Why all the clinging to locality?

[bhobba]

I don't know whether electroweak has the same problem of a Landau pole that QED does. Superficial googling has not answered the question for me.

That's an interesting one.

We had a thread discussing it a while back and the thought was it was an open question.

However that's not what my concern is - its purely to do with the modern EFT view of renormalisation I quoted - and I have seen in a number of sources.

Thanks
Bill

 

[stevendaryl]

That's an interesting one.

We had a thread discussing it a while back and the thought was it was an open question.

However that's not what my concern is - its purely to do with the modern EFT view of renormalisation I quoted - and I have seen in a number of sources.

Thanks
Bill

Well, there are two different claims floating about. One is about EFT. The other is the question of whether the standard model breaks down at high enough energy. It is almost certainly incorrect at high energy (since it doesn't take into account gravity), but is it even consistent at high energy?

 

[bhobba]

Well, there are two different claims floating about. One is about EFT. The other is the question of whether the standard model breaks down at high enough energy. It is almost certainly incorrect at high energy (since it doesn't take into account gravity), but is it even consistent at high energy?

I don't think anyone is doubting the standard model breaks down at high enough energies - there was a claim made it was because it didn't include gravity. That indeed is quite possibly the reason it breaks down.

But I don't think its established for sure that is the reason - I think the modern view is because it relies on renomalisability to extract finite answers, that such theories are best viewed as effective theories valid up to a certain cutoff.

Its a view i have read all over the place eg:
http://cds.cern.ch/record/1281952/files/p145.pdf

Thanks
Bill

 

[stevendaryl]

I don't think anyone is doubting the standard model breaks down at high enough energies - there was a claim made it was because it didn't include gravity. That indeed is quite possibly the reason it breaks down.

I'm not sure what you mean by "breaks down". There are two different issues: (1) Does it become inaccurate at high energies? (2) Does it become inconsistent at high energies?

The answer to number (1) is certainly "yes", because of gravity. But I'm not sure if gravity has anything to do with (2). If the standard model has a Landau pole, then it is actually inconsistent at high enough energies.

 

[stevendaryl]

I don't think anyone is doubting the standard model breaks down at high enough energies - there was a claim made it was because it didn't include gravity. That indeed is quite possibly the reason it breaks down.

But I don't think its established for sure that is the reason - I think the modern view is because it relies on renomalisability to extract finite answers, that such theories are best viewed as effective theories valid up to a certain cutoff.

Its a view i have read all over the place eg:
http://cds.cern.ch/record/1281952/files/p145.pdf

Thanks
Bill

I just remembered another issue that is important for the high-energy behavior of QFT: Even if the theory is renormalizable, the perturbative expansion in powers of the coupling constant may not converge.

 

[bhobba]

I'm not sure what you mean by "breaks down"

By breaks down I mean is valid ie its predictions are true.

Even if there is no issues with things like Landau poles and one can make predictions to any energy scale the question is is it valid to push the SM that far. Well it doesn't include gravity so obviously not.

But a question is - can a renormalisable theory be considered fundamental?

I don't think there is an actual answer to that question in the sense of experiment deciding anything, but the modern EFT view of renormalisable theories is the fact they require a cutoff to extract finite answers means it is viewed as an approximation to a more fundamental theory.

That being the case the SM is really in the same boat as an EFT of gravity - its really only valid up to some energy scale by the inherent fact it's renormalisable.

That's all I am claiming. Its simply keeping the issue of a QFT of gravity in perspective. Its of zero value in actually doing anything useful.

Thanks
Bill

 

[audioloop]

Yes we are - and physical theories, being axiomatic systems, with parts mapped to stuff out there, can also contain things not necessarily mapped to objects. For example in renormalisation a regulator is introduced to allow finite answers to be extracted but some regulators, such as dimensional regulation, are not physically realizable.

Thanks
Bill

how can exist a spin without electrons ?

 

[craigi]

how can exist a spin without electrons ?

One answer is that other fermions and some bosons have spin too, but I don't think that is what you meant.

Did you mean, how can spin exist if not mapped to a particle?

 

[Maui]

how can exist a spin without electrons ?

Isn't this a relic of the inadequacies of the particle model of matter? The fact that physics has managed to experimentally separate spin from point particles seems to give further evidence for the field model of matter.

http://www.nature.com/nature/journal/v485/n7396/full/nature10974.html

 

[audioloop]

Did you mean, how can spin exist if not mapped to a particle?

to a quantum entity

 

[bhobba]

how can exist a spin without electrons ?

Errrrr. You missed the point entirely. Its the claim quantities in a theory must be attached to objects - not that quantities can be attached to objects.

Thanks
Bill

 

[bhobba]

Did you mean, how can spin exist if not mapped to a particle?

The original claim was:

'pre existing properties' are values, values of who or what ? OBJECTS. then there are 'existent things' without values, just that. you can't talk about values without objects.

Theories can, and sometimes do, contain 'values' without them being associated with objects eg the example I gave about dimensional regularization.

Statements like that IMHO show a limited exposure to what a mathematical model is, and understanding that physical theories are basically mathematical models.

However QM has the opposite problem - assigning values independent of a measurement context.

Thanks
Bill

 

[audioloop]

http://www.nature.com/nature/journal/v485/n7396/full/nature10974.html

i posted some time ago that stuff.
spinons, electrons with spin only (splited electrons).
there are too, holons and orbitons.


http://www.nature.com/news/not-quite-so-elementary-my-dear-electron-1.10471

 

[craigi]

i posted some time ago that stuff.
spinons, electrons with spin only (splited electrons).
there are too, holons and orbitons.


http://www.nature.com/news/not-quite-so-elementary-my-dear-electron-1.10471

Are there any measurements or postulates as to how the mass is distributed, why these quantities are so often found at the same location and how they decay once split?

 

[audioloop]

Are there any measurements or postulates as to how the mass is distributed, why these quantities are so often found at the same location and how they decay once split?

yes, QED quantum electrodynamics.-----
same location ? can delve the question please ?.

 

[bohm2]

So I say:
EPR Realism = objective reality =
hidden variables = pre-existing properties =
non-contextual reality = counterfactual definiteness

I don't see that any of these can be said to exist or be ruled out except along with the others.

Why can't one exist (or be ruled out) without the others? Bohmian mechanics is an example. In Bohmian mechanics all properties are contextual except position. So one can have an objective realism (with respect to position) but with contextuality of other properties. Moreover, some recent papers suggest that there are contextual classical systems, so I don't think one can conclude that objective reality=non-contextual reality:

Contextuality lays at the heart of quantum mechanics. In the prevailing opinion it is considered as a signature of "quantumness" that classical theories lack. However, this assertion is hardly justified. Although contextuality is certainly true of quantum mechanics, it can not be taken by itself as discriminating against classical theories. Here we consider a representative example of contextual behavior, the so-called Mermin-Peres square, and present a simple discrete model which faithfully reproduces quantum predictions that lead to contradiction with the assumption of non-contextuality. This shows that quantum-like contextual effects have their analogues in the classical realm too.

Classical systems can be contextual too: Analogue of the Mermin-Peres square
http://arxiv.org/pdf/1310.4990.pdf

An interesting question posed by this author:

If contextuality by itself is not a token of non-classicality, then what makes quantum theory so different? Or more generally, which conceptual features distinguish quantum mechanics from classical theories.

Isn't non-locality/entanglement (whether the realistic or non-realistic variety) the key feature that distinguishes QM from classical theories?

 

[stevendaryl]

Why can't one exist (or be ruled out) without the others? Bohmian mechanics is an example. In Bohmian mechanics all properties are contextual except position. So one can have an objective realism (with respect to position) but with contextuality of other properties. Moreover, some recent papers suggest that there are contextual classical systems, so I don't think one can conclude that objective reality=non-contextual reality:

Classical systems can be contextual too: Analogue of the Mermin-Peres square
http://arxiv.org/pdf/1310.4990.pdf

An interesting question posed by this author:

Isn't non-locality/entanglement (whether the realistic or non-realistic variety) the key feature that distinguishes QM from classical theories?

I don't think that contexuality by itself is particularly weird. Since a measurement necessarily involves an interaction between the measuring device and the object being measured, it's perfectly understandable that result may not have existed prior to the measurement process.

However, in the specific case of EPR type experiments, one finds perfect correlations between distant measurements of different particles. That was Einstein's original argument: If measuring one particle tells us something with certainty about the result of a second distant measurement (one that may not have even been performed yet), then the result in some sense "already existed" before the second measurement. Or at least, that's one would expect based on pre-quantum intuitions.

So it's not that contexuality by itself is weird, it's that contextuality, together with perfect distant correlations, is weird.

 

[bohm2]

So it's not that contexuality by itself is weird, it's that contextuality, together with perfect distant correlations, is weird.

I agree but then why equate non-contextual realism (by itself) with objective realism and/or counterfactual definiteness? Note that even experiments demonstrating violation of Leggett's inequalities (e.g. Groblacher et al.) do not rule out objective reality but only certain types of non-local realism. For example, Bohmian mechanics is consistent with such experiments because position takes priority over all other properties.

 

[DrChinese]

1. Why can't one exist (or be ruled out) without the others? Bohmian mechanics is an example. In Bohmian mechanics all properties are contextual except position. So one can have an objective realism (with respect to position) but with contextuality of other properties. Moreover, some recent papers suggest that there are contextual classical systems, so I don't think one can conclude that objective reality=non-contextual reality:

2. Isn't non-locality/entanglement (whether the realistic or non-realistic variety) the key feature that distinguishes QM from classical theories?

1. I realize that Bohmians view their theory as both contextual and objectively real. Just as MWIers view their interpretation as both local and realistic. But I don't see it that way for either.

All I can agree to is that BM is non-local, and that MWI is subjectively real (since observers in different branches see different things). I think most stop there.

2. I do agree that quantum non-locality is a critical difference relative to the classical world. That also features (under that same name) what might be called "quantum non-temporality*". Ie a future setup can be a participant in the context, just as a distant one can. *I doubt that is even a word.

 

[bohm2]

All I can agree to is that BM is non-local, and that MWI is subjectively real (since observers in different branches see different things). I think most stop there.

I would think most view BM as non-local and realistic. As noted above (I just edited it), even experiments demonstrating violation of Leggett's inequalities (e.g. Groblacher et al.) do not rule out objective reality but only certain types of non-local realism. For example, Bohmian mechanics is consistent with such experiments because position takes priority over all other properties (and those experiments, at the most, rule out realism about polarization).

 

[audioloop]

.

and not hinging on pre-existing electrons v a l u e s
to say that is realistic or not.


.

 

[DrChinese]

I would think most view BM as non-local and realistic. As noted above (I just edited it), even experiments demonstrating violation of Leggett's inequalities (e.g. Groblacher et al.) do not rule out objective reality but only certain types of non-local realism. For example, Bohmian mechanics is consistent with such experiments because position takes priority over all other properties (and those experiments, at the most, rule out realism about polarization).

I agree about the non-local and realistic just fine. It is the comment about "non-realism" about polarization that I object to. I realize that BMers are to a certain degree "polarization deniers". But there is no difference in the evidence that polarization observables are any different than the usual other observables.

Just saying that polarization is "non-realistic" in BM is not really adequate. It is as realistic as anything else is, even if it is a derived property and not fundamental. (Of course, I think it is fundamental.)

 

[bohm2]

I agree about the non-local and realistic just fine. It is the comment about "non-realism" about polarization that I object to. I realize that BMers are to a certain degree "polarization deniers". But there is no difference in the evidence that polarization observables are any different than the usual other observables.

They aren't. Everything is contextual, except the actual particle positions. So all the contextual stuff is contained in the wave function and not primitive/fundamental, unlike position, which is. Maybe you're questioning why position is "real"/primitive unlike all the other contextual stuff/observables?

 

[DrChinese]

Maybe you're questioning why position is "real"/primitive unlike all the other contextual stuff/observables?

It's part and parcel of the theory, as I understand it. So I respect that.

 

[audioloop]

.

and not hinging on pre-existing electrons v a l u e s
to say that is realistic or not.


.

existent objects without values, just that.


.

 

[bohm2]

I do agree that quantum non-locality is a critical difference relative to the classical world.

Just wondering what your opinion is on arguments by this author presenting certain classical systems that are local yet violate Bell's inequality. The author suggests that such "supercorrelated" systems can be both local and realistic (at least contextual realistic):

Bell's Theorem: Two Neglected Solutions
http://arxiv.org/ftp/arxiv/papers/1203/1203.6587.pdf

Violation of the Bell-Inequality in Supercorrelated Systems
http://arxiv.org/vc/arxiv/papers/1211/1211.1411v1.pdf

My impression is that some of the difficulties here is again with the definition of "realism". I'm guessing you interpret contextualism with non-realism since contextuality would imply non-realism? But then, the problem is that such classical systems are contextual yet we don't consider them non-real?

 

[Demystifier]

I'm guessing you interpret contextualism with non-realism since contextuality would imply non-realism? But then, the problem is that such classical systems are contextual yet we don't consider them non-real?

I also think that DrChinese identifies contextuality and non-reality, and I am very curious to see how will he answer your question.

 

[craigi]

My impression is that some of the difficulties here is again with the definition of "realism". I'm guessing you interpret contextualism with non-realism since contextuality would imply non-realism? But then, the problem is that such classical systems are contextual yet we don't consider them non-real?

I think we must consider non-realism to apply to equally to classical systems. Classical systems can exist in an unkown and unkowbable state. The difference with quantum systems is that they exist in a superposition of possible states. Any record of the result and context of a measurement isn't real in the sense that it is unkown, unkowable and all possibilites exist, until conveyed to the subjective observer, but we don't require that they exist in a superposition for them to lack objective reality.

 

[Demystifier]

I think we must consider non-realism to apply to equally to classical systems. Classical systems can exist in an unkown and unkowbable state. The difference with quantum systems is that they exist in a superposition of possible states. Any record of the result and context of a measurement isn't real in the sense that it is unkown, unkowable and all possibilites exist, until conveyed to the subjective observer, but we don't require that they exist in a superposition for them to lack objective reality.

You might like
http://arxiv.org/abs/quant-ph/0505143 [Found.Phys.Lett. 19 (2006) 553-566]
http://arxiv.org/abs/0707.2319 [AIPConf.Proc.962:162-167,2007]
where some similar ideas are elaborated.

 

[stevendaryl]

I think we must consider non-realism to apply to equally to classical systems. Classical systems can exist in an unkown and unkowbable state. The difference with quantum systems is that they exist in a superposition of possible states. Any record of the result and context of a measurement isn't real in the sense that it is unkown, unkowable and all possibilites exist, until conveyed to the subjective observer, but we don't require that they exist in a superposition for them to lack objective reality.

This is getting down to very subtle matters of definition, but I think when people talk about realism, they are not making any assumptions about whether a state is knowable or not. That is, in a realistic model, the system has a state at every moment, whether or not that state is knowable; it may not be, because there may be no way to probe the state without disturbing it.

That's sort of the point of Bell's theorem. He was investigating whether there were any testable consequences to the assumption that there was a pre-existing state prior to measurement, even if that state is not knowable.

 

[DrChinese]

Just wondering what your opinion is on arguments by this author presenting certain classical systems that are local yet violate Bell's inequality. The author suggests that such "supercorrelated" systems can be both local and realistic (at least contextual realistic):

Bell's Theorem: Two Neglected Solutions
http://arxiv.org/ftp/arxiv/papers/1203/1203.6587.pdf

Violation of the Bell-Inequality in Supercorrelated Systems
http://arxiv.org/vc/arxiv/papers/1211/1211.1411v1.pdf

My impression is that some of the difficulties here is again with the definition of "realism". I'm guessing you interpret contextualism with non-realism since contextuality would imply non-realism? But then, the problem is that such classical systems are contextual yet we don't consider them non-real?

I equate contextuality with non-realism, recognizing fully that they can be defined differently. In EPR terms: contextuality means that the result of a measurement here is dependent on the nature of a measurement elsewhere. So that is a "subjective" reality. On the other hand, they view (elements of) reality as meaning a prediction with certainty can be made even if all such possible predictions cannot be demonstrated simultaneously. I see those as being mutually exclusive. Ie you cannot have contextuality *and* realism.

As to Vervoort's superdeterminism and variants: I do not consider these lines of reasoning to be a part of physical science in their current form. You may as well say evolution is due to superdeterminism rather than being due to natural selection from random mutation.

 

[DrChinese]

To clarify: Ie you cannot have contextuality *and* counterfactual realism within the same system. Again: if you tweat the definitions enough you probably can find a way to make these work, but then you won't match up to the EPR definitions. The EPR definitions have stood the test of time.

 

[craigi]

This is getting down to very subtle matters of definition, but I think when people talk about realism, they are not making any assumptions about whether a state is knowable or not. That is, in a realistic model, the system has a state at every moment, whether or not that state is knowable; it may not be, because there may be no way to probe the state without disturbing it.

That's sort of the point of Bell's theorem. He was investigating whether there were any testable consequences to the assumption that there was a pre-existing state prior to measurement, even if that state is not knowable.

Are you sure that you mean that? Are you not aruging that realist interpretations actually forbid the superposition of states?

 

[bohm2]

I equate contextuality with non-realism, recognizing fully that they can be defined differently... I see those as being mutually exclusive. Ie you cannot have contextuality *and* realism.

As to Vervoort's superdeterminism and variants: I do not consider these lines of reasoning to be a part of physical science in their current form. You may as well say evolution is due to superdeterminism rather than being due to natural selection from random mutation.

I posted a paper previously showing contextuality in classical systems:

Contextuality lays at the heart of quantum mechanics. In the prevailing opinion it is considered as a signature of "quantumness" that classical theories lack. However, this assertion is hardly justified. Although contextuality is certainly true of quantum mechanics, it can not be taken by itself as discriminating against classical theories. Here we consider a representative example of contextual behavior, the so-called Mermin-Peres square, and present a simple discrete model which faithfully reproduces quantum predictions that lead to contradiction with the assumption of noncontextuality. This shows that quantum-like contextual effects have their analogues in the classical realm too.

Classical systems can be contextual too: Analogue of the Mermin-Peres square
http://arxiv.org/pdf/1310.4990.pdf

So if one cannot have both contextuality and realism (as you argue), then such classical systems would then also be non-real? But one doesn't normally think of such systems as being non-real. With respect to Vervoort's papers, I think his focus is on supercorrelated classical systems not superdeterminism.

As a big aside, there are a number of prominent evolutionary biologists that question natural selection as being tautological. See my post here:

Spandrels/Exaptations vs Adaptations
https://www.physicsforums.com/showthread.php?t=701690

 

[craigi]

To clarify: Ie you cannot have contextuality *and* counterfactual realism within the same system. Again: if you tweat the definitions enough you probably can find a way to make these work, but then you won't match up to the EPR definitions. The EPR definitions have stood the test of time.

Now I'm confused. Contextuality is an observerable phenomenon. Counterfactual definiteness is interpretational issue, which is a feature of the de Broglie-Bohm interpretation. So how does the de Broglie-Bohm interpretation explain contextuality?

So if one cannot have both contextuality and realism (as you argue), then such classical systems would then also be non-real? But one doesn't normally think of such systems as being non-real. With respect to Vervoort's papers, I think his focus is on supercorrelated classical systems not superdeterminism.

I wouldn't equate counterfactual definiteness with realism. I think there is an important distinction in that realism, pertains to observer independence, whereas counterfactual definiteness pertains to definite state in the absence of observation. We can have neither, either or both.

I don't consider lack of counterfactual definiteness to be restricted to quantum systems. In fact, I don't see how we can make the Many Worlds interpretation work, for instance, with counterfactual definiteness in the classical realm.

 

[bhobba]

So how does the de Broglie-Bohm interpretation explain contextuality?

I am not an expert on DBB but my understanding is in that interpretation contextuality is hidden in the pilot wave it assumes is very real and actually exists.

That's my understanding anyway - there are some genuine DBB experts that post around here - maybe they can chime in.

Added later:

I did manage to dig up the following:
http://philsci-archive.pitt.edu/3026/1/bohm.pdf

Thanks
Bill

 

[stevendaryl]

Are you sure that you mean that? Are you not aruging that realist interpretations actually forbid the superposition of states?

A superposition of states is another state. The sense in which quantum mechanics is not realistic is that individual particles don't have states. There is a state of the entire universe, but there is no state of a single particle, if it's entangled with another particle.

 

[DrChinese]

So how does the de Broglie-Bohm interpretation explain contextuality?

From the link provided above, Oliver Passon says the following:

"In common jargon these properties are called contextual, i.e. the measurement does not reveal a pre-existing value of a system-property but depends crucially on the experimental arrangement (the context)."

Sounds contextual to me.

Also sounds non-realistic, since the value measured here is dependent on an observer's choice of measurement there. EPR says no reasonable definition of reality would permit this.

Of course EPR also has an explicit out for non-local theories as well, such as superluminal signaling. dBB doesn't exactly feature that so much as everything participates in the context. In the end, I see dBB as both non-local AND non-realistic (or contextual). But that is just me.

 

[Demystifier]

DrChinese, concerning the contextuality/non-reality dilemma, I think it is about english language, not about physics. To test this hypothesis, let me use a simple example not related to quantum mechanics.

Consider the well-known picture attached below. Is it a rabbit or a duck? Is it contextual, in the sense that it is a rabbit when you look at it one way, and a duck one you look at it another way? Is it real, in the sense that it is a duck and a rabbit even if you don't look at it? Or non-real, in the sense that it is neither a duck nor a rabbit when you don't look at it? Or is it real or non-real in some other sense?

I think answering these questions for such a simple example can significantly help to explain what one means by (non)-real and contextual.

 

[DrChinese]

DrChinese, concerning the contextuality/non-reality dilemma, I think it is about english language, not about physics. ...

I quite agree. Although I think it is a difficulty in ANY language other than the language of physics.

 

[craigi]

DrChinese, concerning the contextuality/non-reality dilemma, I think it is about english language, not about physics. To test this hypothesis, let me use a simple example not related to quantum mechanics.

Consider the well-known picture attached below. Is it a rabbit or a duck? Is it contextual, in the sense that it is a rabbit when you look at it one way, and a duck one you look at it another way? Is it real, in the sense that it is a duck and a rabbit even if you don't look at it? Or non-real, in the sense that it is neither a duck nor a rabbit when you don't look at it? Or is it real or non-real in some other sense?

I think answering these questions for such a simple example can significantly help to explain what one means by (non)-real and contextual.

Putting aside my objections that it's not completely objective what "it" is that I'm describing and that "it" doesn't look that much like either; entering into to spirit of the question:

It's contextual in that an observer can get a different result depending upon how they "observe" it.

It's real in the sense that all observers, presuming that they they have sufficient image recognition capability and prior records of ducks and rabbits for comparison, would have the same experience of it.

It's not counterfactual definite in that it doesn't specifically depict either, without the interaction of the observer.

Obviously, we should be careful in extrapolating this to quantum mechanics, but as it happens these match my preferred interpretations. It would be interesting if someone who prefers the de Broglie-Bohm interpretation, would describe it a different way. I suspect if someone were to do so, I would cringe at the abuse of poetic license in the definition of the terms or what "it" is that they choose to describe. Interestingly, I would probably be more forgiving of someone who prefers the same interpretations, yet operates on different definitions.

 

[bohm2]

It would be interesting if someone who prefers the de Broglie-Bohm interpretation, would describe it a different way. I suspect if someone were to do so, I would cringe at the abuse of poetic license in the definition of the terms or what "it" is that they choose to describe. Interestingly, I would probably be more forgiving of someone who prefers the same interpretations, yet operates on different definitions.

1. Rabbit or duck (analogous to contextual properties such as spin, etc. in deBroglie-Bohm) plus
2. An underlying ontological stuff (e.g. the actual picture-analogous to non-contextual Bohmian position) that determines both the rabbit and duck view

As I see it, a non-realist would deny 2. and argue that we can only talk about 1.

 

[Demystifier]

It would be interesting if someone who prefers the de Broglie-Bohm interpretation, would describe it a different way.

I prefer dBB interpretation, and my view is quite similar to that of bohm2 above.

 

[stevendaryl]

1. Rabbit or duck (analogous to contextual properties such as spin, etc. in deBroglie-Bohm) plus
2. An underlying ontological stuff (e.g. the actual picture-analogous to non-contextual Bohmian position) that determines both the rabbit and duck view

As I see it, a non-realist would deny 2. and argue that we can only talk about 1.

It seems to me that the term "realist" or "non-realist" should be augmented by "about ..." Just about any theory can be considered realist about something and non-realist about something else.

MWI and Bohm are realist about the wave function, but not about spin (in the sense that there is no fact about an electron that would make it spin-up; in the Bohm theory, it only becomes a spin-up electron when you try to measure its spin--I think I have that right).

 

[bohm2]

It seems to me that the term "realist" or "non-realist" should be augmented by "about ..." Just about any theory can be considered realist about something and non-realist about something else.

The argument is that some interpretations (e.g. Copenhagen) aren't clear about what is "real"; in particular, there's a clear difference between many of the different versions of Copenhagen on the one hand and realistic interpretations (e.g. BM, GRW). The latter are fully precise about what belongs to the primitive ontology (e.g. particle trajectories, flashes, etc.) whereas the Copenhagen interpretation is vague. The basic philosophy of the necessity for so-called primitive ontology in physical theory for those who favour "realism" in physics can be found here:

Primitive Ontology and the Structure of Fundamental Physical Theories
http://www.niu.edu/~vallori/AlloriWFOlast-dopo%20editing%20finale.pdf

On the Metaphysics of Quantum Mechanics
http://www.niu.edu/~vallori/Allori%20-%20LeBihan-On%20the%20Metaphysics%20of%20Quantum%20Mechanics-finale.pdf

With respect to Copenhagen, the criticism from this perspective is the following:

Thus in contemporary quantum theory it seems that the world must be divided into a wavy quantum system, and a remainder that is in same sense classical... It introduces a fundamental ambiguity into fundamental physical theory (Bell 1987).

Allori repeats this criticism:

Even the Copenhagen interpretation (orthodox quantum theory, OQT) involves a dual structure: what might be regarded as its primitive ontology (PO) is the classical description of macroscopic objects which Bohr insisted was indispensable-including in particular pointer orientations conveying the outcomes of experiments-with the wave function serving to determine the probability relations between the successive states of these objects. In this way, ψ governs a PO, even for OQT. An important difference, however, between OQT on the one hand and BM, GRWm, and GRWf on the other is that the latter are fully precise about what belongs to the PO (particle trajectories, respectively continuous matter density or flashes) whereas the Copenhagen interpretation is rather vague, even noncommittal, on this point, since the notion of ‘macroscopic’ is an intrinsically vague one: of how many atoms need an object consist in order to be macroscopic? And, what exactly constitutes a ‘classical description’ of a macroscopic object?

On the Common Structure of Bohmian Mechanics and the Ghirardi–Rimini–Weber Theory
http://www.niu.edu/~vallori/bmgrw.pdf

 

[infamous80518]

Awesome thread! I've never thought the DBB interpretation was more valid than hearing someone reference descarte as his philosophical source. To conclude that a human nervous system causes wave-function collapse just never sat well with me... Especially considering that the human nervous system, more often than not, doesn't even interact directly with the system; It merely interprets the data...
The best definition for "observation" I've heard is a "change of entropy".

 

[ZapperZ]

Closed, pending moderation.

Zz.