The quantum state cannot be interpreted statistically?

[my_wan]

Isn't realism the position that measurement results reflect preexisting properties?

No, realism takes two main forms. One involves the notion that there exist fundamentally ontic entities and the other only that there exist entities which have ontic properties. A tornado would be an example of the last given no presumptions of what the tornado consist of. Basically in both cases ontic entities refer to partitioned constructs which cannot share the same degree of freedom at the same time, or cross paths without interfering with (or bumping into) each other.

Given the tornado case it most certainly contains definable properties that are not properties of any of the underlying constituents. Hence a measurement need not reflect preexisting properties. However, it does require such properties to be derivative, in that given the underlying properties the emergent properties are a consequence.

On the face of it even something so simple as a velocity measurement is demonstrably not a preexisting thing. Since differing measuring instruments from differing perspectives will not measure the same velocity. To a realist the realness is (somewhere) in the thing being measured, not in the measurement we associate with the thing. Yet the thing is required in order for a measurement to occur. Hence why measurements and things are associated, just not in the way strawman characterizations of realist are applied.

 

[Fredrik]

If the article was so bad why or how can you assume the terms in a referenced article, such as ontic and epistemic, can be characterized in a manner in which the authors provided no prototype use of the terms or variants in their article to judge how those authors would characterize them in a manner consonant with your own? Meanwhile, rejecting the characterization of terms or variants thereof they did use as meaningful indicators of what they were conveying.

I'm not sure I understand what you're asking, but if you're asking what I think you're asking (why do I think that PBR defines the statistical view as what HS calls a ψ-epistemic ontological model?), then I have answered the question several times already. Here it is again: The things they say immediately after

We begin by describing more fully the difference between the two different views of the quantum state [11].​

very clearly match the conditions from the HS definitions of the terms ψ-ontic, ψ-complete, ψ-supplemented and ψ-epistemic. Also, reference [11] is HS.

My Translation:
We are making assumptions about the system independent of assumptions about the model in order to allow the possibility of falsifying claims about what the model represents, in terms of realness as previously outlined.

This doesn't make sense, since you can't make a rational argument about undefined terms, and the authors do leave "property" undefined. I agree that the authors are making assumptions about the system, but it's impossible to use those assumptions in any kind of argument worth discussing. They can be used to provide some motivation for the terminology of HS, but that's it.

No, it's not a mathematical statement. Here's why. You have a system and a mathematical model of that system. If the two were the same thing then empirically invalidating the mathematical model would be impossible since there is nothing other than the model to invalidate it with.

This is wrong. The statement I made is a mathematical statement, about two different ways (a quantum theory and its ontological model) to assign probabilities to members of some set. We are only talking about sets and probability measures. Reality doesn't enter into it. Empirical justification doesn't enter into it. It's just a matter of whether another theory (the ontological model) can make the same predictions as the first one (the quantum theory), and at the same time satisfy a few mathematical conditions (the ones that make it a ψ-epistemic ontological model for the quantum theory).

So, if you want to use terms such as ψ-epistemic, you must restrict its relevance to a particular model, such as QM, and leave alternative models to be judged individually rather than on labels such as ψ-epistemic.

I don't understand what you're saying, but I have made it clear that I define QM as the framework in which quantum theories are defined, and that the concept of ontological model applies to specific quantum theories in that framework. For example, a quantum theory of a qubit (any quantum theory with a 2-dimensional Hilbert space) might have an ontological model. What this means is that there might exist another theory that makes the same predictions as the quantum theory, and satisfies the mathematical conditions we would expect to be satisfied if we think of λ as a complete list of properties.

If the authors own words are labeled gibberish how is it possible to discuss what the paper said?

That's a good question. I think the quality of this paper is so low that it's very questionable if it can be discussed at all. I hope their reviewer will force them to rewrite the article substantially before considering it for publication.

 

[bohm2]

What's kind of surprising is that one of the authors (Terry Rudolph) of the PBR paper co-authored this recent paper with Robert W. Spekkens (October 2011):

Reconstruction of Gaussian quantum mechanics from Liouville mechanics with an epistemic restriction
http://lanl.arxiv.org/PS_cache/arxiv/pdf/1111/1111.5057v1.pdf

 

[DevilsAvocado]

Isn't realism the position that measurement results reflect preexisting properties?

Bingo!

Anyone saying anything else is pure gobbledygook.

 

[Ken G]

What's kind of surprising is that one of the authors (Terry Rudolph) of the PBR paper co-authored this recent paper with Robert W. Spekkens (October 2011):

Reconstruction of Gaussian quantum mechanics from Liouville mechanics with an epistemic restriction
http://lanl.arxiv.org/PS_cache/arxiv/pdf/1111/1111.5057v1.pdf

Yes, that's quite interesting. At first glance it would appear that Rudolph is playing both sides against the middle, as it were, but more careful inspection finds his consistent thread-- he thinks that a subtheory of quantum mechanics, called Gaussian quantum mechanics (which relates somehow to positive Wigner representations, I don't understand but it seems to hold whenever every underlying ontic element connects to a positive probability of being manifest in the actual reality, so this holds when a complete (reductionist) theory can live underneath the epistemologically limited version of that complete theory, but PBR says that cannot be true of all of quantum mechanics). So if you put the two papers together, Rudolph is saying that much of quantum mechanics could be interpreted as a purely statistical description of some inaccessible underlying hidden-variable theory, but not all of it-- and the parts that cannot, which are active in the PBR proof, must be the "non-Gaussian" element. So the bottom line of the intersection of the two papers is something like: to see why only an ontic interpretation of quantum states can work if there is some complete hidden-variable theory underneath quantum mechanics, look for the ways in which such a complete hidden-variable theory must contain non-Gaussian elements.

Of course, once again we find in both of these papers the crucial assumption that we be able to imagine some complete underlying hidden variables theory, some perfect ontological description that is responsible for the reasons that quantum mechanics works. And once again, I find it utterly inappropriate to claim that assumption is the same thing as the assumption of realism. The logic is simply wrong-- realism asserts that we interpret the elements of our actual theories as something real, but nowhere does realism require that we postulate the existence of some complete ontological description of reality. Indeed, it is far more realistic, about the history of science, to recognize that no such ontological convergence is in the process of happening in physics, so it is quite unrealistic to make the necessity of such a convergence a requirement for the interpretations of our current theories.

Note also that much of Rudolph's mindset appears to be gauged by several quotes from Jaynes, which express an attitude I have been sharply critical of: that it is coherent within scientific language to distinguish between what is real and what we can know about what is real. It would seem to me that the very first step in doing science is to dispense with any such distinction, but dispense in favor of what we can know-- not in favor of what is actually real or which must actually underpin our theories in ways we cannot know.

 

[Ken G]

Why doesn't it involve the notion of a position? Whether we label it or not, or no matter how we choose to label it, it still constitutes a potential degree of freedom. Do you even know what a position is? I already said it, it's not a thing but a degree of freedom of a thing, however you want to contextualize "thing". So in that sense even a point far removed from our Universe still constitutes a possible future degree of freedom. Hence the "position" is not lacking for that lack of any constructs to actually occupy that degree of freedom and possibly put labels on it like we do.

I know all that, indeed it is very much my point. Coordinatizatons are irrelevant to the issue of the ontology of position, as they do nothing but label the ontology. A coordinate is like calling one thing a tiger and something else a lion, but had the labels been reversed the basic ontology of those animals would be unaffected. In relativity, we connect the ontology to the invariants, but my point has been, even invariants are not ontic elements anywhere except in the mathematical structure that defines them. Observations are something different, and only connect to the mathematical ontology when we choose to make that connection and test its usefulness to us. Realism says we should interpret the invariants as real, but it doesn't say what "real" means: I have been saying that what science should say real means is what Bohr said it should mean: it should mean what we can say about nature, which is what we can know about nature, which is epistemology. Ergo, science turns ontology into epistemology in a very particular way that is more or less the definition of science. Ergo, imagining that models that we do have should be underpinned with models that we don't have is nothing like what science should be doing.

And does not an abject denial that a possibly ontic world outside your mind actually consist of something constitute a mind rejection fallacy?

You mistake my point entirely. Nowhere in anything I wrote, or thought, did I deny the possibility of an ontic world outside my mind. Indeed, I am a realist-- I do believe in such an ontic world. The issue is whether any element of a scientific theory should be interpreted as existing in that ontic world. I claim it is nothing short of logically inconsistent to treat science that way. So anyone who would be a "scientific realist" had better do some work on avoiding the mind projection fallacy of imagining their minds can tell what aspects of a scientific theory are actually real, and what aspects are just a useful treatment of reality in some context. I have no such problem-- my view is completely devoid of any mind projection fallacies, I think that what the mind does is just that: what the mind does. No projections at all, just a convenient form of language that usefully pretends that science deals in ontology without first forgetting all of scientific history.

Hence the absolute claim that the Universe is dependent on ontic constructs is a moot scientifically meaningless claim.

But you see, I have no difficulty whatever with that statement. You imagine I must disagree with it, but I completely agree with it. I merely take the next logical step: if it is moot, then science should not pretend to rely on it! Further, I point out that PBR certainly does rely on it, which is the relevance to this whole thread.

 

[DrChinese]

... realism asserts that we interpret the elements of our actual theories as something real, but nowhere does realism require that we postulate the existence of some complete ontological description of reality. ...

I'm not saying that there isn't a version of "Realism" that doesn't match your definition. But I do think that many readers would be more likely to be thinking instead of the kind of realism which, when coupled with the word "Local", is excluded by Bell. I realize that with PBR's paper, we are now delving into what that Realism might look like. But I think we want to keep sight that the kind of Realism which is associated with the EPR "Elements of Reality" is quite different than your definition.

I don't know how we would keep track of these, but we are definitely in danger of confusing rather than enlightening. Objective Realism vs. Model Realism?

 

[my_wan]

I'm not sure I understand what you're asking, but if you're asking what I think you're asking (why do I think that PBR defines the statistical view as what HS calls a ψ-epistemic ontological model?), then I have answered the question several times already. Here it is again: The things they say immediately after

We begin by describing more fully the difference between the two different views of the quantum state [11].​

very clearly match the conditions from the HS definitions of the terms ψ-ontic, ψ-complete, ψ-supplemented and ψ-epistemic. Also, reference [11] is HS.

Look at the two terms with my bold. The "statistical view" is a system interpretation independent of the statistics used in the model, like statistical mechanics. The "ontological model" is a property of the model, independent of the properties of the system itself. hence you are explicitly stating you think the PBR paper defines the model as the system being modeled. This is wrong, which even just the abstract alone makes clear. The PBR paper made no such claim as you have attributed to them here!

To illustrate start with the abstract and move on through the body:

Another is that even a pure state has only a statistical signicance, akin to a probability distribution in statistical mechanics.

It can't be any more clear. Is the statistics simply a property of the model, as it is in statistical mechanics, or is the statistics a property of the system itself in direct conflict with its meaning in statistical mechanics? The results point to the latter, but does not require all possible theories to define it in terms of statistics, like QM does.

Some physicists hold that quantum systems do not have physical properties, or that the existence of quantum systems at all is a convenient fiction. In this case, the state vector is a mere calculational device, used to make predictions of the probabilities for macroscopic events.

This explicitly conveys the notion that the model properties are not the properties of the system but properties of the model. This is a model, not system, specific claim. This immediately follows:

This work, however, proceeds on the assumption that quantum systems - like atoms and photons - exist, and have at least some physical properties. We assume very little about these properties,[...]

Note the term "like atoms and photons" and the explicit use of "quantum systems", not a "quantum model" of the system? That's why they assume so little about those properties. They are not requiring any particular ontological judgement of what atoms and photons are, only that they have properties that are measurable independent of any model used to characterize or quantify them. They then go on to demonstrate that quantum randomness entails properties that are described by these statistics that are measurable independent of any model used to characterize or quantify them. Hence the notion that ψ-model (QM) statistics is a set of model only properties, not referring to any system properties is false. It's false irrespective of any ontic or epistemic notions you want to attach to it.

This doesn't make sense, since you can't make a rational argument about undefined terms, and the authors do leave "property" undefined. I agree that the authors are making assumptions about the system, but it's impossible to use those assumptions in any kind of argument worth discussing. They can be used to provide some motivation for the terminology of HS, but that's it.

I'm finding it increasingly difficult to believe I am on a physics forum of this caliber hearing the term "properties" is an undefined hence meaningless. It's tantamount to saying the term "empirical data" is an undefined hence meaningless.

1) All measurables are properties.
2) A theory (model) may contain properties that are not measurable but needed to produce valid consequences entailing measurable properties.
3) A model may contain properties that the model defines as non-existent in the system being modeled, like randomness in statistical mechanics which PBR demonstrates can't be the case in QM systems, not models.
4) A system may contain properties not contained in the model, or possibly even properties that are not directly measurable.

What ties all this together in a consistent definition of properties? Properties define limits on degrees of freedom. These limits on the degrees of freedom which are empirically accessible as measurements are the empirical data.

This is wrong. The statement I made is a mathematical statement, about two different ways (a quantum theory and its ontological model) to assign probabilities to members of some set. We are only talking about sets and probability measures. Reality doesn't enter into it. Empirical justification doesn't enter into it. It's just a matter of whether another theory (the ontological model) can make the same predictions as the first one (the quantum theory), and at the same time satisfy a few mathematical conditions (the ones that make it a ψ-epistemic ontological model for the quantum theory).

My bold: What then is the point of PBR outlining experimental constructs to Empirical justify it independently from QM. It is completely, totally, and absolutely outrageous to say empirical justification doesn't enter into it, period. You want to consider "quantum theory and its ontological model" irrespective of the empirical content of the system it describes!

Let's take it as a purely mathematical statement having not empirical bearing. Now look at statistical mechanics, which defines a statistical system which the randomness is a purely mathematical statement which the theory itself defines out of the model. So if ψ-epistemic is a purely mathematical statement why can't a ψ-epistemic model use ψ-epistemic to describe a system which the self same model describes as non-epistemic, just like statistical mechanics? That is exactly the shoes you are in when you so flagrantly throw away empirical data as having any relevance!

I don't understand what you're saying, but I have made it clear that I define QM as the framework in which quantum theories are defined, and that the concept of ontological model applies to specific quantum theories in that framework.

Why then have you generalized ψ-epistemic ontic such that the validity of ANY model can be judged on these epistemic/ontic labels? Wait a minute... you said "quantum theories are defined", as in plural. There is only one empirically meaningful QM and it makes no ontological characterizations of anything whatsoever.

For example, a quantum theory of a qubit (any quantum theory with a 2-dimensional Hilbert space) might have an ontological model. What this means is that there might exist another theory that makes the same predictions as the quantum theory, and satisfies the mathematical conditions we would expect to be satisfied if we think of λ as a complete list of properties.

What if it was an "ψ-epistemic ontic" model, whatever that means to you, would that rule out the "might (otherwise) exist"? because I still don't have a clue how you are contextualizing ontic/epistemic definition in an meaningful way, for all quantum theories or otherwise.

That's a good question. I think the quality of this paper is so low that it's very questionable if it can be discussed at all. I hope their reviewer will force them to rewrite the article substantially before considering it for publication.

Why then is what they said so perfectly comprehensible to me. Even though the terms used had conflicting meanings in general, even within physics, they unambiguously defined perfectly well the context in which they used said terms. Not only was it sensible but, what you could relate only to an external referenced work which the authors had no hand in, made perfect sense in reference to what they said themselves within their own paper.

Hence I see the "gibberish" as an excuse to cherry pick your own interpretation. Perhaps your interpretation makes perfect sense, but you are not providing it like the PBR paper did, only contextualizing the terms and leaving the reader guessing about the extent of the generality intended.

 

[my_wan]

Bingo!

Anyone saying anything else is pure gobbledygook.

Explain the non-preexistence of tornados and the properties associated uniquely with them and not their constituents then.

 

[apeiron]

Explain the non-preexistence of tornados and the properties associated uniquely with them and not their constituents then.

Are you arguing that limits have ontic status here? Tornadoes arise because the thermal jostle of air molecules become constrained/entrained in their degrees of freedom. So tornadoes and "vortical properties" could be said to exist as a potential (as part of a broader collection of degrees of freedom) before they become actual (before limits arise on those degrees of freedom).

Note also that the very notion of degrees of freedom seems to imply the possibility of emergent limits as a part of those freedoms. As in Aristotle's doctrine of immanent form.

(Apologies to Fredrik as this seems another thread excursion, but it is in fact important in asking what is "real" about a wavefunction. The degrees of freedom may pre-exist the constraints that arise. But where do the constraints actually arise from? Do they arise from within the degrees of freedom in the manner of a spontaneous symmetry-breaking? So a spontaneous collapse of the wavefunction? Or are they imposed from without - as in an experimenter forcing an interaction though a measurement? Or some combination of the two - which is where the unpredictability arises? A tornado, for example, needs an externally imposed gradient of temperature and pressure on an air mass. But then exactly where and when it self-organises is "chaotic".

Realism, in its simpler reductionist/mechanical form, just presumes the pre-existence of local substantial entities whose properties atomistically inhere. But realism in the systems science/condensed matter sense that My Wan appears to be talking about, opens the question of whether the constraints, the limits on degrees of freedom, are real too. And if so, do they exist inside or outside the wavefunction, and as potential or actual existence. Quite a can of worms gets opened up here. The further ontic dimension of vague~crisp, potential~actual, must be considered when arguing about realism.)

 

[Fredrik]

Look at the two terms with my bold. The "statistical view" is a system interpretation independent of the statistics used in the model, like statistical mechanics. The "ontological model" is a property of the model, independent of the properties of the system itself. hence you are explicitly stating you think the PBR paper defines the model as the system being modeled. This is wrong, which even just the abstract alone makes clear. The PBR paper made no such claim as you have attributed to them here!

I'm sorry, but this is nonsense. PBR declared that they are going to explain what they mean by the statistical view, and then they immediately referenced Harrigan & Spekkens, and started to describe the conditions that are part of the definitions in HS. In the sentence that started with "If the quantum state is statistical in nature (the second view)...", the very next thing was the condition that defines the term "ψ-epistemic". I don't know how you can ignore this. It can't possibly mean anything other than what I've been telling you.

I have no idea how you can claim that I'm "explicitly stating" that "the PBR paper defines the model as the system being modeled." I haven't said anything remotely like that.

To illustrate start with the abstract and move on through the body:


It can't be any more clear.

The authors disagree with you. As I keep saying, page 1 says

We begin by describing more fully the difference between the two different views of the quantum state [11].​

If it can't be more clear, then why are they saying that they are going to describe it more fully? And why are they referencing Harrigan & Spekkens in that very sentence?

I'm finding it increasingly difficult to believe I am on a physics forum of this caliber hearing the term "properties" is an undefined hence meaningless. It's tantamount to saying the term "empirical data" is an undefined hence meaningless.

This isn't hard. PBR doesn't define the term. HS doesn't define the term. No one does. It's clear that the meaning they have in mind is the one that's consistent with the intuitive understanding of the term that we've all had since before we started studying physics and mathematics. So it's not meaningless. It just doesn't have a mathematical definition. But that means that it can't be used in a mathematical argument, unless you intend to throw all of mathematics in the trash (in particular ZFC set theory) and completely start over from scratch with new axioms for mathematics, with "property" as a primitive.

1) All measurables are properties.
2) A theory (model) may contain properties that are not measurable but needed to produce valid consequences entailing measurable properties.
3) A model may contain properties that the model defines as non-existent in the system being modeled, like randomness in statistical mechanics which PBR demonstrates can't be the case in QM systems, not models.
4) A system may contain properties not contained in the model, or possibly even properties that are not directly measurable.

What ties all this together in a consistent definition of properties? Properties define limits on degrees of freedom. These limits on the degrees of freedom which are empirically accessible as measurements are the empirical data.

I don't know how you can consider this a definition. #1 can perhaps be thought of as a partial definition, but it has nothing to do with how the term is used in PBR or HS.

It is completely, totally, and absolutely outrageous to say empirical justification doesn't enter into it, period.

This is wrong. Maybe you have just forgotten that the statement we're talking about is "No quantum theory has a ψ-epistemic ontological model".

Why then have you generalized ψ-epistemic ontic such that the validity of ANY model can be judged on these epistemic/ontic labels? Wait a minute... you said "quantum theories are defined", as in plural. There is only one empirically meaningful QM and it makes no ontological characterizations of anything whatsoever.

"There is only one empirically meaningful QM". Great. Which one is it? It can't be the quantum theory we all studied first (the theory of a single spin-0 particle in Galilean spacetime, influenced only by a classical potential), because it doesn't apply to photons. It can't be QED, because it doesn't include strong interactions. Is it the standard model with Higgs? I guess we'll have to wait and see...or maybe we should dismiss it too, because it doesn't cover gravity.

You are wrong to think that only one theory is relevant. If you're going to do the Stern-Gerlach experiment, no quantum theory will be more useful to you than the quantum theory of a single qubit.

I don't know why you think I have generalized anything. I'm just being more careful with the details than any of these authors.

When you say

Why then have you generalized ψ-epistemic ontic such that the validity of ANY model can be judged on these epistemic/ontic labels?​

I have no idea what you're asking.

Why then is what they said so perfectly comprehensible to me.

Seriously? Then please state the theorem that's being proved. Don't even try to prove it. Just state it.

 

[Ken G]

I realize that with PBR's paper, we are now delving into what that Realism might look like. But I think we want to keep sight that the kind of Realism which is associated with the EPR "Elements of Reality" is quite different than your definition.

I agree, I'm not saying that people need to start using the word "realism" differently (though I do in fact think that), because it's just a word, and it has its traditional meanings. What I am arguing is that if we use that rather limited (and I would say scientifically unsound) version of the meaning of "realism", as PBR does, then we should not feel it is a mild assumption that quantum mechanics should work because of it. And if that is not a mild assumption, then the constraints of the PBR theorem do not significantly limit the possible interpretations of quantum mechanics that invoke a different idea of what scientific realism should entail.

I don't know how we would keep track of these, but we are definitely in danger of confusing rather than enlightening. Objective Realism vs. Model Realism?

I'd suggest "Absolute Realism (referring to theories that don't actually exist in our textbooks) vs. Model Realism (referring to those that do)", and then ask-- which one has to do with science? What seems to be quite crucial in the PBR proof is that they assume the existence of properties (in the system, not in the model-- the properties of the model of quantum mechanics are perfectly explicit and could be enumerated, they certainly don't need to be treated as hypothetical), and claim that they don't need to assume much about these properties for their proof to hold. Yet the key assumption seems to be that the properties determine the outcome of experiments on the system, and that the predictions of quantum mechanics must match those property-determined outcomes, which I claim is a stringent (and unlikely) assumption about quantum mechanics, not a mild one.

 

[my_wan]

Are you arguing that limits have ontic status here? Tornadoes arise because the thermal jostle of air molecules become constrained/entrained in their degrees of freedom. So tornadoes and "vortical properties" could be said to exist as a potential (as part of a broader collection of degrees of freedom) before they become actual (before limits arise on those degrees of freedom).

Actually that is well said. Though some peoples perspectives appear to entail that definition, I was not arguing that limits have have ontic status myself (previously I said I was ambivalent on that issue). Yet operationally they can have ontic-like properties. I made this argument previously also. Consider and zoo of tornado like constructs which can constrain/entrain individual tornadoes. Then the set of tornadoes can produce even higher order entities in generally the same way the atmosphere produced tornadoes.

Essentially what we as humans are is a higher order construct of first molecules, then atoms, then subatomic particles and who knows after that. Yet the ordering is as important, which is why people and rabbits are not the same thing. There is nothing unique about building one order of complexity on top of another. From a reductionist perspective it's what the bottom might look like, if that bottom contains objects, or even if there is a bottom.

Note also that the very notion of degrees of freedom seems to imply the possibility of emergent limits as a part of those freedoms. As in Aristotle's doctrine of immanent form.

Yes, it most certainly does imply the possibility of emergent limits as a part of those freedoms, just as I described with the large set of tornadoes. I've never thought about that particular doctrine of Aristotle, but yes, as long as you limit the point to that doctrine then the implication is there in a very general sense. We certainly don't think that because a fox was raised on rabbits it must inherit rabbit properties.

(Apologies to Fredrik as this seems another thread excursion, but it is in fact important in asking what is "real" about a wavefunction. The degrees of freedom may pre-exist the constraints that arise. But where do the constraints actually arise from? Do they arise from within the degrees of freedom in the manner of a spontaneous symmetry-breaking? So a spontaneous collapse of the wavefunction? Or are they imposed from without - as in an experimenter forcing an interaction though a measurement? Or some combination of the two - which is where the unpredictability arises? A tornado, for example, needs an externally imposed gradient of temperature and pressure on an air mass. But then exactly where and when it self-organises is "chaotic".

Yes, this might not articulate the particular argument or constraints PBR did in fact demonstrate, but it does help articulate those issues that are at this time outside of the reach of PBR, or any other no-go theorem. When you use the term pre-exist, I'm not sure if you mean it in a Parmenidean or Heraclitean context, so I'll leave it alone. Joy Christian wrote an essay on these issues here.

My default answer (opinion) wrt what they arise from, would be something existential or ontic at the most fundamental level, having no properties of its own except restricting the paths (degrees of freedom) of other such entities. Though for the same reason I don't jump on boat with any of the interpretive theories of QM, lacking any empirical value, the notion of claiming it must be or factually is this way is beyond the pale. I'm open to much more than my own default opinion. I cannot get into particulars of these modeling attempts without going too far beyond what is appropriate here with or without the rules.

Realism, in its simpler reductionist/mechanical form, just presumes the pre-existence of local substantial entities whose properties atomistically inhere. But realism in the systems science/condensed matter sense that My Wan appears to be talking about, opens the question of whether the constraints, the limits on degrees of freedom, are real too. And if so, do they exist inside or outside the wavefunction, and as potential or actual existence. Quite a can of worms gets opened up here. The further ontic dimension of vague~crisp, potential~actual, must be considered when arguing about realism.)

I certainly would say these no-go theorems do it fact rule out substantial entities whose properties atomistically inhere. Whether or not they can still axiomatically form the basis of an empirically valid model remains to be seen. Likely not finite even then. Yet, with or without substantial entities at the foundation, it appears fairly straightforward to me that the notion of properties that atomistically inhere is a dead horse, regardless of what exist if anything at the bottom of the turtles. This is the horse that the no-go theorems are good a shooting dead, not realism. Empirically the properties appears only to be constrained such that we can formally partition them, and not that they inhere to a singular object at the center of its external properties.

 

[DevilsAvocado]

[my bold]

... But I think we want to keep sight that the kind of Realism which is associated with the EPR "Elements of Reality" is quite different than your definition.

Thanks DrC!

I’ve been trying to communicate this without success; it’s like talking to a brick wall. And please note the "deep answer" which includes this very profound and groundbreaking reflection – "it's just a word"!

What is this?? A Confederacy of Dunces??

Mamma Mia... I have never seen a more confused thread on PF...P.S. Note that Mr. Gobbledygook is absolutely 100% sure that Bell's theorem has absolutely nothing whatsoever to do with Local Realism, NOTHING!

 

[DevilsAvocado]

Explain the non-preexistence of tornados and the properties associated uniquely with them and not their constituents then.

I think apeiron did a great job (thanks!), and I don’t know what to add...

 

[apeiron]

Joy Christian wrote an essay on these issues here.

Thanks, that looks like a great find for me. Really close to the view I have been taking. Especially where Christian notes that the property-forming constraints on the degrees of freedom "exist" both locally and globally. They define the fundamentally small, as well as the fundamentally large. So rather than substantive turtles all the way down (or up), we run into the limits on being (the limits that in fact shape being, in bootstrap fashion). And through a notion like reciprocal Planck time, we can make this perhaps a measurable claim.

 

[DevilsAvocado]

When you use the term pre-exist, I'm not sure if you mean it in a Parmenidean or Heraclitean context, so I'll leave it alone.

I think you guys just make it much more complicated than ever needed. How many post have you spent on the word "realism"? One hundred? Or more?? And some come up with "groundbreaking statements" like; "well, if the hidden variables are hidden, they are not real, and if they are not hidden, they are not hidden variables anymore!"... Who the heck is this interested in this kind of "kindergarten logic"??

If you’re not sure what pre-exist or pre-assign means in a Parmenidean or Heraclitean context, run it thru the Parmigiano-Reggiano context, i.e. if you cook your spaghetti at home, and you don’t put the Parmesan on the spaghetti there AT THE LOCATION, then if you later go to work to have your lunch, you have to deal with a situation with non-parmesan spaghetti!

(And if you don’t like non-parmesan spaghetti, then the only way is to pretend it's virtual, non-existing spaghetti. Capice?)

How hard can this be to comprehend!?

Joy Christian wrote an essay on these issues here.

Please my_wan, you are way too smart for Joy Christian. Haven’t you seen the Quantum Crackpot Randi Challenge??

(Wasn’t there infractions on people who linked to Christian’s papers? )

I'm open to much more than my own default opinion.

This is great my_wan, and this is how it should be. Though I’m a little surprised that you don’t see the 'main problem' with all these toy-models; tornado, raisin, temperature particles, etc, i.e. all this stuff is to be 'contained' in the form of a QM particle, like a photon, hitting the detector. I mean, the temperature particles looks really nice, and who knows, someday it may turn out to be that way. But in exactly the same way as Newton’s apple will always fall to the ground, not matter what fancy theories might come along in the future, QM photons in EPR-Bell experiments will always show correlations when entangled.

Example, here are two "QM photons" revealed in their true nature as my_wan "Temperature Particles", and the surrounding square is the "old QM interface":

[PLAIN]http://upload.wikimedia.org/wikipedia/commons/6/6d/Translational_motion.gif<---->[PLAIN]http://upload.wikimedia.org/wikipedia/commons/6/6d/Translational_motion.gif

Explain to me in plain English how the "Temperature Particles" are going to change anything in the current Bell framework?

If you can convince me, I’ll "give up" immediately, I’m not in love with Bell, non-locality, EPR, or anything else – just empirical evidence and common sense.


https://www.physicsforums.com/images/icons/icon4.gif P.S. Yup, infraction it was! https://www.physicsforums.com/Prime/buttons/report.gif

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[my_wan]

I think you guys just make it much more complicated than ever needed. How many post have you spent on the word "realism"? One hundred? Or more?? And some come up with "groundbreaking statements" like; "well, if the hidden variables are hidden, they are not real, and if they are not hidden, they are not hidden variables anymore!"... Who the heck is this interested in this kind of "kindergarten logic"??

Yet in all those post I'm still seeing strawman characterizations of realism. Like the gas molecules pics. I use such analogies only because it is easier to express the contextualization by analogy, not because the space, time, and inherent properties contained in or implied by such pics are valid in a quantum context.

As far as EPR it is a very interesting problem but the notion that properties are not something which inhere to parts implies a lot of possibilities that don't require any refutation of Bell's theorem as it applies to classical properties. It's well known that quantum computers are capable of feats classical computers are not, and this is directly related to the non-digital character of quantum bits. So make of it what you will under the limits of what we know.

As far a Joy Christian, had I been trying to push some kind of specific model I could have referenced the toy model he presented in International Journal of Modern Physics covering the model based on that essay, but I didn't see the science he had to offer as particularly useful. The essay was more suited to general issues being overlooked, and more relevant to conveying the range of possibilities which are ignored.

One thing is near certain, if these issues are ever resolved it will not come from the same kind of thinking that created them. Nor is trotting out the same thinking in response to any mention of the space of possibilities anything more than creating a strawman to refute.

 

[Fra]

... realism asserts that we interpret the elements of our actual theories as something real, but nowhere does realism require that we postulate the existence of some complete ontological description of reality. ...

I'm not saying that there isn't a version of "Realism" that doesn't match your definition. But I do think that many readers would be more likely to be thinking instead of the kind of realism which, when coupled with the word "Local", is excluded by Bell. I realize that with PBR's paper, we are now delving into what that Realism might look like. But I think we want to keep sight that the kind of Realism which is associated with the EPR "Elements of Reality" is quite different than your definition.

I don't know how we would keep track of these, but we are definitely in danger of confusing rather than enlightening. Objective Realism vs. Model Realism?

I didn't follow each turn in the discussion but I often use the term "structural realism" to denote the more subtle form or realism, that I'd say MANY physicists hold (not me however) as to be distinguished from the more classic or naive realism that more refer to existence and location in for example spacetime.

I personally just see the latter as a special case of the former though.

"Structural realism is considered by many realists and antirealists alike as the most defensible form of scientific realism."
-- http://plato.stanford.edu/entries/structural-realism/

Since I'm moderately interested in the pure philosophy part the observer is a key part in my world, and realism in the sense I think of it in physics, is closely realted to observer invariance. Elements of structural realism are the observer invariants that are not INFERRED by the real observers, but are merely to "consistent" with the observers. My only issue is wether the ACTION of hte obsevers are also consistent with the unobservable invariants OR with the imperfects quasiinvariants?

This is where the epistemoligical nature of symmetry enters... I reject the strucutral realist notion of symmetry. But it's not a mind projection fallacy since I do not deny anything, I only take the inside perspective and conclude that an observer that does not have confident evidence for invariants, does not rationally make that assumption and base it's actions on. It would be ad hoc.

In short, the realist stance in my description contains MORE information than the observer has at hand. All I do is insist that we should acknowledge the de facto undecidability. This in no way hardly restricts future information state, all it does is yielding EXPECTATIONS of the future. But that's exactly what we need to guess the future.

/Fredrik

 

[Fra]

In the extension and in the poppian classica philosphy of science dogma, elements of structural realism are close to the "state of science" in the sense that either predictions are CONSISTENT with predictions based on the realism elements (such as symmetries of nature etc that encodes the laws of phyiscs as science knows them) in which case they ar corroborated, or they FAIL to be so, in which case they are falsified.

So far, that type of structural realism is perfectly consistent with the most common abstraction of the scientific method.

My guess is that this is somethinkg like Ken G's stance?

Myself however, while thinking the above is fine, things this is a simplification and FAILS to analyser the most important part of science, which is the induction step. But this failure of analysis traces back to the scientific method.

Popper as we know, disliked induction. He tried to disguise it into more deductive style. But the result is that he relegated the most important part: induction - how to move from falsified theory to new hypothesis in the event of falsification in A RATIONAL way.

Poppers opionon was that this question did not belong to science. It belongs to psychology of scientists brains, of which Popper obvious had no opinon.

The inductivist instead, things the falsification step is TRIVIAL, the hard part is to find a rational way to revaluate and rearrange your information by mergen two inconsistenet parts - the prior theory and the new evidence that is in conflict with prior opinion. How do we CHOOSE a new prior when the old one is shattered? Clearly evolution can not go back to square one!

Ie. the hard part is not to make a statement that can be shown wrong! The hard part is to find a way to ask questions, collect data and generate new questtios in a way thay yields steady learning.

Without this, on each falsification event ALL accomplishments are destroyed. In this picture, there is a massive fine tuning problem to deal with, that doe not exist in the inductive view.

/Fredrik

 

[bohm2]

Most of the papers that I have looked usually do define "realism" in this sense (pre-existing properties):

The theories under investigation describe experiments on pairs of particles. It is sufficient for our purposes to discuss two-dimensional quantum systems. We will hence focus our description on the polarization degree of freedom of photons. The theories are based on the following assumptions: (1) all measurement outcomes are determined by pre-existing properties of particles independent of the measurement (realism)

http://arxiv.org/PS_cache/arxiv/pdf/0704/0704.2529v2.pdf

Of course, there is a problem with these views because as was pointed in previous threads, Bell's theorem doesn't have anything to do with "realism". As suggested by Bell and here in this long but important quote below and in also in other papers/books (some of which I have linked below):

As will be shown more in detail later, the whole enterprise depends crucially on the claim that the Bell theorem has within its premises both locality and a condition called ‘realism’, a condition which is often formulated, even recently, as the idea that physical systems are endowed with certain pre-existing properties, namely properties possessed by the systems prior and independently of any measurement interaction and that determine or may contribute to determine the measurement outcomes (Gröblacher S. et al (2007), p. 871). Although it has been clearly shown – from the original 1964 Bell paper right up to more recent instances (Maudlin (1996), Norsen (2007))-that the Bell theorem does not include any ‘realism’ among its assumptions and that the non-locality established by the theorem holds for any theory that preserves quantum-mechanical predictions, be it ‘realistic’ or ‘non-realistic’, there seems to be a die-hard tendency to regard the Bell theorem as a result that does not establish non-locality but rather the impossibility of any objective (i.e. observer-independent in principle) account of the physical world, provided quantum mechanics is taken for granted. As a matter of fact, not only is the correct interpretation of the Bell theorem not fully acknowledged but also complex experimental settings are designed in important laboratories around the world, in order to test what appear as the implications of a clearly incorrect interpretation of the Bell theorem. Moreover, such ill-founded interpretations of one of the most relevant results for the whole field of the foundations of physics are disseminated

http://www.springerlink.com/content/h202073726227t52/fulltext.pdf
http://arxiv.org/abs/0809.4000
http://arxiv.org/PS_cache/quant-ph/pdf/0607/0607057v2.pdf
http://arxiv.org/PS_cache/arxiv/pdf/0904/0904.0958v1.pdf

Moreover, from what I have read, "realism" even in this sense (e.g. pre-existing properties) does not imply determinism.

 

[Fredrik]

(Wasn’t there infractions on people who linked to Christian’s papers? )
...
https://www.physicsforums.com/images/icons/icon4.gif P.S. Yup, infraction it was! https://www.physicsforums.com/Prime/buttons/report.gif

()

ZapperZ is on vacation, so it might be safe to talk about Christian now.

I have actually seen several discussions about his stuff since I got that warning, but perhaps not about the specific article I linked to that time.

 

[Fra]

I'm trying to think in terms of this is making any difference to inferences and predictions. Unlike postulating the colour of gods underwear (which might well be consistently added to the existing postulates of quantum mechanics, it's just that it doesn't help in any way)

"(1) all measurement outcomes are determined by pre-existing properties of particles independent of the measurement (realism)"

This line in itself carries no information to me - unless supplemented with something...

"and that determine or may contribute to determine the measurement outcomes"

... like this

That means like the statement of realism as per above (note I didn't read your sources/context) is that there is exists an inference whereby the initial state (including the hidden properties referred to above) if not DETERMINES, at least INFLUENCES the prediction of the future.

There is just one problem with that. The whole point of an inference is that I'm not even sure what it MEANS to assume that it's influenced in an unknown way. To me, it should be clear that in can not influence it in any way.

I think the confusion here is between the EXPECTATION and PREDICITON, vs the ACTUAL OUTCOME (ie the BACKREACTION from the system onto the observer).

It should be clear that in a scientific sense we NEVER KNOW anything, ALL we have are expectations. We really aren't describing the future, we are only describing our expectations of the future.

Thus, I focus not on orcale-type predictions, I only focus on decisions of how to choose action. And in this context, it's clear that information not at hand, simply can't rationally influence the decision. It can certainly influence the backreaction, but this is a different question, and is part of a bigger context interaction observer-observed where both are evolving.

That alone clear up a lot of fog IMO at least. I have a hard time to even accept the way the problems are described in many of these papers. The main "problem" seems to be the philosophical strain of loosing realism.

/Fredrik

 

[bohm2]

Note this quote in the conclusion of Leifer's paper/blog:

The PBR theorem rules out psi-epistemic models within the standard Bell framework for ontological models. The remaining options are to adopt psi-ontology, remain psi-epistemic and abandon realism, or remain psi-epistemic and abandon the Bell framework.

http://mattleifer.info/2011/11/20/can-the-quantum-state-be-interpreted-statistically/

I'm guessing here by "realism" Leifer is using KenG's/Bohrian more stringent definition? The authors of PBR also note that one can avoid PBR:

More radical approaches are careful to avoid associating quantum systems with any physical properties at all.

This is the Bohrian or neo-Copengagen position outlined in Leifer's paper.

So does this just mean that Bell's + PBR should be interpreted this way:

1. Bell's theorem implies non-locality irrespective of any realist/non-realist/semi-realist position.
2. PBR implies that the wave function has pre-existent properties influencing/determining measurement outcome.

So the wave functions are non-local objects with pre-existent ("physical")properties influencing/determining measurement outcome?

What else could it mean? I'm totally lost. I mean "properties" seem to be the magic word in all 3 of these PBR-type papers. Is this why Valentini (de-Broglian) and Wallace (MWI) are foaming in the mouth or am I totally lost and confused?

 

[Fra]

http://mattleifer.info/2011/11/20/can-the-quantum-state-be-interpreted-statistically/

I skimmed that page...apparently in his terminology I'm a case 2 "anti-realist" since I don't talk about objective reality in any other sense than emergent: where subjective views are tuned.

The problem would neverthelss to identify this reality; either you acknowledge that problem and you are back to observer dependent inferences. Or you deny the problem, but then you are left with Poppian style reset of evolution after each falsification (which does not seem very constructive).

A realist though, would easily think that a case 2 person is subject to the MPF by thinking that what she does not know can not be true, but that is not at all how a category 2 necessarily means.

All I am claiming is: My CHOICE of infinitesimal instant ACTION is independent of information not in my possesion (this includes objective reality). the only dependence on the unknown comes in the form of feedback from the environment. But this is an inertial process which guarantees that not unknown or remote things can have instant influence on locla choices.

Another version of this, that applies to any observing system rather than ME, would be:
The instatant (ie infinitesimal) "naked" (non-renormalized) ACTION of A, as observed by me, is expected to depend ONLY on the information O has about it's environment. This can in principle have observable consequences as it for examply forbids FTL communication. This is IMO the sensible meaning of locality. But the renormaliezd action as observed by me, might well prove to contain information in a neigbhourhood of A because I am really not observing hte naked A - I am observing the entire environment of which A is a subsystem.

When Bell people talk about non-locality they are talking about correlations, this has IMO nothing do to with non-locality in it's original meaning, because the correlation is always locally evaluated, so it's not non-local? It even seems like a logical contradiction to make a local inference that of non-locality. It just doesn't make sense.

This is all my "anti-realism" means. It has nothing at all to do with denying future possibilites. It just is a stance about rationality in chosing actions.

/Fredrik

 

[DevilsAvocado]

I'm guessing here by "realism" Leifer is using KenG's/Bohrian more stringent definition?

I can guarantee you that Leifer is not using "Ken G realism", because it does not have an official name nor any peer-reviewed papers, it’s just a personal philosophical 'construct' that seems to be flip-flopping depending on the situation.

And he’s hardly referring to Niels Bohr either; the EPR paper was an attack on Bohr’s interpretation that the quantum state alone constitutes a complete description of reality, i.e. the ψ-complete view. And, as we now know – EPR(B) was successful in that mission.

The answer is in your own quote "The PBR theorem rules out psi-epistemic models within the standard *Bell framework* for ontological models".

This can only mean one thing; DrC is right (as always).

Realism which is associated with the EPR "Elements of Reality"

1. Bell's theorem implies non-locality irrespective of any realist/non-realist/semi-realist position.

Wrong. Bell's theorem does not tell us one thing about which is the actual state of affairs in non-local or non-real. It simply states that:

No physical theory of local hidden variables can reproduce all of the predictions of quantum mechanics.​

And to avoid further misunderstandings; Local Hidden Variables (LHV) is equal to Local Realism (LR).

2. PBR implies that the wave function has pre-existent properties influencing/determining measurement outcome.

Wrong. There is nothing preventing us from remaining 100% ψ-epistemic (no LHV), and still be within the Bell framework.

So the wave functions are non-local objects with pre-existent ("physical")properties?

The person who can prove that the world is non-local or non-real will get at least one Nobel Prize.

What else could it mean? I'm totally lost.

You’re not alone. I think Fredrik is right; this paper is badly written and has a misguiding title. For instance, somewhere in the paper they should have clearly pointed out if they are abandoning the Bell framework, or not. If they are within the Bell framework, they should have included something like Leifer's blog + specification of non-locality/non-realism:

epistemic state = state of knowledge
ontic state = state of reality

• ψ-epistemic/non-local: Wavefunctions are epistemic and there is some underlying ontic state.
  
  
• ψ-epistemic/non-real: Wavefunctions are epistemic, but there is no deeper underlying reality.
  
  
• ψ-ontic/non-local: Wavefunctions are ontic (and must describe some underlying ontic state).

 

[DevilsAvocado]

ZapperZ is on vacation, so it might be safe to talk about Christian now.

Yeah! Let’s go crackpot!

()

 

[DrChinese]

So does this just mean that Bell's + PBR should be interpreted this way:

1. Bell's theorem implies non-locality irrespective of any realist/non-realist/semi-realist position.
2. PBR implies that the wave function has pre-existent properties influencing/determining measurement outcome.

So the wave functions are non-local objects with pre-existent ("physical")properties influencing/determining measurement outcome?

Norsen's view is that your 1 is correct. But this is not a generally accepted viewpoint. As Leifer points out: "I am pretty sure that no theorem on Earth could rule out option 2" ("Wavefunctions are epistemic, but there is no deeper underlying reality").

It's almost as if you could ask the question: Where/when are the (hypothetical) hidden variables? If you think they are in the past light cone, you are a Local Realist. If you think they are in the present but outside the light cone, you are a Bohmian. And if you think they reside in the future light cone (i.e. a context which include elements of both the future and past setup), you reject Realism (because there is no objective reality now, only subjective realities).

I think it is clear that hypothetical HVs don't reside in the past light cone, we know that from Bell and others. The Bohmian thinks there is an objective reality now. However, I question whether the PBR result helps or hurts that cause, because it seems to me to run counter to their main idea. They say that lack of knowledge of the initial conditions leads to a statistical distribution of results that matches the predictions of QM. That sounds to me exactly the same as what PBR rules out.

It seems to me that PBR is saying that if the wave function is real, then collapse is real as well. Only the anti-realist stance matches that, because all other interpretations are essentially predeterminisitic. But I am not really sure on this point yet.

 

[DevilsAvocado]

When Bell people talk about non-locality they are talking about correlations

Just for everybody’s knowledge: "Bell people" might sound like some obscure sect on Easter Island – it’s not.

"Bell people" = The Whole Scientific Community​

 

[Fra]

Just for everybody’s knowledge: "Bell people" might sound like some obscure sect on Easter Island – it’s not.

"Bell people" = The Whole Scientific Community​

"Obscure sect" would be an overstatement, agreed.

I felt when I posted it that "bell peope" was not quite the term I was lookig for

/Fredrik