The quantum state cannot be interpreted statistically?

[my_wan]

Fair enough DevilsAvocado
I haven't been idle on the issue either

 

[DevilsAvocado]

Peace In Mississippi!

()

 

[Ken G]

We absolutely know, even without QM or the classical thermodynamics verses statistical mechanics analogy, that position is purely contextual.

Hang on-- from what I've seen on here, you and I are absolutely the only two people who believe that statement with the "even without" part in there. PBR certainly don't-- they hold that anyone who is a "realist" must hold that the basic building blocks of any theory that works must work because they are real. So if classical mechanics says there is a concept of exact position and it helps us get the answers right, then only some whacko "anti-realist" in 1860 could have claimed that exact position is not real. Indeed, if some analog of the PBR theorem were applied to classical mechanics, you can see what a "complete set of properties" would be interpreted as: exact positions. Everyone else seems happy with defining a realist as someone who believes a theory is about reality until it is found to not agree with some experiment, and that is certainly how PBR interpret realism in regard to quantum mechanics.

We even new it in terms of Galilean relativity in Newton's time. It's the main motivation behind a very fundamental principle called coordinate or background independence. Hence a coordinate choice is by definition not a physical choice.

The coordinate choice determines the label for the position, not the idea that there is a position there. By the definition of "realist" that everyone here seems all too happy to use, any classical mechanics realist would have to hold that exact positions are real, even if a coordinate choice is required to give those exact positions a numerical label. I'm saying it's high time we didn't require realists to be that naive.

Relativity merely articulated how these contextual variables are related. Even on the face a velocity can be both zero and nonzero at the same time, depending on the nonphysical coordinate choice chosen.

Again, that is conflating the numerical label of a velocity with the ontological construct of an exact velocity that may yet be unlabeled. Classical mechanics is usually framed as advancing that ontological construct, even though everyone knows the numerical labels are coordinate dependent. (Personally, I don't think classical mechanics should require that ontological construct at all, or indeed any fundamental ontological constructs, and on that I believe we are the only two here who agree.)

The main point is that these contextual variables do not rule out ontic constructs in which we are then free to contextualize in a bewildering number of coordinate choices or spaces. Yet all valid choices transform into one another in one way or the other, no matter how different they appear on the surface or involve apparently incongruent definitions in one coordinate choice as opposed to another.

Sure, they transform into one another in ways that are described by the theory. That means even the transformations between these fundamentally non-ontological constructs are also fundamentally non-ontological, they are all borrowed from the only place they actually exist: mathematical structures. The same holds for symmetries and group properties, all borrowed from the places where they actually exist to be used in epistemological applications to the real world, said like a true realist should say it.

To many ontic realist this is precisely because a nonphysical coordinate choice is merely an invention for contextualizing a common underlying ontic state.

Yes, I agree that self-styled "ontic realists" would say that, but that doesn't change the fundamental oxymoron living behind the term "ontic realist." Those words are contradictory because belief in a true ontology means committing to a reality that exists in one's own mind, where those mathematical structures exist, and the belief the reality is fundamentally housed in our minds is idealism, not realism.

Even the apparent degrees of freedom can vary as a result of coordinate choice. Yet any valid model involving any coordinate choice still must transform via symmetries into each other, because the ontic system is the same system and is doing nothing different as a result of our coordinate choice.

There is only one reason these transformation have to work like that: science demands they get the same answer. That's it, we throw out what doesn't get the same answer, and we are left with those kinds of transformations. There's nothing ontic about it, it's still pure scientific epistemology.

Epistemicists have their own varying ways of conceptualizing this commonality, which is no less empirically valid.

True, and also has the added advantage of being internally consistent, avoiding the mind projection fallacy.

We even have coordinate independent mathematical formulations to explicitly recognize this fact.

Yes, we have all kinds of useful mathematical structures that we borrow from to fit into scientific epistemology. None of that changes the demonstrable fact that the ontology is always housed in the mathematical structure, so always in the minds that recognize that structure. To claim that is where the reality lives is thus idealism, or else it is the quintessential mind projection fallacy.

Symmetries provide a good example. The ability to conceptualize a symmetry, and recognize its usefulness in practice, is demonstrably housed in the intelligence. A symmetrical rock has no idea it is symmetrical. We find that symmetries are exceptionally simple and powerful, so the temptation to imagine a true ontology there is hard to resist. Yet the realist should resist it, because the realist should recognize the trappings of idealism-- if reality has to look like my thoughts, then I am equating reality with my thoughts about reality. That's the mind projection fallacy! It doesn't make any difference how useful the thought is, it's still idealism. The realist should expect that ultimately, every symmetry was made to be broken.

I'll even go a step farther and say, in my opinion, that philosophical stances, so long as they are not at odds with the underlying facts of the system, are equivalent to a nonphysical coordinate choice. No matter how diametrically opposed two philosophical stances appear on the surface.

I agree with that to some degree-- but I would point out that if an ontic view can be transformed seamlessly into an epistemic one, which one was fundamentally correct in the first place?

So a coordinate choice by definition defines the coordinate space as nonphysical, while whatever it is that defines the commonalities that allows one to be transformed into the other is the reality.

The commonalities are commonalities in the mathematical structures that are being borrowed from. So if they are the reality, then the mathematical structures are the reality, yet the mathematical structures are recognized and identified and characterized in our intelligence. When reality is housed in the mind, that is idealism, or it is the mind projection fallacy. One cannot have one's cake and eat it too.

If you think of a model strictly in terms of the coordinate choice used to define it, and the apparent definitions that particular choice entails, then of course the only sane perspective to take is a purely epistemic one.

But the epistemic view can also include the recognition that the coordinates don't matter. It's still epistemic to notice that-- indeed, it is even more epistemic to notice the commonalities of thoughts that all lead to the same place. When there was an "aether", there was something much more ontic there than where there is relativity. What aspect of having all observers able to use the same laws makes those laws ontic in character? It is a quintessentially epistemic law that works for any mind that would try to use it, an ontic law shouldn't care if it requires preferred minds because it is true outside of those minds.

 

[Ken G]

A more accurate analogy could be two vortices mixing. The "raisins" are contextual, the product of boundary constraints.

Yes, this brings up an important limitation to what gets called "realism" in regard to quantum mechanics, which should really be called "reductionism." If there is a "complete set of properties" that determines everything, that is the reductionist dream-- properties removed from any contextual meaning, they just are. The whole is the sum of its properties, and nothing else is "realism." You talk a lot about the importance of top-down contraints, so where is the space for them in this "complete set of properties?" Is the PBR theorem still proving something if top-down constraints are fundamental to how any complete physical theory must work? I don't think it is, it seems to be relevant to hidden variables theories, but top-down constraints are not what most people mean by hidden variables, such variables are generally reductionist in character.

The definition of a scientific realist is someone who takes the elements of scientific theories literally in regard to reality. To avoid foolish naivete, they must at least allow that the correspondence still counts if it has been shown to be only approximate. Notwithstanding the logical quandary around "how approximate still counts", we still have the problem that scientific theories that are not purely reductionist still don't fit the PBR program, so taking the attributes of any top-down constraint literally as part of the reality is an example of a "realist" stance that PBR do not even recognize as realist.

 

[Fredrik]

I do think the PBR theorem considers an "ontological model" to be one that can be conceived as producing only probabilities of 0 or 1,

It's clear that they don't, since they reference Harrigan & Spekkens, and they don't. They might however be thinking that "What we really want to rule out are the ψ-epistemic models that only assign probabilities 0 and 1, but it's no more difficult to rule out the ones that assign arbitrary probabilities in the interval [0,1], so we'll do that just because we can."

If they say the complete set of properties only sets the probabilities, how is that a complete ontological description?

Since the term "property" is left undefined, there can't be a strong argument for it. You can only assume it, or explain why the definition of an ontological model makes it convenient to think of an ontic state as representing all the system's properties.

An expectation value in QM can be expressed as $$\langle\psi|A|\psi\rangle=\sum_k P(k|A,\psi)k.$$ Here k is a measurement result, and $P(k|A,\psi)$ is the probability of getting the result k, given that we're measuring A, after subjecting the system to one of the preparation procedures represented by $|\psi\rangle$. The ontological model is required to satisfy something like
$$P(k|A,\psi)=\sum_{\lambda\in\Lambda} P(\lambda|\psi) P(k|A,\lambda)$$ I say "something like", because this notation is only appropriate when $\Lambda$ is finite. The two functions on the right are also required to exist as part of the definition of an ontological model for the quantum theory. This equality makes it very convenient to think of $P(\lambda|\psi)$ as the probability that the system has properties λ, given that the preparation procedure was consistent with $|\psi\rangle$, and to think of $P(k|A,\lambda)$ as the probability that the result will be k, given that we're measuing A, and that the system's properties are λ. So I'd say that the definition gives us a reason to think of λ as properties, but obviously not a reason to think we know that λ "really" represents properties.

 

[apeiron]

You talk a lot about the importance of top-down contraints, so where is the space for them in this "complete set of properties?" Is the PBR theorem still proving something if top-down constraints are fundamental to how any complete physical theory must work? I don't think it is, it seems to be relevant to hidden variables theories, but top-down constraints are not what most people mean by hidden variables, such variables are generally reductionist in character.

I think the difference is that reductionism/hidden variables attempts to locate the critical information inside the wavefunction, whereas a contraints approach is about what happens outside.

If you take the case of a pair of entangled particles, then an act of measurement is an act of constraint, imposed from without, that reduces the degrees of freedom of what lies within. If there was a choice of up/down, then "wavefunction collapse" is a constraint of that freedom.

The difference is that the reductionist view is that all things are secretly definite, and so carry this definiteness around from one place to another. But a constraints-based view (after Peirce, I might say, who seems a little misunderstood here) is that the particles are ontically indeterminate until some further constraint is imposed to give them more definite properties.

Of course, you then have to accept some kind of retrocausality and non-locality. But that's OK.

So I took the PBR theorem to be closing the loophole of a statistical interpretation and increasing the weight of evidence for ontic realism of the wavefunction. It then seems a separate matter how the wavefunction is actually viewed - either as some kind of material object, like a pilot wave, in its own right, or instead merely the framework of measurements/interactions which impinge on some local potential to give it a more definite identity.

The definition of a scientific realist is someone who takes the elements of scientific theories literally in regard to reality. To avoid foolish naivete, they must at least allow that the correspondence still counts if it has been shown to be only approximate. Notwithstanding the logical quandary around "how approximate still counts", we still have the problem that scientific theories that are not purely reductionist still don't fit the PBR program, so taking the attributes of any top-down constraint literally as part of the reality is an example of a "realist" stance that PBR do not even recognize as realist.

I agree with you that we only model reality, so there is always the problem we can never claim we know reality in an absolute way. Which makes the Copenhagen interpretation a worthy default position.

But then the Peircean approach (which pre-dates QM) does seem to offer something of interest. It is a way of arguing that reality is itself "epistemic". It says the way our minds work (with ideas shaping impressions) is also the way that reality works (with top-down constraints shaping local events).

So epistemology says we only know our own minds. But what if we then actually can appreciate how our minds work. Is this not a form of ontic certainty? Probably not, but it seems at least a stronger basis for speculation than epistemic agnosticism (that anything might be the case, we can't even say anything definite about how our minds get more organised).

Then applying this to QM interpretations, we can start with the fact of how reality seems to us - classical until we get down to the kinds of experiments where some further constraint, some act of measurement, is needed to "collapse the wavefunction". Or rather, place still further limits on the degrees of freedom that are present at some location.

We know that it is at least definitely our choices that are limiting these degrees of freedom (the CI position). But we also have now a grounds to say that reality itself is operating the same way. There is still no surety. There never can be. But it is a reasonableness argument.

By contrast, a hidden variables argument seems very unreasonable. The idea of things that are secret and unmeasureable goes against the spirit of modelling. Whereas the constraints that impinge on a locale are visible and measurable.

 

[my_wan]

Hang on-- from what I've seen on here, you and I are absolutely the only two people who believe that statement with the "even without" part in there. PBR certainly don't-- they hold that anyone who is a "realist" must hold that the basic building blocks of any theory that works must work because they are real. So if classical mechanics says there is a concept of exact position and it helps us get the answers right, then only some whacko "anti-realist" in 1860 could have claimed that exact position is not real. Indeed, if some analog of the PBR theorem were applied to classical mechanics, you can see what a "complete set of properties" would be interpreted as: exact positions. Everyone else seems happy with defining a realist as someone who believes a theory is about reality until it is found to not agree with some experiment, and that is certainly how PBR interpret realism in regard to quantum mechanics.

We are obviously not the only two given that the community didn't need our help to define background independence as fundamental to all physical sciences. Yet you approach is making no distinction between the background and what is happening in the background. The simple fact that we cannot empirically define a background in a space with no immediate causal interactions with the Universe doesn't mean we can define it and derive the transforms that recreate the empirical background. It still constitutes potential degree of freedom, such that position can still have indirect meaning.

The coordinate choice determines the label for the position, not the idea that there is a position there. By the definition of "realist" that everyone here seems all too happy to use, any classical mechanics realist would have to hold that exact positions are real, even if a coordinate choice is required to give those exact positions a numerical label. I'm saying it's high time we didn't require realists to be that naive.

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.

Again, that is conflating the numerical label of a velocity with the ontological construct of an exact velocity that may yet be unlabeled. Classical mechanics is usually framed as advancing that ontological construct, even though everyone knows the numerical labels are coordinate dependent. (Personally, I don't think classical mechanics should require that ontological construct at all, or indeed any fundamental ontological constructs, and on that I believe we are the only two here who agree.)

You seem to be conflating a numerical coordinate label as an ontic thing in the minds of realist. Then when we label an ontic thing to track what (nonphysical) degree of freedom it partakes in you are accusing ontic realist of assigning ontic realness to those labels. Unless or until you can get what those differing from you actually think you can never even formulate a valid (much less correct) rebuttal of their opinions. So far, in terms of your characterizations of what ontic realist think, you are dead wrong at every turn. Presumably honestly, but that just means you believe your own strawman.

Sure, they transform into one another in ways that are described by the theory. That means even the transformations between these fundamentally non-ontological constructs are also fundamentally non-ontological, they are all borrowed from the only place they actually exist: mathematical structures.

So what (perhaps who) is doing the calculating when scientist are not paying attention?

Those words are contradictory because belief in a true ontology means committing to a reality that exists in one's own mind, where those mathematical structures exist, and the belief the reality is fundamentally housed in our minds is idealism, not realism.

And does not an abject denial that a possibly ontic world outside your mind actually consist of something constitute a mind rejection fallacy? You and I are on opposite ends of the spectrum in our approach to understanding the world. The difference to me seems to be that I try really hard to recognize all the ways I can be wrong, and even if not how what I can know is fundamentally limited. Hence the absolute claim that the Universe is dependent on ontic constructs is a moot scientifically meaningless claim.

The question is why would you then turn it around and deny such a possibility when you have no more access to what is "real" than I do. You even make it worse by conflating degrees of freedom with ontic entities as if they are the same thing, then using the logical consequences of coordinate choices as the basis upon which you justify your criticism of ontologist. It makes you demonstrably wrong even if you are right. Only I see no recognition of the "if" in "if" you are right in your own claims about what constitutes a legitimate characterization of the world. Even if an ontological characterization is wrong, so long as it is empirically valid it lacks no less legitimacy.

Why is ontology important even if it is wrong? Consider classical thermodynamics, CT, verses statistical mechanics, SM, again for instance. It is fundamentally impossible to derive SM from CT, but quiet trivial to derive CT from SM. Without SM we could not have properly predicted Brownian motion. Not to mention making a lot of engineering a lot simpler with a lot less empirical data to be experimentally derived on a case by case basis. Now the fact that the atoms and molecules upon which is rested may not themselves be constructs of ontic entities does not detract from that in the least. It added empirical value that a strict epistemological approach to science could not have derived. We would not be where we are at if ontologist hadn't stuck in there when epistemologist had the game wrapped up with CT. So right or wrong you do NOT throw away ontology for the sake of philosophical expediency, period. And I see no other case besides philosophical expediency provided, unless your motives are less transparent than I have any right to speculate on.

 

[Fredrik]

Haven't we gone too far off topic now? All I see are lengthy discussions about philosophical terms. Is anyone at all interested in discussing the actual articles and arguments?

 

[my_wan]

Haven't we gone too far off topic now? All I see are lengthy discussions about philosophical terms. Is anyone at all interested in discussing the actual articles and arguments?

Yes, I agree. I'll refrain from any more of the philosophical issues not directly concerned with interpreting PBR. Yours and other post have made significant contributions, and a few of mine I hope, to the PBR issue. Some I am still chewing on and well worth continuing with.

 

[Ken G]

Haven't we gone too far off topic now? All I see are lengthy discussions about philosophical terms. Is anyone at all interested in discussing the actual articles and arguments?

The issue behind the philosophical arguments is directly related to the article. The article assumes that realism implies that a "complete set of properties" determine everything that happens. The proof appears to require this assumption. So the question is, is this actually a fair statement of realism? I am saying it is only a fair statement of reductionism, which is not a "mild assumption". I haven't seen anyone suggest the proof is wrong if it is really true that some complete set of hidden variables (properties) determines everything that happens, in terms of either 0 or 1 probability (which is not probability at all). So the real question is, what does a proof that requires that assumption really tell us about quantum mechanics? I'm saying it depends entirely on one's philosophical commitments, so there is no way to discuss the importance of the proof without first understanding the landscape of philosophical possibilities. That's more or less the tenor of those blogs as well.

 

[Ken G]

If you take the case of a pair of entangled particles, then an act of measurement is an act of constraint, imposed from without, that reduces the degrees of freedom of what lies within. If there was a choice of up/down, then "wavefunction collapse" is a constraint of that freedom.

A fully reasonable perspective, in my view.

The difference is that the reductionist view is that all things are secretly definite, and so carry this definiteness around from one place to another. But a constraints-based view (after Peirce, I might say, who seems a little misunderstood here) is that the particles are ontically indeterminate until some further constraint is imposed to give them more definite properties.

Yes, I generally respect Peirce so I was dubious with taking his views paraphrased through someone else, I meant only to critique the paraphrasing.

So I took the PBR theorem to be closing the loophole of a statistical interpretation and increasing the weight of evidence for ontic realism of the wavefunction.

But I don't think it really closes much of a loophole, because it assumes that there are some complete set of properties that are deterministic of the outcomes. The properties cannot just produce statistical trends, perhaps engaged by the constraints, they have to really determine what happens or the PBR proof does not scan. To me, they have assumed away most of what they are trying to argue cannot work-- they say that a single set of properties cannot be in the hidden space of two different wavefunctions, so two overlapping wavefunctions cannot be statistical groupings that overlap.

But this requires the relatively naive structure of the properties to make true-- a single set of properties that nevertheless requires interaction with constraints in order to be active on the statistics of the outcomes can therefore still appear in two different wavefunction groupings, if what is statistical in the wavefunction includes what is being treated statistically about the interactions with the constraints. In other words, if properties are themselves only statistically deterministic, then the PBR proof does not go through, yet they claim their proof goes through for all "realist" interpretations. The constraint-based approach is being downgraded to being "non-realist" and absent from any set of "mild assumptions."

You raised some interesting philosophical points that I'd like to respond to, but I don't want to derail the thread, so I'll PM my reactions.

 

[Fredrik]

The article assumes that realism implies that a "complete set of properties" determine everything that happens.

The word "realism" (or "realist") doesn't even appear in the article. In the introduction, they're suggesting that the idea that systems don't have properties implies that a state vector is just a tool to calculate probabilities. Then they assume that systems do have properties, and that those determine the probabilities of measurement results.

I don't see the assumption you're talking about. I think their choice of words suggest that they believe that the converse of the implication I mentioned above holds too, even though they aren't actually saying it. Is this what you have in mind?

The proof appears to require this assumption.

I don't see why you think so.

You don't seem to be taking into account just how bad this article is. These guys either haven't figured out how to tie their ideas together, or are unbelievably bad at explaining them. Let me try to translate a few of the things they're saying to non-gibberish.

Our main assumption is that after preparation, the quantum system has some set of physical properties.​

Translation: "We're going to talk about ontological models for quantum theories, as defined by Harrigan and Spekkens".

We will show that the statistical view is not compatible with the predictions of quantum theory.​

Translation: "We will show that if state vectors correspond to epistemic states of some other theory, that theory can't make the same predictions as QM".

A better way of saying that is: "We will show that no quantum theory has a ψ-epistemic ontological model." This is a mathematical statement, so there's no way the correctness of a proof can depend on someone's opinion about what "realism" should mean.

 

[bohm2]

I'm guessing here that KenG is referring to page 6 of the PBR paper(Appendix B)?

An assumption is that the quantum system after preparation has physical properties, and that a complete list of these properties corresponds to some mathematical object λ. Each preparation method is associated with a probability distribution μ_i(λ) (i = 0, 1). This is to be thought of as the probability density for the system to have properties  after preparation.

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

 

[Fredrik]

I'm guessing here that KenG is referring to page 6 of the PBR paper(Appendix B)?

I didn't read that far, but the quote is saying essentially the same thing as the introduction on page 1. It's clear that the authors think of λ as properties, but that doesn't imply that you somehow have to think of them that way for the argument to make sense. (An argument that requires you to think that way would be garbage). The article by Michael Hall agrees with me about this point. The ontological model is required to satisfy a few mathematical conditions, as part of the definition of ontological model. Those conditions may not be intuitive unless we think of λ as a complete list of properties, but the argument is based on the mathematical conditions, not on their intuitiveness.

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

I like to avoid such terms entirely. They're all like "the Copenhagen interpretation". You won't be able to find two people who agree about what it means.

 

[my_wan]

The word "realism" (or "realist") doesn't even appear in the article.

No they don't but, but unlike epistemic or ontic or any variant thereof which is not contained in the article, the term "real" does occur in the context of realism as a variant. Hence any use of the term epistemic or ontic in characterizations of the article leaves me without any reference point as to how the authors used it, since they never did. The HS reference does not specify how the authors chose to contextualize those terms. But wrt "realism" or "real" there is some significant content to determine the PBR authors intended characterization, which I will outline.

In the introduction, they're suggesting that the idea that systems don't have properties implies that a state vector is just a tool to calculate probabilities.

Naturally, this is a direct result of the state vector characterized as not being "real" in the sense used by the authors. Note: This is a far more limited specification for realness than is often implied, such as in the debate between Ken G and I. It merely associates what is empirically accessible in real experiments as real, as opposed to to abacus procedure which has nothing to do with what the result is applied to.

Then they assume that systems do have properties, and that those determine the probabilities of measurement results.

Naturally. This in itself does not imply circular reasoning due to a simple fact. In order to formulate a proof it must first be stated in a form that allows a method of falsification. By making the statement that the state vector had empirically accessible properties they are not presuming it to be so a priori, they are merely putting it into a falsifiable form.

I don't see the assumption you're talking about. I think their choice of words suggest that they believe that the converse of the implication I mentioned above holds too, even though they aren't actually saying it. Is this what you have in mind?

I don't see why you think so.

Here I agree with you. It seems to me that an extreme position has characterized a differing position as an inverse yet equally extreme position wrt a more moderate point that the authors were trying to convey with the term "real".

You don't seem to be taking into account just how bad this article is. These guys either haven't figured out how to tie their ideas together, or are unbelievably bad at explaining them.

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.

Let me try to translate a few of the things they're saying to non-gibberish.

So let's compare our translations. Your translation:

Our main assumption is that after preparation, the quantum system has some set of physical properties.​

Translation: "We're going to talk about ontological models for quantum theories, as defined by Harrigan and Spekkens".

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.

Note how this translation specifically refers back to the same author provided content you characterized as gibberish, rather than a different paper altogether containing none of the words or variants thereof the authors actually used or had any hand in writing?

Your translation:

We will show that the statistical view is not compatible with the predictions of quantum theory.​

Translation: "We will show that if state vectors correspond to epistemic states of some other theory, that theory can't make the same predictions as QM".

My translation:
We will show that the empirical significant of the statistics defined by the state vector exceeds what is empirically possible if it only has "statistical significance".

So what does the term "statistical significance", used by the actual authors mean? Exactly what the authors said it means when they said in their own words (not the words of a referenced proxy author): "[...]statistical significance, akin to a probability distribution in statistical mechanics." To understand you have to consider the model and the system as two different things. In the statistical mechanics model the statistics are only a property of the model, not a property of the system being modeled. Thus the above translation says they will show it is impossible to define the statistics of a state vector as a model only property, that it must in some way also be a property of the system itself, unlike the statistical interpretation used in statistical mechanics.

A better way of saying that is: "We will show that no quantum theory has a ψ-epistemic ontological model."

No, it say nothing explicit about any other model than the one provided by standard QM. Though it does put hard constraints on how an alternative model can characterize the statistics used in QM. That is that the statistics, whether an alternative model characterizes them in terms of statistics or not, must not treat the QM statistic as if it is solely as a modeling property rather than a system property. Throwing in the term ψ-epistemic in the context of all possible models it can entail is invalid. It is only valid when you restrict it to one particular model and the characterizations that one model entails, even if that model is a derivative construct of the alternative model.

This is a mathematical statement, so there's no way the correctness of a proof can depend on someone's opinion about what "realism" should mean.

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 does not depend on any version of "realism", only that the empirical justification is external to the model itself. So if you include the set of all potentially valid models, not systems, the supposed "mathematical statement" of what ψ-epistemic means takes a different character in each case.

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 really get the impression that when the words used by PBR are characterized as gibberish it is the direct result of failing to note when they switch back and forth between characterizations of the model and characterizations of the system providing the empirical justification for the model.

If the authors own words are labeled gibberish how is it possible to discuss what the paper said? Even the ψ-epistemic terminology wouldn't be such a hindrance if it wasn't so inappropriately generalized as if its validity in the context of one model was an indicator of the validity in all possible models of the system in question.

 

[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