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Why is there no 'classical' interpretation of movements in quantum mechanics?

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Xilor
#1
Feb25-12, 06:40 AM
P: 90
There are tons of interpretations of quantum mechanics, but I'm unaware of any that are 'classical' as in being local, having realism and determinism.
There is Bells famous work proving that that can't be true for certain aspects of quantum mechanics, but why aren't there any classical interpretation which apply to the movements of particles and which call entanglement just a completely different phenomena?

Using a real wave and by using chaos it seems to me that all the movement issues such as the double-slit experiment but even the quantum erasure experiment or the delayed choice experiment can be described at least conceptually just fine, some of the details would be strange, but far less so than breaking realism is to me. What am I missing here?
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IttyBittyBit
#2
Feb25-12, 06:53 AM
P: 159
Did you look at: http://arxiv.org/abs/0908.3408 ?
Xilor
#3
Feb25-12, 08:01 AM
P: 90
Unfortunately that goes quite a bit over my head, but from reading through it I couldn't really find any experimental evidence besides Bell work that shows that quantum mechanics can't be solved classically, any arguments seemed to be based on that and not for example particle movements.

juanrga
#4
Feb25-12, 12:18 PM
P: 476
Why is there no 'classical' interpretation of movements in quantum mechanics?

Quote Quote by Xilor View Post
There are tons of interpretations of quantum mechanics, but I'm unaware of any that are 'classical' as in being local, having realism and determinism.
There is Bells famous work proving that that can't be true for certain aspects of quantum mechanics, but why aren't there any classical interpretation which apply to the movements of particles and which call entanglement just a completely different phenomena?

Using a real wave and by using chaos it seems to me that all the movement issues such as the double-slit experiment but even the quantum erasure experiment or the delayed choice experiment can be described at least conceptually just fine, some of the details would be strange, but far less so than breaking realism is to me. What am I missing here?
There exists QM (which is taught at ordinary textbooks) and then tons of misinterpretations of QM (e.g., many-worlds).

It is not true that by using «a real wave and by using chaos» you can describe quantum motion. 5 is not 2+1.
Xilor
#5
Feb25-12, 01:13 PM
P: 90
Quote Quote by juanrga View Post
There exists QM (which is taught at ordinary textbooks) and then tons of misinterpretations of QM (e.g., many-worlds).

It is not true that by using «a real wave and by using chaos» you can describe quantum motion. 5 is not 2+1.
Misinterpretations? I always thought they were quite well supported.

Anyway, where does it go wrong using real waves? Which parts of it don't work out?
juanrga
#6
Feb25-12, 01:24 PM
P: 476
Quote Quote by Xilor View Post
Misinterpretations? I always thought they were quite well supported.
Many-worlds and similar stuff are nonsense:

http://www.mth.kcl.ac.uk/~streater/lostcauses.html#XII

http://www.mat.univie.ac.at/~neum/ph...ics/manyworlds

and so on.

Quote Quote by Xilor View Post
Anyway, where does it go wrong using real waves? Which parts of it don't work out?
There are not «real waves» in QM. The state of a pure state in quantum mechanics is described by a ket [itex]\left| \Psi \right\rangle[/itex], which can have associated a complex phase.
StevieTNZ
#7
Feb25-12, 01:31 PM
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The Copenhagen interpretation can be ruled out by probing a macroscopic superposition state (again in reference to my love for Ghirardi's thought experiment).
Xilor
#8
Feb25-12, 03:46 PM
P: 90
Quote Quote by juanrga View Post
So which interpretation is the right one according to you?

There are not «real waves» in QM. The state of a pure state in quantum mechanics is described by a ket [itex]\left| \Psi \right\rangle[/itex], which can have associated a complex phase.
That unfortunately doesn't really aid in helping to understand why it is that real waves don't work out. Fine, they aren't used in quantum mechanics, but why not? At least conceptually it seems very possible to me to use a real wave like a guiding wave of a particle with a defined position. Why doesn't this work out?
Mr_Physicist
#9
Feb25-12, 04:36 PM
P: 19
Any interpretation of quantum mechanics must be consistent with experiment. A model or interpretation that only works if you ignore or exclude certain phenomena is not a model or interpretation worth pursuing.
Xilor
#10
Feb25-12, 04:55 PM
P: 90
Quote Quote by Mr_Physicist View Post
Any interpretation of quantum mechanics must be consistent with experiment. A model or interpretation that only works if you ignore or exclude certain phenomena is not a model or interpretation worth pursuing.
Well Bells argument only works on entangled particles, that seems to be something clearly different than the movement of particles. If a theory like that could predict all particle movements but leaves entanglement for different theories, why not use it? I understand it wouldn't be a perfect solution, but I don't really see why it isn't even mentioned anywhere as a reasonably valid idea.
Maui
#11
Feb25-12, 05:33 PM
P: 724
Why is there no 'classical' interpretation of movements in quantum mechanics?



Is there classical motion in quantum mechanics?
Xilor
#12
Feb25-12, 06:20 PM
P: 90
There's no motion in straight lines. But classically held notions about realism determinism and locality seem to be be preservable, at least with my limited amount of knowledge. And I'm wondering either why it's impossible like that, or at least why no one really seems to think that models preserving all 3 of those are viable.
juanrga
#13
Feb27-12, 01:45 PM
P: 476
Quote Quote by Xilor View Post
So which interpretation is the right one according to you?


That unfortunately doesn't really aid in helping to understand why it is that real waves don't work out. Fine, they aren't used in quantum mechanics, but why not? At least conceptually it seems very possible to me to use a real wave like a guiding wave of a particle with a defined position. Why doesn't this work out?
I think already said that QM is explained in textbooks. The two-volume set by Cohen Tannoudji gives a rather good treatment.

«Real waves» are not used in QM by the same reason that kinetic energies as 1/5 mv2 are not used, because world is not made in that way. «At least conceptually» is not a valid scientific argument. Sure that kinetic energy (mv2) is 'conceptually' simpler, but just does not work.

It is completely incorrect to use «a real wave like a guiding wave of a particle with a defined position», because even if we were to admit that particle has one always (it does not as QM explains), if we were to ignore mixed states, and if were to confound a pure quantum state with a real wave, this whole mess does not describe particle correlations among other stuff.
DrChinese
#14
Feb27-12, 02:07 PM
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Quote Quote by Xilor View Post
There's no motion in straight lines. But classically held notions about realism determinism and locality seem to be be preservable, at least with my limited amount of knowledge. And I'm wondering either why it's impossible like that, or at least why no one really seems to think that models preserving all 3 of those are viable.
Why would someone prepare a model which is less useful that the one currently in use?

Also, not sure if you use the word "real" in the same context as juanrga does. He means real as opposed to complex. You may real as opposed to mathematical constructs. Or do you mean real as in realistic (which is yet again different) ?
Naty1
#15
Feb27-12, 02:34 PM
P: 5,632
two basic ideas:

You can argue that there is no 'classical description' of QM in part because they are 'different' theories. The former covers generally large scale apparently, continuous, observations, the other discrete, quantized,discontinuous behavior at small scales.

Secondly, we have different mathematical models....we haven't been completely smart enough to unify all our mathematics yet.....so we have [classical] theory for gravity (GR) on one hand and quanum theory for the standard model of particle physics. [Nothing is able to tie those together yet, but 'quantum gravity' is one effort to do so.]

wiki introduction on quantum mechanics:

http://en.wikipedia.org/wiki/Quantum_mechanics
Quantum mechanics, also known as quantum physics or quantum theory, is a branch of physics dealing with physical phenomena where the action is of the order of Planck constant; quantum mechanics departs from classical mechanics primarily at the atomic and subatomic scales, the so-called quantum realm. It provides a mathematical description of much of the dual particle-like and wave-like behavior and interactions of energy and matter. In advanced topics of quantum mechanics, some of these behaviors are macroscopic and only emerge at very low or very high energies or temperatures. The name "quantum mechanics" derives from the observation that some physical quantities can change only by discrete amounts, or quanta in Latin. For example, the angular momentum of an electron bound to an atom or molecule is quantized.[1] In the context of quantum mechanics, the wave–particle duality of energy and matter and the uncertainty principle provide a unified view of the behavior of photons, electrons and other atomic-scale objects.
I know some will disagree with parts of this description, but a fundamental constraint of quantum mechanics does not meet classical notions, not classical mathematics:

In the context of quantum mechanics, the wave–particle duality of energy and matter and the uncertainty principle provide a unified view of the behavior of photons, electrons and other atomic-scale objects.[/
[There is not real 'wave-particle duality' within the context of QM; it is what it is....but 'classically' we use such descriptions to convey the analogy.]

Heisenberg uncertainty: I would argue that IS a 'classical' description....it bridges a gap between the commutativity and non-commutativy of classical and quantum mathematics...
It may make little sense in 'classical' reasoning [that you can't measure two particular observables simultaneously to whatever degree of accuracy your instruments will allow] because we don't such restrictions on large scales....we can make such measurements of,say,planets.

Xilor: To some extent you are reasoning from incorrect assumptions and reaching dubious conclusions...we all do that, so take it as a criticism if you must, but after you need do more homework you won't start from such perspectives...example:
Since no one else has taken issue, let me:

But classically held notions about realism determinism and locality seem to be be preservable, at least with my limited amount of knowledge.
...In physics, the principle of locality states that an object is influenced directly only by its immediate surroundings. Experiments have shown that quantum mechanically entangled particles must violate either the principle of locality or the form of philosophical realism known as counterfactual definiteness.....
http://en.wikipedia.org/wiki/Principle_of_locality

we don't describe entanglement classically because nobody knows how!

One simple way to start getting broader perspectives : read the Wikipedia articles on each of those three... realism, determinism,locality....pick out a few things you don't get and question them in the forums...this stuff is subtle and we all gain from reading others descriptions...that's one reason I'm here.
Xilor
#16
Feb27-12, 07:36 PM
P: 90
Quote Quote by DrChinese View Post
Why would someone prepare a model which is less useful that the one currently in use?
How would it be less useful? Is usefulness determined by how unified things are? I don't see a problem with placing all particle interactions and inner particle workings in different models. Perhaps finding out what is really happening is less important than finding out how to do predictions, but surely if there's only a small chance that that is what is really happening and the same predictions are made are the same, why isn't the thought at least worthy of exploration?
I would be convinced that it would be worthy if it wasn't already disproven somehow. What however would be disproving is what I'm mainly asking about, as I do not know.


Also, not sure if you use the word "real" in the same context as juanrga does. He means real as opposed to complex. You may real as opposed to mathematical constructs. Or do you mean real as in realistic (which is yet again different) ?
I meant with the wave being real as in opposed to mathematical constructs. For example it seems to me that in Bohmian mechanics (correct me if I'm wrong), there is a guiding wave which is more like some sort of nonlocal calculating device taking all particles in the universe into account. Replace that calculating device with something local and realistic which is actually out there, flying around, propagating due to it's own shape, interacting with the particle it is guiding and other particles (observers which eliminate the wave, mirrors, and so on), and you pretty much have the real wave I mean.
Thanks for clearing that confusion up, I was already wondering why he would respond about kets and complex phases which didn't seem to have a lot to do with what I was trying to ask.

Quote Quote by Naty1 View Post
two basic ideas:

You can argue that there is no 'classical description' of QM in part because they are 'different' theories. The former covers generally large scale apparently, continuous, observations, the other discrete, quantized,discontinuous behavior at small scales.

Secondly, we have different mathematical models....we haven't been completely smart enough to unify all our mathematics yet.....so we have [classical] theory for gravity (GR) on one hand and quanum theory for the standard model of particle physics. [Nothing is able to tie those together yet, but 'quantum gravity' is one effort to do so.]

wiki introduction on quantum mechanics:

http://en.wikipedia.org/wiki/Quantum_mechanics


I know some will disagree with parts of this description, but a fundamental constraint of quantum mechanics does not meet classical notions, not classical mathematics:
Well I didn't really mean it should be called classical mechanics, I meant an interpretation of quantum mechanics which is split into two parts. One about the movements and positions or particles and interactions which would be local, realistic and deterministic. And one about inner particle variables like spin which would also handle entanglement which would not be local, but realistic and possibly deterministic.

Xilor: To some extent you are reasoning from incorrect assumptions and reaching dubious conclusions...we all do that, so take it as a criticism if you must, but after you need do more homework you won't start from such perspectives...
That's why I'm here, to find out where my thinking is going wrong.

example:
Since no one else has taken issue, let me:





http://en.wikipedia.org/wiki/Principle_of_locality

we don't describe entanglement classically because nobody knows how!

One simple way to start getting broader perspectives : read the Wikipedia articles on each of those three... realism, determinism,locality....pick out a few things you don't get and question them in the forums...this stuff is subtle and we all gain from reading others descriptions...that's one reason I'm here.
Well I'm aware locality must be broken in entanglement, I'm wondering why this combinations of realism, determinism and locality seems to be excluded by everyone for particle movements as well as entanglement. I just don't understand why a rule found for quantum entanglement must be true for all of quantum mechanics, the terms both have the word 'quantum' in them but that doesn't really seem like a reason strong enough to force them together in that way. Maybe I'm still too much in a classical mindset, but locality and realism especially still give me the: "it must be like that!" vibe, and while locality is broken in entanglement it would be great if it could be preserved in particle movements in my mind. Locality breaches through entanglement might still make some 'sense' (physics isn't about sense of course, but it helps) but I just can't picture particles being nonlocally influenced by all particles in the universe.

The articles which I had red a few times before didn't really spawn any questions, these were luckily not the pages containing maths that probably require a few years of study.

Edit: In hindsight, I've always wondered how close true locality would be. Is that only particles less than a Planck length away? Or should particles even overlap?
juanrga
#17
Feb28-12, 04:58 AM
P: 476
Quote Quote by DrChinese View Post
Also, not sure if you use the word "real" in the same context as juanrga does. He means real as opposed to complex. You may real as opposed to mathematical constructs. Or do you mean real as in realistic (which is yet again different) ?
Excellent point! Yes, I had taken to him to mean "real" in the sense of complex numbers. But he means something different, thanks by your correction!
juanrga
#18
Feb28-12, 05:15 AM
P: 476
Quote Quote by Xilor View Post
How would it be less useful? Is usefulness determined by how unified things are? I don't see a problem with placing all particle interactions and inner particle workings in different models. Perhaps finding out what is really happening is less important than finding out how to do predictions, but surely if there's only a small chance that that is what is really happening and the same predictions are made are the same, why isn't the thought at least worthy of exploration?
I would be convinced that it would be worthy if it wasn't already disproven somehow. What however would be disproving is what I'm mainly asking about, as I do not know.
It is less useful on that (i) explains less than current models and (ii) cannot be used to do predictions.

Quote Quote by Xilor View Post
I meant with the wave being real as in opposed to mathematical constructs. For example it seems to me that in Bohmian mechanics (correct me if I'm wrong), there is a guiding wave which is more like some sort of nonlocal calculating device taking all particles in the universe into account. Replace that calculating device with something local and realistic which is actually out there, flying around, propagating due to it's own shape, interacting with the particle it is guiding and other particles (observers which eliminate the wave, mirrors, and so on), and you pretty much have the real wave I mean.
Thanks for clearing that confusion up, I was already wondering why he would respond about kets and complex phases which didn't seem to have a lot to do with what I was trying to ask.
Although you mean real in the sense of non-mathematical, the remarks given before about quantum states still apply. It is also evident that you do not understand what is math and what is real. Your claim that a wave is something REAL, when is a mathematical construct with a limited validity, says it all.


Quote Quote by Xilor View Post
Well I didn't really mean it should be called classical mechanics, I meant an interpretation of quantum mechanics which is split into two parts. One about the movements and positions or particles and interactions which would be local, realistic and deterministic. And one about inner particle variables like spin which would also handle entanglement which would not be local, but realistic and possibly deterministic.
Another problem of your philosophical approach is that the movements and positions of particles and their interactions are non-local, realistic, and non-deterministic.


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