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audioloop
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and not hinging on pre-existing electrons v a l u e s
to say that is realistic or not.
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and not hinging on pre-existing electrons v a l u e s
to say that is realistic or not.
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bohm2 said:I would think most view BM as non-local and realistic. As noted above (I just edited it), even experiments demonstrating violation of Leggett's inequalities (e.g. Groblacher et al.) do not rule out objective reality but only certain types of non-local realism. For example, Bohmian mechanics is consistent with such experiments because position takes priority over all other properties (and those experiments, at the most, rule out realism about polarization).
They aren't. Everything is contextual, except the actual particle positions. So all the contextual stuff is contained in the wave function and not primitive/fundamental, unlike position, which is. Maybe you're questioning why position is "real"/primitive unlike all the other contextual stuff/observables?DrChinese said:I agree about the non-local and realistic just fine. It is the comment about "non-realism" about polarization that I object to. I realize that BMers are to a certain degree "polarization deniers". But there is no difference in the evidence that polarization observables are any different than the usual other observables.
bohm2 said:Maybe you're questioning why position is "real"/primitive unlike all the other contextual stuff/observables?
audioloop said:.
and not hinging on pre-existing electrons v a l u e s
to say that is realistic or not.
.
Just wondering what your opinion is on arguments by this author presenting certain classical systems that are local yet violate Bell's inequality. The author suggests that such "supercorrelated" systems can be both local and realistic (at least contextual realistic):DrChinese said:I do agree that quantum non-locality is a critical difference relative to the classical world.
I also think that DrChinese identifies contextuality and non-reality, and I am very curious to see how will he answer your question.bohm2 said:I'm guessing you interpret contextualism with non-realism since contextuality would imply non-realism? But then, the problem is that such classical systems are contextual yet we don't consider them non-real?
My impression is that some of the difficulties here is again with the definition of "realism". I'm guessing you interpret contextualism with non-realism since contextuality would imply non-realism? But then, the problem is that such classical systems are contextual yet we don't consider them non-real?
You might likecraigi said:I think we must consider non-realism to apply to equally to classical systems. Classical systems can exist in an unkown and unkowbable state. The difference with quantum systems is that they exist in a superposition of possible states. Any record of the result and context of a measurement isn't real in the sense that it is unkown, unkowable and all possibilites exist, until conveyed to the subjective observer, but we don't require that they exist in a superposition for them to lack objective reality.
craigi said:I think we must consider non-realism to apply to equally to classical systems. Classical systems can exist in an unkown and unkowbable state. The difference with quantum systems is that they exist in a superposition of possible states. Any record of the result and context of a measurement isn't real in the sense that it is unkown, unkowable and all possibilites exist, until conveyed to the subjective observer, but we don't require that they exist in a superposition for them to lack objective reality.
bohm2 said:Just wondering what your opinion is on arguments by this author presenting certain classical systems that are local yet violate Bell's inequality. The author suggests that such "supercorrelated" systems can be both local and realistic (at least contextual realistic):
Bell's Theorem: Two Neglected Solutions
http://arxiv.org/ftp/arxiv/papers/1203/1203.6587.pdf
Violation of the Bell-Inequality in Supercorrelated Systems
http://arxiv.org/vc/arxiv/papers/1211/1211.1411v1.pdf
My impression is that some of the difficulties here is again with the definition of "realism". I'm guessing you interpret contextualism with non-realism since contextuality would imply non-realism? But then, the problem is that such classical systems are contextual yet we don't consider them non-real?
stevendaryl said:This is getting down to very subtle matters of definition, but I think when people talk about realism, they are not making any assumptions about whether a state is knowable or not. That is, in a realistic model, the system has a state at every moment, whether or not that state is knowable; it may not be, because there may be no way to probe the state without disturbing it.
That's sort of the point of Bell's theorem. He was investigating whether there were any testable consequences to the assumption that there was a pre-existing state prior to measurement, even if that state is not knowable.
I posted a paper previously showing contextuality in classical systems:DrChinese said:I equate contextuality with non-realism, recognizing fully that they can be defined differently... I see those as being mutually exclusive. Ie you cannot have contextuality *and* realism.
As to Vervoort's superdeterminism and variants: I do not consider these lines of reasoning to be a part of physical science in their current form. You may as well say evolution is due to superdeterminism rather than being due to natural selection from random mutation.
Classical systems can be contextual too: Analogue of the Mermin-Peres squareContextuality lays at the heart of quantum mechanics. In the prevailing opinion it is considered as a signature of "quantumness" that classical theories lack. However, this assertion is hardly justified. Although contextuality is certainly true of quantum mechanics, it can not be taken by itself as discriminating against classical theories. Here we consider a representative example of contextual behavior, the so-called Mermin-Peres square, and present a simple discrete model which faithfully reproduces quantum predictions that lead to contradiction with the assumption of noncontextuality. This shows that quantum-like contextual effects have their analogues in the classical realm too.
DrChinese said:To clarify: Ie you cannot have contextuality *and* counterfactual realism within the same system. Again: if you tweat the definitions enough you probably can find a way to make these work, but then you won't match up to the EPR definitions. The EPR definitions have stood the test of time.
bohm2 said:So if one cannot have both contextuality and realism (as you argue), then such classical systems would then also be non-real? But one doesn't normally think of such systems as being non-real. With respect to Vervoort's papers, I think his focus is on supercorrelated classical systems not superdeterminism.
craigi said:So how does the de Broglie-Bohm interpretation explain contextuality?
craigi said:Are you sure that you mean that? Are you not aruging that realist interpretations actually forbid the superposition of states?
craigi said:So how does the de Broglie-Bohm interpretation explain contextuality?
Demystifier said:DrChinese, concerning the contextuality/non-reality dilemma, I think it is about english language, not about physics. ...
Demystifier said:DrChinese, concerning the contextuality/non-reality dilemma, I think it is about english language, not about physics. To test this hypothesis, let me use a simple example not related to quantum mechanics.
Consider the well-known picture attached below. Is it a rabbit or a duck? Is it contextual, in the sense that it is a rabbit when you look at it one way, and a duck one you look at it another way? Is it real, in the sense that it is a duck and a rabbit even if you don't look at it? Or non-real, in the sense that it is neither a duck nor a rabbit when you don't look at it? Or is it real or non-real in some other sense?
I think answering these questions for such a simple example can significantly help to explain what one means by (non)-real and contextual.
craigi said:It would be interesting if someone who prefers the de Broglie-Bohm interpretation, would describe it a different way. I suspect if someone were to do so, I would cringe at the abuse of poetic license in the definition of the terms or what "it" is that they choose to describe. Interestingly, I would probably be more forgiving of someone who prefers the same interpretations, yet operates on different definitions.
I prefer dBB interpretation, and my view is quite similar to that of bohm2 above.craigi said:It would be interesting if someone who prefers the de Broglie-Bohm interpretation, would describe it a different way.
bohm2 said:1. Rabbit or duck (analogous to contextual properties such as spin, etc. in deBroglie-Bohm) plus
2. An underlying ontological stuff (e.g. the actual picture-analogous to non-contextual Bohmian position) that determines both the rabbit and duck view
As I see it, a non-realist would deny 2. and argue that we can only talk about 1.
The argument is that some interpretations (e.g. Copenhagen) aren't clear about what is "real"; in particular, there's a clear difference between many of the different versions of Copenhagen on the one hand and realistic interpretations (e.g. BM, GRW). The latter are fully precise about what belongs to the primitive ontology (e.g. particle trajectories, flashes, etc.) whereas the Copenhagen interpretation is vague. The basic philosophy of the necessity for so-called primitive ontology in physical theory for those who favour "realism" in physics can be found here:stevendaryl said:It seems to me that the term "realist" or "non-realist" should be augmented by "about ..." Just about any theory can be considered realist about something and non-realist about something else.
Allori repeats this criticism:Thus in contemporary quantum theory it seems that the world must be divided into a wavy quantum system, and a remainder that is in same sense classical... It introduces a fundamental ambiguity into fundamental physical theory (Bell 1987).
On the Common Structure of Bohmian Mechanics and the Ghirardi–Rimini–Weber TheoryEven the Copenhagen interpretation (orthodox quantum theory, OQT) involves a dual structure: what might be regarded as its primitive ontology (PO) is the classical description of macroscopic objects which Bohr insisted was indispensable-including in particular pointer orientations conveying the outcomes of experiments-with the wave function serving to determine the probability relations between the successive states of these objects. In this way, ψ governs a PO, even for OQT. An important difference, however, between OQT on the one hand and BM, GRWm, and GRWf on the other is that the latter are fully precise about what belongs to the PO (particle trajectories, respectively continuous matter density or flashes) whereas the Copenhagen interpretation is rather vague, even noncommittal, on this point, since the notion of ‘macroscopic’ is an intrinsically vague one: of how many atoms need an object consist in order to be macroscopic? And, what exactly constitutes a ‘classical description’ of a macroscopic object?