is a question of whether or not the physical world is conspiratorial. Superdeterminism postulates a conspiratorial physical world in which the choices any experimenter and her partner will make in the future in any Bell-test experiment are predetermined by the initial conditions that have originated in the overlap of their backward lightcones. Fortunately, no such conspiracy is needed to explain the strong quantum correlations:

https://arxiv.org/abs/1911.11578

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[Jarek]

Superdeterminism does not need any conspiracy, only accepting time/CPT symmetry of nearly all physics we use - that the history of the universe was chosen by e.g. the least action principle, hence shifting to Euler-Lagrange perspective its state was chosen also accordingly to all future measurements.

[Joy Christian]

Superdeterminism does not need any conspiracy, only accepting time/CPT symmetry of nearly all physics we use - that the history of the universe was chosen by e.g. the least action principle, hence shifting to Euler-Lagrange perspective its state was chosen also accordingly to all future measurements.

Answer this question: Are the choices of the settings made by the experimenters in any EPRB experiment predetermined by the initial state of the spin system? Yes, or No?

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[Jarek]

Assuming e.g. the least action principle is the way physics works, everything is predetermined, superdetermined.

This way we can imagine that our universe was fixed in the past in Big Bang and in the future e.g. in Big Crunch, and physics has chosen action optimized history of the universe between them.

This philosophy of just traveling through already chosen spacetime is called (Einstein's) block universe, eternalism: https://en.wikipedia.org/wiki/Eternalis ... hy_of_time)
Alternative is presentism - spacetime does not exist, only the current moment: https://en.wikipedia.org/wiki/Philosophical_presentism

So which philosophy of time is the proper one?

[Joy Christian]

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I take it that this is your longwinded way of answering my question affirmatively. In that case, you believe in a conspiratorial world. I don't. And we don't have to.

***

[Jarek]

What conspiratorial do you see in the principle of least action?
https://en.wikipedia.org/wiki/Principle_of_least_action

[Joy Christian]

What conspiratorial do you see in the principle of least action?
https://en.wikipedia.org/wiki/Principle_of_least_action

I see its irrelevancy for the question I asked and you (I think) answered in Yes.

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[Jarek]

We use Lagrangian mechanics from QFT to GR - if physics use it through the principle of least action, then everything is predetermined - including what you have written.
Yes, just using this principle, I don't know what's conspiratorial about it.

[Joy Christian]

We use Lagrangian mechanics from QFT to GR - if physics use it through the principle of least action, then everything is predetermined - including what you have written.
Yes, just using this principle, I don't know what's conspiratorial about it.

Then you don't understand Bell's argument (which is often called a "theorem"), as I have always suspected. Think about the question I asked and you answered in "Yes."

Here is a quote from Zeilinger that makes the problem with superdeterminism very transparent [Dance of the Photons, Farrar, Straus and Giroux, New York, 2010, p. 266]:

[W]e always implicitly assume the freedom of the experimentalist... This fundamental assumption is essential to doing science. If this were not true, then, I suggest, it would make no sense at all to ask nature questions in an experiment, since then nature could determine what our questions are, and that could guide our questions such that we arrive at a false picture of nature.

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[Jarek]

The problem pointed by Bell is existence of inequalities which are satisfied by standard probabilistics, but can be violated by QM formalism.

E.g. 3rd probability axiom ( https://en.wikipedia.org/wiki/Probability_axioms ) says that
probability of alternative of exclusive events is sum of their probabilities.
what e.g. allows to conclude for binary variables A, B, C that:
Pr(A=B) + Pr(A=C) + Pr(B=C) >=1
however, quantum formalism allows to violate it ( https://arxiv.org/pdf/1212.5214 ).

It says that QM allows for statistics essentially different than standard probability axioms.
It can be seen in Born rule: probability of alternative of exclusive events is proportional to squares of sums of their amplitudes. - which allows to violate above inequality.

The problem of Bell theorem does not regard free will of observers, but understanding nonintuitive correlations of QM, especially the Born rule ... which is natural for time symmetric models like the least action principle.

[Joy Christian]

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Ok, I give up. You are not going to get it.

***

[Jarek]

So how would test/violation of Pr(A=B) + Pr(A=C) + Pr(B=C) >=1 look like?
- assume you have a source of prepared identical states,
- for some you measure AB, for others AC, for others BC,
- estimate the probabilities from these measurements and calculate Pr(A=B) + Pr(A=C) + Pr(B=C).

Where exactly do you need "free will" assumption here?
If nowhere, please let's not mix physics with theology - leave "free will" arguments for the latter.
The difficulty is understanding Born rule, which already can be seen in Malus law in EM - the question is how to take it e.g. to spins?

[Joy Christian]

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You are the one who is introducing theology into science. Superdeterminism is a conspiratorial theology, not science.

***

[Jarek]

I am not introducing anything, only reminding 18th century principle of least action - do you see it controversial or a part of theology?

Assumption that physics works accordingly to this principle is stronger than just determinism - state in a given moment is literally chosen accordingly to both past and future situation there - similarly as in superdeterminism.

I only accept assumption of this principle here.

[Joy Christian]

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Here is another quote regarding the conspiratorial nature of superdeterminism from Abner Shimony, Michael Horne and John Clauser, Epistemological Letters, 13, 1 (1976):

In any scientific experiment in which two or more variables are supposed to be randomly selected, one can always conjecture that some factor in the overlap of the backward light cones has controlled the presumably random choices. But, we maintain, skepticism of this sort will essentially dismiss all results of scientific experimentation. Unless we proceed under the assumption that hidden conspiracies of this sort do not occur, we have abandoned in advance the whole enterprise of discovering the laws of nature by experimentation.

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[Jarek]

- assume you have a source of prepared identical states,

I deliberately emphasized identical states there - so that selection for various measurements does not matter.

This "free will" selection is not a problem here.
The problem is understanding Born rule: probability of alternative of exclusive events is proportional to squares of sums of their amplitudes, what disagree with standard probability axioms.

[local]

Jarek, as an unbiased observer, I have to say that you are sounding incoherent.

[Jarek]

Please elaborate what exactly do you see incoherent in considering assumption of physics working accordingly to the least action principle?

[local]

I don't see how an action principal must entail superdeterminism.

[Jarek]

In the least action principle ( https://en.wikipedia.org/wiki/Principle_of_least_action ) you fix values in past and future, getting evolution between them as the one optimizing action.
From Universe perspective, we need to fix it somewhere far in the past e.g. in Big Bang, and somewhere in the future e.g. Big Crunch, infinity etc..

Now having chosen such action optimizing history of the universe, we can switch to standard forward in time evolution using Euler-Lagrange equation, which is mathematically equivalent (if already having a solution).
It uses information only e.g. in current moment, but not only value e.g. of a field, but also of time derivatives.

If physics works accordingly to the least action principle (or other time/CPT-symmetric formulations like path ensembles), then this hidden Euler-Lagrange internal state was already chosen to be compatible also with all future measurements.