- #211
audioloop
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rubi said:I know that it doesn't solve all the problems. But i think splitting the world into "quantum" and "classical" is wrong (but useful for practical purposes).
i agree and just another theory.
rubi said:I know that it doesn't solve all the problems. But i think splitting the world into "quantum" and "classical" is wrong (but useful for practical purposes).
ttn said:in response to "we can't trust our senses"
Then it is impossible to base conclusions (like, for example, the conclusion that classical mechanics failed to correctly predict things like the H spectrum and all the other stuff that convinced us to abandon classical mechanics in favor of QM!) on empirical data, period.
stevendaryl said:The meaning of "we can't trust our senses" isn't that "our senses give us no information about the world", it's just that we can't assume that there is a close relationship between the way things are and the way things appear to our senses.
rubi said:I think i can't explain my point any clearer than this now. I hope you can at least understand my thinking and why i find it appropriate.
ttn said:Yes, obviously this is a complex issue. Is the white color of the flag intrinsic in the flag, or is it somehow a relational property between the flag and my sensory apparatus, or what? All of these sorts of things are tricky and subtle and probably none of us want to get into them here! My point is just: if you think we can get any useful information at all about the external world from our senses (and I certainly do), then surely this will have to include basic facts like that there is a 3D world full of stuff that moves around and interacts and that includes things like little flag-shaped hunks of material that sometimes pop up and down. My view is that, if you regard that as even-possibly-mistaken, then you are never going to get anything remotely resembling empirical science off the ground; certainly, if such things "might be wrong", then *literally everything we have ever taken as empirical evidence for anything in science ever* "might be wrong", and then, well, we're totally at sea.
Seems very reasonable to me. By the way, I'm sure everyone appreciates your contribution and detailed posts. Irrespective of the "truth", I always seem to get depressed by reading pro-instrumentalism arguments who seem to consider physics to be the science of meter-readings. Physics in that way would be pretty boring. It kinda of reminds me of behaviourism in the cognitive sciences.ttn said:I therefore declare all the votes for "anti-realism" to be void, and hence the correct answer, "non-locality", to be the winner of the poll. :rofl:
ttn said:I think I do understand it. For you, QM is *merely* a mathematical algorithm for generating statistical predictions. It is not actually a *physical theory* at all. I'm not sure that's the wrong way to understand "ordinary QM".
Physics is physics, not math. Surely it must be the end goal always to say what the world is like. So if you have some mathematical statistics-generating algorithm that really truly says *nothing* about the physical world, that is totally inadequate.
It may be perfectly useful to have it, but it is not a physical theory and I think any true physicist wants a satisfactory physical theory and won't be satisfied by anything less. Hence the search for theories (like Bohm's theory, GRWm/f, MWI) which actually tell (or, in the case of MWI, at least purport to tell) a coherent story about what the *world* is like physically -- a story which doesn't involve any shifty splits and which, at the end of the day, both produces recognizable macroscopic objects and gets the details right for the statistics of how often they should move this way and that.
ttn said:Just as one final thought on the original topic of the thread, I hope people who voted for "anti-realism" in the poll will make sure not to miss my post #204 in which I sketch a mathematically rigorous version of the EPR argument *from locality to* what (I think) people who voted "anti-realism" mean by "realism". Clearly, just as a matter of sheer elementary logic, anybody who thinks that we can elude the spectre of nonlocality by denying (this) "realism", has something pretty serious to think about there. I will note also that, despite a couple of half-hearted attempts, nobody rose to the challenge of showing how the perfect correlations (observed in the usual EPR-Bell scenario when a=b) can be explained by a local but non-realist model. From the point of view of the theorem in #204 this is of course not surprising: "realism" (meaning here deterministic non-contextual counterfactually-definite hidden variables) is the *only* way to explain these particular correlations locally. The correlations and the assumption of locality *logically entail* "realism". That is what that little mini-theorem says.
I therefore declare all the votes for "anti-realism" to be void, and hence the correct answer, "non-locality", to be the winner of the poll. :rofl:
rubi said:I think that's not a fair way to end the discussion. After all, you just said that the instrumentalist viewpoint might not be "the wrong way to understand ordinary QM". I think that if you take ordinary (instrumentalist) QM and give beable status to only the statistical properties it predicts (including the correlations), then you can formally check Bell's locality criterion (it's just a formal mathematical criterion that can be formally applied to any theory, independent of whether you classify it as physical or not) and it would turn out that instrumentalist QM obeys it. So instrumentalist QM does classify as a Bell-local, non-realistic model that explains the correlations. So in the end, whether there exists such a theory depends on whether you accept individual outcomes as beables or not. There is no mathematical reason that prevents us from applying the Bell-criterion to a theory, which doesn't have individual outcomes as beables and instead gives this status to statistical properties.
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In the end, i also want to thank you for the discussion. I've also learned something and i will definitely try on a piece of paper, whether the Bell-locality criterion applied to instrumentalist QM classifies it as local. That would probably be one of the coolest things I've come across in the last months.
ttn said:Unfortunately, the first thing you'll write down on your paper is "P(A..." and then you'll realize that there's trouble, since "A" here refers to the actual outcome of an experiment -- something you've said isn't part of your instrumentalist version of QM at all. How can the probabilities, attributed by a theory to a certain event, satisfy (or even fail to satisfy) a certain mathematical condition, when according to the theory there is no such event?
Anyway, good luck, and thanks again for the enjoyable discussion.
rubi said:The beables are the statistical properties like probability distributions, mean values and so on. I will not start writing down [itex]P(A[/itex], but instead i will write down [itex]P(<A>|...)[/itex] and then check whether the formal criteron is obeyed.
ttn said:Cool. But please describe this as "Rubi's formulation of locality", not Bell's, when you publish...
J. S. Bell's concept of local causality (Travis Norsen) said:[itex]b_i[/itex] refers to the value of some particular beable in space-time region [itex]i[/itex] and [itex]B_i[/itex] refers to a sufficient (for example, a complete) specification of all beables in the relevant region.
But agreement with everything you wrote is not inconsistent with violation of Bell's implying non-locality. And I personally agree with pretty well everything you wrote.Len M said:The question as to how close empirical reality is to independent reality is an untestable one, so I tend to stay on the side of caution – a miss is as good as a mile, I can’t see the point of assuming a degree of closeness, as if perhaps we only need to concern ourselves with the mechanistic alteration to the “thing in it’s self” by the characteristics of the eye – that to me seems a bit of a cop out, it restores a comfortable feeling that what lay within independent reality is a rough approximation of phenomena...
bohm2 said:But agreement with everything you wrote is not inconsistent with violation of Bell's implying non-locality. And I personally agree with pretty well everything you wrote.
As I said in my post, I see nothing at all wrong in simply accepting that science (as an experimental discipline) belongs quite properly within phenomena. ttn seems to me to picking and choosing in an arbitrary manner between science as practiced within empirical reality (in terms of testability) and the extrapolation of those models to an independent reality that cannot (and does not) involve testability, without seemingly keeping track of what he is doing (at least not in a formal transparent manner that identifies the difference between the scientific status of a model in terms of empirical reality and the same model in terms of independent reality). It's easier for me to keep track of the mix between empirical reality and independent reality because I go the whole hog, I confine the scientific method to phenomena and I reserve the realm of independent reality as being unknowable in a scientific sense and having no correspondence to empirical models, but philosophically being free to conjecture about the nature (and importance) of its existence. For a less extreme stance though, it becomes more difficult to keep track, but I think you have to and be quite transparent about it in public because there is no question that a mix is being invoked between the scientific method involving testability and the extrapolation of that model to a realm of independent reality that cannot involve testability.ttn said:My point is just: if you think we can get any useful information at all about the external world from our senses (and I certainly do), then surely this will have to include basic facts like that there is a 3D world full of stuff that moves around and interacts and that includes things like little flag-shaped hunks of material that sometimes pop up and down. My view is that, if you regard that as even-possibly-mistaken, then you are never going to get anything remotely resembling empirical science off the ground; certainly, if such things "might be wrong", then *literally everything we have ever taken as empirical evidence for anything in science ever* "might be wrong", and then, well, we're totally at sea.
if you regard that as even-possibly-mistaken
But agreement with everything you wrote is not inconsistent with violation of Bell's implying non-locality
Maui said:Correct me if i am wrong, but the fundamental constituent of reality are not inadequate classical concepts like 'particle' and 'wave', but information. We are not seeing particles, but always seeing information about particles. The brain is not just a simple collection of particles(as Newtonain perspective would dictate), but an(emergent) information processor. At the rock bottom of things, we are not seeing tables and chairs but information about tables and chairs. While there could be a stunning correspondence between tables and our sensation of tables, we should not overlook the simple fact that we only have access to the information about tables, not the tables themselves. Tthe ultimate nature of tables is not accessible, hence it is not a valid scientific question. I totally agree with Bohr, it's only what we can say about Nature, not what or how Nature is.
Len M said:As I said in my post, I see nothing at all wrong in simply accepting that science (as an experimental discipline) belongs quite properly within phenomena. ttn seems to me to picking and choosing in an arbitrary manner between science as practiced within empirical reality (in terms of testability) and the extrapolation of those models to an independent reality that cannot (and does not) involve testability, without seemingly keeping track of what he is doing...
I agree; regretfully that was the paradigm for the last century, it seems.stevendaryl said:[..] If all you care about is the pragmatics of predicting what happens when we perform specific experiments, then fundamental physics is over, it seems to me.
rubi said:Why? You write in your own paper that for the locality criterion ...
That's a good question and I'm not sure? But my gut hunch is that ttn would not agree with the Kantian and/or epistemic structural realist position that I think both you (if I'm understanding you) and myself seem to subscibe to but who knows?Len M said:so perhaps that would also be the viewpoint of ttn?
bohm2 said:While many of these have been mentioned on various threads/posts I thought I'd post a list of the major papers I've come across arguing that violations of Bell's inequality implies non-locality, irrespective of any other issues (e.g. realism, determinism, hidden variables, pre-existent properties, etc.): ...
Probability of "what"?rubi said:Standard quantum mechanics is basically a theory that describes the evolution of probability, so you would choose the beables to be the probability distributions.
bohm2 said:Probability of "what"?
Observable of what? If I'm understanding you (I may not be) this has been considered:rubi said:The probability to measure a given value for an observable, just as every standard textbook says. But the value itself isn't included in QM, only it's probability distribution. There is no prediction about concrete values. QM just says that the statistics of the measurement is given by the probability distribution. There is no underlying "real" observable that has a particular value.
Can quantum theory and special relativity peacefully coexist?Muller (1999) stresses that no space-time formulation of quantum mechanics is as of yet available—thus it can not be regarded a spacetime theory—, and that it is a hard job to formulate one, be it in Minkovskian or Galilean spacetime. However, despite being true, this is not relevant for the problem here. All that is needed to consider the question of local causality are predictions for measurement outcomes at certain space-time locations as in Fig. 3 (see Appendix), and quantum mechanics does give such predictions when the measurements and the state to be measured are specified. It does not matter that the theory itself cannot be taken to be a spacetime theory on some appropriate differentiable manifold.
bohm2 said:Observable of what? If I'm understanding you (I may not be) this has been considered: ...
What is your definition of locality?rubi said:To say it as briefly as possible: These above papers prove that if a theory can account for the individual outcomes of the experiment, then it must be non-local. Standard QM doesn't do it, so it can be a local theory.
bohm2 said:What is your definition of locality?
How about this model? One of the papers just came out today. The author argues that it is local and makes all the predictions of QM:DrChinese said:Relational BlockWorld is local. I consider it non-realistic.
Failure Of The Bell Locality Condition Over A Space Of Ideal Particles And Their PathsBut, by combining Richard Feynman’s formulation of quantum mechanics with a model of particle interaction described by David Deutsch, we develop a system (the “space of all paths,”- SP) that (1) is immediately seen to replicate the predictions of quantum mechanics, has a single outcome for each quantum event (unlike MWI on which it is partly based), and (3) contains the set λ of hidden variables consisting of all possible paths from the source to the detectors on each side of the two-particle experiment. However, the set λ is nonmeasurable, and therefore the above equation is meaningless in SP. Moreover, using another simple mathematical expression (based on the exponentiated-action over a path) as an alternative to the above equation, we show in a straightforward argument that SP is a local system.
The interesting thing, though, is that all proofs of Bell’s theorem (his original arguments and those by others in the same vein) for two entangled particles involve a probability distribution. This means that there is indeed a hidden premise, a tacitly assumed “X”—namely, that the underlying space for a quantum system is measurable. In other words, if we choose “X” to be “measurable” then in Maudlin’s formula we have the proposition, “No local, measurable theory can make The Predictions for the results of experiments carried out very far apart.” We consider Bell’s simple proof of this specific proposition (that is, when “measurable” is substituted for X) to be obviously valid.
bohm2 said:How about this model? One of the papers just came out today. The author argues that it is local and makes all the predictions of QM:
Failure Of The Bell Locality Condition Over A Space Of Ideal Particles And Their Paths
http://lanl.arxiv.org/ftp/arxiv/papers/1302/1302.5418.pdf
Bell inequalities and hidden variables over all possible paths in a quantum system
http://lanl.arxiv.org/ftp/arxiv/papers/1207/1207.6352.pdf
The Space of all paths for a quantum system: Revisiting EPR and BEll's Theorem
http://lanl.arxiv.org/ftp/arxiv/papers/1109/1109.6049.pdf
What is interesting is the author's argument is similar to rubi's, I think (?), but he arrives at it using a different model:
It seems surprising that no one until now has noticed the hidden premise of measurability in Bell’s definition of locality
bohm2 said:What is interesting is the author's argument is similar to rubi's, I think (?), but he arrives at it using a different model:
rubi said:The problems with measurability that i mentioned earlier don't apply to the argumentation of ttn, because Bell locality doesn't require something like a translation-invariant measure on the space of wave-functions. It's only needed if you want to rule out all theories with huge hidden-variable spaces using Bell's theorem. That's why the counterexamples stevendaryl mentioned can work.
bohm2 said:While many of these have been mentioned on various threads/posts I thought I'd post a list of the major papers I've come across arguing that violations of Bell's inequality implies non-locality, irrespective of any other issues (e.g. realism, determinism, hidden variables, pre-existent properties, etc.):
Bertlmann’s socks and the nature of reality
http://cds.cern.ch/record/142461/files/198009299.pdf
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