Ontology is to quantum theory what hardware is to computation theory

[vanhees71]

It's in the connection between the formalism and their meaning for the description of observations.

 

[martinbn]

TP: The randomness is in the wave function collapse, which happens during the measurement.
R: But collapse contradicts locality.
TP: No, because collapse is just an update of our subjective knowledge. The collapse is not a change of real physical stuff.
R: But do you assume that real physical stuff exists?
TP: Of course.
R: But Bell proved that if real physical stuff exists, then, during some types of measurements, this real physical stuff necessarily changes in a way which contradicts locality.

Ok.

TP: Yes, by which he proved that "real physical stuff" does not exist.

Nooooo. How is this a textbook answer? You are doing it again! You keep changing the meaning. Noone says that! How could anyone say that Bell proved that electrons dont exist!!!!!!

R: But you just said that you assume that real physical stuff exists.
TP: The notion of "real physical stuff" is a vague concept without a true relevance to physics.

Same here. Not a textbook answer. And i already answered that.

R: So you don't care about about ontology?
TP: Exactly, I'm a serious scientist so I don't care much about the vague notion of "ontology".
R: I rest my case.

!!!

 

[Demystifier]

It's in the connection between the formalism and their meaning for the description of observations.

The problem, of course, is the precise meaning of the word "observation".

 

[vanhees71]

That's what our experimental colleagues do in their labs.

 

[Demystifier]

You keep changing the meaning.

That's why I wanted that YOU speak for the TP, which you refused.

 

[Demystifier]

That's what our experimental colleagues do in their labs.

So one cannot understand the theory in its own terms, without referring to things outside of the theory. For me, it means that the theory is incomplete.

 

[martinbn]

That's why I wanted that YOU speak for the TP, which you refused.

No, you were asking me questions about operators, equations, time dependence. Those are the textbook questions which i dont know why you asked. The moment i said to assume the answers of those you jumped back to the metaphisical ones. These i will answer ask them.

 

[PeterDonis]

TP: The randomness is in the wave function collapse, which happens during the measurement.
R: But collapse contradicts locality.
TP: No, because collapse is just an update of our subjective knowledge. The collapse is not a change of real physical stuff.

Here you are having TP adopt a particular interpretation. Not all TPs will agree with that interpretation.

R: But do you assume that real physical stuff exists?
TP: Of course.
R: But Bell proved that if real physical stuff exists, then, during some types of measurements, this real physical stuff necessarily changes in a way which contradicts locality.
TP: Yes, by which he proved that "real physical stuff" does not exist.
R: But you just said that you assume that real physical stuff exists.
TP: The notion of "real physical stuff" is a vague concept without a true relevance to physics.

Now you're having TP contradict himself. Of course you can make TP look silly by putting contradictory words in his mouth. But what relevance does that have to anything?

TP: Exactly, I'm a serious scientist so I don't care much about the vague notion of "ontology".

You evidently failed to read my TP response to your earlier question along these lines.

 

[Demystifier]

No, you were asking me questions about operators, equations, time dependence. Those are the textbook questions which i dont know why you asked. The moment i said to assume the answers of those you jumped back to the metaphisical ones. These i will answer ask them.

The question of ontology is a metaphysical one, I cannot talk about it without metaphysics.

 

[vanhees71]

So one cannot understand the theory in its own terms, without referring to things outside of the theory. For me, it means that the theory is incomplete.

Obviously we understand the standard theories of physics well enough to compare their predictions to observations. In this sense they are complete as long as there are not observations which cannot be satisfactorily described by these theories.

 

[Demystifier]

You evidently failed to read my TP response to your earlier question along these lines.

So you care, but admit that you cannot answer it. I'm fine with that, but that's not a typical answer by physicists.

 

[martinbn]

The question of ontology is a metaphysical one, I cannot talk about it without metaphysics.

Yes, and that is fine, i will answer these questions. I onky refuse to answer standard questions about the equation and so on. Go back to where i said noooo about Bell proving that things dont exist and we can resume from there.

 

[martinbn]

TP: The randomness is in the wave function collapse, which happens during the measurement.
R: But collapse contradicts locality.
TP: No, because collapse is just an update of our subjective knowledge. The collapse is not a change of real physical stuff.
R: But do you assume that real physical stuff exists?
TP: Of course.
R: But Bell proved that if real physical stuff exists, then, during some types of measurements, this real physical stuff necessarily changes in a way which contradicts locality.

MBN: So?

 

[romsofia]

I attended a conference on quantum spacetimes this week, and I think there are two relevant things I'd like to add.

One day, the focus was on singularities, and if they needed to be resolved, and if quantum gravity would solve it. Naively, I assumed the field would be split into 2 distinct ideals, but one professor who presented did literature review and found there were actually 4 real attitudes on people who approached the problem, and they were:
1) Singularities are actually resolved in the theories themselves, and they worked on how to show that.
2) Singularities will be resolved in quantum gravity, and they worked on how to show that.
3) Singularities are actually predictions of the theories, so they simply accepted them.
4) Indifference to singularities, these theories aren't fundamental, so the singularities that arise in QFT and GR don't matter.

So, maybe by doing more literature review, you may find there are more than 2 positions on this matter.

Finally, I think it's important to acknowledge something John Bell wrote at the start of his paper titled "The moral aspect of quantum mechanics" in which he stated, "Very practical people who are not interested in logical questions should not read it". If you're not interested in ontology, and the logical questions associated with formalism, don't bother yourself with it. Stick to more practical matters!

 

[PeterDonis]

So you care, but admit that you cannot answer it. I'm fine fine that

Ok.

that's not a typical answer by physicists.

I'm not so sure. I think the physicists you refer to might just not be as patient as I am with "realists" who insist on pestering them with questions that everyone already knows we have no good answers to. Their dismissiveness might not mean they don't care about those questions, but just that they have better things to do with their time than try to explain to "realists" that they don't want to engage in discussions that can never come to any resolution since they're about questions we don't have good answers to.

 

[Structure seeker]

Even in non-relativistic QFT, where a consistent 1st-quantization formulation exists, the wave function has a probabilistic meaning. The idea that it represents, e.g., an electron as Schrödinger thought originally, contradicts basic observations about electrons, and that's how the probabilistic interpretation by Born became unavoidable.

What basic observations contradict this idea?

 

[Demystifier]

MBN: So?

Your view (correct me if I misrepresent it) is that real stuff exists and is "nonlocal" in the Bell sense, which is not in contradiction with the fact that physics is also "local" in another sense. In that sense you and me agree, and it's not at all obvious what do we really disagree about. With intention to clarify the source of our disagreement, let me ask you one additional question. In your view, does this violation of locality in the Bell sense imply a violation of some sort of Lorentz invariance?

 

[Demystifier]

I think the physicists you refer to might just not be as patient as I am with "realists" who insist on pestering them with questions that everyone already knows we have no good answers to. Their dismissiveness might not mean they don't care about those questions, but just that they have better things to do with their time than try to explain to "realists" that they don't want to engage in discussions that can never come to any resolution since they're about questions we don't have good answers to.

I appreciate your patience. Can you try to explain the following to me? If they don't want to engage in such discussions, but still care about these questions, then how is their care manifested?

 

[Demystifier]

Obviously we understand the standard theories of physics well enough to compare their predictions to observations. In this sense they are complete as long as there are not observations which cannot be satisfactorily described by these theories.

Yes, in that sense they are complete. But there is also another sense in which they are not complete. You may call it metaphysical, but whatever you call it, many physicists think that this is important and interesting too.

 

[PeterDonis]

If they don't want to engage in such discussions, but still care about these questions, then how is their care manifested?

There is no useful way to manifest it since the questions are unanswerable at our current state of knowledge and that doesn't appear likely to change any time soon. The best we can do is to continue trying to expand the boundaries of what we can test by experiment, in the hope that eventually that will enable us to find answers for more of these questions.

 

[Demystifier]

There is no useful way to manifest it

So do they manifest it in an unuseful way? If yes, what way is it?

 

[PeterDonis]

So do they manifest it in an unuseful way? If yes, what way is it?

Why do they have to "manifest" it?

 

[martinbn]

Your view (correct me if I misrepresent it) is that real stuff exists and is "nonlocal" in the Bell sense, which is not in contradiction with the fact that physics is also "local" in another sense. In that sense you and me agree, and it's not at all obvious what do we really disagree about. With intention to clarify the source of our disagreement, let me ask you one additional question. In your view, does this violation of locality in the Bell sense imply a violation of some sort of Lorentz invariance?

I expressed my opinion in the very first post i wrote.

No, i think it doesnt imply Lorentz invariance violation.

 

[vanhees71]

Yes, in that sense they are complete. But there is also another sense in which they are not complete. You may call it metaphysical, but whatever you call it, many physicists think that this is important and interesting too.

You never say, what you consider incomplete. That's also typical for philosophical discussions. You keep it nebulous enough just to never end debates about it ;-).

 

[DrChinese]

... I've just come to wonder about whether the phenomenon of entanglement is due to how the wavefunctions of quantum information are "objectively defined". In the paper "A system's wave function is uniquely determined by its underlying physical state" it is concluded based on free choice that interpreting the wavefunction as an objective reality is possible regardless of all the probability involved (contrary to a classical or hidden variable state of a quantum property as proven by the Bell tests). The article poses a thought experiment with an info set ##\Lambda## of complete knowledge of the starting setup, consisting of wavefunctions etc.

Then for instance, it would be easy with two photons ~100% entangled in polarization to explain it such that the wavefunction of polarization of both photons is determined ~100% by the same subset of ##\Lambda##.

A link to your reference: https://iopscience.iop.org/article/10.1088/1367-2630/aa515c

The paper is quite similar to (and comes to essentially the same conclusion as) the much better known PBR paper (his reference 14): https://arxiv.org/abs/1111.3328

The psi-ontic and psi-epistemic debate is a complicated subject, and certainly worth the study. But I would like to say something about your statement in bold. You cannot have 2 identical copies of a predetermined entangled wavefunction and get the QM statistical predictions. That is what Bell demonstrated, even though on the surface it appears as if you easily could. (Of course, if there is action at a distance (nonlocality) then all bets are off.)

If that point is not clear from your readings, I would suggest starting a thread in the main QM forum to discuss why. QM is contextual, which means it is dependent on context (the settings of the measurement devices) for its statistical predictions. There are no other known inputs for entangled scenarios with respect to the observed outcomes.

 

[Demystifier]

Why do they have to "manifest" it?

You think that they care, so I assume that they manifest it somehow, for otherwise why would you think that?

 

[PeterDonis]

You think that they care, so I assume that they manifest it somehow, for otherwise why would you think that?

To be precise, I did not say I think they care; I just said I don't think you can infer that they don't care, from the fact that they don't want to engage in endless discussions with "realists". They might just have better things to do with their time.

However, I also do not think caring about something requires "manifesting" that care in a way that you perceive as showing they care. Who made you the judge?

 

[Demystifier]

I expressed my opinion in the very first post i wrote.

No, i think it doesnt imply Lorentz invariance violation.

So you think something exists, and it is nonlocal in the Bell sense, but it does not violate Lorentz invariance. This, indeed, is very textbook like. But I am not satisfied with it, it's too vague for my taste. For example, textbooks say that it is Lorentz invariant because you cannot send signals faster than light. But I'm not satisfied with it, because I don't think that Lorentz invariance is only about sending signals. Bohmian mechanics is a counterexample, where the equations violate Lorentz invariance and yet signals still cannot be faster than light.

The problem with the textbook style explanation is that it does not write down equations that describe how existing things change during the measurement (unless they write down the collapse postulate, which, as an explicit equation, violates Lorentz invariance), so it is impossible to understand mathematically why Lorentz invariance is not violated. Most attempts to write explicit equations of that sort (Bohmian mechanics is an example, but not the only one) lead to violation of Lorentz invariance, but textbooks reject such equations because they are not useful in making new measurable predictions. Since such equations attempt to explicitly describe the existing things, and since textbooks reject it as useless, I see that as a kind of rejection of realism. They still say that something exists, but they reject a need for writing down equations that describe it. Their reason for rejection is - because it does not make new measurable predictions. But their claim that "something exists" also does not make new measurable predictions, so why do they not reject this claim as well? If they are not anti-realists, then they are inconsistent, which for me is even worst. When I think of them as anti-realists, that's because I'm trying to save their consistency.

Any thoughts?

 

[Demystifier]

To be precise, I did not say I think they care; I just said I don't think you can infer that they don't care, from the fact that they don't want to engage in endless discussions with "realists". They might just have better things to do with their time.

However, I also do not think caring about something requires "manifesting" that care in a way that you perceive as showing they care. Who made you the judge?

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?

 

[TonyStewart]

I have heard of but do not know the many interpretations of QM yet none are definitively Ontological.

Yet the ones that try are: the Copenhagen interpretation and Heisenberg's counter-theory, Many-worlds interpretation, Pilot-wave theory, and String Theory.

Eric Weinstein has boldly stated ST has stagnated progress in TP for at least the last 40 years. He fears but has openly challenged Edward Witten to end the poisoned-well on String Theory (which is useful for QFT) and make way for funding more progress in TP like 100 years ago. Ref Eric & Lex

 

[haushofer]

You describe astrology accurately but that's exactly not what's done in physics and theory building in physics, which is based on empirical facts and not some epistemological prejudices. If the latter approach is applied, nothing fruitful comes out (e.g., Einstein's search for a so-called "unified field theory" or in more modern times string theory). It's even worse with philosophy. I've not a single example, where philosohpical reasoning has brought any progress in the natural sciences. There's the incomprehensible ineffectiveness of philosphy in the natural sciences (Weinberg)!

Einstein's conviction that the equivalence principle entailed the true nature of gravity, even though the small empirical deviations from Newton would suggest a small adjustment.

And ironically, your attitude towards ontology is highly philosophical.

 

[Structure seeker]

You never say, what you consider incomplete. That's also typical for philosophical discussions. You keep it nebulous enough just to never end debates about it ;-).

If you say the theories are complete because there are no phenomena observed yet that falsify it, I don't understand how you discard realism of everything in general. Either the theories are about reality, or they are fantasies per definition of what fantasy is. If you discard realism, then I am only interested in your theories from the perspective of a psychiatrist. But if you claim the theories are applicable always and everywhere, that means in real life, and that means the physics it describes must be real.

So my question only is: what is about reality in your own interpretation and what isn't? Then we can discuss clearly, for otherwise I'm only interested if I want to connect to the world in your head.

 

[Structure seeker]

And if you don't know what to say, I think that is what @Demystifier means when he says the theories are incomplete in another sense. They don't fulfill the "get real" requirement.

 

[haushofer]

Physicists who proudly proclaim they can do without philosophy remind me of protestant christians who read the bible Sola Scriptura. What good has tradition ever brought us anyway? The text speaks for itself!

Well, only after you've assumed some very non-Sola Scriptura assumptions you're probably not aware of.

The same goes for physics and philosophy/ontology. It already starts with classical physics. If the math and observations would speak for themselves we wouldn't have this deluge of topics on PF about centrifugal forces, the twin paradox etc. etc. And what to think about anomalies? Lack of theory? Observations? Both? Why is dark matter such a big issue now if observations speak for themselves? Why 50 years of string theory with all those false expectations?

Downplaying the role of philosophy turns physics into mere bookkeeping. Mere bookkeepers are capable persons, but don't ask them to develop new economic theories.

 

[Simple question]

Then he'd be wrong. The program can work on a wooden computer, or on a paper/pencil system. The software algorithm is entirely independent of the hardware on which one might choose to run it.

That’s is incorrect.

After reading all those posts, I think that mistake is common, and is a good starting point to focus back on the OP analogy.

Programs are NOT algorithm. Computer do not compute. The ontology is pretty clear:an initial finite sate, with the turing machine. Can it be made out of in wood ? Yes. Can it run Angry Birds ? No.
I dont mean no in a FAPP sense. Understanding what ontology really means boils down to fixing that misconception.

Of course there will be at least two camps, even in computing, about every Paradigm. Like the Functionalist vs the procedurealist. But the issue is not to claim moral high ground. The issue is to produce and explains results, which I would map to Observation in physics.

Any pure algorithm will fail if you do not cope with those menial ontological basics like memory availability. Angry birds don t exist if at least million of bits changes state 30 times per second.
Why ? Because the complete ontology, the territory, include a human brains and eyes able to react to birds, and this is not, at a fundamental level, equivalent to reading millions of penciled Encyclopedia full off one and zero.

Clear ontologies are better than confused ones. Even if string (in physics not computing) is not a successfully ontology, it is a clear and coherent one. I don t think proponent of that ontology where adamant that those string were ’real’ nor interested of what they would be made of.

But formalizing what the territory could be is useful to choose amongs the maps available