Find your ideal quantum interpretation

[bhobba]

It's utter nonsense. Already the conservation laws prevent the moon from vanishing when nobody looks at it. This is really superfluous philosophical gibberish!

Indeed. It's caused by not being careful about what you mean by observation. The moon is observed all the time by the environment so is never not observed.

Thanks
Bill

 

[bhobba]

Griffiths ends his book with "...quantum theory indicates that the nature of this independent reality is in some respects quite different from what was earlier thought to be the case."

Well probably - but things are not quite as simple as a quote like that would indicate:
https://www.sciencenews.org/blog/context/gell-mann-hartle-spin-quantum-narrative-about-reality

Note the above just uses the formalism of QM - no interpretation. You can take questions like that a long way without an actual interpretation. Maybe, just maybe, when all the issues of the above are sorted out we will not really need an interpretation other than something minimal like the Ensemble. Fingers crossed.

Thanks
Bill

 

[A. Neumaier]

The moon is observed all the time by the environment so is never not observed.

This is a quite nonstandard view. What then do you call an observation?

 

[bhobba]

This is a quite nonstandard view. What then do you call an observation?

An example would be a dust particle. A few stray photons from the CBMR is enough to give the dust particle an exact position. And since it's bombarded all the time by such the wave-packet will not spread. I consider the photons an observer.

Thanks
Bill

 

[A. Neumaier]

I consider the photons an observer.

Where are its observation records?

 

[DarMM]

Well probably - but things are not quite as simple as a quote like that would indicate:
https://www.sciencenews.org/blog/context/gell-mann-hartle-spin-quantum-narrative-about-reality

Note the above just uses the formalism of QM - no interpretation. You can take questions like that a long way without an actual interpretation. Maybe, just maybe, when all the issues of the above are sorted out we will not really need an interpretation other than something minimal like the Ensemble. Fingers crossed.

Thanks
Bill

I always found this an interesting view, in some ways you can't say much else if you go Copenhagen/Ensemble or any of the other non-representational views. QM doesn't talk about the microscopic world as it is, only its statistics, but you can prove in some regimes those statistics become/are compatible with Kolmogorov probability and thus in that regime you're fine to think about objects with comprehensible properties.

It's like "The world is fundamentally ineffable, but you can track when it becomes effable". Perhaps there is nothing more than this (combined with ones favorite view on probabilities) as you say.

 

[Lord Jestocost]

Just choose one of the offered answers to a couple of questions on the graph.

As an experimental physicist, I would say - using Adan Cabello's words: A map of madness

 

[martinbn]

I am stuck on the first question.

The ontology is simple: all that exists is the wavefunction.

To me this makes absolutely no sense. The verb exist cannot be applied to the wavefunction.

 

[DarMM]

To me this makes absolutely no sense. The verb exist cannot be applied to the wavefunction.

I think it's just shorthand for the wavefunction represents an actual "field" or "fluid" rather than representing the observer's knowledge. Like how $\textbf{B}(x)$ is meant to represent the Magnetic field in Maxwellian electromagnetism.

 

[martinbn]

I think it's just shorthand for the wavefunction represents an actual "field" or "fluid" rather than representing the observer's knowledge. Like how $\textbf{B}(x)$ is meant to represent the Magnetic field in Maxwellian electromagnetism.

But if you have more than one particle, this doesn't work.

 

[julcab12]

I am stuck on the first question.
To me this makes absolutely no sense. The verb exist cannot be applied to the wavefunction.

I'm(They) referring to the wavefunction treated as a classical field (i.e. a field that actually exists, despite being complex valued and of indefinite dimension) which obeys causal, local, relativistic laws and so never collapses. In the purest form, the universal wavefunction encodes a surfeit of splitting timelines, one for each possible history. No filler just a straight on "take something at face value" but that is a natural direction given of what we have. Whether it is true, intuitive or not. It's an honest approach. But for me, I'm a bit squeamish. It would be funny if interpreting it like Einstien ring or any extended images.

 

[DarMM]

But if you have more than one particle, this doesn't work.

How so? Are you referring to the wave function being a function on configuration space?

 

[George Jones]

I am stuck on the first question.

I, too, am stuck on the first question, but possibly for a different reason.

My answer to the first question is "a) and b)."

 

[Mentz114]

If you follow along the path of clean QM formalism. I would say you would likely end up with Many World on face value. Simply because it is simple. The ontology is simple: all that exists is the wavefunction. The dynamics are simple: the wavefunction obeys unitary evolution according to the Schrodinger equation. Measurement problem is simple: decoherence selects a basis, and the relative state gives you definiteness; both of these are natural quantum processes and don't have to be added in. The derivation of the Born rule for probability is -- well maybe not simple -- but it is elegant: proceeding in analogy to classical Savage decision theory. It is an entirely local theory. It generalizes straightforwardly to quantum field theories... Ok I get it. But my personal bias led me to Relational bec of my GR mentality-- Mirages and Gravitational Effect produces illusions.

Probability (nor amplitude) is not stuff. How can the universe be made of something that is not energy/matter or anything detectable ?

 

[julcab12]

Probability (nor amplitude) is not stuff. How can the universe be made of something that is not energy/matter or anything detectable ?

Please read post 46.

 

[PeterDonis]

Probability (nor amplitude) is not stuff.

But not all QM interpretations interpret the wave function as a probability amplitude. The MWI, for example, interprets it as describing an actual reality in which every branch exists; there are no probabilities. (Which is why one of the main issues with the MWI is how to make sense of the fact that, when we are actually using the wave function to do practical calculations, we do interpret it as giving probability amplitudes, and that practical method works.)

 

[PeterDonis]

My answer to the first question is "a) and b)."

So is mine. And if I just go ahead and follow both answer trees, I end up with the statistical ensemble interpretation and the Nelson stochastic interpretation. So now I have the problem of interpreting what this means: does it mean I have some probability of using one or the other of these interpretations, or does it mean I'm in a superposition of using both?

 

[Mentz114]

Please read post 46.

Treat the wave function as a classical field ? I don't think that is what the MWI proponents are saying.
Apologies if I seemed to be critical of you personally. MWI brings on the red mist !

Believing that QM is a fundamental theory and that probability is stuff is wildly optimistic.

 

[StevieTNZ]

An example would be a dust particle. A few stray photons from the CBMR is enough to give the dust particle an exact position. And since it's bombarded all the time by such the wave-packet will not spread. I consider the photons an observer.

Thanks
Bill

all that happens is entanglement. No 'wave function' collapse occurs. Otherwise the measurement problem doesn't exist, as I've stated many times before if you go with your reasoning.

 

[Mentz114]

But not all QM interpretations interpret the wave function as a probability amplitude. The MWI, for example, interprets it as describing an actual reality in which every branch exists; there are no probabilities. (Which is why one of the main issues with the MWI is how to make sense of the fact that, when we are actually using the wave function to do practical calculations, we do interpret it as giving probability amplitudes, and that practical method works.)

The bit I've bolded seems to contradict the MWI axiom : "the wave function is all that there is."
The existence of branches is plucked from nothing and amounts to new physics.

 

[julcab12]

Treat the wave function as a classical field ? I don't think that is what the MWI proponents are saying.
Apologies if I seemed to be critical of you personally. MWI brings on the red mist !

Believing that QM is a fundamental theory and that probability is stuff is wildly optimistic.

I don't know about believing. But they interpret exactly like that(Originally-- Some versions). Well. I'm not saying I adhere to it. To be honest, I'm still in a superposition of a) and b) of the first question.

 

[PeterDonis]

The bit I've bolded seems to contradict the MWI axiom : "the wave function is all that there is."

No, it doesn't.

The existence of branches is plucked from nothing

No, it isn't; the branches are right there in the wave function. Nothing needs to be added.

If you disagree, then please show me explicitly, with math, where branches get "plucked from nothing".

 

[martinbn]

I, too, am stuck on the first question, but possibly for a different reason.

My answer to the first question is "a) and b)."

So is mine.

 

[martinbn]

How so? Are you referring to the wave function being a function on configuration space?

Yes.

 

[MathematicalPhysicist]

Just sum over all possible interpretations of QM, if what you get is nonsense then as you know - "no one understands QM".

 

[microsansfil]

I don't think that's saying there's no external world or that things aren't there when not observed, it's just the standard "measurement creates measurement outcomes" you have in Copenhagen views like Haag's

Qbism is about the interpretation of QM and, therefore, examines the epistemic foundation of quantum mechanics, placing the subject at the heart of the construction of our knowledge.

https://www.quantamagazine.org/quantum-bayesianism-explained-by-its-founder-20150604/

Schrödinger thought that the Greeks had a kind of hold over us — they saw that the only way to make progress in thinking about the world was to talk about it without the “knowing subject” in it. QBism goes against that strain by saying that quantum mechanics is not about how the world is without us;

QBism treats the wave function as a description of a single observer’s subjective knowledge.

/Patrick

 

[DarMM]

But if you have more than one particle, this doesn't work.

How so? Are you referring to the wave function being a function on configuration space?

Yes.

They simply think that configuration space is what is real as such, or more that reality is some kind of "object" that is directly described by the wavefunction. They would say that space as we normally see it is just something effective that arises through decoherence.

 

[Mentz114]

No, it doesn't.

I agree there a no contradiction but a restatement both of which are impossible.

No, it isn't; the branches are right there in the wave function. Nothing needs to be added.

If you disagree, then please show me explicitly, with math, where branches get "plucked from nothing".

I think the proponents should produce the equations. It is not possible to prove existence (by maths) except for mathematical objects, so that can't be done.

(PS: I end up in the same preferences as you did. But things don't look good for stochastic QT)

 

[martinbn]

They simply think that configuration space is what is real as such, or more that reality is some kind of "object" that is directly described by the wavefunction. They would say that space as we normally see it is just something effective that arises through decoherence.

So we are back to the beginning. To me it seems meaningless to say that configuration space is real.

 

[DarMM]

So we are back to the beginning. To me it seems meaningless to say that configuration space is real.

Again it's just a shorthand, sometimes expanding this stuff is tedious and physicists will just say "the Riemann curvature is strong near a black hole" rather than "that element of physical reality whose consequences upon the trajectories of objects close to the black hole seems to be near isomorphic to the effect of large Riemann curvature upon nearby geodesics in a Lorentzian manifold".

Similarly here Many Worlds people would just mean a physically real system that is directly described by configuration space.

In simplest terms in a state like:
$$\frac{1}{\sqrt{2}}\left(|\uparrow\downarrow\rangle + |\downarrow\uparrow\rangle\right)$$
MWI people would say that there are elements of physical reality directly corresponding to and modeled by both terms in the sum.

 

[DarMM]

So we are back to the beginning. To me it seems meaningless to say that configuration space is real.

If you want an even simpler analogy from Kolmogorov probability, when we write down for a dice:
$$p(1) = p(2) = \cdots = p(6) = \frac{1}{6}$$
Some would say (analogue to $\psi$-epistemist) that these numbers just reflect one's knowledge, where as Many Worlders would say they reflect something out there in the world like the values $h \in \mathbb{Q}$ used in discussing height reflect something out there in the world.

 

[martinbn]

Similarly here Many Worlds people would just mean a physically real system that is directly described by configuration space.

That is the problem for me. The original statement was that the wavefunctions is all there is, the only ontological object. Now you say that is just a short hand for - there is a physically real system that is described by... So which one is it? Is the wavefunction the only real thing or is there a physically real system described by it?

 

[DarMM]

That is the problem for me. The original statement was that the wavefunctions is all there is, the only ontological object. Now you say that is just a short hand for - there is a physically real system that is described by... So which one is it? Is the wavefunction the only real thing or is there a physically real system described by it?

Will it's not intended as an "or" choice. I'm saying the "Wavefunction is physically real" is a shorthand for the more explicit expression, it's not an alternative to it, i.e. "The wavefunction is physically real" is a shorthand for "There is a physical object that acts exactly like the wavefunction describes". This is no different from saying "$\textbf{B}(x)$ is real/ontological" in electromagnetism, it's just a shorthand for "The magnetic field exists and behaves as described by the vector field $\textbf{B}(x)$"

Post #66 states things about as succinctly as I can. Take that post, what isn't clear?

 

[bhobba]

Where are its observation records?

As usual you hit the crux of the matter. I do not believe an observation needs to leave a record. If you have some apparatus that measures say position and there is no record kept I think its position has still been measured. In the case of the dust particle it has a position to a high degree of accuracy, so I think it still has been measured. What I believe an observation does is put the system in a state that if you were to look at it, record it, etc then you would get a sensible answer. Even in classical physics if nobody observes the moon (in the usual sense of observation) then there is no record so you can say the moon is not there if you do not look at it. What makes it silly in a classical sense is we know the moon has the same properties if you look at it or not - that's one of the assumptions of classical physics. So I would say observation by the environment on a system means we know it properties to a high degree of accuracy regardless of if it is actually recorded or not. I suppose a better way of expressing it is interaction with the environment makes it behave classically to very good accuracy.

Thanks
Bill

 

[bhobba]

To me this makes absolutely no sense. The verb exist cannot be applied to the wavefunction.

One can view the wave-function like probabilities - simply as an aid to calculation of results observations that are very real. There is an issue Dr Neumaier has correctly bought up with my view of what an observation is. You may wish to think about that one yourself rather than be swayed by what I think.

Thanks
Bill