Gerard 't Hooft on the incompleteness of quantum mechanics

[martinbn]

That's also true for determinism. The difference between determinism and superdeterminism is the following: Determinism postulates deterministic equations of motion, while superdeterminisim, in addition, postulates also a law for the initial conditions. In QM, the idea of superdeterminism (as opposed to mere determinism as in Bohmian mechanics) is to get rid of the need of nonlocal instantaneous action at a distance, by postulating a special law for initial conditions that can explain correlations violating Bell inequalities.

And those initial conditions have to contain nonlocal correlations, which are worse than what they try to explain!

 

[pines-demon]

Here's an analogy. Determinism would say that the outcome of every soccer match is predetermined. Or, at least, that the outcome follows deterministic laws. Two soccer matches in two countries, however, would be independent systems.

Superdeterminism additionally produces otherwise inexplicable correlations between soccer matches. For example, Glasgow Celtic's results in Scotland might be exactly correlated with Bayern Munich's in Germany.

This is the point that the superdeterminists try to sweep under the carpet. That the initial conditions conspire to produce otherwise inexplicable but experimentally repeatable correlations between seemingly independent events. And, not only that, but these correlations are precisely those that would convince some of us that QM is an appropriate theory of nature. Whereas, as Scott Aaronson points out, the superdeterminists believe that nature is leading us astray by making it look like QM is correct. And, equally critically, that these otherwise inexplicable correlations extend to nothing except those experiments that support QM.

Exactly. Superdeterminism is not much about determinism but about avoiding statistical independence. Under superdeterminism we are unable to REDUCE the correlations between systems no matter what we do.

 

[gen x]

You do not have interest in engaging in any other points I made? Only in showing me this YouTube video?

Yes I read your posts.
Do you think nature at all scales must be only random or only deterministic or it can be random in micro-world and deterministic in macro-world? If latter, where is border where random become deterministic?


I don't understand concept of randomness( absence of cause-effect), if nature is random why projectile with angle alpha and initial velocity v1, always land on same spot?

 

[PeterDonis]

randomness( absence of cause-effect)

These are not the same. An event that is random can still cause something else to happen.

 

[gen x]

These are not the same. An event that is random can still cause something else to happen.

But electron around nucleus don't follow any law, any pattern, nothing cause it that he behave like it is.. that is what randomness say.

 

[jeffn1]

But electron around nucleus don't follow any law, any pattern, nothing cause it that he behave like it is.. that is what randomness say.

Doesn't the Schrodinger equation apply to the electron like other quantum particles? We can only detect a location when when it is measured (but with the familiar tradeoff of location/momentum). So, we currently have "probabilities" (that, as I understand it, correspond to the shapes of orbitals we see in chemistry textbooks) . The question (at least as I see it it) is whether there is something going on we cannot measure that leads to these probabilities. (That's my understanding, but I'm not a physicist...or even a chemist!)

 

[PeterDonis]

electron around nucleus don't follow any law, any pattern, nothing cause it that he behave like it is

Um, what? It's like you don't even understand that QM itself is a set of such laws and patterns. Sure, they aren't laws and patterns that predict a single outcome with 100% confidence in every single experiment, but so what? They're still laws and patterns, and we can make predictions based on them, and those predictions get confirmed in experiments, sometimes to as many as 13 decimal places. That includes things like the energy levels of electrons in atoms, the spectra of radiation emitted or absorbed by electrons in atoms, etc. So your description here is simply wrong.

 

[Matterwave]

Do you think nature at all scales must be only random or only deterministic or it can be random in micro-world and deterministic in macro-world? If latter, where is border where random become deterministic?

I don't understand concept of randomness( absence of cause-effect), if nature is random why projectile with angle alpha and initial velocity v1, always land on same spot?

It seems that your mental model of "random" is different than the "random" relevant for the discussion here.

It appears that your usage is "completely random" meaning arbitrary and not following any physical law. However, as others have noted, that is not the kind of random that appears in Quantum Mechanics (or any physical theory, by definition).

In Quantum Mechanics there are events, for example "we will measure the particle to be here or there", which we can not predict with 100% certainty. But this does not mean that we can't predict anything, or that the event is arbitrary and not subject to physical laws and/or causality. We can calculate the probability distribution for said events.

 

[gen x]

It seems that your mental model of "random" is different than the "random" relevant for the discussion here.

It appears that your usage is "completely random" meaning arbitrary and not following any physical law. However, as others have noted, that is not the kind of random that appears in Quantum Mechanics (or any physical theory, by definition).

In Quantum Mechanics there are events, for example "we will measure the particle to be here or there", which we can not predict with 100% certainty. But this does not mean that we can't predict anything, or that the event is arbitrary and not subject to physical laws and/or causality. We can calculate the probability distribution for said events.

Um, what? It's like you don't even understand that QM itself is a set of such laws and patterns. Sure, they aren't laws and patterns that predict a single outcome with 100% confidence in every single experiment, but so what? They're still laws and patterns, and we can make predictions based on them, and those predictions get confirmed in experiments, sometimes to as many as 13 decimal places. That includes things like the energy levels of electrons in atoms, the spectra of radiation emitted or absorbed by electrons in atoms, etc. So your description here is simply wrong.

We don't have theory for path of single electron, we don't know what he do, so we say electron movement is random.

 

[Matterwave]

We don't have theory for path of single electron, we don't know what he do, so we say electron movement is random.

Wrong.

Why is left as an exercise to the reader.

 

[physika]

can be random in micro-world and deterministic in macro-world?

Who knows, maybe both.

...

 

[PeroK]

if nature is random why projectile with angle alpha and initial velocity v1, always land on same spot?

It doesn't. It depends on the wind.

 

[pines-demon]

we don't know what he do, so we say electron movement is random.

maybe he is rude to physicists only

 

[gen x]

It doesn't. It depends on the wind.

That is your example that nature is random?
Weather is not probabilistic, it is deterministic chaos (NS equations).

Real fluids are not continuum and we don't know all initial conditions.

 

[PeterDonis]

That is your example that nature is random?

I don't see @PeroK claiming that nature is random. The only one who keeps fixating on that claim is you.

Weather is not probabilistic, it is deterministic chaos (NS equations).

If we use a classical model, yes. But we don't know whether the underlying quantum physics is deterministic or not.

Real fluids are not continuum and we don't know all initial conditions.

This is true, but in itself it tells us nothing about whether the fundamental physics of our world is deterministic or not.

 

[pines-demon]

That is your example that nature is random?
Weather is not probabilistic, it is deterministic chaos (NS equations).

Real fluids are not continuum and we don't know all initial conditions.

Hey even classical mechanics can be inderterministic at times. Check Norton's dome.

 

[Matterwave]

Hey even classical mechanics can be inderterministic at times. Check Norton's dome.

Tbh, Norton's dome always felt more like a mathematical curiosity to me than any actual proof of indeterminism of "classical mechanics". We can add some relatively weak additional requirements, like that forces should be Lipshitz, which would preclude the dome. Requiring smoothness of solutions would also kill it, though that might kill other solutions we'd like to keep as well.

In any case, it seems more of a "the mathematics allows this" rather than "the physics forces this" situation to me.

 

[bhobba]

Also can a mod change the title to "Views of 't Hoof on incompleteness of quantum mechanics" or something like that.

I think it's fine as is. It is obviously 't Hoof's view and those following the thread should become acquainted with it, if they aren't already.

Personally, I think he is on the wrong track; incomplete would be a better description (which was Einstein's final view), but it is only one of the myriad opinions about the foundations of QM. Also, as 't Hoof knows only too well these days, everything is thought of as fields, with the particles, he says we should deterministically know about being excitations of the field (the Unruh effect, for example, is problematic to a deterministic particle view):
https://en.wikipedia.org/wiki/Unruh_effect

Still, IMHO, it would be unwise to dismiss someone of 't Hoof's calebre.

Thanks
Bill

 

[pines-demon]

I think it's fine as is. It is obviously 't Hoof's view and those following the thread should become acquainted with it, if they aren't already.

To be fair, the original title was "Not even wrong" or something like that, I already forgot because it was vague.

 

[javisot]

To be fair, the original title was "Not even wrong" or something like that, I already forgot because it was vague.

The title was "shut up and calculate", a title that had nothing to do with the development of the thread.

 

[gen x]

@Matterwave

If all of these theories — whether standard Copenhagen, Bohmian pilot-wave, or 't Hooft's cellular automata — yield identical mathematical predictions for any experiment we can conduct today, who decide which theory we will learn our students at universities, which theory will write in physcis book as correct version?

 

[martinbn]

@Matterwave

If all of these theories — whether standard Copenhagen, Bohmian pilot-wave, or 't Hooft's cellular automata — yield identical mathematical predictions for any experiment we can conduct today, who decide which theory we will learn our students at universities, which theory will write in physcis book as correct version?

These are not theories. They are interpretations of a theory. The theory is quantum mechanics and that is what is thought in the universities.

 

[gen x]

These are not theories. They are interpretations of a theory. The theory is quantum mechanics and that is what is thought in the universities.

Quantum mechanics is branch of physics, not theory.

 

[javisot]

which theory will write in physcis book as correct version?

The "right" question would be, as martinbn rightly points out: which "interpretation" will write in physcis book as correct version?

The answer is none, because the textbook deals with formalism, not interpretations. Even if it did cover interpretations, there is no single one that could be considered the "most correct."

 

[martinbn]

Quantum mechanics is branch of physics, not theory.

What exactly do you mean by 'theory'?

 

[Matterwave]

@Matterwave

If all of these theories — whether standard Copenhagen, Bohmian pilot-wave, or 't Hooft's cellular automata — yield identical mathematical predictions for any experiment we can conduct today, who decide which theory we will learn our students at universities, which theory will write in physcis book as correct version?

One thing is for sure, I won't be the one who decides.

So I'm not sure my opinion here is worth anything. But for what it's worth, for my undergrad and grad career, mostly I was taught the mathematical formalism of QM, along with the phenomenology of key experiments with a very light smattering of asides that hint at interpretation mostly along Copenhagen ideas. If experimental evidence does not pick out one interpretation from another, I expect that "mostly we teach the mathematical formalism + experimental phenomenology" continues to be the dominant mode of teaching QM in physics.

By "phenomenology" here I mean just "this is what happened when we tried XYZ". You do the double slit experiment and you see dots appear on the detector screen that exhibit an interference pattern. Things like that.

 

[gen x]

One thing is for sure, I won't be the one who decides.

So I'm not sure my opinion here is worth anything. But for what it's worth, for my undergrad and grad career, mostly I was taught the mathematical formalism of QM, along with the phenomenology of key experiments with a very light smattering of asides that hint at interpretation mostly along Copenhagen ideas. If experimental evidence does not pick out one interpretation from another, I expect that "mostly we teach the mathematical formalism + experimental phenomenology" continues to be the dominant mode of teaching QM in physics.

By "phenomenology" here I mean just "this is what happened when we tried XYZ". You do the double slit experiment and you see dots appear on the detector screen that exhibit an interference pattern. Things like that.

Is it true that Bell didn't prove that hidden variables can't exist, as Tim told?

 

[PeterDonis]

Is it true that Bell didn't prove that hidden variables can't exist, as Tim told?

In the sense that you can certainly have a nonlocal hidden variable theory that violates the Bell inequalities, yes. Bohmian mechanics is precisely such a theory.

 

[gen x]

In the sense that you can certainly have a nonlocal hidden variable theory that violates the Bell inequalities, yes. Bohmian mechanics is precisely such a theory.

I don't like explanation that speed of light is not broken because we can't send information faster then light, that sound as cheap diplomatic excuse to save Einstein.
Entangled particles somehow "communicate" or how to explain their instantaneous interaction?

 

[PeterDonis]

I don't like explanation that speed of light is not broken because we can't send information faster then light

I'm not sure what you're referring to here. The no signaling theorem in QM is not a circular argument as you seem to be implying.

Entangled particles somehow "communicate" or how to explain their instantaneous interaction?

Not every QM interpretation agrees that there is an "instantaneous interaction" between entangled particles. But entangled particles in QM do not violate the no signaling theorem, so again I'm not sure what your point is here.