The Impact of Weak Realism on Bell's Theorem and Bohmian Interpretations

[mn4j]

Pretty much, this is the standard hidden variable (a/k/a realistic) interpretation. The requirement stems from the fact that we have "perfect" correlations at matching angle settings for entangled pairs. I separated your definition from the rest of your post so we could see that I do agree with this idea as being the basis for realism, either naive or otherwise.

If this is the definition of realism at issue in Bell, then it is obvious why Bell and his proponents have missed the mark. Using my previous analogy of the sun and it's "color", you would be saying realism means the sun has a color when nobody is looking. You can see this by having two people wear different colored goggles. If you believe the realism means the sun has a color when nobody is looking, then you must also admit that the realism of the sun can be changed instantaneously by changing the color of goggles you put on (ie FTL). It is obvious to see how such a person would conclude that local hidden variable theorems are forbidden -- because in fact no local hidden variable theorem can explain being able to change the color of the sun superluminally. But as I hope is getting obvious already, the error was made by attributing to the sun only, properties that belong to the combined "sun + observer system". Correctly recognizing that the appropriate system must include the observer, you then realize that it becomes possible to use a hidden variable theorem to explain the results. The local hidden variable theorem in this case being along the lines that the sun produces a spectrum of electromagnetic radiation which when combined with the goggles results in absorption of some regions and not others resulting in different perceived colors.

I do not agree with the portion that requires there to be underlying attributes for every possible angle setting. I.e. if you divided a circle into 360 degrees and made each one an atrribute, there would be 360 attributes to describe spin. I do not believe realism asserts that there are 360 (or 360 million, or infinity, etc.) such attributes. Realism is merely the expression of the idea that there is a definite real outcome to a measurement of a specific observation, regardless of whether or not such observation is made. The mapping to an underlying physical attribute, operator, etc. is optional.

It may seem reasonable until you realize that the concept of "polarization" includes the measuring device in this particular case. You can't have it both ways. So then it is inconsistent to talk of the photon having a polarization even when no measurement has been made.

Note that to say the sun does not have a color when nobody is looking is not the same thing as saying the moon does not exist when nobody is looking. We are merely saying "color" by definition includes the object, observer and medium in the system.
Therefore
1) it doesnot even make sense to talk of "measuring" the color of the sun, because the sun does not have a color
2) it does not make sense to talk of the "sun+goggles+observer" system having a color when no measurement has been made because, the "color" of the "sun+goggles+observer" system is by definition, the result of a measurement.

Therefore I would modify your definition of realism to: Realism is merely the expression of the idea that there are objective facts about a system, whether or not observers know them (or can know them) and Local causality is therefore merely the expression of the idea that FTL or psychokinesis is unreasonable. This is the only definition of "realist local causality" that is exhaustive and consistent with EPR.

Naive realism is limited to the concept that all observations are passive revelations of properties owned by the objects being observed. But as we have seen, even if the objects own objective properties, their revelation need not be passive, in which case the revealed outcomes will be properties of the combined object/observer system. So naive realism is unreasonable. Any attempt to limit the EPR definition of reality to naive realism for the purpose of arguing against it is a straw-man argument.

In order to argue against all local realist theories therefore, you MUST prove that either:
1) No objective facts can exist about a system OR
2) argue why FTL or psychokinesis is reasonable.

Arguing against (1) is self defeating because the validity of any argument against (1) depends on the validity of (1). In other words, in order for the statement "No objective facts can exist about a system" to be valid, it must be an objective fact about all systems. So then we are left with (2). Has (2) been proven?

 

[mn4j]

It really doesn't matter to Bell whether or not this version of realism is somehow different than the previously agreed version (per above post). And I don't think it matters to EPR either. But let's review the facts before we go much further. What DO we need to have? It is not 1 attribute for photon spin, it is at least 2!

You contradict yourself, Why MUST you have at least 2. Clearly that means Bell's treatment does not apply to situations in which you have only one. Why can it not be just one. You also have admitted that Bell's inequalities can not be derived from less than 3. So it seems you are saying there must be at least 3 not 2.

The reason is that across 360 degrees, there are completely independent results at 0 and 45 degrees (and all multiple thereof) that have no value overlaps. But the strange thing is, it doesn't matter how you orient the 0 degrees direction, there are still at least 2. There could be more, but maybe not. So I certainly do not assert that realism requires there be some large number of independent attributes - I only think there are 2 to begin with (using spin of linear polarized photons as the example). But we need to allow for the facts, which definitely point to at least 2.

The issue is not merely the number of attributes but the mechanism of revelation of the outcome. Passive or not.

I believe the QM description is essentially correct or complete or whatever you want to call it.

I believe the QM description is correct but incomplete, and so did EPR. The correctness of QM has never been in question.

After Bell, the question is whether a correct QM is non-local or non-realistic (or possibly both).

QM can not be correct and non-realistic because QM is a theory about real systems. As I have shown in my previous post, the argument against realism is self-defeating. It is like saying "reality" is not realistic. I would say the real issue is what the nature of "reality" is. In otherwords, is reality local or non-local, or in yet other words, is FTL reasonable or not. You believe it is reasonable so maybe you can convince me that it is.

Now, if you are a realist, and believe there is a reasonable alternative and physical explanatory mechanism that fits the facts: please come forward with a potential model.

I don't need to have such a model in order to appreciate that FTL is unreasonable because to believe FTL will require that I simultaneously hold contradictory beliefs which would be intellectually dishonest.

In any case, an alternative explanation has been provided. See

Event-by-Event Simulation of Einstein-Podolsky-Rosen-Bohm Experiments
Shuang Zhao · Hans De Raedt · Kristel Michielsen
Found Phys (2008) 38: 322–347​

Read it and we can discuss it in a separate thread.
All that this boils down to is the question: Is a deterministic local hidden variable explanation for Malus Law possible? This question has been answered in the affirmative.

 

[DrChinese]

1. If this is the definition of realism at issue in Bell, then it is obvious why Bell and his proponents have missed the mark. ... But as I hope is getting obvious already, the error was made by attributing to the sun only, properties that belong to the combined "sun + observer system".

2. It may seem reasonable until you realize that the concept of "polarization" includes the measuring device in this particular case. You can't have it both ways. So then it is inconsistent to talk of the photon having a polarization even when no measurement has been made.

3. Naive realism is limited to the concept that all observations are passive revelations of properties owned by the objects being observed. But as we have seen, even if the objects own objective properties, their revelation need not be passive, in which case the revealed outcomes will be properties of the combined object/observer system. ...

You are arguing pro or con realism here, yet the question is whether realism is an assumption of EPR/Bell. And NOT whether it is valid or not.

1. The issue is whether the observer determines reality. In this case, there are 2 observers, Alice and Bob. Does Alice determine Bob's reality? EPR argues NO.

As to whether the choice of pink or blue goggles determines anything: no one is arguing against your point. But a local realist requires the result for Bob to be independent of the choice of goggles made by Alice. Further, what if Alice instead chooses yellow goggles? Bell showed that the results were incompatible with your idea.

2. Of course, once Alice has made a measurement, Bob does have a definite polarization.

3. Essentially, it is passive but only in the sense that the interaction of the particle and the apparatus reveals a value that, due to whatever rules were in place, would always be revealed by a measurement of that type (per EPR). Now, if there were elements being introduced from the observer, and that is your idea, then it is incumbent that the observer's choice be communicated from Alice to Bob (per Bell).

 

[DrChinese]

1. You contradict yourself, Why MUST you have at least 2. Clearly that means Bell's treatment does not apply to situations in which you have only one. Why can it not be just one. You also have admitted that Bell's inequalities can not be derived from less than 3. So it seems you are saying there must be at least 3 not 2.

2. I believe the QM description is correct but incomplete, and so did EPR. The correctness of QM has never been in question.

QM can not be correct and non-realistic because QM is a theory about real systems. As I have shown in my previous post, the argument against realism is self-defeating. It is like saying "reality" is not realistic. I would say the real issue is what the nature of "reality" is. In otherwords, is reality local or non-local, or in yet other words, is FTL reasonable or not. You believe it is reasonable so maybe you can convince me that it is.

3. In any case, an alternative explanation has been provided. See

Event-by-Event Simulation of Einstein-Podolsky-Rosen-Bohm Experiments
Shuang Zhao · Hans De Raedt · Kristel Michielsen
Found Phys (2008) 38: 322–347​

Read it and we can discuss it in a separate thread.
All that this boils down to is the question: Is a deterministic local hidden variable explanation for Malus Law possible? This question has been answered in the affirmative.

1. Why must you have at least 2? Because you can do an experiment on 2 (although the experiment does not prove conclusively that local realism cannot be correct). Why can't you have 3, as local realism requires? Because Bell shows that 3 are incompatible with the predictions of QM.

2. EPR did vary from QM. They were wrong in their assumption that p1 and q2 could be determined, violating the HUP. We now know that for entangled particles, you cannot learn anything additional about Alice by measuring Bob.

3. I won't discuss local realistic papers as they are a complete waste of my time. Of course, you cannot have a local realistic theory that postulates Malus and gets past Bell. So go ahead and start the thread, I just won't be there.

 

[DrChinese]

In the words of Zeilinger (1999), on EPR and Bell:

In 1935 Einstein, Podolsky, and Rosen (EPR) studied entangled states of the general type used in the twophoton experiment discussed above. They realized that in many such states, when measuring either linear momentum or position of one of the two particles, one can infer precisely either momentum or position of the other. As the two particles might be widely separated, it is natural to assume validity of the locality condition suggested by EPR: ‘‘Since at the time of measurement the two systems no longer interact, no real change can take place in the second system in consequence of anything that may be done to the first system.’’ Then, whether or not momentum or position can be assigned to particle (system) 2 must be independent of what measurement is performed on particle 1 or even whether any measurement is performed on it at all. The question therefore arises whether the specific results obtained for either particle can be understood without reference to which measurement is actually performed on the other particle. Such a picture would imply a theory, underlying quantum physics, which provides a more detailed account of individual measurements.

... A most important development was due to John Bell (1964) who continued the EPR line of reasoning and demonstrated that a contradiction arises between the EPR assumptions and quantum physics. The most essential assumptions are realism and locality. This contradiction is called Bell’s theorem.


As can be seen from the above (and there are no shortage of similar comments from others), the general view matches what I am saying: Norsen is ignoring the arguments that have been made, and addressed experimentally, with his presumed objective being to recast the local realistic debate in a different form than was made originally (i.e. to make it about locality alone). OK, fine, but we are missing the support for this point of view! Clearly, there is substantial support for the traditional view.

If Norsen - or any reader - thinks realism is superfluous to the debate about Bell, there is a simple solution: write it up without realism and see if it is accepted by your peers. I do not see that as possible, but maybe someone smarter that me could do it.

On the other hand: there are quite a number of arguments to the effect that realism is not only central to Bell, but that locality itself is not an issue. Examples: Kochen Specker, GHZ, etc. These demonstrate that realism must be rejected in ANY physical theory. I am not personally arguing that position, but there is certainly strong support for it. Again, from Zeilinger:

...It was initially argued by Specker (1960) for Hibbert spaces of dimension larger than two that quantum mechanics cannot be supplemented by additional variables. Later it was shown by Kochen and Specker (1967) and by Bell (1966; for a review see Mermin, 1993), that for the specific case of a spin-1 particle, it is not possible to assign in a consistent way measurement values to the squares of any three orthogonal spin projections, despite the fact that the three measurements commute with each other. This is a purely geometric argument which only makes use of some very basic geometric considerations. The conclusion here is very important. The quantum system cannot be assigned properties independent of the context of the complete experimental arrangement. This is just in the spirit of Bohr’s interpretation. This so-called contextuality of quantum physics is another central and subtle feature of quantum mechanics.

(Contextuality being essentially equivalent to the non-realistic position.)

 

[p764rds]

Non-commuting observables get in the picture because they can not be simultaneously real and thus lead to contradictory descriptions (ie, being able to instantaneously change the reality of a remote quantity by deciding which measurement to perform locally).

When a measurement is performed locally -for two entangled particles - nothing changes remotely apart from the local and remote states that are no longer correlated.
So, in my view there is no physical-like communication needed between the two particles. Its just that what was once correlated is no longer correlated (after local observation). Its a 'negative' logic-wise which is different from a positive logic-wise.

I can't see how a Bohmian pilot wave comes in here - its not needed - and its different from a particle arriving at its destination and reporting back (through time) to its initial position (which I see might possibly be the case) in the normal preparation and observation of one particle. Entanglement correlations is different and IMO requires that both particles refer to the same data point in information space wherever they are in spacetime - after local observation (or remote) that data point is no longer flagged as belonging to the particles.

 

[Ilja]

Not for entangled particles. Otherwise: you could measure p1 and q2, and q2 would tell you what q1 was to any desired precision. You would then know both p1 and q1. And we know that is wrong. You cannot learn more about the entangled system than the HUP permits. Now, please, don't confuse that with being able to measure p1 and q2 as that point is not in question. The question is whether p1 and q2 are non-commuting where particles 1 and 2 are entangled in p and q.

Yep. And if the operators p1 and q2 commute or not depends only on the operators, but in no way on the particular state (however entangled or not). And the operators q2 and -i\hbar\partial_1 commute.

What we, by measuring q2, obtain a previously existing value q1 is a consequence of the EPR argument, and needs locality. Quantum theory is nonlocal, therefore this is not essential.

 

[Ilja]

From my reading of this thread, it is obvious that DrChinese clearly understands reality as defined by EPR to be what Norsen calls "naive realism". So my understanding is that both Ilja and DrChinese agree on this point that realism ala EPR is "naive realism".

There are two different meanings of "realism a la EPR": What EPR use as their assumptions (the EPR criterion of reality), and what EPR obtain as a consequence of this assumption, locality, and the QM correlations. It is only the last which, in case one starts with it, could be (and has been by Norsen) named "naive realism".

Just to be clear, using the photon polarization example at three different angles (A, B and C), "naive realism" would mean the photon has simultaneously three different internal physical quantities corresponding to polarization at those angles, and that those quantities belong to the photon. So the claim then is that this is what EPR meant by realism.

No, this is only what follows, after the EPR argument (including locality) from the EPR criterion, which does not make such an assumption.

If this is your claim, then both of you could not be further from the truth for the following reason.

It has never been my claim.

 

[Ilja]

In the words of Zeilinger (1999), on EPR and Bell:

... A most important development was due to John Bell (1964) who continued the EPR line of reasoning and demonstrated that a contradiction arises between the EPR assumptions and quantum physics. The most essential assumptions are realism and locality. This contradiction is called Bell’s theorem.


As can be seen from the above (and there are no shortage of similar comments from others), the general view matches what I am saying: Norsen is ignoring the arguments that have been made, and addressed experimentally, with his presumed objective being to recast the local realistic debate in a different form than was made originally (i.e. to make it about locality alone). OK, fine, but we are missing the support for this point of view! Clearly, there is substantial support for the traditional view.

First, referencing Zeilinger as an authority is not very impressive. Second, Norsen quotes AFAIR himself a lot of such references to locality and realism as the assumptions, thus, you prove nothing against him with this quote. He has provided arguments against this mainstream position. If ignoring his arguments and quoting the questioned mainstream position as the mainstream position is the new way of solving scientific problems, we have
finally reached the state of democratic science, where majority decides about truth without
hearing any arguments. That's the end of science as science.

If Norsen - or any reader - thinks realism is superfluous to the debate about Bell, there is a simple solution: write it up without realism and see if it is accepted by your peers. I do not see that as possible, but maybe someone smarter that me could do it.

How often I have to repeat that realism is not superfluous, but has to be precisely defined. And once this is done, it appears that the used version of realism is so weak that to reject it becomes nonsensical, and to mention it as a nontrivial assumption unnecessary.

On the other hand: there are quite a number of arguments to the effect that realism is not only central to Bell, but that locality itself is not an issue. Examples: Kochen Specker, GHZ, etc. These demonstrate that realism must be rejected in ANY physical theory.

Not at all. These demonstrate that the rather nonsensical restriction of non-contextuality is incompatible with quantum predictions. This has nothing to do with realism.

(Contextuality being essentially equivalent to the non-realistic position.)

LOL. Contextuality has something to do with naive realism, but not with the metaphysical notion of realism Norsen and I defend. In particular, pilot wave theory is a quite nice, realistic theory, but contextual. Thus, in your words pilot wave defenders would be antirealists. Which is complete nonsense.

 

[DrChinese]

1. First, referencing Zeilinger as an authority is not very impressive. Second, Norsen quotes AFAIR himself a lot of such references to locality and realism as the assumptions, thus, you prove nothing against him with this quote. He has provided arguments against this mainstream position. If ignoring his arguments and quoting the questioned mainstream position as the mainstream position is the new way of solving scientific problems, we have
finally reached the state of democratic science, where majority decides about truth without
hearing any arguments. That's the end of science as science.

2. LOL. Contextuality has something to do with naive realism, but not with the metaphysical notion of realism Norsen and I defend. In particular, pilot wave theory is a quite nice, realistic theory, but contextual. Thus, in your words pilot wave defenders would be antirealists. Which is complete nonsense.

1. Don't get this, you are essentially saying Norsen should be considered more of an authority than Zeilinger? Zeilinger is one of the pre-eminient authorities in the area, and entanglement is his specialty. Certainly this is relevant. Norsen is primarily a theorist as best I know, although I thought he was doing some experimental work more recently. I would certainly like to see something from him that delved into some new areas more at the forefront of the field, as Zeilinger is doing. Just last week, Zeilinger was co-author on a Bell experiment with entanglement on 2 degrees of freedom (finding a Bell Inequality violated by 24 SD).

Now anyone can be wrong, and anyone can be right, regardless of their prior background or reputation. But what we are discussing is not the outcome of an experiment, but rather the relevance of that outcome. So certainly, we *should* consider the opinion of the scientific community in this case.

Also: Travis frequently interprets sections of standard texts and comes up with his own views on their meaning and context - against standard opinion. OK, sometimes that can be good too. But he often ignores any text or argument which goes against his opinion. Example: Norsen says EPR is about locality and not realism. Yet EPR references locality only ONCE, versus over a dozen times for realism. He never addresses this obvious flaw in his reasoning. In addition, EPR provides the standard definition of realism ("elements of reality"). Yet Norsen seeks his own definition, changing the character of the paper in the process. It has been my hope to learn if there is any "meat" to Travis' argument that I am missing in his work. Thus, I was hoping you could enlighten me on this in some fashion. If the best anyone can do is quote Norsen over EPR, quote Norsen over Bell, and quote Norsen over Zeilinger, given the huge gaps I have just mentioned... well, that fails on every level.

2. I'm laughing... There are plenty who believe that a Bohmian interpretation is deterministic and therefore realistic. And additionally ruled out by contextual no-go proofs. I don't happen to fall in that camp. But clearly, there is something odd about asserting that a theory has hidden variables, is deterministic, and yet is also contextual. Essentially, that viewpoint agrees with the EPR conclusion that a more complete specification of the system IS possible. And I reject that.

 

[Ilja]

1. Don't get this, you are essentially saying Norsen should be considered more of an authority than Zeilinger? Zeilinger is one of the pre-eminient authorities in the area, and entanglement is his specialty. Certainly this is relevant.

He is a good experimenter, but I don't value his theoretical considerations. The issue we are talking about is a theoretical, almost philosophical. In this domain, Zeilinger is no authority for me.

Norsen is primarily a theorist as best I know, although I thought he was doing some experimental work more recently. I would certainly like to see something from him that delved into some new areas more at the forefront of the field, as Zeilinger is doing.

If your position is that experimenters are more on some imaginary "forefront" than theoreticians, I disagree.

Now anyone can be wrong, and anyone can be right, regardless of their prior background. But what we are discussing is not the outcome of an experiment, but rather the relevance of that outcome. So certainly, we *should* consider the opinion of the scientific community in this case.

The point is that the opinion of the scientific community has been referenced by Norsen and there is no disagreement about this opinion. Thus, for the discussion of Norsen's arguments against this opinion the facts about this opinion are irrelevant.

Also: Travis frequently interprets sections of standard texts and comes up with his own views on their meaning and context - against standard opinion. OK, sometimes that can be good too. But he often ignores any text or argument which goes against his opinion. Example: Norsen says EPR is about locality and not realism. Yet EPR references locality only ONCE, versus over a dozen times for realism.

This is something I would count as "minor objections". The word-count of "realism" and "locality" in the EPR paper is clearly not relevant for any interesting philosophical or physical question.

He never addresses this obvious flaw in his reasoning. In addition, EPR provides the standard definition of realism ("elements of reality").

Yet Norsen seeks his own definition, changing the character of the paper in the process. It has been my hope to learn if there is any "meat" to Travis' argument that I am missing in his work. Thus, I was hoping you could enlighten me on this in some fashion. If the best anyone can do is quote Norsen over EPR, quote Norsen over Bell, and quote Norsen over Zeilinger, given the huge gaps I have just mentioned... well, that fails on every level.

I don't consider Norsen as a historian of science and have not evaluated if historical claims in his paper are correct. The argumentation he gives about realism is what interests me. And these arguments are quite nice.

2. I'm laughing... There are plenty who believe that a Bohmian interpretation is deterministic and therefore realistic. And additionally ruled out by contextual no-go proofs. I don't happen to fall in that camp. But clearly, there is something odd about asserting that a theory has hidden variables, is deterministic, and yet is also contextual. Essentially, that viewpoint agrees with the EPR conclusion that a more complete specification of the system IS possible. And I reject that.

Of course, a more complete specification is possible, and there is an explicit example of such a more complete specification, pilot wave theory.

About the reasoning "deterministic and therefore realistic" - hm, one can imagine superdeterministic theories, and I would not consider them as realistic in the EPR-Bell sense, because they do not give any realistic explanations. Thus, better omit the "therefore". Pilot wave theory is deterministic and realistic.

But that pilot wave theory is contextual is correct, it is simply a fact. There is no disagreement in the scientific community about it, as far as I know. Contextuality is not in conflict with common sense realism.

 

[p764rds]

excuse me if I am a little off the current dispute/argument)

Norsen's paper Quote:
"We have carefully surveyed Bell’s concept of local causality, emphasizing several points which are often misunderstood:
...
• A theory’s violation of the criterion means that it
posits non-local causation, not mere non-local correlations.
• A theory’s violation of the criterion does not necessarily" End Quote
from:
http://arxiv.org/PS_cache/arxiv/pdf/0707/0707.0401v1.pdf

My point is this:
As far as SR goes, then Lorentz Invariance must apply to strong causal phenomology. But this does not mean that weak causal structures such as entangled correlations need obey Lorentz. ALternatively (my personal preference) is that the so-called physical distance is not in fact a real distance but a metric - indentifiers for the particles (or indeed waves if QFT considered). So the particles are not actually separated as far as correlation of states is concerned at all - indeed IMO that is how they behave and why I said in an early post that I thought the correlation effect is instantaneous (or very nearly!) - and as experiment has shown too.
Particles not physically separated (only by a metric), is equivalent, to both having simultaneous access to the same 'correlation data'. (Don't forget a 'mechanism' is still helpful to explain correlation IMO)
Lorentz Invariance would not need to be invoked because there is no strong cause and effect violation with correlation.

 

[DrChinese]

1. If your position is that experimenters are more on some imaginary "forefront" than theoreticians, I disagree.

2. The point is that the opinion of the scientific community has been referenced by Norsen and there is no disagreement about this opinion. Thus, for the discussion of Norsen's arguments against this opinion the facts about this opinion are irrelevant.

3. This is something I would count as "minor objections". The word-count of "realism" and "locality" in the EPR paper is clearly not relevant for any interesting philosophical or physical question.

4. Of course, a more complete specification is possible, and there is an explicit example of such a more complete specification, pilot wave theory.

... But that pilot wave theory is contextual is correct, it is simply a fact. There is no disagreement in the scientific community about it, as far as I know.

1. If your opinion is that Norsen is more on some imaginary theoretical forefront than Zeilinger, I respectfully disagree. Perhaps you recall GHZ? I cannot comprehend how you could dismiss Zeilinger's theoretical work, which has opened important new areas. I am not trying to defend Zeilinger, but come on! Get your facts straight before you blow people off.

2. There is almost universal opinion that Norsen is wrong. Not sure your point here. What you were arguing a few posts back that numbers didn't matter, now you are claiming that Norsen is in the majority.

3. If the words of the author count for nothing, I guess I could claim that EPR is about tea leaves. My point, as always, is that EPR and Bell frame the conclusion, well documented, that:

No physical theory of local Hidden Variables can ever reproduce all of the predictions of Quantum Mechanics.

EPR set the stage, and you can see from Bell's title - "On the EPR Paradox" - what Bell's paper is about. And it is NOT about locality (as an assumption) alone.

4. Spoken in the words of a true believer. You might want to consider labeling your opinions next. There is a big difference between saying "a more complete specification is possible" and saying "it is possible to construct a candidate theory in which a more complete specification is possible". These are not the same at all, are they?

My summary: Norsen has missed the mark and overstepped in his conclusion. I welcome a reformulation of Bell which does not require realism a la EPR as a part of the proof. If Norsen would provide that, then he would have something of substance. Until then, I don't expect much to come from this piece except as references by others with the same opinion. If you have any new insights on Norsen's arguments, I welcome those. Otherwise, I will leave you to the last word on this subject.

 

[DrChinese]

excuse me if I am a little off the current dispute/argument)

Norsen's paper Quote:
"We have carefully surveyed Bell’s concept of local causality, emphasizing several points which are often misunderstood:
...
• A theory’s violation of the criterion means that it
posits non-local causation, not mere non-local correlations.
• A theory’s violation of the criterion does not necessarily" End Quote
from:
http://arxiv.org/PS_cache/arxiv/pdf/0707/0707.0401v1.pdf

My point is this:
As far as SR goes, then Lorentz Invariance must apply to strong causal phenomology. But this does not mean that weak causal structures such as entangled correlations need obey Lorentz. ALternatively (my personal preference) is that the so-called physical distance is not in fact a real distance but a metric - indentifiers for the particles (or indeed waves if QFT considered). So the particles are not actually separated as far as correlation of states is concerned at all - indeed IMO that is how they behave and why I said in an early post that I thought the correlation effect is instantaneous (or very nearly!) - and as experiment has shown too.
Particles not physically separated (only by a metric), is equivalent, to both having simultaneous access to the same 'correlation data'. (Don't forget a 'mechanism' is still helpful to explain correlation IMO)
Lorentz Invariance would not need to be invoked because there is no strong cause and effect violation with correlation.

I don't think it is clear either way that Lorentz invariance need apply to wave state collapse. In fact, as I understand Demystifier's position, there may or may not be preferred frames; and key elements of the theory might or might not be Lorentz Invariant. In other words, this is not a per se requirement of the pilot wave theory either way.

Personally, I try to picture that in 4D spacetime, 2 points may be separated. But in higher dimensions, perhaps there is a shorter path between those same 2 points. That would give a non-local character. Of course, that is just a mental picture. In other words, there could be a number of non-local mechanisms out there, and Demystifier is exploring those.

 

[Ilja]

1. If your opinion is that Norsen is more on some imaginary theoretical forefront than Zeilinger, I respectfully disagree. Perhaps you recall GHZ? I cannot comprehend how you could dismiss Zeilinger's theoretical work, which has opened important new areas. I am not trying to defend Zeilinger, but come on! Get your facts straight before you blow people off.

I simply state as a fact that Zeilinger is no authority for me, whatever his credentials. This is not a blow, because there are simply very few people I accept as authorities, but even these are not beyond critical examination and can loose this status easily for a single nonsensical claim.

But let's simply compare not people but arguments.

2. There is almost universal opinion that Norsen is wrong. Not sure your point here. What you were arguing a few posts back that numbers didn't matter, now you are claiming that Norsen is in the majority.

You have misunderstood me. Norsen has quoted opinions of the majority he disagrees with. This is certainly not a claim that Norsen is in majority, but that he has clarified the situation, and in particular the mainstream opinion about the question he is discussing. And this simply shows that you have no point if you quote the same majority which Norsen has already quoted.

3. If the words of the author count for nothing, I guess I could claim that EPR is about tea leaves. My point, as always, is that EPR and Bell frame the conclusion, well documented, that:

No physical theory of local Hidden Variables can ever reproduce all of the predictions of Quantum Mechanics.

EPR set the stage, and you can see from Bell's title - "On the EPR Paradox" - what Bell's paper is about. And it is NOT about locality (as an assumption) alone.

Let's repeat: Of course, EPR and Bell use other assumptions as well: classical logic, elementary probability theory, and also some minimal assumptions about realism and causality which are necessary to do science. These are assumptions which are implicitly used in almost every scientific paper and in this sense it is not necessary to mention them explicitly. One can as well omit realism from the list of explicit assumptions and put it into the standard list of implicit ones, and, reversely, put logic into the list of explicit assumptions. If one does this, one can show that local logic is incompatible with quantum theory, which is as meaningful and correct as to say the same about local realism. It would be even better, because there is only one logic, standard classical mathematical logic, thus, this does not invite confusion between minimal metaphysical EPR-Bell realism and plainly wrong naive realism.

I do not object that one makes these assumptions explicit, but Norsen clearly has a point here.

4. Spoken in the words of a true believer. You might want to consider labeling your opinions next. There is a big difference between saying "a more complete specification is possible" and saying "it is possible to construct a candidate theory in which a more complete specification is possible". These are not the same at all, are they?

In principle, yes, but in this case "a more complete specification is possible" becomes unprovable, because all we can do is to construct candidates for such a more complete specification. To prove that a given candidate is the true completion is impossible. Therefore, with "a more complete specification is possible" one usually means that such candidate theories can be constructed.

My summary: Norsen has missed the mark and overstepped in his conclusion. I welcome a reformulation of Bell which does not require realism a la EPR as a part of the proof. If Norsen would provide that, then he would have something of substance.

I summarize that you have simply not understood his point.

Until then, I don't expect much to come from this piece except as references by others with the same opinion. If you have any new insights on Norsen's arguments, I welcome those. Otherwise, I will leave you to the last word on this subject.

I don't claim to have any new insights, I simply have understood his point, which is a simple and valid one: Using "realism" without specification in the list of assumptions invites confusion between the extremely weak notion of EPR-Bell-realism, which cannot be given up in a reasonable way, and naive realism (or the requirement for non-contextuality), which is simply wrong. And to require realism to be mentioned in the list of assumptions is inconsistent, because then one has to mention equally well logic and probability theory.

About references by others: I already don't expect anything at all from the mainstream. The mainstream works in a "publish or perish" world with short time jobs where one has to follow the authorities to get published and to get future grants. For a mainstream scientist, alternative approaches are simply too dangerous. He has to care for future jobs and grants.