I Ontology is to quantum theory what hardware is to computation theory

[vanhees71]

That the physical terminology is also not always consistent is unfortunately true. Of course has "localization" also a meaning in non-relativistic QT. It simply makes that you can prepare states, where the probability to find a particle is sharply peaked around some mean position. This doesn't imply that the theory is local in the usual sense of relativistic QFT. In fact you can localize particles much more within non-relativistic QM than it is possible within relativistic QFT, which is due to pair creation in the latter case: If you try to localize, e.g., an electron at a certain accuarcy of localization you rather create new electron-positron pairs than to better localize the one electron you tried to localize. The typical length scale involved here is the Compton wavelength of the electron, $\lambda_{\text{C}}=h/m_{\text{e}}c$.

 

[A. Neumaier]

This link gives me a page in German with a password requirement, without any info about the book. Is there another link, like Amazon's?

https://www.amazon.com/dp/B0818SNQFY/?tag=pfamazon01-20

 

[Demystifier]

(https://arxiv.org/abs/2208.04618)

I have read the paper and now I better understand how Lev thinks about MWI. In particular, now I better understand the origin of misunderstanding between Lev and Tim in the video.

The crucial part of the paper is section "VII. CONNECTION BETWEEN OUR EXPERIENCE AND THE UNIVERSAL WAVE FUNCTION". In this section Lev does not provide any explanation why we see the world as 3-dimensional. Instead, he just accepts the phenomenological fact that we do, and discusses how to describe this fact with the wave function. Explicitly, he says

"the macroscopic objects are well localised and are not entangled within the world wave function, so every macroscopic object is represented by a product of the wave function of some collective variables defined in three dimensions, times the entangled state in the configuration space of degrees of freedom of the microscopic parts of the object."

While every practical physicist may accept that it is true in a FAPP sense, Lev does not attempt to explain why this is true, and this is what pisses Tim out. Other MWI-ers try to explain it in terms of emergence, but Lev dismisses the emergence program as useless:

"The “emergence” program [25] is not simple, and it is also not needed. In any case, we have very little information about the universal wave function, so the emergence program, even if successful, is of little practical value."

Lev thinks of MWI as a practical tool, not as a deep ontological theory of "everything", which is the exact opposite of what Tim thinks that MWI (or any other interpretation of QM) is supposed to be.

I remember at one conference where I was talking about my relativistic version of Bohmian mechanics, Lev objected that my interpretation does not offer a simple intuitive story of what happens in spacetime. For Lev, the purpose of interpretation is to offer a simple intuitive story, not to propose an ambitious, general, deep and fundamental vision of "truth". For Lev, any interpretation is good, as long as it offers a simple intuitive way of thinking about at least some phenomena.

 

[junjunjun233]

I sometimes wonder if Einsteins objections to QM is misinterpreted or have more components? The lack of determinism etc may be a bit simplistic, I guess where was more to it! Especially his quest for a unified field theory?

It's a pity we can't listen to Einstens view of the ideas of holography and dualities between theories of different topologies etc.

Even if SR and GR is not at all a theory of "measurements" - like QM, Einstens seems to make forceful use of thinking tools with gedanken observers, what was "inside the system". And then adding the idea of observer equivalence. And somehow, the construction of SR is the purest example of constructing a theory by enforcing observer equivalence (+ invariant sup speed limit)!! Then when he widened the class of "observer" there was quite a challenge to find the equivalence relations, but via some not as pretty turns he made something up.

But conicidently this is exactly the problem with QM, as alot centeres around the "problem of the observer", and this was as far as I understand, the key constructingprinciple of Relativity as well. But the gedanken observer in QFT, really isn't inside the system, they are at scattering distance. This is a headache, that I would presume Einstein - giving the central use of obserer equivalence and gedankend observers - that would bother him with QM. This way of seeing it, has little todo with "dice" issues, its something much harder to grasp.

/Fredrik

Einstien is more of geometry, some 'things' and forces - Reimannian. In my field, approximation is what makes reality.. Or should i say enough to fool you down to the pixels for a projected images or vids. We used quasi/ monte carlo to simulate lighting. We cant avoid dispersion and noises even in projection. Our reality is geometry -triangles. Its the only form and shape that behaves well. What im saying is even, in a projected image we cant avoid approximations.. For us, we.. locality is a myth that we put value and holds for it purposes. Like when we stop the machine to render and stick to that quality.

 

[gentzen]

I remember at one conference where I was talking about my relativistic version of Bohmian mechanics, Lev objected that my interpretation does not offer a simple intuitive story of what happens in spacetime. For Lev, the purpose of interpretation is to offer a simple intuitive story, not to propose an ambitious, general, deep and fundamental vision of "truth". For Lev, any interpretation is good, as long as it offers a simple intuitive way of thinking about at least some phenomena.

But the MWI story is that there are many worlds, so if Lev manages to defend this story, he should be fine, no? Of course, you may claim that deep in his heart, Lev does not believe this story himself. But I don't find your evidence for that claim convincing.

Moreover, I find it totally natural that Lev wanted to know which underlying story you are trying to defend.

Lev thinks of MWI as a practical tool, not as a deep ontological theory of "everything", which is the exact opposite of what Tim thinks that MWI (or any other interpretation of QM) is supposed to be.

My personal opinion is that defending the MWI story at some point also includes addressing the problematic behavior of the "Simon Saunders' decoherence/emergence" school. Otherwise, you risk to run into embarrassing situations sooner or later, like for example happened to me in
https://blog.computationalcomplexit...howComment=1667820461887#c8320038219898848189
Don't get me wrong, both David Deutsch and David Wallace made important contributions to current "ambitious, general, deep and fundamental programs," but ...

OK, maybe at this point, I should really find some MWI proponent that explicitly used the word "cheat". My link below starts at 1:05:42, and at 1:06:38 Sean says "... and I do think that even most Everettians kind of cheat when they write down a set of classical variables and then construct a wavefunction using them":


Before, Sean talked about "Quantum Mereology: Factorizing Hilbert Space into Subsystems with Quasi-Classical Dynamics," by Sean M. Carroll, Ashmeet Singh (https://arxiv.org/abs/2005.12938)
He described the crucial point where things go wrong at 21:55 "... interestingly, once you set things up this way and say I am going to start with a generic Hamiltonian, and try to factorize it into system tensor environment so that it has these nice features, a generic Hamiltonian never does have these nice features."