4 ms·

Chaos: The Problem with Quantum Mechanics

70 points by nsoonhui 4y ago

deleted 4y ago
[deleted]
asfarley 4y ago
Very interesting, I had no idea there was a conflict between qm and chaotic dynamics. Whenever “weirdness due to wave function collapse” comes up, I wonder: what is the multi-universe equivalent of this discussion?
- bil7 4y ago
  various unfalsifiables.
- catchclose8919 4y ago
  > what is the multi-universe equivalent of this discussion Probably it's a smeared out infinity of quasy-equal probability arising... and the people that see multi-universe as a "real thing" in that multiple classical universes actually exist get queasy by this because they intuitively feels this is off as an inifinity of infinity etc. of universes would violate the conservation of some meta-universal thinggy. ...but if you just take the Everett / many-worlds interpretation that many quantum phisicists say they subscribe too as just meaning "the wave function is the only real thing" and "we're just talking of multiple classical universes" as an "interpretation" because classical universes are the only thing that human intuition can grasp, so we'll talk about this to at least get some semblance of useful intution, as the real thing is intuitively incomprehensible and you can only "shut up and do the math" with regards to it :P Humans are really bad at accepting the limitations of their own minds so they try to come up with all sorts of "interpretations" and "understandings" to paper over it and the fret out about made-up problems with these made up interpretations not agreeing with each-other. (Though tbh, I'm not even sure that intuitively working with a non-real-probabilities universe is beyond our intuition... even examples from stuff like human legal practice and other cases where we work with incomplete information allow useful ways to grok this stuff... there's also extra-boolean logical systems like the pentavalent buddhist logic that could be generalized to include negative interactions and quantitative represantations... dunno, maybe we're just very early in understanding the universe... closer to cockroaches than the quasi-gods we imagine ourselves :P ...probably we should just be humble and focus on the math when intuition fails but not give up on trying to expland intuition too...) Edit+: P.S. And it's probably obvious that I dislike superdeterminists because of their conceited lack of humility... but I actually think superdeterminism is a very useful stance, because if there are some/many extra hidden variables, then we need to assume their existence if we are ever to devise experiments to actually get to them... otherwise we're stuck. So maybe the superdeterministic stance is the best for moving experimental particle phisics further faster, the Everettian worldview could get too many people stuch in weird philosophical traps and dead ends. Kind of like Nietzsche said that christianity helped modern science arise and grow (with it's focus of clearly separating good vs. evil, then by extension true vs. false theories etc. rising in the end to the scientific methodology)... superdeterminism could probably helps us make the next baby-steps forward faster :)
Koshkin 4y ago
See also https://news.ycombinator.com/item?id=31544372 https://news.ycombinator.com/item?id=31544372
foxes 4y ago
Yes, clearly there is an issue with the Schrodinger equation. I think it is very obvious that basic quantum mechanics (with the Shcrodinger equation) does not apply to the entire universe. It would be better to talk in terms of quantum field theory, and maybe the scattering matrix there is unitary, but already know that is in contradiction with general relativity. Basic quantum mechanics is only a very rudimentary model. Basic quantum mechanics is only a local theory, and there is zero reason to apply it at the scale of the universe. Not to mention, if there is such a thing as a universal wavefunction, it is probably extremely complicated and contains a lot of information. Looking at a very small slice of it (a planet) may indeed look very complicated. While the entire system might be unitary, that doesnt mean every component is unitary.
- deleted 4y ago
  [deleted]
spacemanmatt 4y ago
I've really been enjoying the coverage of QM's challenges from PBS SpaceTime as well as Sabine Hossenfelder's videos.
dhimes 4y ago
QM is a linear theory (its equations are linear). Chaos arises from non-linear interactions. Until we have a non-linear version of of the Shrodinger/Dirace/Klein-Gordon/Whatever-the-cool-kids-are-using-these-days equations, we're going to have a problem reconciling them.
- d_tr 4y ago
  Newton's second law is also linear but you can study chaotic systems just fine. You can study coupled weird oscillators in QM too. You just take the classical problem and derive the Hamiltonian operator. I do not understand what the problem is here (I mean with the SE being linear) and I saw this repeated a couple times in the other thread too.
  - dhimes 4y ago
    The linearity of NII depends on the linearity of F and a. QM has certain postulates that have to be overcome first, such as any state can be written as a linear combination of eigenstates, etc. You can see them here: http://vergil.chemistry.gatech.edu/notes/quantrev/node20.html http://vergil.chemistry.gatech.edu/notes/quantrev/node20.htm...
- catchclose8919 4y ago
  ...or you just take the wave function as the real-reality, and in this reality a "chaotic system" is one with even macroscopic position probabilities "smeared out" too uniformly have any one be "classically-real". If classic reality is the illusion, and our intuition is fundamentally limited and incapable of grasping the actual reality, then even many-worlds is a bit of clutch... we imagine an infinity of "parallel" classical universes simply because it's the best we can do: one wave function universe where all the variants are "real" at the same time only that being real is a complex-numbered-probability so some are more real than other with different orientations and magnituded too. ...we could just give up hoping that our ape-brains can fully "grasp" reality, and just focus on getting the math to work: if some math systems make chaos and qm both work, then move on with that regardless of our primitive intuitions and preconceptions/superstitions of that the workld ought to be!

70 points by nsoonhui 4y ago

deleted 4y ago

[deleted]

Very interesting, I had no idea there was a conflict between qm and chaotic dynamics. Whenever “weirdness due to wave function collapse” comes up, I wonder: what is the multi-universe equivalent of this discussion?

bil7 4y ago
various unfalsifiables.
catchclose8919 4y ago
> what is the multi-universe equivalent of this discussion Probably it's a smeared out infinity of quasy-equal probability arising... and the people that see multi-universe as a "real thing" in that multiple classical universes actually exist get queasy by this because they intuitively feels this is off as an inifinity of infinity etc. of universes would violate the conservation of some meta-universal thinggy. ...but if you just take the Everett / many-worlds interpretation that many quantum phisicists say they subscribe too as just meaning "the wave function is the only real thing" and "we're just talking of multiple classical universes" as an "interpretation" because classical universes are the only thing that human intuition can grasp, so we'll talk about this to at least get some semblance of useful intution, as the real thing is intuitively incomprehensible and you can only "shut up and do the math" with regards to it :P Humans are really bad at accepting the limitations of their own minds so they try to come up with all sorts of "interpretations" and "understandings" to paper over it and the fret out about made-up problems with these made up interpretations not agreeing with each-other. (Though tbh, I'm not even sure that intuitively working with a non-real-probabilities universe is beyond our intuition... even examples from stuff like human legal practice and other cases where we work with incomplete information allow useful ways to grok this stuff... there's also extra-boolean logical systems like the pentavalent buddhist logic that could be generalized to include negative interactions and quantitative represantations... dunno, maybe we're just very early in understanding the universe... closer to cockroaches than the quasi-gods we imagine ourselves :P ...probably we should just be humble and focus on the math when intuition fails but not give up on trying to expland intuition too...) Edit+: P.S. And it's probably obvious that I dislike superdeterminists because of their conceited lack of humility... but I actually think superdeterminism is a very useful stance, because if there are some/many extra hidden variables, then we need to assume their existence if we are ever to devise experiments to actually get to them... otherwise we're stuck. So maybe the superdeterministic stance is the best for moving experimental particle phisics further faster, the Everettian worldview could get too many people stuch in weird philosophical traps and dead ends. Kind of like Nietzsche said that christianity helped modern science arise and grow (with it's focus of clearly separating good vs. evil, then by extension true vs. false theories etc. rising in the end to the scientific methodology)... superdeterminism could probably helps us make the next baby-steps forward faster :)

Koshkin 4y ago

See also https://news.ycombinator.com/item?id=31544372 https://news.ycombinator.com/item?id=31544372

foxes 4y ago

Yes, clearly there is an issue with the Schrodinger equation. I think it is very obvious that basic quantum mechanics (with the Shcrodinger equation) does not apply to the entire universe. It would be better to talk in terms of quantum field theory, and maybe the scattering matrix there is unitary, but already know that is in contradiction with general relativity. Basic quantum mechanics is only a very rudimentary model. Basic quantum mechanics is only a local theory, and there is zero reason to apply it at the scale of the universe. Not to mention, if there is such a thing as a universal wavefunction, it is probably extremely complicated and contains a lot of information. Looking at a very small slice of it (a planet) may indeed look very complicated. While the entire system might be unitary, that doesnt mean every component is unitary.

deleted 4y ago
[deleted]

spacemanmatt 4y ago

I've really been enjoying the coverage of QM's challenges from PBS SpaceTime as well as Sabine Hossenfelder's videos.

dhimes 4y ago

QM is a linear theory (its equations are linear). Chaos arises from non-linear interactions. Until we have a non-linear version of of the Shrodinger/Dirace/Klein-Gordon/Whatever-the-cool-kids-are-using-these-days equations, we're going to have a problem reconciling them.

d_tr 4y ago
Newton's second law is also linear but you can study chaotic systems just fine. You can study coupled weird oscillators in QM too. You just take the classical problem and derive the Hamiltonian operator. I do not understand what the problem is here (I mean with the SE being linear) and I saw this repeated a couple times in the other thread too.
- dhimes 4y ago
  The linearity of NII depends on the linearity of F and a. QM has certain postulates that have to be overcome first, such as any state can be written as a linear combination of eigenstates, etc. You can see them here: http://vergil.chemistry.gatech.edu/notes/quantrev/node20.html http://vergil.chemistry.gatech.edu/notes/quantrev/node20.htm...
catchclose8919 4y ago
...or you just take the wave function as the real-reality, and in this reality a "chaotic system" is one with even macroscopic position probabilities "smeared out" too uniformly have any one be "classically-real". If classic reality is the illusion, and our intuition is fundamentally limited and incapable of grasping the actual reality, then even many-worlds is a bit of clutch... we imagine an infinity of "parallel" classical universes simply because it's the best we can do: one wave function universe where all the variants are "real" at the same time only that being real is a complex-numbered-probability so some are more real than other with different orientations and magnituded too. ...we could just give up hoping that our ape-brains can fully "grasp" reality, and just focus on getting the math to work: if some math systems make chaos and qm both work, then move on with that regardless of our primitive intuitions and preconceptions/superstitions of that the workld ought to be!