The quantum state cannot be interpreted statistically?

[Fredrik]

As a SA you are of course aware that personal theories/interpretations/philosophies are not allowed on PF.

The best example I've seen of an overly speculative personal theory in this thread is your post #380. I haven't read all of Ken G's statements, but the ones I've read haven't been personal speculation. He's been talking about how words are defined, and how he thinks words should be defined, etc., and you can argue that some of it doesn't belong in this thread (I would agree), but I haven't seen any personal theories.

"Not interested enough to go look for evidence", well, I can’t see how that makes your attack any different from what you think I’ve have done. You’re just guessing that I have no evidence at all.

Do you always mischaracterize what you're replying to? I'm not guessing. I told you that I distinctly remember that my reaction to several of your posts was that you had clearly misunderstood Ken. When I said that I'm not going to look for evidence, that only means that I'm not willing to spend two hours finding the relevant posts in a 29-page thread, highlighting the relevant parts, etc. You can consider it just an opinion if you want to, but it's not a guess.

Edit: Here I misunderstood what you said. I'm sorry about that. I thought you were saying that I was just guessing that you had misunderstood some of his statements, but you were saying that I'm guessing that you don't have evidence to back up your claims. I concede the point that I don't know if you have any evidence against him, and I obviously retract my suggestion that what you said in the quote above was a mischaracterization of what I said. That was a misunderstanding on my part.

I’m not interested in spending time in a forum that support this kind of ideas, which according to the rules should not be supported.

What ideas are you talking about?

Don't you think that leaving the forum because a few people disagree with you, about whether your personal attacks on Ken G are appropriate, would be a pretty bizarre overreaction?

 

[mattt]

All Ken G is trying to say (in my opinion) is that we should not mistake our models with whatever our models are trying to model.

And I suppose everybody agrees with him on that.

 

[apeiron]

Then we could perhaps finally get an official name of the theory/interpretation/philosophy, or whatever, that have occupied almost 400+ posts in this thread. As a SA you are of course aware that personal theories/interpretations/philosophies are not allowed on PF.

The baffling thing is that your misconceptions were corrected many pages ago...

https://www.physicsforums.com/showpost.php?p=3642301&postcount=271

Idealism is quite different from what I'm advocating, I'm actually advocating something more along the lines of "scientifically consistent realism." The difference between idealism and realism is simple-- idealism asserts that reality is fundamentally mind-constructed, so there is no reality outside the mind. This would also require I speak of my mind, because if there is no reality outside my mind, then your mind does not exist outside of my mind. I've never said any such thing, just look.

Indeed, scientists often find it useful to adopt realism, and I am no exception. Realism asserts that there is a reality outside our minds, and our minds are trying to figure it out. This is the stance I take. But here we must distinguish two brands of realism, which I would call "naive realism" (the idea that when we conceptualize reality, we hit it spot on, in complete contradiction with both the obvious limitations of our senses and our intelligence, and ignoring the clear evidence to the contrary from the history of our own physics), versus what I would call "scientifically consistent realism" (a realism that does not disregard that evidence).

This seems to be utterly straight-forward and uncontroversial. So examine these words again and make it clear what your quarrel is about.

 

[bohm2]

This was KenG's criticism of PBR in this quote from a previous post:

What is incorrect here? Well, it certainly isn't "technically" true, because it leaves out a very important step in the logic. Hsu, and many others it would seem, have tacitly, and without even realizing, assumed this huge leap of faith:

(ia) the existence of an "underlying reality" requires that what happens in that reality be determined by the parameters in some theory!

And that last PBR critical paper appears to argue this same point:

The positions that collide here are the empirical tradition that assumes that the existence of an object is known by its observable effects (and nothing else), and the idealist or dogmatic position that we know about the existence of an object from an authoritative theory.

http://lanl.arxiv.org/PS_cache/arxiv/pdf/1112/1112.2446v1.pdf

But is that what the authors of PBR are claiming? Consider again Matt's response:

The idea is that the physical properties are "real" in the sense that they are not merely calculation devices in our heads, and can therefore be the cause of measurement outcomes. I suppose it is difficult to talk about physical reality without being "theory-relative" at all - for example the very ideas of photon and electrons come from theory. The result doesn't really depend on your exact philosophical standpoint on the nature of physical reality - we simply show that if a "reality" of some sort exists and satisfies our assumptions then the quantum state is "real" in whatever sense of the word "reality" the assumptions hold.

 

[qsa]

The baffling thing is that your misconceptions were corrected many pages ago...

https://www.physicsforums.com/showpost.php?p=3642301&postcount=271





This seems to be utterly straight-forward and uncontroversial. So examine these words again and make it clear what your quarrel is about.

while I understand the sentiment, but I beg to differ. You are saying in effect that our mind and all the instruments we can muster could be blind to some aspects of nature. But there is no proof of that. If anything, our intelligence and the history of science has shown that we are doing damn good if history to be taken as evidence.

Our models have been getting better and better representing reality , so who is anybody to stop that progress. We are at the edge of the deepest secrets of reality, we are producing Quantum Gravity theories and spitting them out like candies, and people say we cannot really know reality! If anything, it is clear that reality is astonishingly comprehendible.

Even today and it has been for a while , it has been conjectured that reality could be just a mathematical structure , in that case there is a window that we can have an isomorphic structure to reality. who is to stop that possibility.

I think we should totally ignore the mind thing (and be very suspicious of it), it is unconstructive. We should be bold and go where no man has gone before.

 

[bohm2]

Our models have been getting better and better representing reality , so who is anybody to stop that progress. We are at the edge of the deepest secrets of reality, we are producing Quantum Gravity theories and spitting them out like candies, and people say we cannot really know reality! If anything, it is clear that reality is astonishingly comprehendible.

Even today and it has been for a while , it has been conjectured that reality could be just a mathematical structure , in that case there is a window that we can have an isomorphic structure to reality. who is to stop that possibility.

The argument is pretty straight forward. Whether one buys it or not is a different story. Personally, I do:

A type of mind M is cognitively closed with respect to a property P (or theory T) if and only if the concept-forming procedures at M's disposal cannot extend to a grasp of P (or an understanding of T). Conceiving minds come in different kinds, equipped with varying powers and limitations, biases and blindspots, so that properties (or theories) may be accessible to some minds but not to others. What is closed to the mind of a rat may be open to the mind of a monkey, and what is open to us may be closed to the monkey. Representational power is not all or nothing. Minds are biological products like bodies, and like bodies they come in different shapes and sizes, more or less capacious, more or less suited to certain cognitive tasks.

http://art-mind.org/review/IMG/pdf/McGinn_1989_Mind-body-problem_M.pdf

This does not imply that there is no progress. In fact, human knowledge may have no limit and continue to grow/progress indefinitely but that doesn't imply that we can know everything or that there are no limitations to human knowledge. To use an analogy used by those who espouse this view, the set of prime numbers is infinite but that does not exhaust the set of all natural numbers.

And here's a very short section of a paper on that argument just in case you want further arguments:

 

[apeiron]

Our models have been getting better and better representing reality...

Which could be both true and also what proves the point here. As Ken G already pointed out.

If our models were that correct in the first place, then there would be little room for their improvement. And if you feel there looks to be no end in sight for further improvement, then clearly we have not managed to "represent reality" just yet. And even then - as you say - representing is all that we will be doing.

Nothing is being said that prevents our modelling becoming more effective with time. And we can even measure that in "objective" fashion. Epistemological theory would argue that "better" is being able to predict ever more based on ever fewer measurements. At least this is the basis of current models of cognition such as the Bayesian Brain.

The logical end-point of this would be - as you say - theories that don't need any measurements at all. Arguments from pure maths, like perhaps string theory , where maybe even the fundamental constants will spring forth from the right equations.

A step too far most likely. But these kinds of interesting speculations would count as "controversies in epistemology", whereas Ken G was merely outlining epistemology 101.

And DA went off on a misunderstanding thinking Ken was suggesting instead that consciousness somehow causes or embodies reality - the stance of idealist philosophy. But maybe I misunderstood his misunderstanding and DA can be more specific about what is wrong with the quoted passage.

 

[my_wan]

Your refusal to accept that the PBR argument is an attempt to rule out what HS calls ψ-epistemic ontological models is quite bizarre. I have explained it lots of times, so I'm not going to do it again.

I have no idea why you think that the Pusey quote somehow means that I'm wrong about something.

I cannot refuse to accept that which the scope of remains undefined. Just like the PBR use of the term "interpreted statistically" more generally contains a scope of meaning that makes its use meaningless the ψ-epistemic ontological does the same. The difference is that PBR, even before getting to the math, perfectly well stated the limits of the scope in which it was used. Something you, or the HS authors, have not done with the ψ-epistemic ontological labels.

Note, more fully, how the PBR article introduced the HS reference:

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

(My bold)
Yet you have thrown out the PBR articles more fully as incomprehensible babble and input the ψ-epistemic ontological terminology without more fully defining the scope of its validity. In fact, by using the term more fully, the PBR article was stating straight up not that it was wrong but that the HS paper lacked a well defined scope of applicability.

Again, I have no clue how right or wrong you may be in whatever way you are scoping the ψ-epistemic ontological terminology. Unless or until you more fully provide that the notion that I refuse to accept the PBR argument is at best moot, and more realistically a non sequitur given my complete acceptance of the PBR argument under the scope in which they provided it. It was you who said that scope was incomprehensible babble, not me.

 

[Fredrik]

As I have said several times, the stuff they're talking about right after the "more fully" comment is Harrigan & Spekkens. Reference [11] is Harrigan & Spekkens, and the things they say right after that reference very clearly match the definitions in Harrigan & Spekkens. That sentence tells the readers that they haven't yet presented their fullest description of what they mean by the statistical view, and now they're going to do it "more fully". And they do it by referencing Harrigan & Speckens, and then describing the content of the definitions in Harrigan & Speckens. This can only mean one thing: The definitions from Harrigan & Speckens is the "fuller" description.

As you can see, I did not throw out the words "more fully" as incomprehensive babble. I took it very seriously.

 

[my_wan]

Perhaps we can agree, if I get you right, "certain advantages" are indeed compatible, or even an integral part of my view:

Absolutely, and also indispensable. My proclivities toward realism do not blind me to the validity and value of information centric models that do not pay reverence to such proclivities. I even think the "certain advantages" goes deeper than the ones you rightly articulated below.

Each observer, IMHO, has an empirically justified view of an "effective reality", and this contains the best match to observer invariants - to the extent that observer has inferred. And indeed, the concept of rational action means that THIS is definitely working as a constraint on the observer actions; in the sense that it's EXPECTATIONS of "invariants" with respect to OTHER observers, helps this observer to make place his bets - this is IMO the "certain advantage".

Aptly put.

Interpreting in this way, I can agree on your last point as well. What I think is important though, is that we do not confuse OUR (or say MY OWN) view of "effective reality with invariants" with the concept that ANY observer (read any piece of matter) has it's potential OWN subjective view of another "effective reality".

Exactly. If I restricted myself to my own default perspective then recognizing the consistency of views which by definition reject the predicates of my own would be a no-go, but it's not. Yet the debates between (non)realist, even in the peer literature, tend to treat the other as mutually exclusive. Which is not valid. IMO, any model which is not transformable between the two views is incomplete, not necessarily wrong.

Side point: When you equate an observer with a piece of matter I would not suspect that it is possible to equate the predicates of an ontic physics model to bits of mass, or even information in the empirical sense. Essentially for reasons Dr Chinese points out in Hume's[/PLAIN] Determinism Refuted. A mass bit would have to fall under an information centric derivative. Hence any such theoretical constructs along these lines must be purely axiomatic, no more or less provable in an absolute sense than any choice of purely mathematical axioms. Yet the axiomatic foundations do not limit the scope of the predictive power or limit such predictive power to singular information centric perspectives at any given mass point.

The mind trap as I see it, that is easy to fall into, is the mental picture that there exists in some absolute timeless sense some "real reality" that connects all the "effective realities" by some master symmetry. One might first thinkg that "what's the difference" between effective reality and real reality? From the empirical point within the view of a GIVEN observer, there is no difference since the whole point is that there is no way to distinguish them!

The inability to distinguish them likely only applies if you presume that no new predictions can be predicated on such a model. This is likely even if none of the predictions of the standard model are invalidated even in the limit. Of course this would not entail provability of the axioms, no matter how successful the empirical predictions, but that's standard logic mathematical or physical. The point of such a model is not about justifying one point of view over the other but providing the causal basis for why apparently incongruent perspectives are if fact perfectly congruent. Essentially doing the same thing for ψ as Einstein did for bits of mass.

But the real issue is when one expects the two "effective realities" of two INTERACTING observer to be the same. This is IMO an unjustified expectation that only makes sens in some mathematical realm, and insisting on it tend to result in other pathologies that I think are related to this simply becaue in mathematical realm there are no selection principles except inconsistencies. For example certain landscape problems or hard initial value and finetuning problems.

Absolutely, there is simply no justification for anyone observers perspective to have any precedence over the other. My point is that this not only makes sense in the mathematical realm it also makes sense in the purely physical realm when you quit trying to force fit a particular perspective one to one onto a particular unique physical state. However, this requires defining a mass, not as a single physical state but, as a set of physical states in much the same way as relativity defines the relational components between sets of mass points rather than a singular mass. He had no cause to formulate relativity at a level below that of a localized mass until QM came along. If this is recoverable the evidence points to requiring us to go to the sub-Planck level. It's funny that PBR makes its case on measurable constraints imposed by ψ when the same argument applied to relativity demonstrates the same with a man coming back younger than his son. It only fails to make sense as a purely physical effect if you keep insisting that physical entails Newtonian absolutes, or in the modern sense as properties that are uniquely inhere to mass objects, like in the EPR case.

Still there is no denial that the "effective reality" is an essential to any given observe, and this of course INCLUDES *expectations* on how this observers observations relates to fellow observers etc. One can imagine semi-equilibriums, where a group of observers can actuall agree on observer invariants. But this presumes the group has equilibrated.

Yes, ultimately any theoretical construct must eventually come back to characterize the expectation values of the effective perspectives all observers are limited to. Neither can anyone valid perspective be given precedence over any other. What the physical invariants provide is not a uniquely valid singular perspective but the transforms that allows any set of perspectives to be compared equally. Mass objects are wholly inadequate at any modeling level below which a mass point can be meaningfully defined, though they were complete enough for its purpose in 1905. Yet this does not automatically entail ontic non-reality of the momentary constituents of mass objects, just as relativity did not automatically entail the non-reality of a physical state, or classically the non-wave properties of particles entails the non-reality of momentary constituents of sound waves. So long as we are trying to force fit properties of systems of parts onto properties of individual parts the consequence always will be a fallacy of division, or conversely a composition fallacy, rather than a proof of what nature can and cannot be.

PBR, EPR, Kochen-Specker, Weinberg–Witten, etc., are perfectly valid against any model that attempts to force fit λ onto ψ as if λ contains λ. Just like you can't force fit the properties of a jet onto a jet engine. And anybody who expects a singular unique observer perspective to be uniquely valid in any ontically real model is doing just that. That went the way of the dodo bird in 1905. The over-generalization of what these no-go theorems entail is doing just that. And I am NOT rejecting the validity of the no-go theorems in saying that.

 

[my_wan]

As I have said several times, the stuff they're talking about right after the "more fully" comment is Harrigan & Spekkens. Reference [11] is Harrigan & Spekkens, and the things they say right after that reference very clearly match the definitions in Harrigan & Spekkens.

That [11] was HS was my point. In exactly what way does it match given that not a single term used by HS was used by PBR?

That sentence tells the readers that they haven't yet presented their fullest description of what they mean by the statistical view, and now they're going to do it "more fully"

.
Before the HS[11] reference they provided a qualitative description of what their theorem was going to clarify. After the HS[11] reference they provided a more complete mathematical characterization of what they stated prior to that reference. Hence the "more fully" referred to the more precise quantitative characterization, not to HS being the "more fully" outlined case.

And they do it by referencing Harrigan & Speckens, and then describing the content of the definitions in Harrigan & Speckens.

Nowhere did PBR describe the contents of HS. If they did show a single instance where they used any term that is even a variant of a term used by HS!

This can only mean one thing: The definitions from Harrigan & Speckens is the "fuller" description.

So if I say I'm going to provide a more complete description of A than provided by B, your saying what I really mean is that B is the more complete description?!

Look at the PBS statement again (just for reference):

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

My bolding: We [PBR] describ[e] more fully the difference between the two different views, not HS. The HS reference merely points to a source containing the "different views", not a more complete or exacting specification of those differences.

As you can see, I did not throw out the words "more fully" as incomprehensive babble. I took it very seriously.

Perhaps not but here you claim "more fully" really means "less fully". The "We" that started the sentence most certainly did not mean HS.

 

[Ken G]

All Ken G is trying to say (in my opinion) is that we should not mistake our models with whatever our models are trying to model.

And I suppose everybody agrees with him on that.

Yes, it's a funny issue-- some say that the point is almost too obvious to bother mentioning, others feel it is totally wrong! What really matters is how the brand of realism one adopts connects with the perceived importance of the PBR theorem. Certainly PBR think their theorem should seem important to any realist who wants to think a state is an epistemic entity, but the question I've asked is, what do PBR think a realist is? The standard definition is of someone so naive that I cannot imagine any serious scientist holding that position, so just who is the theorem supposed to be informing?

It seems to me that the way PBR interprets "realism" is that a real system has real properties that determine what happens to it. If this were not an important assumption, I cannot see why PBR would care if we are realists or not. But many of the commentators have equated realism with the belief that a real world exists, which seems like an important assumption for any conventional scientist, yet I've pointed out that the belief in the existence of a real world should not require that we imagine that real systems have real properties, or indeed even that there is any such thing as "real systems." We can talk about reality, but as soon as we talk about something else, like "real X", our minds have already entered the discussion-- in the interpretation of the meaning of X.

 

[my_wan]

Here's what I need to possibly make sense of ψ-epistemic ontological in the broader context of possible models.

(Characterized means characterized in terms of epistemic/ontological.)
(1) How would classical thermodynamics (CT) be characterized?
(2) How would statistical mechanics (ST) be characterized?
(3) How would the state variables pressure, volume, temperature, energy and entropy be characterized differently in (1) and (2)?
(4) Given that a velocity is not uniquely definable for all observers, how would velocity be characterized?

Clear consistent answers would at least provide a context to your words. Although I think that once you even try it becomes painfully obvious why, even in the relativistically concrete backdrop of classical physics, the terminology lands on a slippery slop.

 

[my_wan]

Yes, it's a funny issue-- some say that the point is almost too obvious to bother mentioning, others feel it is totally wrong!

I have never met any physicist, realist or otherwise, who thought it was totally wrong to make a distinction between the model and what the model described. What most realist object to is the a priori disqualification of considerations of what the actual system might entail that is not contained in the model. As I noted, Feynman ran into this kind of rejection when his little pictorials even hinted that he might be trying to picture what nature actually was, which wasn't the case in that instance.

The difference is that non-realist reject even considering a the system constraints outside the model itself as unponderable. Your criticism here is well patterned after the criticisms used against 19th century realist trying to develop a mechanistic model of thermodynamics. It was proven to be impossible to derive a mechanistic model of thermodynamics directly from classical thermodynamics, and remains impossible to this day. Yet statistical mechanics did just that not by deriving statistical mechanics from classical thermodynamics, but by starting over from scratch with pure mechanics and deriving classical thermodynamics. And wouldn't you know it, it turns out to be empirically superior.

This was NOT accomplished by poopooing theoretical notions of what nature really was independently from the (classical thermodynamics) model. Today people just presume that the physicist of that day were all realist in the classical absolute sense simply because that's what the models imply. Not so.

What really matters is how the brand of realism one adopts connects with the perceived importance of the PBR theorem. Certainly PBR think their theorem should seem important to any realist who wants to think a state is an epistemic entity, but the question I've asked is, what do PBR think a realist is? The standard definition is of someone so naive that I cannot imagine any serious scientist holding that position, so just who is the theorem supposed to be informing?

Nature doesn't care what we think is or isn't naive. It remains equally important to prove that what we think is naive really is naive as it is to prove what we think is valid is in fact empirically valid. Many things we historically thought was naive have been proven otherwise and visa versa. We are thus informed whether a single human thought it was anything other than naive or not.

It seems to me that the way PBR interprets "realism" is that a real system has real properties that determine what happens to it. If this were not an important assumption, I cannot see why PBR would care if we are realists or not. But many of the commentators have equated realism with the belief that a real world exists, which seems like an important assumption for any conventional scientist, yet I've pointed out that the belief in the existence of a real world should not require that we imagine that real systems have real properties, or indeed even that there is any such thing as "real systems." We can talk about reality, but as soon as we talk about something else, like "real X", our minds have already entered the discussion-- in the interpretation of the meaning of X.

The only empirical handle we have on a system, independent of the model, is empirically distinguishable experimental outcomes. Hence the type of relationships possible between experimental outcomes and any perspective of realism is very important. For you to say that to think properties could represent anything other than what was demonstrated is naive, though I agree, implies that we should have simply took your word for it, eat your philosophical pill, and forgot about the science. Well no! Let's do the science and work out the PBR theorems of various flavors, because nature doesn't give a crap what any of us think is naive.

 

[Len M]

Our models have been getting better and better representing reality , so who is anybody to stop that progress. We are at the edge of the deepest secrets of reality, we are producing Quantum Gravity theories and spitting them out like candies, and people say we cannot really know reality! If anything, it is clear that reality is astonishingly comprehendible.

I think we should totally ignore the mind thing (and be very suspicious of it), it is unconstructive. We should be bold and go where no man has gone before.

I don’t know, it seems to me that getting closer and closer to reality through verified mathematical models is a pretty obvious thing to say. What’s not so obvious is what we mean by reality, and I think that comes through in the posts of Ken G. Empirical reality (or whatever one wants to call it) involves us – end of argument. The “truth” of what science tells us is only applicable as a “truth” to our reality as we live and perceive it – it’s a pretty powerful "truth" because the verified models work with everything we do in our reality.

Now if anyone wants to say that the “truth” of science is applicable in the same manner to a reality that does not involve us then they are going to have to tell me how we can step outside of our reality and stare into its face without using our minds. We cannot do such a thing, therefore any attempt to extrapolate our verified mathematical models as a “truth” (in the manner we can assert them as a “truth” within our reality) is an assumption. In fact it is a philosophical assumption because the notion of a reality existing outside of us is a philosophical question.

To ignore the “mind thing” as you put it is to adopt naive realism, to accept the “mind thing” is to realize that science is a “truth” within the remits in which it is practiced, and that remit cannot be anything other than the reality we find ourselves in. There is absolutely no justification to take that truth as being a universal truth that is applicable to mind independent reality.

It seems to me that all Ken G is saying is that physics is exploring our reality, and that has to include us. The models we produce are “real” because they work within our reality, nothing more than that. Once you get on board with this, a distinction appears between science as a means of informing us of our reality and the extrapolation of that science to reality outside of the means in which the science is practiced, i.e. a reality that has no referral to us in any manner. I think that distinction is important because we have established a scientific “truth” in the former case (“truth” because it works within our reality – that is the only criteria needed), but in the latter case, we can only speculate on what science can tell us about mind independent reality, it is not comparable to the “truth” that science gives us within our reality.

The former case is not an opinion or a stance, it is simply what is – science cannot give us a truth about a reality that sits outside of the means in which the science is practiced, it can only give a truth referred to our observation and verification, and that can only happen within the reality that we find ourselves in.

I feel some on this thread blur this distinction and I don’t think that helps the process of science, people start believing that scientific truth is a universal truth – that the process of establishing scientific “truth” is applicable to a reality that does not refer to us and that’s just wrong. There is nothing to stop anyone extrapolating scientific “truth” to mind independent reality, but let's all be clear that that process is not the same process of science that goes on within our reality – rather it is a process of “pushing” scientific models having a defined remit of “truth” into an arena that is forever outside of that remit of truth. So the validity of that process is entirely a philosophical question and will always be so.

Now all of this just seems pretty obvious to me, and I honestly can’t see what the fuss is about, but it just doesn’t seem obvious to many others, here and elsewhere. So I do wonder if I am being overly simplistic, pedantic, seeing things in black and white, or whatever. If I am then I need to know.

 

[Fredrik]

I can't believe we're still talking about this... This will definitely be the last time.

That [11] was HS was my point. In exactly what way does it match given that not a single term used by HS was used by PBR?

I have told you that several times. The possibilities they're listing are exactly the conditions that define the terms in HS. Have you even looked inside HS? It's irrelevant that PBR doesn't use those those terms, since they are describing the conditions that define the terms.

Before the HS[11] reference they provided a qualitative description of what their theorem was going to clarify. After the HS[11] reference they provided a more complete mathematical characterization of what they stated prior to that reference. Hence the "more fully" referred to the more precise quantitative characterization, not to HS being the "more fully" outlined case.

I agree with your first two sentences. What they're saying before the reference to [11] is a much less accurate version of what they're saying after it. The sentence that contains the [11] reference announces that they're about to describe what they mean more fully, and then they immediately proceed to describe the content of the definitions in [11].

Nowhere did PBR describe the contents of HS. If they did show a single instance where they used any term that is even a variant of a term used by HS!

The terms themselves are irrelevant. What matters is the conditions listed in the definitions of the terms.

What we're talking about is analogous to this: Someone is talking about two different kinds of integers, but hasn't yet explained what the two kinds are. Then he says "I'm going to explain more fully what I meant when I said that there are two kinds of integers [1]", and continues "either an integer is 2 times another integer, or it's equal to 2 times another integer, plus 1". Then he derives a contradiction from the assumption that there's an integer of the first kind that's both >2 and a prime number.

Now we look at reference [1] and find this:

An integer n is said to be even if there's an integer m such that n=2m. An integer n is said to be odd if there's an integer m such that n=2m+1.​

Then I say that he proved that prime numbers >2 are odd, and someone shows up and repeatedly says that I have no clue what I'm talking about; the guy was clearly not using the definitions of [1] since he never used the term "odd"; he was just providing a fuller description of the two kinds of integers than the one provided by [1].

This is precisely what's going on here, except that we're talking about ψ-epistemic ontological models for quantum theories instead of even prime numbers >2.

So if I say I'm going to provide a more complete description of A than provided by B, your saying what I really mean is that B is the more complete description?!

Of course not, but they didn't say that they were going to provide a more complete description than HS. They said that they were going to provide a more complete description than they had provided so far. And in that sentence, they referenced HS. And right after that, they gave us the conditions from the definitions of HS.

Here's what I need to possibly make sense of ψ-epistemic ontological in the broader context of possible models.

(Characterized means characterized in terms of epistemic/ontological.)
(1) How would classical thermodynamics (CT) be characterized?
(2) How would statistical mechanics (ST) be characterized?
(3) How would the state variables pressure, volume, temperature, energy and entropy be characterized differently in (1) and (2)?
(4) Given that a velocity is not uniquely definable for all observers, how would velocity be characterized?

Clear consistent answers would at least provide a context to your words. Although I think that once you even try it becomes painfully obvious why, even in the relativistically concrete backdrop of classical physics, the terminology lands on a slippery slop.

The terminology doesn't apply to any of this. HS is about ontological models for quantum theories.

 

[my_wan]

The terminology doesn't apply to any of this. HS is about ontological models for quantum theories.

So when PBR said: "Another is that even a pure state has only a statistical significance, akin to a probability distribution in statistical mechanics.", they were not making a direct comparison with classical analogs?

In fact what distinguishes a quantum system is its distinctions from a classical system. Hence any attempt to restrict your terminology strictly to QM requires some kind of distinction in what those distinctions are. The PBR theorem was explicitly formulated to directly compare classical and quantum systems in a certain respect, yet you want to swap in a terminology for it which you say no such a comparison is even applicable? That is tantamount to claiming the PBR theorem is not relevant to the PBR theorem.

 

[Fredrik]

So when PBR said: "Another is that even a pure state has only a statistical significance, akin to a probability distribution in statistical mechanics.", they were not making a direct comparison with classical analogs?

In a classical theory, each point in the theory's phase space determines all measurement result, and each probability measure on the phase space determines the probabilities of all measurement results.

In a quantum theory, each state vector determines the probabilities of all measurement results. It is therefore reasonable to ask if the state vectors in a quantum theory correspond to probability measures in some other theory that makes the same predictions as as the quantum theory. This is the question they're trying to answer.

An ontological model for a quantum theory is essentially just another theory that makes the same predictions. It just needs to satisfy one additional mathematical condition to be called an ontological model for the quantum theory, and then another one to be called ψ-epistemic.

 

[Ken G]

I have never met any physicist, realist or otherwise, who thought it was totally wrong to make a distinction between the model and what the model described. What most realist object to is the a priori disqualification of considerations of what the actual system might entail that is not contained in the model. As I noted, Feynman ran into this kind of rejection when his little pictorials even hinted that he might be trying to picture what nature actually was, which wasn't the case in that instance.

But I just don't see anything at all in what Feynman did that requires the way you are characterizing it. He came up with a model for how to think about a certain process, just like every scientific theory did for the whole history of science. Nothing Feynman did was particularly ontological, indeed it really required getting "outside the box" of normal ontologies. So I don't see where the Feynman story has any significance to the idea that reality agrees with our models more than it is demonstrated to agree with our models. Science makes models, they work either pretty good, or great, depending. There's just nothing more to say, it makes no difference to the science, including Feynman's science, if people want to brand themselves "realists" or not.

The difference is that non-realist reject even considering a the system constraints outside the model itself as unponderable.

No, that is not correct. Why are so many people on this thread claiming that anyone said anything about what does not exist? The point being made is what is demonstable about what does exist, that's it, period. Further, the point has been made that it is neither demonstrable, nor any requirement of the workings of science, to claim that reality contains true properties that determine what happens. No one has said that such properties don't exist, what has been said is that nothing in science relies on them or indicates that they exist, and countless good theories of science, which worked quite well thank you, relied on properties that we perfectly well know do not exist in reality. These are all facts, nothing is being claimed that is not perfectly demonstrable as true.

Your criticism here is well patterned after the criticisms used against 19th century realist trying to develop a mechanistic model of thermodynamics.

No, nothing I have said even remotely resembled "do not derive scientific theories by entering into ontological thinking." Indeed, I have quite specifically said, on many occasions, words to the effect of "absolutely do enter into ontological thinking when deriving theories, it is convenient and effective to do so. Just don't take it literally, because the ontology is not going to be unique, and is probably not going to be true, and is very likely going to get replaced sooner or later in some better theory." That's it, that's all I said. So no, I never said, or thought, that it would be any kind of mistake to try to derive thermodynamics by imagining an ontology in which a bunch of particles were bouncing around statistically. What would be a mistake, and what is demonstrably erroneous in fact, is to conclude that the success of classical statistical mechanics proves that the ontology of little particles with exact positions and momenta is a true ontology of nature.

 

[qsa]

In fact it is a philosophical assumption because the notion of a reality existing outside of us is a philosophical question.

There, you said it. Even worse, what is exactly the notion of reality existing "outside" of us. No such a thing can be of any use, scientific or otherwise. Hence, trying to know the truth of "real reality mind independent" is meaningless.

And it is bad enough to deal with one reality which we have. Stepping outside it has no meaning. How can you study and enjoy the Grand Canyon if you are not there.

 

[Len M]

There, you said it. Even worse, what is exactly the notion of reality existing "outside" of us. No such a thing can be of any use, scientific or otherwise.

And it is bad enough to deal with one reality which we have. Stepping outside it has no meaning. How can you study and enjoy the Grand Canyon if you are not there.

Mind dependence simply poses the question: what is the nature of reality outside of the only means we have in which to examine nature? Is it the same, is it approximately the same, is it utterly different, so much so that we have no language to describe "different" or is there nothing outside of our minds? They are the options in which to describe a reality that may or may not exist outside of us ("us" being minds and consciousness involving the perception of space, time and objects).

Stepping outside of our reality (which means stepping outside of our minds, because our reality cannot be divorced from our minds) in order to examine the nature of that reality is impossible (which equates to it being meaningless as you say), so yes mind independent reality is a philosophical notion - it can’t be otherwise and it certainly is not of any scientific use. For me the notion is simply a philosophical extrapolation (and one that I strongly choose to adopt in opposition to radical idealism) from the important issue of mind dependence (and the inescapable nature of it) within science. Mind dependence places the "truth" derived through physics in a proper context – it is not a "truth" that is applicable to mind independent reality. In other words, we cannot use physics to describe “something” outside of our perceptions in the same way that we use physics to describe our perceptions – the “truth” of the latter is not the “truth” of the former. Thus science is the means of deriving "truths" about the "whole", and within that "whole" lay minds and consiousness. That for me is the important general point rather than a notion of mind independent reality – that notion is a personal philosophical choice one can adopt in order to retain realism. In fact radical idealists would dismiss out of hand the notion of a mind independent reality.

 

[bohm2]

Mind dependence places the "truth" derived through physics in a proper context – it is not a "truth" that is applicable to mind independent reality. In other words, we cannot use physics to describe “something” outside of our perceptions in the same way that we use physics to describe our perceptions – the “truth” of the latter is not the “truth” of the former. Thus science is the means of deriving "truths" about the "whole", and within that "whole" lay minds and consiousness.

So everything is filtered through our cognitive structures and there's no guarantee that there will be a close correspondence between the two. In fact, one may argue that it would be kinda surprising if there was. But, what do you think of this fallback scientific realist position that some use:

What we call "natural science" is a kind of chance convergence between aspects of the world and properties of the human mind/brain, which has allowed some rays of light to penetrate the general obscurity

Thus, some have argued that theoretical physics is one of those areas where some of "those rays of light" have penetrated somewhat thus allowing for genuine progress/"deeper" understanding, etc.

In some of his later works, Pierce goes further and suggests (unconvincingly, in my opinion?) that because we are a product of nature/natural law, we may have a natural instinct at somehow being able to arrive at some of those laws of nature:

In this way, general considerations concerning the universe, strictly philosophical considerations, all but demonstrate that if the universe conforms, with any approach to accuracy, to certain highly pervasive laws, and if man's mind has been developed under the influence of those laws, it is to be expected that he should have a natural light, or light of nature, or instinctive insight, or genius, tending to make him guess those laws aright, or nearly aright...This would be impossible unless the ideas that are naturally predominant in their minds was true...The history of science, especially the early history of modern science, on which I had the honor of giving some lectures in this hall some years ago, completes the proof of showing how few were the guesses that men surpassing genius had to make before they rightly guessed the laws of nature...

 

[Ken G]

Thus, some have argued that theoretical physics is one of those areas where some of "those rays of light" have penetrated somewhat thus allowing for genuine progress/"deeper" understanding, etc.

Indeed, there is no reason to dispute that-- nor anything in that first Pierce quote. It's all demonstrably true, but only because the quote clearly separates "aspects of the world" from "properties of the human mind/brain" (which I am associating with aspects of physics theories created by the mind/brain, not the biology of the mind/brain which is its own set of theories and is no clearer than aspects of the world). Where it gets sticky is when we ask, what is the connection between an aspect of the world and a property of a theory? The naive realist says they are exactly the same thing, the reductionist realist says they reduce to the same building blocks for all scientific purposes (including theorems like the PBR theorem), and the structural realist says they are only "structurally" the same, which again is all that matters for doing science (but might not be appropriate to use as an axiom in theorems because it's not clear how "structurally similar" they really are).

Of course the idealist says they are exactly the same also, but only because there is no such thing as aspects of the world since they are merely projections of the properties of the mind/brain. Still, this is also what naive realism concluded for different reasons, so once again we see that too naive a form of realism is just idealism in disguise, and we need to move well down towards "structural" forms to get away from idealism, as the latter is supposed to be the antithesis of realism.

So I think Pierce is completely right there, but the sticky point is what will we make of this "ray of light", why we do achieve such great successes with our models in certain well defined (and highly selective) circumstances? When we get "genuine understanding", does that mean something different from "very effective understanding"? Can understanding be something different from knowing the "true nature" of something? I agree that Pierce's suggestion that we have these successes because our minds are evolved to have them is not convincing-- the human brain evolved to use basic logic, not quantum mechanics. But maybe basic logic is some kind of building block that is somehow embedded in reality (the rationalist dream)-- or maybe it's just that logic is flexible enough to fashion almost any kind of tool that will then go out and work at some job. I've always felt the claim that "it wouldn't work so well unless it were true" is like saying "a saw wouldn't be so effective at cutting down trees if trees weren't made for cutting down by saws."

 

[bohm2]

Indeed, there is no reason to dispute that-- nor anything in that first Pierce quote.

So I don't get screamed at, I got the first quote from Lycan who is actually quoting Chomsky not Pierce but Chomsky is receptive to some of Pierce's insights on this issue (the second quote which is Pierce's) but Chomsky doesn't agree with Pierce's conclusions; that is, with Peirce's idea that

nature fecundates the mind of man with ideas which when those ideas grow up, will resemble their father, Nature.

Peirce seems to think that since the laws of nature were used in the design of our mental structures, it will allow us to have access to those laws (e.g. our models will be close approximations to the "true" mind-independent laws/reality).

 

[Ken G]

OK, thanks for correcting that, I wasn't sure if that first quote was supposed to be Peirce. I suspect Peirce would have agreed with it anyway-- it's more his idea that "nature fecundates the mind" that seems controversial here. I don't agree with Peirce on that score because it ignores the phenomenon described by S. J. Gould, summarized on his Wiki page by "In particular, he considered many higher functions of the human brain to be the unintended side consequence or by-product of natural selection, rather than direct adaptations." Such "exaptations" are also called "spandrels", after the architectural feature necessitated by the use of arches. The idea is, you might have a brain that evolves to figure its way out of a sabre-tooth tiger battle, but as a consequence of having a brain like that, you might also inherit the ability to do quantum mechanics. It's not that the quantum mechanics is selected for, and it's not that the selection process is ruled by quantum mechanics, it is simply that a brain capable of doing logic has to be capable of doing quantum mechanics (though some students might not agree!).

 

[bohm2]

Such "exaptations" are also called "spandrels", after the architectural feature necessitated by the use of arches. The idea is, you might have a brain that evolves to figure its way out of a sabre-tooth tiger battle, but as a consequence of having a brain like that, you might also inherit the ability to do quantum mechanics. It's not that the quantum mechanics is selected for, and it's not that the selection process is ruled by quantum mechanics, it is simply that a brain capable of doing logic has to be capable of doing quantum mechanics (though some students might not agree!).

Yes, we discussed this in another thread, I think? See link below. The basic argument was that this ability (to do abstract mathematics/language) so useful in doing physics/science wasn't selected for but may have been put there for "physical reasons" (e.g. space limitations of evolution of larger brain) as S. J. Gould argued. See See post #266 of this thread:

https://www.physicsforums.com/showthread.php?t=523765&page=17

They basically argue that this uniquely human part of our language faculty (FLN-see links for details) having the properties of recursion (also found in our mathematical abilities) emerged in human brains for "physical" reasons yet to be fully comprehended; but unlike most innatists/ nativists (e.g. Pinker/Jackendoff) the reasons suggested are not due to "natural selection" but instead are guided by principles of elegance and compactness (not "tinkering" in Pinker’s sense, I guess). So to give one example, "why did Helium evolve after Hydrogen in the evolution our universe", etc. It wasn’t for reasons of "natural selection" in any sense of the term. There were physical laws dictating it that it occur. Same with this uniquely human abstract abilities in language and mathematics (or so, it is argued by this position).

Assuming this position is accurate, what I’m having trouble understanding is this:

1. Does this make it any easier to understand why our ability to do higher mathematics is so useful in studying physical phenomena even though it did not evolve for reasons of “natural selection” (or so, they argue); that is, does evolution of abstract mental structures (from more primitive language and mathematical cognitive structures) that is guided by physical law versus natural selection make it more plausible why mathematics is so useful for doing physics, etc?

2. What would be the implications (if any) on the mind-body problem, if this view is accurate?

3. If accurate would this strengthen, weaken or have no effect on Peirce's notion that "nature fecundates the mind of man with ideas which when those ideas grow up, will resemble their father, Nature". I'm hoping 'strengthen', since Chomsky's more skeptical position with respect to knowledge (ie. match between our mental constructs and "true" laws) is something I would like to avoid, even though I find it pretty convincing.

 

[bohm2]

I thought this was an interesting quote by Matt Leifer on his most recent comment on his blog:

Generally speaking, I think that PBR will turn out to be the strongest of the no-go results, which is why I am so keen on promoting it. I think it may imply all of the others in some suitable sense. For example, given PBR, the EPR argument is enough to establish nonlocality, without having to bother with Bell inequalities.

 

[ThomasT]

I thought this was an interesting quote by Matt Leifer on his most recent comment on his blog:

Generally speaking, I think that PBR will turn out to be the strongest of the no-go results, which is why I am so keen on promoting it. I think it may imply all of the others in some suitable sense. For example, given PBR, the EPR argument is enough to establish nonlocality, without having to bother with Bell inequalities.

Hi bohm2. What does Leifer mean by "nonlocality"?

 

[bohm2]

What does Leifer mean by "nonlocality"?

At the least, some type of superluminal "influence", I think.

 

[ThomasT]

At the least, some type of superluminal "influence", I think.

That's understandably and, imho, unacceptably, vague. Nonlocality is defined by some (most? ... I don't know) quantum physicists as referring to entangled quantum states, which might ultimately refer to ftl propagations or not. No way to currently make that leap, afaik.

But wrt EPR, afaik, the term 'nonlocality' refers to instantaneous 'effects'. That is, events that happen at the same time. So, there's no ftl propagation involved in EPR 'nonlocality'. Or in Bell 'nonlocality' for that matter, afaik.

It seems that the term "nonlocality" is taken, by some, to refer to ftl propagations. But there doesn't seem to me to any evidence for that assumption.

Can you tie this into the OP, ie., the acceptability of the statistical interpretation of QM?

 

[bohm2]

That's understandably and, imho, unacceptably, vague. Nonlocality is defined by some (most? ... I don't know) quantum physicists as referring to entangled quantum states, which might ultimately refer to ftl propagations or not.

With respect to the OP, I'm not sure what you are asking. If one buys Leifer's argument, it's pretty clear which models PBR scraps. With respect to non-locality, some physicists (e.g. Bell, Maudlin, Laudisa, Norsen, etc.) interpreted Bell's theorem as already implying non-locality (ftl) irrespective of "realism" issues. Others, however, did not interpret Bell's theorem in that way. I think it has to be vague (e.g. "influence") because some have argued that non-locality does not imply incompatibility with relativity since it may depend on which interpretation of relativity is true. A Lorentzian interpretation of relativity (single preferred frame) is compatible with non-locality. Does this mean just some finite v>c or instantaneous influence? I think it implies the latter. Here's what Bell wrote on non-locality implied by his theorem:

I think it’s a deep dilemma, and the resolution of it will not be trivial; it will require a substantial change in the way we look at things. But I would say that the cheapest resolution is something like going back to relativity as it was before Einstein, when people like Lorentz and Poincare thought that there was an aether -a preferred frame of reference-but that our measuring instruments were distorted by motion in such a way that we could not detect motion through the aether...that is certainly the cheapest solution. Behind the apparent Lorentz invariance of the phenomena, there is a deeper level which is not Lorentz invariant...what is not sufficiently emphasized in textbooks, in my opinion, is that the pre-Einstein position of Lorentz and Poincar´e, Larmor and Fitzgerald was perfectly coherent, and is not inconsistent with relativity theory. The idea that there is an aether, and these Fitzgerald contractions and Larmor dilations occur, and that as a result the instruments do not detect motion through the aether - that is a perfectly coherent point of view...The reason I want to go back to the idea of an aether here is because in these EPR experiments there is the suggestion that behind the scenes something is going faster than light. Now if all Lorentz frames are equivalent, that also means that things can go backwards in time...[this] introduces great problems, paradoxes of causality, and so on. And so it is precisely to avoid these that I want to say there is a real causal sequence which is defined in the aether.”

More recently a number of "realist" spontaneous collapse and Bohmian interpretations that are Lorenz-invariant (and even narrative) have been developed:

http://arxiv.org/PS_cache/arxiv/pdf/1111/1111.1425v1.pdf
http://arxiv.org/PS_cache/quant-ph/pdf/0406/0406094v2.pdf
http://xxx.lanl.gov/abs/1002.3226

But I have come across some criticisms about these models as well (for example, Valentini). From Towler's site:

Valentini’s Aristotelian spacetime: Galilean invariance not a fundamental symmetry of the standard low-energy pilot-wave theory. The search for a Lorentz-invariant extension thus seems misguided. In Valentini’s view, the difficulties encountered in such a search are no reflection on the plausibility of the pilot-wave theory. Rather, they show that the theory is not being interpreted correctly. Pilot-wave theory then has a remarkable internal logic - both structure of dynamics, and operational possibility of nonlocal signalling away from equilibrium (see later) independently point to existence of natural preferred state of rest.

http://www.tcm.phy.cam.ac.uk/~mdt26/PWT/lectures/bohm5.pdf

 

[ThomasT]

I'm not sure what you are asking.

I'm not really asking anything. Just stating my opinion wrt my admittedly limited take on the current state of affairs. Wrt which I welcome any criticisms you might be inclined to offer.

If one buys Leifer's argument, it's pretty clear which models PBR scraps.

Well, no, I don't buy Leifer's take on things.

With respect to non-locality, some physicists (e.g. Bell, Maudlin, Laudisa, Norsen, etc.) interpreted Bell's theorem as already implying non-locality (ftl) irrespective of "realism" issues.

Bell didn't speak of FTL, he spoke of instantaneous effects. Big difference, imo. Norsen is just wrong in his analysis, imho. Don't know about the others you mention.

Others, however, did not interpret Bell's theorem in that way.

Indeed, imo, the most sophisticated analyses of Bell's theorem interpret it as being applicable only to formalizations of quantum entanglement and not informing wrt nature.

I think it has to be vague (e.g. "influence") because some have argued that ftl does not imply incompatibility with relativity since it may depend on which interpretation of relativity is true.

SR is pretty clear imo. No matter what interpretation is assumed. It states that there's a limit on the propagational speed of material objects.

A Lorentzian interpretation of relativity (single preferred frame) is compatible with non-locality.

Not if nonlocality is taken to refer to acceleration to faster than light propagations of material entities. And if we're not talking about that, then we might as well be talking about pink unicorns or whatever.

Does this mean just some finite v>c or instantaneous influence? I think it implies the latter.

The problem is that "instantaneous influence" doesn't imply ftl progagation, it implies that event B is happening at the same time as event A. There's no propagation, ftl or whatever, involved.

 

[bohm2]

Well, no, I don't buy Leifer's take on things.

Why?

 

[ThomasT]

Why?

Because I don't think that Bell's theorem informs wrt physical reality -- but only wrt viable formalisms.

 

[bohm2]

A very interesting paper that came out today. Two of the authors are the same as per PBR in this thread:

Many quantum physicists have suggested that a quantum state does not represent reality directly, but rather the information available to some agent or experimenter. This view is attractive because if a quantum state represents only information, then the collapse of the quantum state on measurement is possibly no more mysterious than the Bayesian procedure of updating a probability distribution on the acquisition of new data. In order to explore the idea in a rigorous setting, we consider models for quantum systems with probabilities for measurement outcomes determined by some underlying physical state of the system, where the underlying state is not necessarily described by quantum theory. A quantum state corresponds to a probability distribution over the underlying physical states, in such a way that the Born rule is recovered. We show that models can be constructed such that more than one quantum state is consistent with a single underlying physical state-in other words the probability distributions corresponding to distinct quantum states overlap. A recent no-go theorem states that such models are impossible. The results of this paper do not contradict that theorem, since the models violate one of its assumptions: they do not have the property that product quantum states are associated with independent underlying physical states.

The quantum state can be interpreted statistically
http://lanl.arxiv.org/pdf/1201.6554.pdf

Edit: This sounds similar to Demystifier's criticism of PBR's assumptions? This is from Demystifier's earlier post (#95) from this thread:

In short, they try to show that there is no lambda satisfying certain properties. The problem is that the CRUCIAL property they assume is not even stated as being one of the properties, probably because they thought that property was "obvious". And that "obvious" property is today known as non-contextuality. Indeed, today it is well known that QM is NOT non-contextual. But long time ago, it was not known. A long time ago von Neumann has found a "proof" that hidden variables (i.e., lambda) were impossible, but later it was realized that he tacitly assumed non-contextuality, so today it is known that his theorem only shows that non-contextual hidden variables are impossible. It seems that essentially the same mistake made long time ago by von Neumann is now repeated by those guys here.

Let me explain what makes me arrive to that conclusion. They first talk about ONE system and try to prove that there is no adequate lambda for such a system. But to prove that, they actually consider the case of TWO such systems. Initially this is not a problem because initially the two systems are independent (see Fig. 1). But at the measurement, the two systems are brought together (Fig. 1), so the assumption of independence is no longer justified. Indeed, the states in Eq. (1) are ENTANGLED states, which correspond to not-independent systems. Even though the systems were independent before the measurement, they became dependent in a measurement. The properties of the system change by measurement, which, by definition, is contextuality. And yet, the authors seem to tacitly (but erroneously) assume that the two systems should remain independent even at the measurement. In a contextual theory, the lambda at the measurement is NOT merely the collection of lambda_1 and lambda_2 before the measurement, which the authors don't seem to realize.

 

[Ken G]

That helps put words to my earlier objection also, the reliance on the idea that "properties" determine outcomes. This I believe is the same idea as "non-contextuality", because we normally think of a "property" as something that exists in and of itself, independently of anything else. That's what I was imagining they meant by "properties", and I objected to their claim that it would be "radical" to reject that assumption. I think Demystifier put a more accurate word to it: non-contextual properties. Or another way to put it might be, reductionist properties rather than holistic elements of the system and its interactions.

 

[Demystifier]

Let me just note that I have sent an e-mail to the authors with a content similar to the above, but they have not mentioned me in the Acknowledgements of the new paper. (In fact, they don't have Acknowledgements at all.)

 

[bohm2]

Just in case anybody is interested, here's that exchange from Demystefier’s posts 123 + 124:

I had a brief exchange of e-mails with the authors of that paper. After that, now I am even more convinced that I am right and they are wrong. Here are some crucial parts of that exchange, so that you can draw a conclusion by yourself:

> Prof. Barrett:
> Briefly, the vectors in Eq.(1) are entangled, yes but they don't represent
> the state of the system. They are the Hilbert space vectors which
> correspond to the four possible outcomes of the measurement.

Me (H.N.): But in my view, the actual outcome of the measurement (i.e., one of those in Eq. (1) ) DOES represent the state of the system. Not the state before the measurement, but the state immediately after the measurement. At the measurement the wave function "collapses", either through a true von Neumann collapse, or through an effective collapse as in the many-world interpretation or Bohmian interpretation.
...

> Prof. Barrett:
> The assumption is that the probabilities for the different outcomes of
> this procedure depend only on the physical properties of the systems at a
> time just before the procedure begins (along with the physical properties
> of the measuring device).

Me (H.N.): Yes, I fully understand that if you take that assumption, you get the conclusion you get. (In fact, that conclusion is not even entirely new. For example, the Kochen-Specker theorem proves something very similar.) But it is precisely that assumption that I don't find justified. Any measurement involves an interaction, and any measurement takes some time (during which decoherence occurs), so I don't think it is justified to assume that the measurement does not affect the probabilities for the different outcomes.

In short, to make their results meaningfull, a correct title of their paper should be changed to "The quantum state cannot be interpreted non-contextually statistically" But that is definitely not new!

 

[bohm2]

Here's another post from Leifer talking about this more recent paper:

The issue of measurements causing a disturbance is not relevant here since we are only considering a simple prepare-and-measure experiment. If we were concerned with what happens after the measurement then it would be relevant, but this is not involved in the PBR scenario.

There is no assumption in the PBR paper that xi^k_p depends only on the projector. It may also depend on the other projectors in the measurement, i.e. it may be different for different measurements that share a common projector. However, the proof of the PBR theorem only makes use of a single measurement, so it doesn't get into trouble with the KS theorem in any case.

Since http://arxiv.org/abs/1201.6554 came out, we now know that psi-ontology and contextuality are definitely separate issues, since a psi-epistemic theory can be obtained for any Hilbert-space dimension, whereas a noncontextual theory cannot. This also shows that the factorization assumption is crucial in the PBR proof.

https://plus.google.com/u/0/104569184257973656413/up/#104569184257973656413/posts

 

[bohm2]

Another interesting paper by Leifer posted on his site and a newsletter but gives a bit more detail on the implications of PBR:

We have seen that the PBR result can be used to establish some known constraints on hidden variable theories in a very straightforward way. There is more to this story that I can possibly fit into this article, and I suspect that every major no-go result for hidden variable theories may fall under the rubric of PBR. Thus, even if you don’t care a fig about fancy distinctions between ontic and epistemic states, it is still worth devoting a few braincells to the PBR result. I predict that it will become viewed as the basic result about hidden variable theories, and that we will end up teaching it to our students even before such stalwarts as Bell’s theorem and Kochen-Specker.

PBR, EPR, and all that jazz
http://www.aps.org/units/gqi/newsletters/upload/vol6num3.pdf

Quantum Times Article on the PBR Theorem
http://mattleifer.info/2012/02/26/quantum-times-article-on-the-pbr-theorem/

 

[Fredrik]

Anyone know if the PBR paper has been published, or at least accepted for publication yet?

 

[ThomasT]

... some have argued that non-locality does not imply incompatibility with relativity since it may depend on which interpretation of relativity is true.

Or which definition of quantum nonlocality is used?

I think it’s a deep dilemma, and the resolution of it will not be trivial; it will require a substantial change in the way we look at things. But I would say that the cheapest resolution is something like going back to relativity as it was before Einstein, when people like Lorentz and Poincare thought that there was an aether -a preferred frame of reference-but that our measuring instruments were distorted by motion in such a way that we could not detect motion through the aether...that is certainly the cheapest solution. Behind the apparent Lorentz invariance of the phenomena, there is a deeper level which is not Lorentz invariant...what is not sufficiently emphasized in textbooks, in my opinion, is that the pre-Einstein position of Lorentz and Poincar´e, Larmor and Fitzgerald was perfectly coherent, and is not inconsistent with relativity theory. The idea that there is an aether, and these Fitzgerald contractions and Larmor dilations occur, and that as a result the instruments do not detect motion through the aether - that is a perfectly coherent point of view...The reason I want to go back to the idea of an aether here is because in these EPR experiments there is the suggestion that behind the scenes something is going faster than light. Now if all Lorentz frames are equivalent, that also means that things can go backwards in time...[this] introduces great problems, paradoxes of causality, and so on. And so it is precisely to avoid these that I want to say there is a real causal sequence which is defined in the aether.”

Wrt the above, my current opinion is that John Bell's view was just wrong.

 

[bohm2]

Two more papers on this theorem. The first paper is difficult to understand. I don't understand what the author is trying to say.

Can quantum mechanics be considered as statistical? An analysis of the PBR theorem
http://lanl.arxiv.org/pdf/1203.2475.pdf

Alternative Experimental Protocol for a PBR-Like Result
http://lanl.arxiv.org/pdf/1202.6465.pdf

 

[Demystifier]

Anyone know if the PBR paper has been published, or at least accepted for publication yet?

This perhaps will never happen after the two of the authors in PBR has somewhat contradicted themselves in
http://xxx.lanl.gov/abs/1201.6554

See also posts #485 - #488.

 

[Fredrik]

This perhaps will never happen after the two of the authors in PBR has somewhat contradicted themselves in
http://xxx.lanl.gov/abs/1201.6554

This doesn't seem to be a reason to not publish it, since the abstract says that "The results of this paper do not contradict that theorem, since the models violate one of its assumptions". However, if it was up to me to decide if the PBR paper should be published or not, I would at least demand that they rewrite the paper. I think it's just a mess. There isn't even a clear statement of the theorem in the article, and the "proof" is extremely non-rigorous.

 

[bohm2]

The author of the last paper on PBR http://lanl.arxiv.org/pdf/1203.2475.pdf posted in Leifer's blog and Leifer doesn't seem to agree with his take on it:

I don’t really agree with your take on the PBR theorem. According to Harrgian and Spekkens, and also PBR, λ is supposed to be the full ontic state of the system. If the wavefunction is ontic in the model under consideration, then it is considered to be specified by λ and is not considered a separate variable. This is the reason why the term “ontic state” is used instead of “hidden variable state” because the latter is often interpreted to be variables in addition to the wavefunction. Most people would consider the wavefunction to be ontic in de Broglie-Bohm theory. I know there is some discussion of whether it should instead be regarded as nomological (lawlike) in the literature, but this is not really relevant here. The fact is, even if we know the exact values of the position variables in Bohm’s theory, we will still also need the wavefunction in addition to the position variables to compute the outcome probabilities for any experiment because it is needed to find the trajectories. Anything you need to compute the final outcome probabilities, over and above the primitive ontology (beables), is considered part of the ontic state by PBR by definition. You might not like that definition, but by using it we see that one feature of Bohmian theory is actually necessary for any hidden variable theory, namely that the wavefunction is ontic (in the sense of being required to compute the probabilities of any possible experiment). Therefore, Bohmians should be pretty happy about the PBR result as it vindicates one of their assumptions.

Also, I just wanted to note that I do not understand your discussion around eq. (10). Why do you think we can always replace a qubit state with one that has equal amplitudes up to a relative phase?

Quantum Times Article on the PBR Theorem
http://mattleifer.info/2012/02/26/q...-the-pbr-theorem/comment-page-1/#comment-2618

 

[Demystifier]

Another new paper on it:
http://lanl.arxiv.org/abs/1203.4779

 

[bohm2]

I thought I'd post these PBR-related papers here for reference:

Physics papers:
The quantum state cannot be interpreted statistically (original PBR paper)
http://lanl.arxiv.org/abs/1111.3328

Generalisations of the recent Pusey-Barrett-Rudolph theorem for statistical models of quantum phenomena
http://xxx.lanl.gov/abs/1111.6304

Completeness of quantum theory implies that wave functions are physical properties
http://arxiv.org/PS_cache/arxiv/pdf/1111/1111.6597v1.pdf

The quantum state should be interpreted statistically
http://lanl.arxiv.org/pdf/1112.2446.pdf

Alternative Experimental Protocol for a PBR-Like Result
http://lanl.arxiv.org/pdf/1202.6465.pdf

The quantum state can be interpreted statistically
http://lanl.arxiv.org/pdf/1201.6554.pdf

Can quantum mechanics be considered as statistical? an analysis of the PBR theorem
http://lanl.arxiv.org/pdf/1203.2475.pdf

On a recent quantum no-go theorem
http://lanl.arxiv.org/pdf/1203.4779.pdf

Popular:
Quantum theorem shakes foundations
http://www.nature.com/news/quantum-theorem-shakes-foundations-1.9392

PBR, EPR, and all that jazz
http://www.aps.org/units/gqi/newsletters/upload/vol6num3.pdf

The PBR Argument - a simplified presentation
http://astairs.posterous.com/the-pbr-argument-a-simplified-presentation

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

Quantum Times Article on the PBR Theorem
http://mattleifer.info/2012/02/26/quantum-times-article-on-the-pbr-theorem/

Philosophical papers:
Statistical-Realism versus Wave-Realism in the Foundations of Quantum
Mechanics
http://philsci-archive.pitt.edu/902...m_in_the_Foundations_of_Quantum_Mechanics.pdf

 

[Demystifier]

Bohm2, thank you for the very useful list!

 

[ThomasT]

Thanks for the references/links bohm2. I think that quantum states can be interpreted statistically, ie., that quantum states don't necessarily represent real physical states. But if you think otherwise, then it would be interesting to read your opinion on that.