why is superdeterminism not the universally accepted explanation of nonlocality?

DrChinese

Ditto to the above. bill's comments are typical of a new breed of local realist who conveniently skirt the issue, claiming this is some kind of "naive realism" as if that means it can be dismissed. Guess it's great to assert something ("realism") that by their definition actually has no specific meaning.

Anyway, my apologies to everyone for responding to ThomasT's comment and accidently steering the discussion away from the topic at hand. If we need to continue, we can start a new thread.

billschnieder

Thanks TT, nice to see you around too. To me there is not just one way of characterizing "Bell stuff" and it is definitely possible to carve out some aspects of it that are valid and correct. However, some may say the interpretation is also "Bell stuff" and criticize everything together, which may come off as implying they think those more narrow aspects are individually wrong, which they don't -- get my drift?

Not sure I understand what it means for Bell-type LR to be "general", all I can see is a logical contradiction in the "DrC Challenge" which I've pointed out many times. It is simply the fact that it is impossible to produce a dataset from an impossible experiment. And failure to do so says nothing about the validity or lack there-of of any Bell-type or realist arguments. Now this is not an unreasonable critique of the DrC challenge, is it?

ThomasT

Following DrC's suggestion, it might be better if this were introduced as a new thread in the philosophy forum if you want to pursue it. Including any and all posts that motivated you to post in this thread. Or maybe the QM forum, where you might get some more knowledgeable contributors, but I think it's more of a philosophical consideration.

This thread is about superdeterminsism, and why it isn't universally accepted as an explanation for nonlocality?
Any thoughts on that?

lugita15

I'm not sure what this means.
No, Bell did not just prove that a particular local realist model failed to match the predictions of QM. He proved that any possible local deterministic universe which is not superdeterministic must satisfy the Bell inequality. If you disagree with this, look at the 12-step outline of Bell's argument I gave in a previous post and tell me what step does not apply to ALL local deterministic universes which are not superdeterministic.

lugita15

billschnieder, we clearly have different definitions of what realism means. As DrChinese and ThomasT said you should start a new thread if you want to discuss your definition.

ThomasT

It means that BI violations don't tell you anything about the reality underlying the instrumental behavior.

Well, that's just an unwarranted interpretation of the meaning of Bell's theorem, imho.

I've looked at it. Your conclusion is unreasonable, imho.

If you really think you're on to something, then make a superdeterministic model of quantum entanglement.

lugita15

So then tell me which of the 12 steps need not hold in all (non-superdeterministic) local deterministic theories.
Um, I'm not sure what you're talking about. When did I say I'm on to a superdeterministic model?

ThomasT

You didn't, afaik. But you seem to be defending the notion that superdeterminism can explain BI violations. So, I'm just suggesting, make a superdeterministic model that can be experimentally tested. Otherwise, what are you talking about?

As for your 12-step recounting of Bell's argument, the conclusion that the correlation between the angular difference of the crossed polarizers and the rate of coincidental detection should be linear given the assumption of local determinism is wrong.

lugita15

All I'm saying is that Bell's theorem as such does not necessarily rule out superdeterminism, but it definitely rules out all other forms of local realism.
If my conclusion is wrong, one of my steps must be wrong. Which one is it?

ThomasT

I basically agree with this ... with the qualifier that what Bell's theorem definitively rules out are Bell-type LR models of quantum entanglement. Whether non-Bell-type LR models can be definitively ruled out is still an open question, afaik. (Because, it's still an open question as to whether certain non-Bell-type LR models are actually LR models.)

You're saying that the local realist would expect a linear correlation between θ and coincidental detection. Why would the local realist expect that?

My point is that if the local realist is aware of the historically documented characteristic behavior of light, then he wouldn't expect, in a local deterministic world, a linear correlation between the angular difference of the crossed polarizers and the rate of coincidental detection. He would, rather, expect a nonlinear correlation ... something approximating cos²θ.

The fact that Bell inequalities are, more or less, based on formal constraints which require the light in Bell tests to behave in an uncharacteristic way suggests that there's something in those constraints which is not corresponding to Bell test preparation and associated data processing. But not necessarily that nature is nonlocal.

lugita15

To repeat, the fact that local realism implies a linear correlation is NOT some arbitrary assumption or constraint we place on local realist theories. It is the conclusion of a careful argument, and if you're claiming the conclusion is wrong then there must be something wrong with this argument.

ThomasT

Why does the argument assume that the correlation between θ and rate of coincidental detection should be linear?

lugita15

Argh! ThomasT, I told you, the argument does not assume it, it proves it.

ThomasT

I didn't get that. How does it prove it?

zonde

Under local realism cloning of entangled pair is completely valid operation. From that follows that "DrChinese challenge" is applicable to LR models.

While I am proponent of local realism I side with DrChinese in this. Have to say that you can have constructive discussions with DrChinese and I am grateful to him as discussions with him have shaped a lot my own understanding about entanglement problem.

zonde

Can you give one good reason why your position is not subject to confirmation bias?

zonde

I would like to see this. Hmm, my guess would be that you are assuming perfect (anti-)correlations for matching measurement settings.