The quantum state cannot be interpreted statistically?

[bohm2]

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

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

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

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

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

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

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

 

[Fredrik]

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

()

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

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

 

[Fra]

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

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

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

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

... like this

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

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

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

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

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

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

/Fredrik

 

[bohm2]

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

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

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

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

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

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

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

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

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

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

 

[Fra]

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

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

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

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

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

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

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

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

/Fredrik

 

[DevilsAvocado]

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

 

[DevilsAvocado]

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

Yeah! Let’s go crackpot!

()

 

[DrChinese]

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

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

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

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

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

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

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

 

[DevilsAvocado]

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

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

"Bell people" = The Whole Scientific Community​

 

[Fra]

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

"Bell people" = The Whole Scientific Community​

"Obscure sect" would be an overstatement, agreed.

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

/Fredrik

 

[DrChinese]

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

Yay! I am surprised more folks don't identify with Leifer's Option 2 for exactly this reason. Strangely, it seems to me, the anti-realist position is completely consistent with these 2 ideas:

a) The subjective (from our perspective) future is related to the present, preventing us from witnessing an objective "now".
b) Wave function collapse occurs by a mechanism we don't understand, but has no underlying root cause.

Both of the above which are what most scientists believe anyway, as best I can tell.

 

[DevilsAvocado]

"Obscure sect" would be an overstatement, agreed.

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

/Fredrik

No worries mate! :rofl:

 

[DevilsAvocado]

Yet in all those post I'm still seeing strawman characterizations of realism. Like the gas molecules pics.

Agreed, there’s a lot of strawmen in this thread.

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.

I understand, but don’t you think it would be 'suitable' to clearly state that these models has nothing to do with empirical data? I think there might be readers out there, misinterpreting the situation...

(As you can see, I’m one of them... )

 

[DevilsAvocado]

a) The subjective (from our perspective) future is related to the present, preventing us from witnessing an objective "now".

Is this related to retrocausality...?

 

[DrChinese]

Is this related to retrocausality...?

Yes, I prefer to think time symmetric (TSQM) or block world (RBW). But I guess it comes down to the direction of time having a degree of freedom in some way. From our perspective, that would have a "non-realistic" appearance.

 

[Fra]

a) The subjective (from our perspective) future is related to the present, preventing us from witnessing an objective "now".

I think this is a different phrasing(?) of what I called the observer dependent EXPECTATION of the future in which any observer by definition is captured?

And, whatever the observer invariant (=objective) future (wether EXPCETED or ACTUAL history in retrospect) MEANS it's by construction out of reach for any real observer.

As I see it, the ONLY way for the observer to actually get hold of this information in certain domains, is that all the observers subjective views are TUNED to be consistent with an "objective reality" and then this is either a "conicidence" or an equilibrium point (this is my view, that there are only sort of "local objectivity" referring local groups of interacting observers; the objectivity simply lacks meaning outside this group; moreover this local objectivity refers to equilibrium points - this is I am sure, NOT what most people would agree on though. But this is also "compatible" with his case 2 I think. so case 2 is a wide group)

/Fredrik

 

[Ken G]

"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/

From those various versions of structural realism, the comments I have made in this thread most closely align with what is called "constructive empiricism" by Bas van Frassen, who is summarized thusly:
"He allows that terms such as ‘sub-atomic particle’ and ‘particle too small to see’ are perfectly meaningful and should be taken literally (note that the former term is theoretical and the latter term is not but both purportedly refer to unobservable entities). On the other hand, he holds that it is perfectly rational to remain agnostic about whether there are any such particles because he argues that to accept the best scientific theories we have only requires believing that they are empirically adequate, in the sense of correctly describing the observable world, rather than believing that they are true simpliciter."

Despite the semi-hysterical objections by one commentator on this thread, I feel I could not have put my arguments any better than that, and indeed it seems like so reasonable a position that to term it "anti-realist" seems like an unfortunate nomenclature at best-- because "empirical adequacy" is about the most realistic thing I've ever heard said about science.

In regard to PBR, I think this kind of standpoint clearly argues that we should not regard it as necessary for some complete set of properties to dictate the outcomes of events, or even influence them (as if there were a difference there)-- expressly because no such theory exists, and the only rationale for expecting it is to imagine some "true simpliciter". What's more, when PBR said their theorem does not apply to such "radical" viewpoints, they were rather stretching to breaking the meaning of the term "radical."

 

[bohm2]

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

Leifer refers to the second wavefunction option:

2. Wavefunctions are epistemic, but there is no deeper underlying reality.

Regarding those physicists who favour option 2, Leifer writes:

Option 2 is broadly anti-realist, although there can be some subtleties here...I would classify the Copenhagen interpretation, as represented by Niels Bohr, under option 2. One of his famous quotes is:

"There is no quantum world. There is only an abstract physical description. It is wrong to think that the task of physics is to find out how nature is. Physics concerns what we can say about nature…"

and “what we can say” certainly seems to imply that we are talking about our knowledge of reality rather than reality itself. Various contemporary neo-Copenhagen approaches also fall under this option, e.g. the Quantum Bayesianism of Carlton Caves, Chris Fuchs and Ruediger Schack; Anton Zeilinger’s idea that quantum physics is only about information; and the view presently advocated by the philosopher Jeff Bub. These views are safe from refutation by the PBR theorem, although one may debate whether they are desirable on other grounds, e.g. the accusation of instrumentalism.

From his posts I assumed that KenG lies close to this position, I think. Maybe I'm mistaken?

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

I agree. But I wasn't implying anything like that. Only that nonlocality is a necessary feature of any physical theory accounting for the observed violations of Bell’s inequality.

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

I'm guessing spontaneous collapse models like GRW would be consistent with this?

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

Thanks. That was really useful. Although, I'm still lost

 

[Ken G]

From his posts I assumed that KenG lies close to this position, I think. Maybe I'm mistaken?

You are right on. I'm glad to see there are some philosophers of science who are on a similar page, so I can refer the objections from this thread to them. The issue, in regard to the PBR theorem, is how much philosophy is embedded in the assumptions of that proof-- and just how "radical" (or truly realistic!) is it to reject those assumptions. I've argued that the narrow way that "realism" gets defined is actually either a form of idealism, or an example of the mind projection fallacy-- take your pick.

 

[Fra]

we should not regard it as necessary for some complete set of properties to dictate the outcomes of events, or even influence them (as if there were a difference there)-- expressly because no such theory exists, and the only rationale for expecting it is to imagine some "true simpliciter"

I fully agree with this. Either such influence mechanism is known or it's not. If it's not, it does not make a difference to the relevant problem at hand. We are still left dealing with the empirical situation, and in this situation we need to make decisions, based on accessible information (which is of course ALWAYS sort of "incomplete", but there is no escape).

(as if there were a difference there)

There would be a difference if the influence mechanism was known. But as long as they are unknown, I agree there is no difference.

/Fredrik

 

[Ken G]

I think what I object to about the notion of "influence" (as a weaker version of "determine") is that we have two ways that an influence can actually occur: either it creates a probability of something happening, or else it is one of several more factors that completely determine what happens. I don't view either of those possibilities as making sense-- if an influence creates a probability, what actuates the probability? There's a key piece missing from that story, which I think is why PBR can rule out a statistical interpretation of QM if it is underpinned by an ontological core. Or if the influence is but one of several determining factors, then if we know all the factors, the outcome is determined already and has no need for influences, or if we don't know all the factors, how can we say that such factors even exist, such that we know how to place the influence into its proper context? That's my objection to the PBR assumptions about properties, I think the only way to talk about influences (or properties) that makes sense is to completely divorce from any separable ontological picture, and simply embrace the epistemological one-- an influence is part of how we understand the causation of something, perhaps you would call it an expectation of ours. I think where we differ here is that you like to elevate such expectations to a level of ontology, but I don't think they are ever anything more than our expectations, though I admit the distinction is purely philosophical because in science, an expectation is what an expectation does-- no more and no less.

 

[Fra]

I think what I object to about the notion of "influence" (as a weaker version of "determine") is that we have two ways that an influence can actually occur: either it creates a probability of something happening, or else it is one of several more factors that completely determine what happens. I don't view either of those possibilities as making sense-- if an influence creates a probability, what actuates the probability?

Ken, from past discussions I think we are often more or less in agreement but you're right that we seem to differ on certain things. I'll try to focus on these differences in this post:

Here we get into the details of how to classify inference system, and this also overlaps to philosophy of science.

A ~> B

The most determinate form of inference is the easiest: logical deduction: A => B
In this picture, the inference itself is always perfect and any "uncertainty" is blamed on the premises.

The other way which is more complex is inductive reasoning. This could be expanded alot, but in short, the "simplest" form of induction is deductive probabilty: A => P(B)

But this is in fact a deduction applied to a new state space of probability distributions.

But the obvious problem with this is that probability distributions, as opposed to frequencies, refer to abstractions, in particular infinite trials and infinite amount of information. As is probably clear from most of my posts on here I have a lot to object to this.

The problem here has nothing to do with probability theory as mathemtics. It has to do with the applicability of this mathematics to reality. IMO, physics is operating in the interface between mathematical modelling and actual predictions of reality. But I won't expandon this in this thread.

The short comment is that what we really need is a model for rational reasoning based upon incomplete information: Surely in SOME cases probability theory is the answer. But in some other cases it doesn't quite make sense. I'm advocating a reconstruction of what JAynes did (probability as the logic of science) but in a different way where attention is paid to things he did not pay attention to. When you do this, one gets IMHO a discretised version of probability that is even MORE empirical since it considers actual frequences rather than limiting distributions (that are never established before the cards are on the table) and this introduces differences.

In such reconstuction, the word "probability" would be replaced by a "plausability measure" (that in limiting cases is the same as probability, but in other cases is a generalization thereof). And this is actuated by the retained observers empirical experience.

I know this SOUNDS like ontological terms but it's not how I mean it, because all the "ontological terms" are always implicitly observer dependent, and thus subjective. This means that each observer has what might hold a kind of "effective ontology" ut which is not really a proper ontology.

The problem here is that it's hard to even explain this in english. Somehow any plain text message is necessarily an imperfect analogy at best.

I think where we differ here is that you like to elevate such expectations to a level of ontology, but I don't think they are ever anything more than our expectations.

Well I perfectly agree with you! This is exactly what I meant to say above. The "effective" ontological terms I use are not really ontological, they are like "expectated ontologies" that are observer dependent, but it's hard to describe this without using the words :) Maybe you can do it better than I can.

The apparent disagreement is I think mainly due to difficulty of formulating this in language.

/FRedrik

 

[Ken G]

All right then, I believe I understand the distinction you draw between a mathematically formal probability distribution, and a scientifically effective plausibility measure. I'm happy with any words like "effective ontology", because I think that is the currency of science. What a lot of people don't understand, and they raise objections, is that usually the difference between "true ontology" and "effective ontology" is unimportant, we safely gloss right over it. It's only when we are really doing something foundational that we have to notice that difference-- some can, some can't. I think this issue is at the heart of what PBR have proven, and what they have not proven.

 

[bohm2]

In case anyone is interested in how Pusey of PBR may have come to this theorem, his paper just before the PBR may give some guidance. I hope it wasn't posted but I'm too lazy to look.

Stabilizer notation for Spekkens' toy theory
http://arxiv.org/PS_cache/arxiv/pdf/1103/1103.5037v1.pdf

 

[Fra]

that usually the difference between "true ontology" and "effective ontology" is unimportant, we safely gloss right over it. It's only when we are really doing something foundational that we have to notice that difference-- some can, some can't.

We agree here too.

/Fredrik

 

[bohm2]

This is really bothering me as I still can't believe how physicists can have such opposing interpretations of PBR theorem:

Leifer:

Pretty much all of the well-developed interpretations that take a realist stance fall under option 3, so they are in the psi-ontic camp. This includes the Everett/many-worlds interpretation, de Broglie-Bohm theory, and spontaneous collapse models. Advocates of these approaches are likely to rejoice at the PBR result, as it apparently rules out their only realist competition, and they are unlikely to regard anti-realist approaches as viable.

Oscar Dahlsten:

Let me try to summarise their argument. They suppose a particular kind of PSI-epistemic model is possible and then show a contradiction with quantum statistics. The kind of model they consider is essentially a hidden-variable one. The idea is that at the time of preparation of a quantum system one also sets the value of some hidden variable q. This is *not* assumed to be local as far as I can tell...So the argument, modulo potential subtleties like hidden assumptions, puts another nail in the coffin for hidden variable theories, adding to the contributions by Bell and others. As it is quite clean and does not appear to assume the hidden variable is local, one can imagine it turning up in text-books at some point.

 

[Fredrik]

They agree that it rules out some ontological models that weren't ruled out by previous theorems. A person who believes that they will eventually all be ruled out, except the ψ-complete ones (which are really just different ways of looking at the theory we already have) could describe this as "another nail in the coffin for hidden variable theories".

The main reason why the theorem can be interpreted differently by different people is of course the extremely non-rigorous nature of the argument in the PBR article. There isn't even a clear statement of the theorem anywhere in the article.

 

[DevilsAvocado]

Yes, I prefer to think time symmetric (TSQM) or block world (RBW). But I guess it comes down to the direction of time having a degree of freedom in some way. From our perspective, that would have a "non-realistic" appearance.

Thanks for the links, it looks interesting. And of course, RUTA’s RBW is very fascinating!

Gosh... I must be stupid... one year ago RUTA explained RBW/OSR and how non-separability resolves the mystery of entanglement! (= "non-realism")

... how could I forget...

(see next post)

 

[Ken G]

C'mon guys, RBW goes from re-interpreting field theory in terms of discrete graphs, to saying that cosmological observations don't require kinematic acceleration? And no one smells a rat? In all honesty, I cannot really judge the article because it would take days or weeks to understand its claims, but I can find fault in this quote from Toffoli that they found motivational:

Rather, the motivation is that principles of great generality must be by their very
nature trivial, that is, expressions of broad tautological identities. If the principle
of least action, which is so general, still looks somewhat mysterious, that means
we still do not understand what it is really an expression of—what it is trying to
tell us.

To me, that quote is a primer on how not to do physics. I think the reasoning is exactly backward to how physics actually works. The reasoning, which we often see, is that there must be some relatively simply and understandable (even tautological) rules of nature, and it is the job of physics to figure them out. I would argue that physics has always worked by entering (temporarily) into a kind of fantasy that this is actually true, and using that fantastical mindset to motivate the discovery of new principles. The "rationalist hat" of a theoretical physicist, if you will. But science dies when we make the error of imagining that this fantasy is actually true. Instead, every new discovered principle opens up a frontier of new mysteries, new questions about why that principle holds, and answers to those frontier questions are never tautological. Every law, and every symmetry, was made to be broken, and science is, above all, the commitment to finding those breaks-- not to finding why they are unbreakable.

 

[DevilsAvocado]

From his posts I assumed that KenG lies close to this position, I think. Maybe I'm mistaken?

First, let’s sort out the ψ-complete view, according to Spekkens:

http://arxiv.org/abs/0706.2661]Einstein,[/URL] incompleteness, and the epistemic view of quantum states

[page 1]
It will be useful for us to contrast hidden variable models with the interpretation that takes the quantum state alone to be a complete description of reality. We call the latter the ψ-complete view, although it is sometimes referred to as the orthodox interpretation².

²Note that while Bohr argued for the completeness of the quantum state, he did so within the context of an instrumentalist rather than a realist approach and consequently his view is not the one that we are interested in examining here. Despite this, the realist ψ-complete view we have in mind does approximate well the views of many researchers today who identify themselves as proponents of the Copenhagen interpretation.

[...]
Einstein had already shown a failure of locality for the ψ-complete view with a very simple argument at the Solvay conference in 1927. It is also well-known in such circles that a slightly more complicated argument given in 1935 — one appearing in his correspondence with Schrödinger, not the Einstein-Podolsky-Rosen paper — provided yet another way to see that locality was ruled out for the ψ-complete view. What is not typically recognized, and which we show explicitly here, is that the latter argument was actually strong enough to also rule out locality for ψ-ontic hidden variable theories. In other words, Einstein showed that not only is locality inconsistent with ψ being a complete description of reality, it is also inconsistent with ψ being ontic, that is, inconsistent with the notion that ψ represents reality even in an incomplete sense. Einstein thus provided an argument for the epistemic character of ψ based on locality.

Confusing, right? The ψ-complete view must be dead as parrot, right? And "many researchers today who identify themselves as proponents of the Copenhagen interpretation" would fit the realist ψ-complete view? This if anything, must be stone dead after PBR, right?

So the only way to survive as a Copenhagenist, is to give up the ψ-complete view, 'transmute' to the ψ-epistemic view, and adhere to Instrumentalism, right?

Is this the clear and unambiguous picture you got from the "Ken G realism"?

Well, you did ask him, didn’t you? And the answer was blurry as always; he proposed a third option... which is supposed to be 100% compatible to his mentor Bohr and the Copenhagen interpretation...??

(It’s an incomprehensible mess if you ask me, and Bohr would probably turn green.)

To add some extra spice, the "Ken G realism" is now also "closely aligned" to Bas van Fraassen’s Constructive empiricism... I don’t know if he appeals to a new form of retrocausality, to make this work, but the fact is that Niels Bohr died in 1962 and van Fraassen introduced Constructive empiricism in 1980, i.e. Niels Bohr can’t possibly have anything to do with this new 'twist' in the "Ken G realism".

So what!? Big deal!

Well, maybe not... except for one 'little' detail; Constructive empiricism oppose instrumentalism.

Get it...? "Ken G realism" ≠ Bohr Copenhagen Instrumentalism

If it’s any relief, I can only say that you’re not first having trouble understanding the "Ken G realism". And I fully understand if you relate "Ken G realism" to Niels Bohr and the Copenhagen interpretation, since he more than often quote Bohr "There is no quantum world", etc. The only problem, if you follow his reasoning; it’s impossible to get a coherent picture.

And this is not the first time this happens. We have had endless discussions on "Classical mechanics 'explaining' the Double-slit experiment", claims that the "Schrödinger equation could easily be replaced with a classical substitute", his support of the (1914) Weak form of the Correspondence principle (dumped by Bohr), etc, etc.

Am I unfair?? Am I on a diatribe against Ken G!?

Well, I have nothing against Ken G on a personal level. This is all about the discussion, that is supposed to deal with science, and some questions are very complex, and still open, and most of us are still stumbling in the dark, searching for knowledge, and we could indeed change our opinions along this journey. I think that’s what science is about (not being a scientist myself).

IMHO, the problem starts when Ken G articulates like he’s the official spokesperson for Niels Bohr and his view, and the beholder of the unquestionable TRUTH, an official representative of a peer-reviewed interpretation or theory, including a belittling and dogmatic attitude towards other users.

And when someone questions this 'setup', his categorization of 'antagonists' is; "naive", "ignorant", "semi-hysterical", "self-styled quantum physics experts", etc. (Which is actually quite funny, considering 'the situation' )

You think he’s advocating a strict Bohr interpretation, others think it is Idealism, and yet none seems to fit the "Ken G realism".

Here’s an advice: Ask for the *official name* of the "Ken G realism", if there is any... That could probably save us all a lot of time and unnecessary posts.

If there is no official interpretation/theory, and Ken G (just as many of us) is here to learn and search for knowledge, he could maybe cut down on the dogmatic TRUTH attitude, and stop delude other users that he represents more than he does.

(Hopefully you get an understandable answer)

P.S. Note that the answer to your question "Maybe I'm mistaken?" was "You are right on"...

I agree. But I wasn't implying anything like that. Only that nonlocality is a necessary feature of any physical theory accounting for the observed violations of Bell’s inequality.

I can understand if pragmatic details get lost in the philosophical Black hole that this thread has developed into. I can guarantee you that the following is not my 'personal view', or guessing on my behalf, but plain basic facts, without any philosophical overhead whatsoever:

• Bell's theorem is a no-go theorem, i.e. a theorem that states that a particular situation is not *physically* possible.
  
  
• And the name of this "particular situation" is the plain good old Local Realism, i.e. the moon is there even when nobody looks, and nothing that happens on the moon can have an instant effect here on earth.
  
  
• Bell's theorem is basically an abstract mathematical theorem that sets the 'limit' for Local Realism, and in its simplest from Bell's inequality looks like this: N(+30°, -30°) ≤ N(+30°, 0°) + N(0°, -30°)
  
  
• I don’t see any extensive discussion about the "philosophical foundation of reality" in that formula... Do you?? I don’t see any discussion or proof of non-locality... Do you??
  
  
• No of course you don’t, because no such derivation could ever be made from this simple, yet ingenious mathematical formulation.
  
  
• So what does it say!? Well, it only say that if you first set the first polarizer to +30°, and completely ignore the other polarizer (because everything happening is a local effect), and then do the inverse and set the second polarizer -30°, the sum of these two measurement should NOT change if you repeat this a third time with the first polarizer set to +30° and the second polarizer set to -30° (at the same time). I.e. the local realistic assumption is that 1 + 1 = 2 and when we check this against QM theory and EPR-Bell experiment we get that 1 + 1 = 3.
  
  
• This is all there is too Bell's theorem, nothing more nothing less! And what the philosophers in this thread are now quarrelling about is if we could really assume that 1 + 1 = 2 ... brilliant isn’t it??

So, now we know that Local Realism (1 + 1 = 2) is not compatible with QM, but this does not prove that non-locality must be the only viable conclusion from the this "no-go situation".

Why!?

Because there is also the option of non-realism, and I’m going to show you one possible route to achieve this, it’s called non-separability. However, this time I can’t guarantee to get everything 100% correct, it’s complicated and I’m still learning... hope it’s okay...

RUTA (PhD involved the foundations community) is a user on PF and one the authors of RBW, he has explained the basics in Relational Blockworld (RBW)/Ontic Structural Realism (OSR). According to RBW/OSR the world consist not of individual objects, but relations between objects, called links. For visualization, take a look at this picture of our "normal 3D world", as we see it:

The twin sisters Quanta & Relativiana

Now, imagine we flatten the picture to 2D, and "fill out" the space between the objects, and the "Holy Grail" () of RBW/OSR emerges out of spacetime.

The "Holy Grail" of RBW/OSR

Get it? It’s the 'stuff' between the "twin sisters" is what matters in RBW/OSR.

Now, let’s move on to the "vertices level", that would be equal to a QM particle:

Note! This picture is slightly wrong; there should be no mesh/vertices in the faces, just between!

And here you can see the non-separability appearing in link that builds the nose tips on the "twin sisters" (and also get an explanation for QM entanglement).

I know lots of questions arises at this point, but can’t give more info (due to ignorance), however if you wonder "What 'stuff' make up the links? Is it wavefunctions?" I can only say that the links are fundamental, they build the "stuff" in the traditional sense: space, time and matter!

Regge calculus provides the equations for the links, and the structure goes from:

4D simplices –> 3D simplex –> 2D triangles –> 1D links/vertices​

Specifying the lengths of the links determines the geometry, and you can get as good an approximation as you like to a smooth 4D manifold:

Get it? This is the alternative to non-locality and it sure looks unreal enough to me! ()


If you’re interested, I can recommend the "OSR bible" Every Thing Must Go - Metaphysics Naturalized (2007) by James Ladyman, Don Ross, David Spurrett, John Gordon Collier, available on Amazon in hardcover and paperback.

Even if this is philosophy of science, it differs completely from what we’ve seen in this thread.

Every Thing Must Go aruges that the only kind of metaphysics that can contribute to objective knowledge is one based specifically on contemporary science as it really is, and not on philosophers' a priori intuitions, common sense, or simplifications of science. In addition to showing how recent metaphysics has drifted away from connection with all other serious scholarly inquiry as a result of not heeding this restriction, they demonstrate how to build a metaphysics compatible with current fundamental physics ("ontic structural realism"), which, when combined with their metaphysics of the special sciences ("rainforet realism"), can be used to unify physics with the other sciences without reducing these sciences to physics itself.

[They say that there is a 'preview version' available, but of course... I know nothing about this... ]

Cheers!


P.S. If you are looking for some amusement, ask the semi-intellectual Professor Gobbledygook "Is the moon there when nobody looks?" the resulting debacle will most probably continue thru over the weekend, and maybe all the way to Christmas... Anyhow, I can guarantee you that you will not get a simple YES/NO, but something much more entertaining, in analogy with the philosophy of Monty Python...


https://www.youtube.com/watch?v=kQFKtI6gn9Y

 

[DrChinese]

C'mon guys, RBW goes from re-interpreting field theory in terms of discrete graphs, to saying that cosmological observations don't require kinematic acceleration?

Yes, they are taking risks by positing an interpretation of QM which makes some slightly different predictions in a couple of areas. I am sure they are quite aware that they are departing from the pack on the cosmological side. But they are professionally well versed in this area. They have written a more recent article explaining the idea in more detail:

http://arxiv.org/abs/1110.3973

In which they are "accounting for distance moduli and redshifts for type Ia supernovae without having to invoke accelerated expansion, i.e., there is no dark energy and the universe is always decelerating." I wouldn't want to debate this here, as it really belongs in the Cosmo side of the forum. Regardless, I am not sure that RBW's future itself depends on the correctness of this controversial conclusion.

But I would not agree (with KenG's additional comments) that this is anti-scientific in any way, quite the opposite. They came up with the theory first and then started working on its application. This is a result, which is rare to see from QM interpretations as you must admit. I would call that first rate science regardless of where it leads. It would have been easy for them to skip this paper precisely because it goes against the grain. But it should be judged on the merits. (I am not strong enough on the details of "supernovae as standard candle" theory to judge it.)

 

[Ken G]

To add some extra spice, the "Ken G realism" is now also "closely aligned" to Bas van Fraassen’s Constructive empiricism... I don’t know if he appeals to a new form of retrocausality, to make this work, but the fact is that Niels Bohr died in 1962 and van Fraassen introduced Constructive empiricism in 1980, i.e. Niels Bohr can’t possibly have anything to do with this new 'twist' in the "Ken G realism".

Apparently now your argument rests on the syllogism that if Bohr died before Bas van Fraassen, the two men could not have agreed on anything. Nope, that's just poor logic. What I love is people who interpret Bohr incorrectly, then argue why their incorrect interpretation proves that he was an idiot. They tend to do the same thing for posters on here, not surprisingly, it's just their modus operandi.

There is just no point in asking if some interpretation or other of quantum mechanics provides a complete description of reality, because only reality gets to answer that, not us. So any argument that starts with "let's assume quantum mechanics is psi-complete, and ask whether this makes it epistemological or ontological" is just a waste of time. Of course quantum mechanics is not psi-complete, no theory of physics ever was, so why should this one be? What's more, we already know that it invokes idealizations right and left, as does all physics, and we already know that it doesn't fit with any global theory of universal gravity, nor with any existing model of gravity at the Planck scale, nor has it ever even attempted to give an accounting of the subject/object interface.

We should just stop making ontological assumptons and asking what they imply about quantum mechanics, I don't care if anyone wants to label themselves as "realists" and say "PBR only applies to us", the simple fact is it is a scientific error to start with ontological assumptions about any theory in science. Theories are verified by experiment, and the need for new theories is motivated by experiment also-- it's just that simple. It's fine to use interpretations of QM to motivate directions for finding new theories, but doing so in the absence of experimental guidance is a long shot at best. That's OK, anyone can decide what long shots they want to take, but pretending that PBR is really telling us something about quantum mechanics seems pretty silly to me-- quantum mechanics is the predictions it makes, and experiments tell us how good they are. Ontological wrangling about that is not telling us anything about either quantum mechanics or reality, so the scientific value of PBR that we should be focused on is just how it might motivate new experiments to find the problems with quantum mechanics to guide whatever comes next.

 

[Ken G]

Regardless, I am not sure that RBW's future itself depends on the correctness of this controversial conclusion.

But that's the problem right there-- they are basically saying "RBW is science because it makes a different prediction", and you are saying it doesn't even matter if the prediction is right, RBW is still science anyway! It can't be both ways-- I agree with you that RBW probably does not live or die by that prediction, which is also why I do not regard it as science. But if it is another way to think about the ontology of quantum mechanics, in the same effective terms we should always think about ontologies, then I agree it is a nice contribution. When people start arguing "here's the real ontology of quantum mechanics, and here's the predictions it makes, which don't really matter if they are wrong", then I see a red flag.

But I would not agree (with KenG's additional comments) that this is anti-scientific in any way, quite the opposite. They came up with the theory first and then started working on its application.

I didn't say RBW is anti-scientific (though I don't see it as science either, for the above reasons), I said the Toffoli quote that they see as motivational is anti-scientific. But in the end, it won't matter how they came upon their theory, it will only matter if it works or not.

This is a result, which is rare to see from QM interpretations as you must admit. I would call that first rate science regardless of where it leads.

Making a different prediction is certainly in the best tradition of science. But you know, people who predict there is no dark energy, or there is no acceleration, are pretty common-- and most of them are flakes. So simply making a prediction like that doesn't really say too much-- it needs to be correct. But if it helps motivate observations that could check it, then it is worthwhile-- that's the bottom line, helping us ask the right observational questions.

 

[Fredrik]

First, let’s sort out the ψ-complete view, according to Spekkens:


Confusing, right? The ψ-complete view must be dead as parrot, right? And "many researchers today who identify themselves as proponents of the Copenhagen interpretation" would fit the realist ψ-complete view? This if anything, must be stone dead after PBR, right?

Harrigan & Spekkens contains at least one explicit example of a ψ-complete ontological model for QM. They call it the Beltrametti-Bugajski model. The ontic state space $\Lambda$ of the Beltrametti-Bugajski ontological model for the quantum theory with Hilbert space $\mathcal H$ is the set $\mathcal P\mathcal H$ of 1-dimensional subspaces of $\mathcal H$.

PBR says nothing about ψ-complete ontological models for quantum theories. Their argument is specifically against ψ-epistemic ontological models.

If you’re interested, I can recommend the "OSR bible" Every Thing Must Go - Metaphysics Naturalized (2007) by James Ladyman, Don Ross, David Spurrett, John Gordon Collier, available on Amazon in hardcover and paperback.

From the preface:

...contemporary analytic metaphysics, a professional activity engaged in by some extremely intelligent and morally serious people, fails to qualify as part of the enlightened pursuit of objective truth, and should be discontinued.
[...]
...a group of highly trained professionals have been wasting their talents—and, worse, sowing systematic confusion about the nature of the world, and how to find out about it...
[...]
We care a great deal about philosophy, and are therefore distressed when we see its reputation harmed by its engagement with projects and styles of reasoning we believe bring it into disrepute, especially among scientists.
​

This reminds me of Steven Weinberg's "Dreams of a final theory". It's been 15 years or so since I read it, but I think I remember a comment that said roughly that the only times when philosophers have made valuable contributions to science, have been when they've told us that we can ignore what some other philosophers have been saying.

 

[DrChinese]

But that's the problem right there-- they are basically saying "RBW is science because it makes a different prediction", and you are saying it doesn't even matter if the prediction is right, RBW is still science anyway!

... So simply making a prediction like that doesn't really say too much-- it needs to be correct. Astronomers feel they have empirical reasons for the acceleration, independent of any theory beyond elements of general relativity that have passed many tests.

Of course, in the end it must be right or wrong. But we need to explore good options where they exist, what else is the effort with String Theory?

I certainly agree that there are a lot of pointers towards cosmological acceleration, and I take that as conventional wisdom these days. But not so many years ago, it wasn't. And I certainly think we are touching the boundaries of knowledge on these issues, we might have to reinterpret some current results in coming years.

------------------------------------------

This next is not intended in any way to be a defense of RBW or even a statement about it. More of an independent parallel. So here's a simple question for which the answer is not so simple using current theory: Do the photons from the CMBR exist free independent of observation? Because some people say that photons are mediators of EM force but are otherwise abstractions. For example, this from Mentz114:

"Photons" only exist at the moment they are emitted or absorbed i.e. when they interact with matter. There is no evidence ( nor any way of getting any ) that photons exist in the EM field when it is not interacting with matter.

Speculations about 'free' photons usually lead to apparent contradictions, as evidenced by your question."

And yet the answer could easily have cosmological implications. I can think of a few choice ones myself. So I am not so sure that a future QM interpretation might not have some things to say about cosmology.