Copenhagen Interpretation vs Pilot Waves

[vanhees71]

its not what it adds, it what it doesnt add - problems. Copenhagen has the measurement problem. Why live with that when you can have a problem free interpretation? Your model should be as simple as possible and no simpler.

But also BM and any other interpretation of QT has a measurement problem, if you think there is one. If I understand the philosophers right, their problem is that they think it's not understood, which outcome a measurement on a single quantum system will have, knowing the state (even if it's complete knowledge, i.e., if the system is prepared in a known pure state).

They exspect that the dynamics of the theory explains, why this state through interaction with a measurement apparatus "collapses" to the eigenstate of the operator that represents the measured observable. That's however in contradiction to the standard version of QT, because unitary time evolution does not lead to such a dynamics. Rather you still have a superposition of entangled states of the measured system and the pointer states of the measurement device. There are two ways out:

(a) One accepts that Nature is inherently random and that the outcome of measurements are thus irreducibly probabilistic. All QT delivers are the probabilities for the outcomes of measurements, and there is nothing more in Nature. That's the minimal statistical interpretation. There's no collapse, the quantum state is purely epistemic. For me that's the most plausible solution of the measurement problem, which is only apparent. It's just a problem for our worldview, which is due to everyday experience with macroscopic systems, whose relevant macroscopic observables behave according to classical physics with determinism as an emergent, approximate phenomenon. All observations and high-precision tests of QT in very many manifestations are consistent with this assumption.

(b) Nevertheless, that's indeed only an educated belief, founded on the overwhelming success and lack of failure of (minimally interpreted) QT. It cannot be ruled out, of course, that maybe QT is nevertheless incomplete, and then QT has to be modified, maybe in such a way that there's an inherent collapse mechanism in the dynamics. What's for sure ruled out is naive EPR "Local Realism". This is the great achievement of Bell's theoretical and Clauser's, Aspect's, et al's experimental work.

Further it explains the uncertainty. Copenhagen and MWI introduce a 'god' of randomness. its not easy to create an RNG. it requires energy and structure. its like when creationists say god created the universe - its a form of hidden complexity. so arguing CI and MWI are simpler is not a given.

What's an RNG? Also one has to accept how Nature is found to behave. Whether there's a god who created the universe the way it looks, is not a question that can decided by the pure sciences. That's a matter of private belief for any individual.

For me CI is inconsistent. Even the versions, which do not assume a collapse (e.g., Bohr's as well as Heisenberg's version, as far as I can guess from their enigmatic philosophical writings), there's still the "quantum-classical cut", which in no way could be hitherto observed. To the contrary with more and more refined metrology bigger and bigger systems can be shown to behave according to QT (e.g., the motions of the LIGO mirrors, sevel 10kg objects, behave quantum theoretical and show "zero-point motion" of quantum oscillators).

I'm not sure about MWI. On the one hand they claim that there's nothing than unitary time evolution and the "wave function of the universe" is all there is. On the other hand, for the application of QT, again I have to assume Born's rule for subsystems as in standard QT. I don't know, what's gained with MWI compared to the minimal interpretation.

the only problem ive found with PW, so far is that its not well researched, which is a human problem not a theory problem. oh plus the non-local thing, but all interpretations should be non-local because we all know about entanglement. maybe i havent understood why CI and MWI are 'local' as that would violate bell.

I guess with PW you mean "pilot wave", i.e., de Broglie-Bohm. Within non-relativistic theory it's a consistent mathematical addition to standard QT, but it's not solving any "measurement problems" either. Particles do not follow Bohmian trajectories but behave probabilistically as predicted by standard QT. All attempts to extend the Bohmian program to relativstic QT I'm aware of are even less convincing, violating in the one or the other way Poincare covariance, i.e., they are not relativstic at the end.

 

[vanhees71]

Exactly, you don't understand it. Please leave it to us who do understand it.

Why? Because it's more convenient to have a skeptic less? ;-)).

 

[Demystifier]

Why? Because it's more convenient to have a skeptic less? ;-)).

No, to attract ten skeptics more who would like to take part in a constructive criticism.

 

[apostolosdt]

No, I am just reminding you what the interpretations subforum is for and what it is not for. It is not for claiming that any interpretation is either right or wrong. You are basically claming that a particular interpretation is wrong. That is off limits in this subforum by the PF rules. […] This discussion was had some time ago in the SA forum, before the intepretations subforum was spun off. It is off topic here. If you really want to make a case for the interpretations subforum being shut down, please do so in a thread in the SA forum.

My bad; I’m going to remind myself to avoid this particular sub-forum, for I don’t care about philosophical arguments about physics. I think it’s fair for both vivid practitioners of QM interpretations and plain physicists like me.

It’s only ironic that Feynman’s name is being cited in a philoZophical sub-forum.

 

[Demystifier]

maybe i havent understood why CI and MWI are 'local' as that would violate bell.

See my https://arxiv.org/abs/1703.08341 Sec. 5.3.

 

[vanhees71]

This once more ignores the fact that standard relativistic QFT is local.

 

[Lord Jestocost]

.... One accepts that Nature is inherently random and that the outcome of measurements are thus irreducibly probabilistic. All QT delivers are the probabilities for the outcomes of measurements, and there is nothing more in Nature....

To my mind, Max Born/1/ hit the nail on the head when he wrote:

“A more concrete contribution to this question has been made by J. v. Neumann in his brilliant book, Mathematische Grundlagen der Quantenmechanik. He puts the theory on an axiomatic basis by deriving it from a few postulates of a very plausible and general character, about the properties of 'expectation values' (averages) and their representation by mathematical symbols. The result is that the formalism of quantum mechanics is uniquely determined by these axioms; in particular, no concealed parameters can be introduced with the help of which the indeterministic description could be transformed into a deterministic one. Hence if a future theory should be deterministic, it cannot be a modification of the present one but must be essentially different. How this should be possible without sacrificing a whole treasure of well-established results I leave to the determinists to worry about.

I for my part do not believe in the possibility of such a turn of things. Though I am very much aware of the shortcomings of quantum mechanics, I think that its indeterministic foundations will be permanent, and this is what interests us from the standpoint of these lectures on cause and chance. There remains now only to show how the ordinary, apparently deterministic laws of physics can be obtained from these foundations.”

/1/ Max Born, Natural Philosophy of Cause and Chance (Clarendon, Oxford, 1949)

 

[gentzen]

Basically, all the randomness is encoded in the initial conditions.....

So what?

Chaos Theory: Because we can never know all the initial conditions of a complex system!

The “in principle knowable unknowns” are grounded in epistemology alone.

Oh sorry, I thought you had a technical question about BM. Good to know that at least I don't have to spend the time to find the technical details again.

The answer was more ment to explain that even in BM, the randomness is still irreducable (or at least could still be irreducable, dependent on the technical details). Not because we cannot know the initial conditions of a complex system, but because we cannot know a real number exactly, and hence not know exactly a set of real numbers describing the initial conditions either.

 

[PeterDonis]

Thread closed for moderation.

 

[PeterDonis]

After moderator review, the thread will remain closed. Thanks to all who participated.