And talk about things for which there is no experimental evidence… many worlds is at the top of that list!

“literal” does not mean “ultimate” – most would accept that it is literally true that I am sitting on a solid chair typing this message but that says nothing about what consciousness is or how subatomic forces operate on the surfaces of my skin, clothes and chair to give the appearance of solidity.

I think the set of all probabilities of instances in the universe is finite and discrete. In particular, instances of especially low frequency cannot be proven to have existed (or have a cause) and must be treated as noise. Also, each instance creates a new set of all probabilities, and instances have varying degrees of effect depending on when they occur. I think that idea is still within the formalism but it would add a cut off to the numbers of eigenvalues and eigenvectors.

Any measurement humans make now cannot noticeably affect the energy levels of, say, the hydrogen atom, but instances corresponding to hypothetical high-energy measurements made just after the Big Bang by a powerful sentient observer could have changed the energy levels of the hydrogen atom and the subsequent evolution of the universe. This means I am less certain that any Higgs Boson created at CERN is in fact a real Higgs Boson. Maybe it is a close facsimile from what is essentially a simulation of the conditions of the Big Bang. Conversely, our existence, despite being miniscule now, might nonetheless have an odd effect on the laws of the future universe as it expands.

I think a certain amount of noise is necessary for making a measurement and is not a consequence of making a measurement but reflects an intrinsic aspect of something. This means we can’t know everything about an electron because it doesn’t actually exist in the ways that we can think of it, but we can reasonably be sure that there is something that we cannot change that corresponds very closely to our idea of it. The higher up we go on the energy scale at a certain time scale, the less certain we are of our measurements. I think this is a reasonable way of looking at things, but it isn’t especially enlightening.

there are multiple different interpretations of quantum mechanics

Is that a fruitful description? It doesn’t appear fruitful elsewhere, where people try to eke out predictions to test.

Say, if decoherence is an actual process, wouldn’t it kill some “interpretations” that, at least in the armchair interpretation, has claimed “instantaneous collapse”? I believe I have read here that instead, for whatever reason, the decoherence process obeys relativity.

And elsewhere experiments on photons in cavities where decoherence is a gradual process that one can back out of as long as it is partial.

Likewise, people have claimed, for whatever reason, the wavefunction can be observed (is real) and is not a calculating device. If so, surely that would reject #11 “shut up and calculate”?

I don’t see why these are not (tried to be) put as theories as elsewhere.

But I still don’t think that implies many-worlds ‘literally’ (!), since you can instead explain superpositions by fundamental randomness at the level of individual states – there is no need for the enitire universe to split.

Also, as I have recently shown, if you look at the (discrete) ‘flow’ of the universal wave-function according to U(t+dt) = e(hL).U(t) – U(t) – ie the ‘change’ in the wave-function, then 3D space falls out trivially as 3 attractive periodic points in C^n.