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]]>“There are still puzzles to be worked out, no doubt, especially around the issues of exactly how and when branching happens, and how branching structures are best defined. [...] But these seem like relatively tractable technical challenges to me, rather than looming deal-breakers.”

I would really like to see how the pointer basis problem can be considered a technical challenge, let alone a tractable one. At best, you’ll need an additional set of axioms in the theory, which should fix the choice of the basis. But the looming feeling is that the task of actually formulating these axioms is equivalent to resolving the measurement problem and the Schrodinger’s cat paradox. And that may prove to be much more difficult than a mere technical challenge — just remember that people like von Neumann tried, failed and gave up on that challenge — so it’s certainly not going to be easy.

Best,

Marko

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]]>Coherence consists of all possible relations

emanating from every point in continually evolving spacetime.

Present moment decoherence

descries an organic universe

exploding from a localizing identity

ceaselessly redefining present experience.

Boundless such states are invariably emergent

within endlessly evolving relations.

Each and every relation within the organic multiverse

resonates with all others;

its influence exponentially attenuating with spacetime remoteness.

It’s useful to recognize the synchronicity of coherence

on scales ranging from quantum to cosmic.

All portrayals of experience

are exquisitely sensitive to

localizing identity.

The experience of the organism

is largely determined by

the point of view, or perspective,

of its identity.

Whatever may be perceived is rooted in organic remembrance,

reflecting naught but current decoherence—

entanglement evolving as natively cognizing environment

energizes present experience

as an ever more discrete subset of boundless probabilities.

I’d love to see a formulaic reduction of these ideas.

Tom

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]]>The real question is not whether MWI is a better way of looking at QM. The real question is whether QM is correct. Every physical law found to date has either proved itself an approximation, or is waiting for its day. QM is exceedingly likely just another law waiting for its day to end.

So if you assume that QM is in someway wrong, will infinite dimensional Hilbert spaces and perfect linearity remain? Because without those things MWI is a non starter.

MWI is built upon the one part of QM that is weakest – the collapse.

Most of the alternative ‘explanations’ of QM have an obvious place where collapse occurs due to limited bandwidth (any non linearity). It will have to be experiment that proves QM wrong, as it is pretty firmly entrenched in the Physics Community.

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]]>“(1) off-diagonal terms are small, so branches evolve almost-independently, therefore (2) we can assign probabilities to branches, and once we do that we can (3) ask about the probability of the off-diagonal terms growing large and witnessing interference between branches.”

So, “almost-independently” isn’t the same as “actually independently”, but let’s leave that aside for now. If the off-diagonal terms do grow large, then that invalidates the “off-diagonal terms are small” assumption, therefore the branches are definitely not independent, therefore you cannot assign probabilities. There’s nothing circular/inconsistent about this?

OK…so I probably don’t understand this too well. Heck, I never even read your paper.

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]]>Eric– I think there is a fair point here, and I’m not sure I’ve thought it through completely. My feeling would be that it’s correct to say (1) off-diagonal terms are small, so branches evolve almost-independently, therefore (2) we can assign probabilities to branches, and once we do that we can (3) ask about the probability of the off-diagonal terms growing large and witnessing interference between branches. At the very least it seems like a self-consistent story.

D– The probabilities are credences at each individual branching. Of course they can lead to frequencies if you do many individual trials of some kind of experiment.

Charlie– The detailed process of branching is a technical problem worthy of more study, no doubt. As you say, there aren’t really any problems with energy conservation, once you understand how it works in regular quantum mechanics. (If you like, the thing that is conserved is the energy times the amplitude squared.)

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]]>Thank you. I am a complete and abject layperson whose skill is reading English, not grasping the mathematics of quantum mechanics. But grasping English alone can you get you a little ways with a message as clear and consistent and easily stated as the Everettian premise: The sophisticated mathematical construction called the wave function, which to date matches quantum observations perfectly, describes the physical superposition of macroworlds. Then I read something like this article — a series of ideas, formulations, qualifications, theories and axioms dedicated to untying knots that, golly, just weren’t there in the beginning when I was promised the breath of simplicity itself — and nothing is quite so plain as the fact that there is nothing at all obvious about the “Many Worlds” interpretation, and that, for all the “evidence” at hand, the physical reality, if any, represented by the wave function is as far from being glimpsed as it has ever been.

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]]>I’m still having trouble with the cartoon representation of MWI where you have a film splitting into two films. Is this supposed to apply only in (simple) cases of binary events? I understand the value of focusing on simple examples (spin-up/down), but what is the cartoon representation for a continuous range of possibilities (electron position)? Does the film split into an infinity of films? (A film shmear?)

[Asked in previous post but too late for answer.] Am I allowed to think of MWI as many superpositions rather than many universes? When the cartoon-filmstrip splits, I imagine all mass/energy doubling. However, when I think of Schrödinger’s Cat, it never occurred to me that you had 10 lbs of cat (before box closed), then somehow 20 lbs of cat (during superposition), then 10 lbs again when I observe it. It’s always been called Schrödinger’s Cat (singular) rather than Schrödinger’s Cats (plural) even before collapse. So why now must we have many worlds rather than one world in superposition?

And I have to ask (even though the answer seems obvious): Are there more worlds today than there were yesterday?

“There are still puzzles to be worked out, no doubt, especially around the issues of exactly how and when branching happens, …” I thought that a major appeal of this approach is that nothing “happens”. We have continuous evolution rather than “collapses” or any other magic moments.

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