Quantum Physics from Classical Physics with an epistemic restriction

yoda jedi

talking about ψ-epistemic, ψ-ontic and ψ-complete models.


How would the world appear to us if its ontology was that of classical mechanics but every agent faced a restriction on how much they could come to know about the classical state?

http://arxiv.org/pdf/1111.5057v1.pdf


...The success of this model in reproducing aspects of quantum theory provides additional evidence in favour of interpretations of
quantum theory where quantum states describe states of incomplete knowledge rather than states of reality...

[a ψ -epistemic hidden variable model]


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Demystifier

But one of the authors is also an author of the recent but already famous PBR theorem which claims the opposite.

yoda jedi

To have one's cake and eat it, too ?

or make room for:

http://www.nature.com/nphys/journal/...nphys2309.html (PBR Theorem, former alluded)
...Here we show that any model in which a quantum state represents mere information about an underlying physical state of the system, and in which systems that are prepared independently have independent physical states, must make predictions that contradict those of quantum theory.....



.

yoda jedi

and this one:


http://arxiv.org/pdf/1205.5334v1.pdf
...However unlike pilot-wave theory, the model is stochastic, the wave function is not physically real and the Born’s statistics is valid for all time by construction. Moreover, the construction is unique given the classical Lagrangian or Hamiltonian. Finally, assuming that |λ| fluctuates around ~ with a very small yet finite width, then the model predicts small correction to the prediction of quantum mechanics. This might lead to precision test of quantum mechanics against our hidden variable model...

DrChinese

You might guess the first thing I look at in a paper like this.

"It is then imperative to ask how our model will deal with Bell’s no-go theory. Since our
model reproduces the prediction of quantum mechanics for specific distribution of λ, then
for this case, it must violate Bell inequality which implies that it is non-local in the sense of
Bell [11], or there is no global Kolmogorovian space which covers all the probability spaces
of the incompatible measurement in EPR-type of experiments [12], or both. We believe that
this question can be discussed only if we know the physical origin of the the general rules of
replacement postulated in Eq. (7). To this end, a discussion on the derivation of the rules
from Hamilton-Jacobi theory with a random constraint is given some where else [13]."

[13] includes a reference to the work of De Raedt et al, as well as others. So basically he ignores the issue. Not sure how he expects that to fly, since the use of Bell is to dig out these issues BEFORE the remainder of the theory is examined closely. Since there is no explicit non-local or non-realistic agent identified in the theory, how can it be internally consistent and agree to QM? Bell says it won't.

yoda jedi

quote to raedt is [12] not [13].

respect nonlocality is, bolded letters.

DrChinese

You are so right about the reference, sorry my eyes are not so good as they used to be. (Other things too.) He references his own work, which is pending publication in Physica. So that's a *start* I guess.

I saw the non-locality deal, which was OK to say, but I didn't see that there was anything non-local in the actual model. The issue is that things like that should be highlighted because they often lead to other testable hypotheses. Not good to ignore a little thing like a new type of non-local mechanism. I read it that he was wiggling, not saying it is non-local explicitly.

It is very good that he includes a testable prediction elsewhere. But hard to believe that it is worth investigating when Bell is not properly addressed. Of course, that is just my take and we know what that's worth.

DrChinese

These are all cool though. As I see it, each is giving us some restrictions on possible theories, in addition to what we got from Bell and some of the other no-gos. Honestly, trying to interleave their conclusions into a meaningful boundary as to what is possible eludes me. It's like a Rubik's cube. But I like the thinking. If we piece enough together, maybe something concrete will drop out!