Insights How I Stopped Worrying and Learned to Love Orthodox Quantum Mechanics - Comments

[stevendaryl]

I did several times in this thread. Then you use the words in different meanings. In this way one cannot discuss scientific issues. That's all I'm saying.

Well, I think you've misdiagnosed the problem.

 

[Demystifier]

That's what makes no sense to me. If detector clicks are natural phenomena that are ultimately described by the physics of particles and fields, then how can they be more real than what they're made out of? To me, that's a schizophrenic point of view.

The pre-quantum theories of physics were not schizophrenic in this way. Bohmian mechanics is not schizophrenic in this way.

Here the problematic word is "ultimately". What if description by the physics of particles and fields is not ultimate but merely provisional? Would it be schizophrenic even then? Different levels of descriptions require different effective paradigms (see Anderson's "More is Different"), and there is nothing schizophrenic about that. On the other hand, even Bohmian mechanics can make you schizophrenic if you apply it to make free will decisions about everyday life actions. (Should I marry Ana or Rebecca? Well, it's already determined by initial Bohmian positions, so there is nothing I can do about it. Except that I can. Which is impossible. But obviously true. Arrrghhh!)

 

[Demystifier]

Hi, firstly, ontic and epistemic are not stuff of philosophy.. even brilliant physicists like Sean Carrol believes in ontic psi as when he made clear in:

http://blogs.discovermagazine.com/c...hysicality-of-the-quantum-state/#.Wa87v7pFxOx

“According to instrumentalism, palaeontologists talk about dinosaurs so they can understand fossils, astrophysicists talk about stars so they can understand photoplates, virologists talk about viruses so they can understand NMR instruments, and particle physicists talk about the Higgs Boson so they can understand the LHC. In each case, it’s quite clear that instrumentalism is the wrong way around. Science is not “about” experiments; science is about the world, and experiments are part of its toolkit.”

Also remember PBR theorem revolves around ontic and epistemic psi, so these are serious physics stuff.

Well, many physicists have also a good understanding of philosophy, and Sean Carroll is one of the best examples. The authors of the PBR theorem went even further, they found a way to translate philosophical terms into scientific ones, which is why their work is so important. But still, most physicists (who are not interested in quantum foundations) are not familiar with concepts of ontology and epistemology.

That said. If psi is really ontic, and there is some kind of actual Hilbert Space in the vacuum or whatever the ontic nature may be based on.. is there possibility that we have new force of nature (or new field such as higgs field like thing) that only work in the dynamics within the actual Hilbert space (or other mechanisms) that produces the ontic psi, etc.? Do you know of references with regards to this? Thank you.

I'm afraid I don't understand your question. Are you implying that electromagnetic force, for instance, does not work within actual Hilbert space? What do you mean by that?

 

[stevendaryl]

Here the problematic word is "ultimately". What if description by the physics of particles and fields is not ultimate but merely provisional? Would it be schizophrenic even then?

If it turns out the QM is not fundamental, but is just a heuristic approximation to a more accurate theory, then I would no longer care whether it is schizophrenic, and would instead turn my scrutiny to that replacement theory.

 

[fanieh]

Well, many physicists have also a good understanding of philosophy, and Sean Carroll is one of the best examples. The authors of the PBR theorem went even further, they found a way to translate philosophical terms into scientific ones, which is why their work is so important. But still, most physicists (who are not interested in quantum foundations) are not familiar with concepts of ontology and epistemology.I'm afraid I don't understand your question. Are you implying that electromagnetic force, for instance, does not work within actual Hilbert space? What do you mean by that?

I meant supposed there was a real Hilbert space.. then you need a set of new forces of nature for the real Hilbert space to work, forces we can't detect because it only works within the machinery that produces all this quantum ontology (for example imagine a super computer inside each of the Planck space in the vacuum whose only job is to produce quantum probabilities and bind them to objects (or whatever)).

 

[Demystifier]

If it turns out the QM is not fundamental, but is just a heuristic approximation to a more accurate theory, then I would no longer care whether it is schizophrenic, and would instead turn my scrutiny to that replacement theory.

Fair enough. And what if, as I propose, non-relativistic QM with Bohmian interpretation is fundamental while relativistic QFT is emergent?

 

[stevendaryl]

Fair enough. And what if, as I propose, non-relativistic QM with Bohmian interpretation is fundamental while relativistic QFT is emergent?

Like I said, if that's the case, then I would no longer care about whether QM seems schizophrenic.

 

[Demystifier]

I meant supposed there was a real Hilbert space.. then you need a set of new forces of nature for the real Hilbert space to work, forces we can't detect because it only works within the machinery that produces all this quantum ontology (for example imagine a super computer inside each of the Planck space in the vacuum whose only job is to produce quantum probabilities and bind them to objects (or whatever)).

I guess it's something like MWI applied not to Standard Model but to the true theory of everything. Well, it's possible but I am not aware of any actual reference.

 

[Demystifier]

Like I said, if that's the case, then I would no longer care about whether QM seems schizophrenic.

Yes, that's why my article is entitled "How I Stopped Worrying and Learned to Love Orthodox QM".

 

[fanieh]

I guess it's something like MWI applied not to Standard Model but to the true theory of everything. Well, it's possible but I am not aware of any actual reference.

I'll give clearer example. In Einstein time, he didn't know of the strong and weak forces because we hadn't know about the quarks and beta decay then. Is it possible there would be a fifth and sixth fundamental forces of nature whose domain of applicability is related to the quantum ontology (or mechanism within such) only?

 

[Demystifier]

Is it possible there would be a fifth and sixth fundamental forces of nature whose domain of applicability is related to the quantum ontology (or mechanism within such) only?

It's possible. See e.g. https://arxiv.org/abs/1703.08341 , Sec. 4.1, last paragraph.

 

[martinbn]

The minimalist interpretation of quantum mechanics seems to do that. I'm sure you've heard it said by many physicists that

(John Wheeler)

In the minimalist interpretation, we are using quantum mechanics to compute transition probabilities between macroscopic states: We start with a preparation procedure and proceed to a measurement. Quantum mechanics gives probabilities for the various possible measurement results, given the preparation procedure. So in this formulation, it seems to be viewing some things as definite---we chose a definite preparation procedure, we got a definite measurement result. But the microscopic details are not assumed to have definite values. The microscopic details seem to be treated as mere calculational tools for predicting macroscopic outcomes, which are the real things.

Yes, but there is a big difference between particles and fields are not real and values of observables are not meaningful without a measurment.

 

[atyy]

Yes, that's why my article is entitled "How I Stopped Worrying and Learned to Love Orthodox QM".

It's funny that Weinberg hasn't come to this conclusion although he knows the lesson of Wilson perfectly well. I guess he is still yearning for the old days in which particle physicists thought they were working on fundamental physics.

 

[fanieh]

It's possible. See e.g. https://arxiv.org/abs/1703.08341 , Sec. 4.1, last paragraph.

I see. May I know if the Hilbert Space in Bohmian Mechanics is located in the quantum vacuum or outside the vacuum or outside spacetime? Please describe where it is located. Thank you.

 

[martinbn]

I see. May I know if the Hilbert Space in Bohmian Mechanics is located in the quantum vacuum or outside the vacuum or outside spacetime? Please describe where it is located. Thank you.

This as phrased doesn't make sense. What do you mean by "the Hilbert space is located" ?

 

[fanieh]

This as phrased doesn't make sense. What do you mean by "the Hilbert space is located" ?

according to atyy: https://www.physicsforums.com/threads/pbr-theorem.789046/page-3

"The configuration space (Hilbert space) is real in dBB. It's not much different from the extra-dimensions of string theory."

Reference https://www.physicsforums.com/threads/pbr-theorem.789046/page-3

 

[martinbn]

Then atyy needs to explain the meaning of that.

 

[stevendaryl]

Yes, but there is a big difference between particles and fields are not real and values of observables are not meaningful without a measurment.

Can you expand on what the big difference is?

 

[martinbn]

Can you expand on what the big difference is?

Well, the particle is real, it exists out there. It is an objective entity, not an abstract construct. On the other hand the coordinates are part of the mathematical description and are things that need not make sense at all times.

 

[Demystifier]

I see. May I know if the Hilbert Space in Bohmian Mechanics is located in the quantum vacuum or outside the vacuum or outside spacetime? Please describe where it is located. Thank you.

In our mind.

 

[fanieh]

In our mind.

I thought Bohmian Mechanics Required the Wave Function to be real.. and needed the PBR theorem to have the wave function real:

https://en.wikipedia.org/wiki/PBR_theorem

"The theorem was first published as an arXiv preprint with Pusey as the principal author,[1] a subsequent version published in Nature Physics,[2] that states the theorem that either the quantum state corresponds to a physically real object and is not merely a statistical tool, or else all quantum states, including non-entangled ones, can communicate by action at a distance."

Is there something wrong with the PBR Theorem?

If the wave function in BM was not real. How can it affect the local particle?

I think it was this line of reasoning or logic that made atyy made the following statements (in the thread mentioned earlier):

"1. “In the Ψ-ontic view, the wave function is a wave like an EM wave. However, the wave function is a wave in Hilbert space, and whereas an EM wave is a wave in spacetime.

2. In both MWI and dBB, the wave function is not a wave in spacetime , it is a wave in Hilbert space.

3. The wave function exists only in Hilbert space in all interpretations of QM, so yes, it is real only in Hilbert space in Ψ-ontic proposals such as MWI and dBB.

4. The configuration space (Hilbert space) is real in dBB. It's not much different from the extra-dimensions of string theory.”"

Reference: https://www.physicsforums.com/threads/pbr-theorem.789046/page-3

How come didn't you have the same reasoning as atyy which was based on the PBR theorem.. did you see any flaw with the PBR line of reasoning? What are they, if any? Thank you.

 

[Demystifier]

I thought Bohmian Mechanics Required the Wave Function to be real

If you want to seriously discuss QM, you must first be well familiar with classical mechanics. Are you? Let me assume that you are. Then wave function is "real" in Bohmian mechanics in the same sense in which principal function of classical Hamilton-Jacobi equation is "real" in classical mechanics. (And if you have no idea what I am talking about, then go and learn classical mechanics first.)

 

[Georgios Bosch]

A very interesting read, thank you. If you don't mind sharing, what was the deep conceptual error in arXiv:1309.0400?

 

[stevendaryl]

Here's what seems strange to me. You have system A, an electron, say. For simplicity, only consider the property of being spin-up in the z-direction. You have system B, some measuring device. Among other things, it has a pointer that can swing from pointing left, where there is a label "U" to pointing right, where there is a label "D". You somehow connect the two systems so that system B measures the spin of system A: If system A is spin-up in the z-direction, then system B will go into the state of pointing to "U", and if system A is spin-down in the z-direction, then system B will go into the state of pointing to "D".

So for people say that properties of system A are meaningless, or have no definite value, until they are measured by system B seems weird if they are both quantum systems. Does system B need a third system, C to make its pointer-value meaningful? That would lead to an infinite regress.

The way I feel about it is that unless one can formulate the Rules of Quantum Mechanics in a way that does not mention, at the fundamental level, any macroscopic quantities such as "measurement", "preparation procedure", "average over many, many systems", then we don't really understand quantum mechanics. That might be fine. There might be limits to what we can understand. But I object to people pretending otherwise.

 

[Mentz114]

Here's what seems strange to me. You have system A, an electron, say. For simplicity, only consider the property of being spin-up in the z-direction. You have system B, some measuring device. Among other things, it has a pointer that can swing from pointing left, where there is a label "U" to pointing right, where there is a label "D". You somehow connect the two systems so that system B measures the spin of system A: If system A is spin-up in the z-direction, then system B will go into the state of pointing to "U", and if system A is spin-down in the z-direction, then system B will go into the state of pointing to "D".

So for people say that properties of system A are meaningless, or have no definite value, until they are measured by system B seems weird if they are both quantum systems. Does system B need a third system, C to make its pointer-value meaningful? That would lead to an infinite regress.

The way I feel about it is that unless one can formulate the Rules of Quantum Mechanics in a way that does not mention, at the fundamental level, any macroscopic quantities such as "measurement", "preparation procedure", "average over many, many systems", then we don't really understand quantum mechanics. That might be fine. There might be limits to what we can understand. But I object to people pretending otherwise.

I never understood why "properties of system A are meaningless, ... until they are measured by system B" and I believe it is not always true.
I can't offer any words of sympathy for your problem but I did find this paper which describes a possible experimental realization of your systems A and B (which you may not have seen). It even has a dial and a pointer.

Continuous Stern-Gerlach effect: Principle and idealized apparatus
HANS DEHMELT
Proc. Nat'l.Acad.Sci.
USA
Vol.83,
April 1986
Physics

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC323282/pdf/pnas00312-0017.pdf
( "I enjoyed discussions with W.E.Lamb,Jr., E.M.Purcell, I.I.Rabi, J.S.Bell, and M.0.Scully" who they ?)

 

[Demystifier]

A very interesting read, thank you. If you don't mind sharing, what was the deep conceptual error in arXiv:1309.0400?

Eq. (182) is only valid after the measurement. On the other hand, Eq. (185) contains a tacit (but wrong) assumption that (182) is valid at all times.
http://www.thethingswesay.com/there...integrity-than-his-behavior-when-he-is-wrong/
http://www.quote-coyote.com/quotes/authors/l/bruce-lee/quote-3714.html

 

[vanhees71]

Here's what seems strange to me. You have system A, an electron, say. For simplicity, only consider the property of being spin-up in the z-direction. You have system B, some measuring device. Among other things, it has a pointer that can swing from pointing left, where there is a label "U" to pointing right, where there is a label "D". You somehow connect the two systems so that system B measures the spin of system A: If system A is spin-up in the z-direction, then system B will go into the state of pointing to "U", and if system A is spin-down in the z-direction, then system B will go into the state of pointing to "D".

So for people say that properties of system A are meaningless, or have no definite value, until they are measured by system B seems weird if they are both quantum systems. Does system B need a third system, C to make its pointer-value meaningful? That would lead to an infinite regress.

The way I feel about it is that unless one can formulate the Rules of Quantum Mechanics in a way that does not mention, at the fundamental level, any macroscopic quantities such as "measurement", "preparation procedure", "average over many, many systems", then we don't really understand quantum mechanics. That might be fine. There might be limits to what we can understand. But I object to people pretending otherwise.

I think the problematic thing is to call properties which are not prepared as "meaningless". If you have a system in a state, the observables that have no determined value are of course not meaning less but measurable, and in measuring them you usually have an influence on the state of the measured system. Which one this is, depends on the interaction between measurement apparatus and measured system. In the special case of von-Neumann-filter measurements (I'd rather call them a certain kind of preparation procedure) you have prepared a state, where the observable takes the corresponding determined value.

 

[martinbn]

Here's what seems strange to me. You have system A, an electron, say. For simplicity, only consider the property of being spin-up in the z-direction. You have system B, some measuring device. Among other things, it has a pointer that can swing from pointing left, where there is a label "U" to pointing right, where there is a label "D". You somehow connect the two systems so that system B measures the spin of system A: If system A is spin-up in the z-direction, then system B will go into the state of pointing to "U", and if system A is spin-down in the z-direction, then system B will go into the state of pointing to "D".

So for people say that properties of system A are meaningless, or have no definite value, until they are measured by system B seems weird if they are both quantum systems. Does system B need a third system, C to make its pointer-value meaningful? That would lead to an infinite regress.

The way I feel about it is that unless one can formulate the Rules of Quantum Mechanics in a way that does not mention, at the fundamental level, any macroscopic quantities such as "measurement", "preparation procedure", "average over many, many systems", then we don't really understand quantum mechanics. That might be fine. There might be limits to what we can understand. But I object to people pretending otherwise.

This is what I don't understand. Why do you insist on the theory being of certain type? Why is it not ok to mention these notions? It seems to me it is a matter of taste. Almost as saying as long as the theory uses differential equations it is not a good explanation. It is incomplete until a purely algebraic description is found.

 

[Demystifier]

This is what I don't understand. Why do you insist on the theory being of certain type? Why is it not ok to mention these notions? It seems to me it is a matter of taste. Almost as saying as long as the theory uses differential equations it is not a good explanation. It is incomplete until a purely algebraic description is found.

In physics, there is a widespread belief that fundamental laws must be fully microscopic. You can compare it with a widespread belief in pure math that all math must be based on set theory. Proposing that macro laws could be fundamental can be compared to a proposal that math should be based on category theory (rather than set theory). Yes, some people propose it, but the mainstream does not buy it.

 

[stevendaryl]

This is what I don't understand. Why do you insist on the theory being of certain type?

I'm not insisting on anything. I'm just explaining why I feel there is something not yet understood about quantum mechanics. My feeling is that macroscopic properties should be derivable from microscopic properties, so that in principle, any mention of macroscopic properties should be eliminable. That's part of the reductionist program, it seems to me.