I Ontology is to quantum theory what hardware is to computation theory

[Simple question]

Does it count if I care about, not ontology of "ultimalte reality" (as we agreed? we can never know), but about the ontology of the MAPs? This is for me the connection. Many TP, doesn't consider the theory as part of reality, it's just part of human science.

Nobody claims ultimate complete knowledge of nature (well that's not true, there is a couple of people that does it on this forum).
"That's turtle all the way down", so we are only interested by the next level of turtle territory layer, and how to leverage it for agency purpose.

We often say, don't mistake the map for the territory, but the map is all we have, and what we revise.

You lost me there, this is plain wrong. We have many maps, and then the ONE territory were we all experiments.

In one extreme one can wonder, does it matter what the territory is?

I am pretty sure that's the only thing that matter (pun intended)
The naming is also not the issue and never was. Reality is not defined, it is experienced. All these choices describe what is done at CERN. Only one is ontological.

1. We verify that QFT is the one and only all knowing truth, by verifying its inability to predict new particles and their mass, and the final stop to human knowledge.
2. We burn money like crazy because we can.
3. We run a particle accelerator
4. We run a field giggler
5. We run a string knitter
6. There is a bunch of magnet, mega miles of cable and other goodies, computer and algorithm, carefully assembled, that spit out number in screens and databases (and a good power source)

Maybe it's just a mess of interacting maps? Part of the idea is of course, that the other maps are hidden, each player only views it's own map.

Maps don't interact. Do you mean when you use many maps to find your way in the territory ? Why call it interaction ? What is your actual ontology, is it "agent" ?

 

[Simple question]

It's an empirical fact that observables don't have predetermined values before the system is not prepared in a state, where this is the case.

That statement applies to anything, including the moon. This is not an empirical fact, but a Lapalissade, whose ontology is known to philosopher.

That's the clear outcome of all the Bell tests, given that relativistic QFT, describing them in accordance with all observations, is local (i.e., microcausal).

Bell test and theorem do not need "given". It stand on its own (non-ontological) feet, outside of QM, and is even accessible to Yong students.
It proved that QFT is not only "un-realistic", but also "incomplete", because the empirical fact is that non-locality is real

 

[Structure seeker]

Hmm, we're getting into not accepting that people don't believe that things that cannot be measured could be real. That is a step too far, if someone cannot believe that if we try to convince, it's his/her loss.

But I do wonder, @vanhees71 , about your answer to

By measurement you apply a fourier transform to the wavefunction and voila, it becomes an observable. How can the second be real and the first not real?

 

[Fra]

Maps don't interact. Do you mean when you use many maps to find your way in the territory ? Why call it interaction ? What is your actual ontology, is it "agent" ?

Yes, i was thinking "agents interact". And the "map" was then the metaphor for the agents understanding of it's environment. And this is constantly challenged and tuned over time. But the agent is of course simply matter. The difference is that abstraction used, and thus the way to ask questions.

When probing high energies from perspective of QFT paradigm, the questions asked take a particular form. The smaller things we probe, the more information do we need to process in the lab. In agent view, I would say this means; it takes a sufficiently massive agent, to even distinguish a small subatomic agent. And the description we get necessarily lives in the low energy domain, and tracing it properly all the way gets too complicated due to divergences. So QFT tells us how a massive agent "maps" a ligt agent (read subatomic systems). But how would one electron "see" or "map" a proton? The elctron maps the nuclues, and the nucles maps the electrons? Here QFT does not apply as neither of these qualify as a classical measurement device. If we could answer that, we could inprinciple understand the interactions, from the native scales, and not work through the chain of renormalizations to make contact to low energy physics.

/Fredrik

 

[PeterDonis]

If they care but not manifest it, then their care is a hidden variable. Would you say that it is justified to think that a hidden variable exists?

I think at this point we are way off topic for both this thread and PF in general.

 

[AndreasC]

I've not a single example, where philosohpical reasoning has brought any progress in the natural sciences.

This is a very weird statement especially when regarding the history of the natural sciences, which weren't even really considered separate from philosophy at all until very recently in relative terms.

 

[Vanadium 50]

My head is spinning.
Perhaps I should see an ontologist.

 

[Morbert]

"Realistic" has a clear meaning in this context: A theory is called realistic if it assumes that all observables always have determined values. This is obviously not fulfilled by QT and that's why QT is non-realistic (though in the case of relativistic QFT it's by construction local).

It's an empirical fact that observables don't have predetermined values before the system is not prepared in a state, where this is the case.

The value of observables prior to measurement is not asserted or rejected by QM. An instrumentalist should not be surprised by this since you cannot measure a system before you measure it.

QM only insists that we don't assign a predetermined value to all observables. We can readily assign a predetermined value to the measured observable prior to measurement. I.e. We can construct propositions about an observable prior to measurement that nevertheless correlate with the possible outcomes of the measurement, even if the measured system was not initially prepared in an eigenstate of the observable to be measured.

 

[Demystifier]

"Realistic" has a clear meaning in this context: A theory is called realistic if it assumes that all observables always have determined values.

By that definition, I don't know (*) any "realistic" interpretation. In particular, Bohmian, GRW and many worlds, which are otherwise regarded as realistic, are not realistic according to your definition.

(*) Or maybe I do. The thermal interpretation by @A. Neumaier might be the only realistic interpretation in this sense, but AFAIK this interpretation is not published in any peer reviewed journal.

 

[vanhees71]

Of course, any interpretation that is in accordance with the observations cannot be realistic. A realistic theory cannot be a mere reinterpretation of QT but must be a new theory. That's the important point of the verification of the violation of Bell's inequality.

 

[Structure seeker]

I'm afraid these interpretations then do not explain objects like the moon until we measure each particle of it. They explain the results of quantum mechanical experiments only.

I prefer to follow the consistent histories interpretation with the addition that the proposition elements of the set of consistent histories are real and parts of a real object that is the complete (probability 1) set of consistent histories of which the propositions at a fixed time together describe the wavefunction at that time. It's the first time I describe this idea, so excuse me if a few technical details are missing.

It's because I think this also has meaning in classical contexts (even though it is pretty complex) such as the reality of the moon. Although the map @vanhees71 uses describes quantum experiments and is thus OK in @Fra his view, it would be nice to have a more complete theory for which I proposed a candidate.

 

[TonyStewart]

Philosophical reasoning used in Science R&D. Which would you ignore?

1. Epistemology
2. Metaphysics
3. Separation of science and pseudoscience
4. Ethics
5. Ontology
6. Scientific Revolutions

 

[Demystifier]

Of course, any interpretation that is in accordance with the observations cannot be realistic. A realistic theory cannot be a mere reinterpretation of QT but must be a new theory. That's the important point of the verification of the violation of Bell's inequality.

Do you distinguish "realistic" from "local realistic"?

 

[gentzen]

I'm afraid these interpretations then do not explain objects like the moon until we measure each particle of it. They explain the results of quantum mechanical experiments only.

I know you are replying to the vanhees71's post just above, but I would really prefer if you could still quote a part of his post nevertheless (in the future). It would simply make my life and the life of other readers of this thread a bit easier.

Philosophical reasoning used in Science R&D. Which would you ignore?

You are not responding to any post in particular, correct?

1. Epistemology
2. Metaphysics
3. Separation of science and pseudoscience
4. Ethics
5. Ontology
6. Scientific Revolutions

I would ignore "2. Metaphysics" and "6. Scientific Revolutions". I am unsure whether "6. Scientific Revolutions" even qualifies as philosophical reasoning in the first place.

 

[TonyStewart]

I know you are replying to the vanhees71's post just above, but I would really prefer if you could still quote a part of his post nevertheless (in the future). It would simply make my life and the life of other readers of this thread a bit easier.

You are not responding to any post in particular, correct?

I would ignore "2. Metaphysics" and "6. Scientific Revolutions". I am unsure whether "6. Scientific Revolutions" even qualifies as philosophical reasoning in the first place.

At least 1 revolution per century on average made paradigm shifts in thinking. ST was one that beckons a replacement. Perhaps less frequently in history but certainly evident in Sumeria (s. Iraq) Mayan calendar, heliocentric era, gravity wave evidence, super-symmetry, now with deep space 10 year tracking black holes exploration, solar weather prediction, evolve more plasma-dynamic theories on dark matter and evolution

 

[vanhees71]

Do you distinguish "realistic" from "local realistic"?

I consider locality and realism as independent. E.g., non-relativistic quantum theory is non-realistic but not local, as expected from a non-relativistic theory.

 

[Demystifier]

I consider locality and realism as independent. E.g., non-relativistic quantum theory is non-realistic but not local, as expected from a non-relativistic theory.

Good. But in your view, what kind of theories are ruled out by the violation of Bell inequalities; all realistic theories, or just the local realistic ones? And am I right that Bohmian mechanics is non-realistic in your view?

 

[Simple question]

Back to the analogy. (I won't change naming, but hardware aware guy VS algorithm only software guy, is the more appropriate naming)

The software guy is wrong… for reasons way deeper than FAPP (on which everyone has different opinions and judgment about what is practical and purposeful).
Even if computers were abstraction only made of bit, even if software guy admits there is a fine number of those (it is probably possible to retrofit this in his mathematical abstractions/language), and even if his work is definitely helpful (i.e evaluate complexities, build certitude for signal processing and cryptographic, and more) ... he will still miss something.

Computer are NOT made of bit, and nothing else matter.

A helpful example within the analogy: the paradigm of those "bits", is UMA, this correspond to a non-local paradigm, were all kind of fantasies can be build. Namely primitive object like pointer and integer. Even worse, those are often abstract away by even more "high level" semantics (array and number). The result: one can build a program that halts after 2 weeks. And it will crash if the 'initial boundaries' don't fit within some ranges.
The hardware guy will produce another program, that halts in 42 seconds, and accept an order of magnitude bigger inputs, by carefully avoiding some singularities.

This is still an FAPP failure, so it is always easy for the software guy to claim equivalences of results. He probably have no-go theorem, involving cost of hardware vs cost of thinking more broadly.

Here is the trick. The hardware guy know that UMA is a fiction and information is not "just bit". He has a precise knowledge of the caches latencies and sizes, WAT per cycle, even silicon rarefaction and cost of electric bill if he is really a good one.
The result is that the deep understanding of those "ontologies", made him develop a theoretical (logarithmic) framework/understanding, a specific domain that allows him to produce results that is simply impossible to do otherwise.
Caches haven't been invented to solve a computing problem, but to solve a computer problem, related to physics, not bits. Now entire stacks of cache-software tools also exist, only to manage that "ontological issue"

The software guy has not incentive, nor even ways in principle, to discover those "useful" domain into the more or less infinite space of algorithm. He could even stumble on it by luck, and not even understand what it would be useful for.

There is also caveat of being too focused on ontology. In computer science the saying is "Premature optimization is the root of all evil". And this is true.
The other less vocalized truth is "Not caring about optimization is the other root of all evil". I've seen more projects fail because of the second than the first.

 

[physika]

If nothing is real before the observable is measured, how can it appear out of things that supposedly are not real?

Part of the problem here, is that some (or someone) confuse the concept of CFD (counterfactual definiteness) with that of realism, that is, that electrons (for example) may not have a definite value of spin, but that doesn't mean they aren't real.

 

[Demystifier]

electrons (for example) may not have a definite value of spin, but that doesn't mean they aren't real.

Yes, but the question is how to represent the real stuff (such as electron) with a mathematical object. If you represent it by a wave function, then you must have collapse (unless you accept many worlds), which leads to non-locality and Lorentz violation. If you say that it is not represented by a wave function, then you should say something about representing real stuff with another mathematical object. And yet people like @martinbn refuse to say anything concrete of this sort. For me they are non-realists at least in some weak sense, not by claiming that reality doesn't exist (which would be a strong non-realism), but by refusing to say something about the mathematical object that represents this real stuff.

 

[martinbn]

Yes, but the question is how to represent the real stuff (such as electron) with a mathematical object. If you represent it by a wave function, then you must have collapse (unless you accept many worlds), which leads to non-locality and Lorentz violation. If you say that it is not represented by a wave function, then you should say something about representing real stuff with another mathematical object. And yet people like @martinbn refuse to say anything concrete of this sort. For me they are non-realists at least in some weak sense, not by claiming that reality doesn't exist (which would be a strong non-realism), but by refusing to say something about the mathematical object that represents this real stuff.

You dont need to represt the object (say the electron) itself. And the wave function doesn't do that. The wave function represents the state of the object.

I don't see how you can claim that any of this implies Lorentz violation!

 

[Demystifier]

You dont need to represt the object (say the electron) itself.

Why not?

And the wave function doesn't do that. The wave function represents the state of the object.

Would you say that state of the object is quantitative, but the object itself is qualitative? Is it why you think that object itself doesn't need to be represented with math?

I don't see how you can claim that any of this implies Lorentz violation!

As soon as you try to represent object with math, you get nonlocality in the Bell sense. Most explicit attempts to write down a mathematical model of this nonlocality violate Lorentz invariance. The best known examples are explicit collapse and Bohmian mechanics. If you have a counterexample in mind, namely a nonlocal Lorentz invariant mathematical representation of the object, I would like to see it.

 

[martinbn]

Why not?Would you say that state of the object is quantitative, but the object itself is qualitative? Is it why you think that object itself doesn't need to be represented with math?As soon as you try to represent object with math, you get nonlocality in the Bell sense. Most explicit attempts to write down a mathematical model of this nonlocality violate Lorentz invariance. The best known examples are explicit collapse and Bohmian mechanics. If you have a counterexample in mind, namely a nonlocal Lorentz invariant mathematical representation of the object, I would like to see it.

I think I probably didn't understand you. What do you mean by represent the object mathematically? What is an example (doesn't have to be quantum)?

 

[Demystifier]

I think I probably didn't understand you. What do you mean by represent the object mathematically? What is an example (doesn't have to be quantum)?

- Classical particle can be represented by the position in space, i.e. by the coordinates $(x,y,z)$. This perhaps does not say everything about the particle (e.g. its mass and charge), but at least says something.

- A classical wave can be represented by a function of the form $f(x,y,z,t)$, or by its Fourier transform $F(k_x,k_y,k_z,\omega)$, which also may not say everything about the wave, but at least says something.

- If one does not know the position of the classical particle, then one can associate a probability distribution $p(x,y,z)$. However, this does not represent the classical particle. Instead, in the Bayesian interpretation of probability, it represents our incomplete knowledge about the particle, because it is assumed that the particle has position even when we don't know it. Alternatively, in the frequentist interpretation of probability, it represents an ensemble of particles, not one particle.

- In quantum physics one may want something similar, some mathematical object that represents some objective property (of the single particle) which exists even when we don't know it. In standard textbook quantum physics, the only mathematical quantity at our disposal is the wave function $\psi(x,y,z)$ (or something closely related to it), but, depending on interpretation, $\psi$ represents an ensemble of particles, or our incomplete knowledge about the particle. Hence the analogy with classical physics suggests that we need another mathematical object that says something about the single particle itself, irrespective of our knowledge. Bohmian mechanics is an example of an attempt to introduce such another mathematical object.

- Or, if the analogy with classical physics is misleading, then the wave function itself should be interpreted as something that represents the particle itself, which leads to $\psi$-realist interpretations such as many worlds or objective collapse on one side, or $\psi$-information interpretations such as QBism and relationalism on the other side. The $\psi$-information interpretations seem to be saying that a mathematical representation of a single particle itself independent of our knowledge - does not exist. They do not say that the particle itself does not exist, but they say that the mathematical representation of the particle itself does not exist. If this is more or less how you (@martinbn) think of it, then would you say that the particle itself is something that only has a quality, not a quantity?

Does it help?

 

[Fra]

I think I roughly understand what Demystifiers seeks, and I also think that this question in principle, does not necessarily restrict itself to only Bohmian meachanics, because I can related to this, even from the "agent/qbism" view in the following way:

We often hear from realist side rethorical questions such as "is the moon there when noone is looking". Note that this question is quite similar to also asking
"does the truth exists even before we learn about it"
"does the laws of physics exist before we learned about them"
"does a piece of information, exist before it's communicated/inferred"
...
ie. there is an idea that there is a "native or local" truth of actual matter, but that that always has to be communicated/inferred to/by an external/remote observer. These "layers" of inference or interactions obviousl screens the "real" from the observer, so the "observable" can never bee anything by the apparent/renormalized information.

The "naked" truth, can in this view never be seen directly, as any inferences must pass through all the layers of interaction/communication.(ie without making a "measurement") For example, there is no way to probe inside a cell, without somehow passing (mechanicall or via electromagnetic radiation) the cell wall, so in principle these layes always "distorts" the image related to the real thing.

I think Demysitifier seeks at least a principal picture of the "naked structure", ie what is an "electron" if we could "peak inside" without goign through all the layers of interactions, out the the pointers in the classical lab?

In QM/QFT this naked structure is not observable, they are finetuned to match the effective structure, as measured essentially at the macroscopic boundary/environment of the system. This structure also takes on the nature of an abstract parameter space, that is defined only statistical in terms of "classical" things and data collected at the far boundary.

This is first of all unsatisfactory, but it also is a problem because it similarly means that the hamiltonian is also fitted exeperimentally, and the worst part is that at leasdt in principle, this has to be done for each observational scale, so we have a set of effective theories only, which is even more unsatisfactory. And the more unified theory we try to find, in order to have ONE theory where we via renormalizations can change the scale, the more fine tuning do we seen to required. And at some point this breaks down, because the complexity of the data likely exceeds our "observational platform".

So what I wanted to say is that, no matter how differently we think about this, Demystifiers quest for ontology here, is actuall quite analogous to what I call the "intrinsic view". This intrinsic view, is exactly (I think) the "ontology" that we talk about here. And as I see it, this does not stay philosophy because if we can find this, we should be able to make som serious progress in unification work (even though the connecttion may be far fetched for some, it is what drives me)

/Fredrik

 

[Fra]

As soon as you try to represent object with math, you get nonlocality in the Bell sense. Most explicit attempts to write down a mathematical model of this nonlocality violate Lorentz invariance. The best known examples are explicit collapse and Bohmian mechanics. If you have a counterexample in mind, namely a nonlocal Lorentz invariant mathematical representation of the object, I would like to see it.

If I am trying to rephrase this in my preferred terms, then it seems the represnetation of all ontologies you ask for, would be like considering the set of all "intrinsic observer views". Ie. it is a generalization of the notion of "observable". I think the solipsist HV are also of this type.

The normal notion of observer, IMO, forbids most observers, and keeps only those that asymptotically form some agreement. While this is not a strange requirement from the perspective of "objevtive science" I think it really misses some deep workings. (Specifically the mechanism by which the objectivity is chosen; ie. it solves the finetuning probelm)

Anyway, if we toy with the idea that we have this set of all ontolgies. Ie. the set of all hidden variables, or the set of all agents "microstates" (that are screened from other agents), then I agree that the "apparent causal rules/correlations" viewed from this set would be completely nuts and violate common sense! In the agent view this has a perfectly natural explanation: two agents does not causally act upon each other based on their hidden states, because that would be completely unlogical and irrational.(And Bells theorem assumes this, which is why it does not apply) They respond only to the "effective view" of the other agent. ie. the view that you get from the screened "naked state". This is why locality (in the einsteinian sense is guaranteeed) because an agent can not respond to anything unless it's first communicated.

The problem is when you try to describe this process in the netwonian paradigm, with state space what is fixed and timeless laws and an initial condition. It forces you to increase the complexity and do alto of fine tuning - to the point where it's not possibe - and and at that point we are also lost in chaos.

/Fredrik

 

[vanhees71]

Good. But in your view, what kind of theories are ruled out by the violation of Bell inequalities; all realistic theories, or just the local realistic ones? And am I right that Bohmian mechanics is non-realistic in your view?

Only local realistic ones. Since Bohmian mechanics is only a reinterpretation of (non-relativistic) QT without any predictions that violates the standard laws of QT, it's also non-realistic.

 

[vanhees71]

You dont need to represt the object (say the electron) itself. And the wave function doesn't do that. The wave function represents the state of the object.

I don't see how you can claim that any of this implies Lorentz violation!

Somehow in the debate with philosophers you have the problem that they don't understand that non-relativistic QM of course violates Lorentz invariance, simply because it's a non-relativistic theory. The only consistent relativistic QT is local relativistic quantum field theory, and there of course nothing violates Lorentz invariance for observables (like transition probabilities or cross sections calculated from Poincare-covariant S-matrix elements).

 

[Morbert]

Somehow in the debate with philosophers you have the problem that they don't understand that non-relativistic QM of course violates Lorentz invariance, simply because it's a non-relativistic theory. The only consistent relativistic QT is local relativistic quantum field theory, and there of course nothing violates Lorentz invariance for observables (like transition probabilities or cross sections calculated from Poincare-covariant S-matrix elements).

You can have a theory that is not Lorentz invariant but still local right? E.g. A lagrangian that is not a scalar or scalar density (therefore not Lorentz invariant) but still depends only on coordinates and time derivatives (therefore local)

 

[vanhees71]

No, locality means that there are no faster-than-light signals. The nonrelativistic interactions are described by instantaneous (potential) forces and thus violate locality by assumption.

The locality is implemented by construction in relativistic QFTs by having Lorentz-invariant-equivalent local Lagrangians and quantization conditions ensuring the microcausality condition for local observables.