I Nature Physics on quantum foundations

[vanhees71]

I'm much less ambitious. My point is that the classical behavior of macroscopic objects can be understood in terms of quantum many-body theory, i.e., classicality is an emergent phenomenon.

 

[Demystifier]

I'm much less ambitious. My point is that the classical behavior of macroscopic objects can be understood in terms of quantum many-body theory, i.e., classicality is an emergent phenomenon.

Yes, but emergent from what? An obvious tentative answer is - from microscopic quantum laws. But one of those laws is supposed to be the law that the probability of a measurement outcome is given by the Born rule. The problem with this law is that it refers to a measurement, which is a macroscopic notion, not a microscopic one. Hence it seems that classicality cannot emerge from purely microscopic laws, simply because we start from the quantum theory not formulated as a purely microscopic theory.

A way out of this problem is to reformulate the Born rule such that it does not refer to measurement. Instead of talking about probability of an observed outcome, we should talk about probability of being in certain state. This is why we need a notion of beable, as distinct from observable. A beable is a variable with which we can associate a probability without specifying the measurement context. Various contextuality theorems (Kochen-Specker etc.) show that it is not possible to have beables for all observables at once. This is why Bohmian-like theories postulate beables only for some of the observables (and not for the others), typically only for particle positions (and not for their momenta).

In essence, this is why Bohmian formulation of quantum theory can explain classicality as emerging from purely microscopic laws, while standard formulation of QM, by referring to macroscopic measurements in one of its most fundamental laws, cannot explain classicality as emerging from purely microscopic laws.

As a byproduct, the argument above contains a very simple explanation of the notion of beable. To repeat, a beable is a variable with which we can associate a probability without specifying the measurement context.

 

[vanhees71]

But the probabilities we calculate with Born's rule are not probabilities for "being in [a] certain state" but the probabilities for the outcome of measurements.

Your definition of "beable" is empty, because you don't specify for what you associate a probability. It cannot be related to quantum theory, because the probabilities of quantum theory are only specified by the measurement context.

 

[Demystifier]

But the probabilities we calculate with Born's rule are not probabilities for "being in [a] certain state" but the probabilities for the outcome of measurements.

In the standard formulation of QM that's true. But it's legitimate to consider a non-standard formulation, if it can lead to some advantages over the standard one.

Your definition of "beable" is empty, because you don't specify for what you associate a probability. It cannot be related to quantum theory, because the probabilities of quantum theory are only specified by the measurement context.

Again, it cannot be related to standard formulation of quantum theory, but it is related to a non-standard formulation. More specifically, when the non-standard formulation is the Bohmian one, then it is shown in the literature that the standard QM probabilities of measurement outcomes are emergent from the non-standard probabilities of beables. In this sense, standard QM emerges from the Bohmian one. This, of course, doesn't prove that the Bohmian formulation is "true", but it does demonstrate that standard QM can emerge from something in which more fundamental probabilities can be defined without a measurement context. I think this is a great theoretical discovery by Bohm that such a more fundamental theory is at least possible.

 

[vanhees71]

These are still empty words. You don't say probabilities of what and you don't specify, how in Bohmian quantum mechanics probabilities are "derived".

 

[martinbn]

These are still empty words. You don't say probabilities of what and you don't specify, how in Bohmian quantum mechanics probabilities are "derived".

He said it is in the literature.

 

[vanhees71]

That's also a nice trick. You just claim "it's in the literature" and don't quote anything concrete. Sometimes people are even more "clever" and quote some literature, where the claimed issue is however not contained ;-).

 

[Demystifier]

You just claim "it's in the literature" and don't quote anything concrete.

See e.g. the reference in my signature.

 

[vanhees71]

But there you also assume the Born rule for position- (configuration-) space-wave functions. That from this it follows also for other observables, is derived in any QM textbooks, which start from wave mechanics without referring to BM at all. I still don't see, where this defines "beables". Your "perceptibles" make much more sense to me, btw.

 

[Lord Jestocost]

But isn't this the perfectly opposite interpretation of "beable" to what Bell intended when introducing this word? He insisted on defining the theory without reference to "observers" and "measurements".

Indeed, that was it in the end: to design an "objective", physical theory in the sense of classical phyics.

 

[Fra]

But isn't this the perfectly opposite interpretation of "beable" to what Bell intended when introducing this word? He insisted on defining the theory without reference to "observers" and "measurements".

Yes, probably. But discussing the actual original old ideas to restore classical mechanics is not interesting at all to me. I think most of us know it just does not work. Those things are indeed the opposite of my own thinking.

What I find entertaining here is to try to reinterpret the concepts in a way that might work a bit like the devils advocate! Just saying Bell was just wrong, is making it too easy.

After all, I suspect some of the original motivations of Einstein and others, was no just to restore "classical mechanics" and "determinism", but to find a novel intuitive understanding of the causal mechanisms in QM, just like we at least thought we have about some of classical mechanics. To understand how the bell pair can in fact end up corrleated and still violate the bell inequality is a challenge. We know nature has found a solution, and we can describe it but the current theory provides no proper explanation on a causal level in between the parts. Note that such an explanation does not necessarily mean that we must restored determinism, at least it does not for me.

Of course, I agree with you that this doesn't make sense within minimally interpreted QT, because there is hinges on the state (i.e., the applied preparation procedure in an experiment) whether an observable takes a defined value or not, and the question is, whether a "beable" must be some quantity which takes determined values. Then this would indeed imply that a "beable" can only be an observable which takes a determined value, and thus this would be state dependent, i.e., dependent on the preparation procedure for the system to be measured.

On the other hand it could also be that a "beable" is simply synomymous with "observable". Then it refers to the measurement procedure, and of course one can measure any observable, independent of the state the measured system is prepared in. But then the "beable" is a quantity which does not necessarily take a determined value, i.e., it makes only sense to talk about the probability for the outcome of a measurement of this "beable", but this again contradicts Bell's declared aim that "beables" should be defined as something independent of measurements.

My creative interpretation is that, if you by independent of "measurements", implicitly refers to "measurements" as per quantum mechanicsm and the statistical ensemble etc. Then, I think this makes sense for a beable.

For me there's no distinction between "classical" and "quantum" domains. The classical behavior of macroscopic objects is due to an effective coarse-grained description of collective observables. E.g., a "classical point particle" never is an elementary particle like an electron but a "macrocopic body", and the position and momentum is something like the center-of-mass position and momentum.

What is an "intrinsic" vs. an "extrinsic" measurement?

By extrinsic measurement I refer to what we consider a measurement in QM. The laboratory setup doing both preparations, detections and signalprocessing are solid and dominant and has unlimited informaiton processing capacity relative to the normalyl small subsystem we consider "the system" we study. This approximation also implies that the records and signal processing system is ot affected to deformed by the backreaction of the system. One can literally "control" the system and make it jump by choosing the right preparation. The observing context can simply consume the backreaction. I think quantum mechanics and QFT essentially dscribes these type of measurements. But they are idealisations.

An Intrinsic measurement follows the same principles of soundness, it employes detectors and counters and can postprocess the data. But this whole process is existing in a submissive state in a much larger environment it can not control. This corresponds more to cosmological observations, where the environment can not be predicted or "repeated", the mesurements themselves are similar to an evolutionary process where the observers itself is the life form. We do not have yet a theory of such intrinsic measurement, based on the same higher stnadard as QM. So this "inside observer" makes measurement in a less controlled way. Any spontaneous interaction is a "measurement", and the inside observer can form rational expectations of it's own future based on interaction history. The big difference is that if one tries to construct a "measurment theory" (ie replacement for QM) in this way, there are several constraints. For example you really can NOT encode arbitrary amounts of information, and you can not consider arbitrary scramling times for data etc. All this information processing, must be accounted for in time, as actual processes. There is also obviously in this view no background spacetime map. It literally has to be constructed by the agent itself.

Anyway, I think the beable is a potential candidate for such an inside measurement. It actually has the similar "standard" you would want from a rational measurement, but it's constrained in it's information capacity, and i think this limitation must be real. But it does NOT makes use of the kind of "observers" and "measurements" that conventional QM defines. So in this sense, it complies to Bells words?

I hope you see the difference between the "inside observer", and modelling/describing the measurement device in terms of QM as well? The latter method avoids the constraints, and allows for a description that is larger and more detailed that what can be encoded in the agent. Information in excess, that can't fit. Forcing this, is I think also not surprisingly a reason for the various divergences when one tries to extrapolate things down to the minimal scale or highest energy.

/Fredrik

 

[Fra]

But the probabilities we calculate with Born's rule are not probabilities for "being in [a] certain state" but the probabilities for the outcome of measurements.
...
Your definition of "beable" is empty, because you don't specify for what you associate a probability

It seems to me the probability for the counters future microstate (ie agents/observers microstate) is the same thing as the outcome of "future observations". But with the difference that you have no strict control over the repeats. Random/uncontrolled preparations?

And observing agent, trying to "survive" has to have good expectations of the future. It's like a hard core experiment, but without control or preparation. And the agents is it's own counter. And unlike a normal experiment, where you compare frequencies from statistics with the expectations from the preparation. The beable probability would be more like a "guide" for the agents action in the game of life.

A theory with descriptive probabilities are corroborated by comparing experiments with frequencies from data.

A theory of guiding probabilities, should I think be corroborated not by frequencies of "unobservable beables", but from the implications of theim - ie, the agents actions should be in compliance with the guidind probabilities. So it's an indirect corroboration, and i think it should be - in principe - possible.

/Fredrik

 

[Demystifier]

But there you also assume the Born rule for position- (configuration-) space-wave functions. That from this it follows also for other observables, is derived in any QM textbooks, which start from wave mechanics without referring to BM at all.

You are right that Born rule for other observables is derived from Born rule for positions without referring to BM, but I am not aware of any general QM textbook that actually derives it. Can you name at least one such textbook?

I still don't see, where this defines "beables". Your "perceptibles" make much more sense to me, btw.

I'm glad that my notion of "perceptible" makes sense to you. Since I have not defined it precisely, it demonstrates that a precise definition is not always necessary for understanding. But it depends on personality. For some people, like you, the notion of perceptible may be more intuitive than that of beable, while for other people it my be the other way around.

If you really want to see a precise mathematical definition of something like a "beable", see the definition of ontic in the context of the PBR theorem. If you want explicit references, I can give you some.

 

[vanhees71]

After all, I suspect some of the original motivations of Einstein and others, was no just to restore "classical mechanics" and "determinism", but to find a novel intuitive understanding of the causal mechanisms in QM, just like we at least thought we have about some of classical mechanics. To understand how the bell pair can in fact end up corrleated and still violate the bell inequality is a challenge. We know nature has found a solution, and we can describe it but the current theory provides no proper explanation on a causal level in between the parts. Note that such an explanation does not necessarily mean that we must restored determinism, at least it does not for me.

This is also an argument, I don't understand. We have QT, that precisely does all that. It explains the correlations, the violation of Bell's inequality, and (in it's realization as relativistic microcausal QFT) respects the causality structure of special relativity. It also provides a "causal explanation" of the correlations: It's just the preparation of, e.g., two photons in an entangled state by, e.g., parametric downconversion. So what do you think is lacking? What do you need in addition to standard Q(F)T to be satisfied with the accurate description of Nature?

My creative interpretation is that, if you by independent of "measurements", implicitly refers to "measurements" as per quantum mechanicsm and the statistical ensemble etc. Then, I think this makes sense for a beable.

My point is that all theoretical physics does is to describe in a more or less abstract mathematical way what we observe in Nature in some situation. There's no difference between classical and quantum physics except that the scientific method of precise, quantitative observation and mathematical model and theory building has revealed that observables can never all take determined values in any possible state of the system under investigation, and that this was hard to accept for the physicists 100 years ago is understandable, because it's indeed not easy to give up successful concepts. On the other hand, it was pretty clear that classical physics could not explain, how given the atomistic structure of matter (which was under heavy debate at the time too!) matter can be stable and how charged particles in bound states forming atoms, molecules, and condensed matter lead to discrete emission and absorption spectra of electromagnetic radiation/light. The answer of the scientific method to all these questions was the development of modern Q(F)T in the mid 1920ies.

By extrinsic measurement I refer to what we consider a measurement in QM. The laboratory setup doing both preparations, detections and signalprocessing are solid and dominant and has unlimited informaiton processing capacity relative to the normalyl small subsystem we consider "the system" we study. This approximation also implies that the records and signal processing system is ot affected to deformed by the backreaction of the system. One can literally "control" the system and make it jump by choosing the right preparation. The observing context can simply consume the backreaction. I think quantum mechanics and QFT essentially dscribes these type of measurements. But they are idealisations.

Of course they are idealizations, and these work, because a more or less "coarse-grained description" of the behavior of macroscopic apparati are sufficient. In this sense it depends on the accuracy you look at a macroscopic system, whether it's "behaving classically or quantum theoretically". E.g., there are these experiments with very large molecules to find the boundary between classical and quantum behavior, and indeed you can handle amazingly large molecules with such precision (particularly cooling them down to very law temperatures) that you can demonstrate quantum behavior on them.

An Intrinsic measurement follows the same principles of soundness, it employes detectors and counters and can postprocess the data. But this whole process is existing in a submissive state in a much larger environment it can not control. This corresponds more to cosmological observations, where the environment can not be predicted or "repeated", the mesurements themselves are similar to an evolutionary process where the observers itself is the life form. We do not have yet a theory of such intrinsic measurement, based on the same higher stnadard as QM. So this "inside observer" makes measurement in a less controlled way. Any spontaneous interaction is a "measurement", and the inside observer can form rational expectations of it's own future based on interaction history. The big difference is that if one tries to construct a "measurment theory" (ie replacement for QM) in this way, there are several constraints. For example you really can NOT encode arbitrary amounts of information, and you can not consider arbitrary scramling times for data etc. All this information processing, must be accounted for in time, as actual processes. There is also obviously in this view no background spacetime map. It literally has to be constructed by the agent itself.

Sure, but all this simply works in practice, as demonstrated by the precision of the predictions of QT in comparison with experiments, and indeed what can be observed today has developed with an amazing speed. For Freedman, Clauser, Aspect, et al who did the first investigations with entangled quantum systems of various kinds, it was cutting-edge technology to be able to just prepare such entangled states and make them "stable" enough to do experiments with them. Today we have amazing technologies to prepare and handle such states. It's at a stage of development, where it becomes an engineering science, i.e., it is so well understood that it's used to develop applications for everyday life. I think quantum cryptography is already in a stage, where it is in principle applicable for everyday work, and really convincing quantum computers won't take too long to be developed given the huge economical effort put into the corresponding engineering research and development.

Anyway, I think the beable is a potential candidate for such an inside measurement. It actually has the similar "standard" you would want from a rational measurement, but it's constrained in it's information capacity, and i think this limitation must be real. But it does NOT makes use of the kind of "observers" and "measurements" that conventional QM defines. So in this sense, it complies to Bells words?

This I don't understand.

I hope you see the difference between the "inside observer", and modelling/describing the measurement device in terms of QM as well? The latter method avoids the constraints, and allows for a description that is larger and more detailed that what can be encoded in the agent. Information in excess, that can't fit. Forcing this, is I think also not surprisingly a reason for the various divergences when one tries to extrapolate things down to the minimal scale or highest energy.

/Fredrik

But most modern measurement devices use QT to model and construct it. All semiconductor technology is obviously based on QT!

 

[Demystifier]

In this sense it may be a beable, but if it isn't observable, what's then the status of a "beable" as a physical property of a system?

Ah, now I see what confuses you. Nobody said that a beable cannot be observed. It can. But it is not "observable" in a technical sense, namely in the sense that beable is not described by a self-adjoint operator on the Hilbert space.

In this technical sense, all classical measurable variables (particle positions, electromagnetic fields) are not "observables", simply because classical theory does not deal with operators in the Hilbert space. Bohmian-like theories propose that, in addition to abstract self-adjoint operators in the Hilbert space, we also need less abstract "classical-like" variables, called "beables", that are not represented by operators in the Hilbert space.

 

[vanhees71]

Ok, so in the Stern-Gerlach experiment is a "beable" then a spot of a silver atom on the photo plate?

 

[Demystifier]

Ok, so in the Stern-Gerlach experiment is a "beable" then a spot of a silver atom on the photo plate?

Yes, it's a beable. (In addition, it's also a perceptible.)

 

[vanhees71]

Ok, then why is Bell giving the example that the electromagnetic field were a beable within classical field theory? In analogy to my example with the spot of a particle on a photo plate shouldn't then also only the directly recognizable actions of this field be beables? But then again, this contradicts the aim given by Bell to avoid all reference to measurements/observations, and indeed it would be a bit too narrow to only call things beables that can be directly observed with our human senses.

 

[Demystifier]

Ok, then why is Bell giving the example that the electromagnetic field were a beable within classical field theory? In analogy to my example with the spot of a particle on a photo plate shouldn't then also only the directly recognizable actions of this field be beables? But then again, this contradicts the aim given by Bell to avoid all reference to measurements/observations, and indeed it would be a bit too narrow to only call things beables that can be directly observed with our human senses.

That's because Bell is primarily interested in fundamental beables. The spot on the photo plate is not fundamental. The EM field is.

 

[Fra]

That's because Bell is primarily interested in fundamental beables. The spot on the photo plate is not fundamental. The EM field is.

Do you have a reference to where Bell defines "fundamental" in this context? What if I associate fundanental beable to say the smallest information unit encoded in a given solipsist view which is also the "primary" or raw distinguishable events from a given solipsist/agent view, ie elementary counters whcih can't be described in smaller units? (Ie from which more, complex beables are built by recoding or assembly)

It would be how i would think of it, and the question is if that might be in compliance with bells definitions?

/Fredrik

 

[Lord Jestocost]

What means in this respect “fundamental”? The notion was constructed by Bell’s mind.
"Fundamental" in an ontological sense or in an epistemological sense?

 

[Fra]

"Fundamental" in an ontological sense or in an epistemological sense?

At least from my perspective, if you require any epistemological results to be encoded in thw agents own state. This sort of relates epistemology and ontology. I wonder if this wasö bells intention as well or not?

/Fredrik

 

[Demystifier]

"Fundamental" in an ontological sense or in an epistemological sense?

Ontological. That Bell considers ontology more fundamental than epistemology is particularly clear from his article "Against measurement". I recommend reading this article to everybody who want to understand how Bell thinks.

@Fra I believe this also answers your question.

 

[vanhees71]

I think that's what makes Bell hard to understand for me. I don't understand, why you are after "ontology" when doing physics. As a natural science it's about what can be objectively and reproducibly be observed, and theoretical physics thus looks for generally valid laws from the patterns we observe.

 

[WernerQH]

I don't understand, why you are after "ontology" when doing physics. As a natural science it's about what can be objectively and reproducibly be observed, and theoretical physics thus looks for generally valid laws from the patterns we observe.

This makes you sound like a positivist. Surely you believe in atoms? Or in photons?
Bell (and, of course, this year's Nobel laureates) ruled out the idea of photons always having a definite state of polarization that they carry from the source to the detectors. (Unless they take part in conspiracy or superluminal communication.) What we think physics is about has an enormous effect on the direction of research.

 

[Demystifier]

I think that's what makes Bell hard to understand for me. I don't understand, why you are after "ontology" when doing physics. As a natural science it's about what can be objectively and reproducibly be observed, and theoretical physics thus looks for generally valid laws from the patterns we observe.

I never understood how someone who thinks this way can, at the same time, be convinced that the Moon is there when it's not observed.

 

[Demystifier]

Bell (and, of course, this year's Nobel laureates) ruled out the idea of photons always having a definite state of polarization that they carry from the source to the detectors. (Unless they take part in conspiracy or superluminal communication.)

When you put it this way, it sounds as if you are suggesting that the mere idea of superluminal communication is a priori non-scientific. Is that what you are suggesting?

 

[WernerQH]

When you put it this way, it sounds as if you are suggesting that the mere idea of superluminal communication is a priori non-scientific. Is that what you are suggesting?

Not a priori - it would be scientific in a Newtonian universe. Today one would have to give up too much of modern physics if one were to take superluminal communication seriously. What I'm suggesting is that photons do not exist, but merely emission and absorption events. (It's a radically nonlocal view that @vanhees71 probably abhors.)

 

[vanhees71]

Exactly that's what I mean. For me with the work of this years Nobel laureats the case is closed. Of course a quantum system always takes a definite pure or mixed state, but observables do not take necessarily determined values, and that's precisely described by QT. I don't need any ontology, only some formalism that precisely describes what's observed.

 

[vanhees71]

I never understood how someone who thinks this way can, at the same time, be convinced that the Moon is there when it's not observed.

The moon is "constantly observed". The CMBR is already sufficient to lead to rapid decoherence to exclude any quantum behavior to be observed on the motion of the moon.

 

[Demystifier]

The moon is "constantly observed". The CMBR is already sufficient to lead to rapid decoherence to exclude any quantum behavior to be observed on the motion of the moon.

How do you know that there is decoherence when no educated scientist observes decoherence? It follows from equations such as Schrodinger equation, but how do you know that those equations correctly describe our world when we don't make observations? Are you saying that theoretical physics can tell us something about what is going with the world even when we don't observe it?

 

[Demystifier]

As a natural science it's about what can be objectively and reproducibly be observed, and theoretical physics thus looks for generally valid laws from the patterns we observe.

Are those laws valid when scientists don't make observations? If yes, how is that scientific if science is only about the objectively observable?

 

[martinbn]

When you put it this way, it sounds as if you are suggesting that the mere idea of superluminal communication is a priori non-scientific. Is that what you are suggesting?

Without a shred of evedence or a working theory it is just wishfull thinking.

 

[vanhees71]

Are those laws valid when scientists don't make observations? If yes, how is that scientific if science is only about the objectively observable?

Of course, why not?

 

[gentzen]

Special Relativity	Quantum theory
1. Relativity Principle	1. No signalling
2. Light Postulate	2. Non-Locality
Absolute simultaneity	Predictability
| V	| V
Relativity of simultaneity	Unpredictability

How to explain something? Just stay silent, in order not to be wrong? Or try to find a better or worse allegory, parable, or analogy, to get some starting point for talking and building intuition.

 

[vanhees71]

Well, if something is found to be unpredictable, then our theories should describe this unpredictability, and so does QT with great success.

 

[A. Neumaier]

What I'm suggesting is that photons do not exist, but merely emission and absorption events. (It's a radically nonlocal view

Events are by definition local. Nonlocal is only their coincidence statistics. Bell excludes a local hidden variable explanation of the latter, but no more.

 

[A. Neumaier]

Of course a quantum system always takes a definite pure or mixed state

Elsewhere you consistently claimed that single quantum systems usually do not have a definite pure or mixed state - since the latter is a property of an ensemble of similarly prepared systems, not of a single system. But now you assign the definite state to each system. What made you change your mind?

 

[Demystifier]

Of course, why not?

Because it's not scientific, there is no experiment showing that things exist when we don't observe them.

Ontology is by definition things that exist even when we don't observe them, and you always say that ontology is not scientific.

 

[WernerQH]

I don't need any ontology, only some formalism that precisely describes what's observed.

Of course a quantum system always takes a definite pure or mixed state

Obviously you do have an ontology, albeit a rather vague one, when you talk about a "system" being in some "state".

Imre Lakatos made this remark in his Lectures on Scientific Method:

I just want to mention that the twentieth century presents us with quantum mechanics developed primarily by Bohr, Schrödinger, Heisenberg and others, according to which certain types of matter sometimes act as if they were waves and sometImes as if they were particles. The whole thing looks again like the Ptolemaic crystal spheres. Since the 1930s, conventionalism has swept through the scientific community once more. Now the majority of physicists believe that scientific theories from quantum mechanics onwards are very much like Ptolemy's theory. The main thing is their predictive effect, and not their truth value.

 

[Demystifier]

What made you change your mind?

The context. His mind is quantum, it changes depending on the question one asks him. Without the question, his mind is in the state in which answers don't have definite values. I wouldn't be surprised if he could even factorize numbers with the Shor algorithm.

 

[Fra]

Ontological. That Bell considers ontology more fundamental than epistemology is particularly clear from his article "Against measurement". I recommend reading this article to everybody who want to understand how Bell thinks.

@Fra I believe this also answers your question.

Ok, then I see essentially one possibly way to makes sense of this (from my view):

It would be to associate the "beables" with the collection of all possible "intrinsic microstates of the agent", defined relative to it's "intrinsic" perspectives, considered the set of all possible observers. Conceptually then I would think of the beables as the "naked" informarton. But of course thse are not directly observable, that is exactly in the sense they are "hidden", they can be "seen" only by inference from a perspective.

This sense of hidden is not in any way related to "ignorance" ,so the only problem for Bell is then that, if the above is true, then bells ansatz made no sense to start with. So maybe he dismissed his own idea due to a flawed ansatz?

This is they way i interpreted also the solipsist HV of Demystifier. This makes sense, but bells inequality is not applicable.

Anyway, I would also think of the "beables" interpreted as above to be a result of intrinisic measurements. So we still have a empistemological perspective. I don't think we have to choose!

/Fredrik

 

[Fra]

I think that's what makes Bell hard to understand for me. I don't understand, why you are after "ontology" when doing physics. As a natural science it's about what can be objectively and reproducibly be observed, and theoretical physics thus looks for generally valid laws from the patterns we observe.

The "ontology" I see, is the "state of knowledge". The record of observations, wether encoded and stored in classical pointers or non-classical ones, is I think related to states of some "hardware". In extrinsic measurement theory, you can get away with not specifying this hardware carefully.

To consider a "measurement" without considering how the results are stored and encoded, and what constraints the encoding hardware has, is I think incomplete. This is why i see ontology and epistemology as both important. I think both are needed. (That's not so say, we should look for naive ontologies)

/Fredrik

 

[Fra]

Exactly that's what I mean. For me with the work of this years Nobel laureats the case is closed. Of course a quantum system always takes a definite pure or mixed state, but observables do not take necessarily determined values, and that's precisely described by QT. I don't need any ontology, only some formalism that precisely describes what's observed.

What about the "ontology" of background spacetime, that you need to formulate QM in the first place? And the "ontology" of classical pointer records?

/Fredrik

 

[CoolMint]

I think that's what makes Bell hard to understand for me. I don't understand, why you are after "ontology" when doing physics. As a natural science it's about what can be objectively and reproducibly be observed,and theoretical physics thus looks for generally valid laws from the patterns we observe.

Yes, 100%. Science can not hope to explain the invisible universal driving force(to stay outside religion we should label this as 'emergent properties/behavior" as is customary now), hence "science it's about what can be objectively and reproducibly be observed"(end of quote).

(Edited)These discussions about interpretations of invisible behavior, can give some sense of 'understanding' but they are still a road to nowhere.

 

[Demystifier]

Yes, 100%. Science can not hope to explain the invisible universal driving force(to stay outside religion we should label this as 'emergent properties/behavior" as is customary now), hence "science it's about what can be objectively and reproducibly be observed"(end of quote).

How did you arrive at those conclusions? By the scientific method, or by philosophy?

 

[CoolMint]

How did you arrive at those conclusions? By the scientific method, or by philosophy?

I just added a paragraph while you responded.

"These discussions about interpretations of invisible behavior, can give some sense of 'understanding' but they are still a road to nowhere."

The science of what happens between measurements does not exist. So, it must be philosophy.

 

[Demystifier]

"These discussions about interpretations of invisible behavior, can give some sense of 'understanding' but they are still a road to nowhere."

Is your philosophic conclusion above (that it's "a road to nowhere") itself a road to nowhere?

 

[vanhees71]

Elsewhere you consistently claimed that single quantum systems usually do not have a definite pure or mixed state - since the latter is a property of an ensemble of similarly prepared systems, not of a single system. But now you assign the definite state to each system. What made you change your mind?

I didn't change my mind. The state represents a "preparation procedure" for a single system, implying probabilities for the outcomes of measurements via Born's rule, and as such the state refers to an ensemble of equally prepared systems since there's no other way to test the probabilistic predictions than by making repeated measurements on such equally prepared ensembles.

 

[vanhees71]

Because it's not scientific, there is no experiment showing that things exist when we don't observe them.

Ontology is by definition things that exist even when we don't observe them, and you always say that ontology is not scientific.

Ontology then is not covered by natural sciences, because natural sciences are about what's observed in nature. That doesn't imply that things don't exist, when not observed.