Le lun. 24 févr. 2025, 23:09, Brent Meeker <meekerbr...@gmail.com> a écrit :
> > > On 2/24/2025 1:07 PM, Quentin Anciaux wrote: > > Brent, > > The issue is precisely that if you start with only unitary evolution and > no additional assumptions, you don’t get probabilities at all—just a > deterministic wavefunction. That’s why the Born rule must be explained > rather than assumed. The problem is not that MWI contradicts the Born rule, > but that it needs to derive it without assuming it. > > Your argument boils down to saying, "The Born rule is empirically > confirmed, so MWI must explicitly postulate it." > > No, you leave out the point that the Born rule can't be derived from just > the Schroedinger equation. As Bruce as explained repeatedly, MWI alone > provides no mechanism for changing the sequences generated by > measurements. You are of course free to postulate a probability measure > based on the wave-function amplitudes...which is assuming the Born rule. > It's what everybody did for 40yrs before Everett wrote his paper and which > everybody has continued doing sense. > > > But any interpretation of QM, including single-world ones, requires some > justification for why the squared amplitude determines probability. If MWI > needs additional reasoning to get there, that’s an open question, not a > refutation. > > What if you can't get there from bare MWI? Many have tried and failed. > Why not just accept that it's a probabilistic rule that needs to be added > to the interpretation. Gleason's theorem shows that there's no other way > to apply a probabilistic measure if there are more than two possible > results. Although Gleason's theorem is independent of choice of basis, so > there's still the preferred basis problem; which we hope decoherence can > solve but I don't think anyone has shown it yet. > > > > You say that different values of a and b still produce the same sequences, > but What you’re missing is that in MWI, observer instances are not evenly > distributed across all sequences—this is fundamental to Everett’s relative > state interpretation. If all sequences contributed equally, there would be > no need for measure at all, and MWI would have been dismissed from the > start. Everett’s entire motivation was to account for probability within a > deterministic framework, meaning your argument misrepresents what MWI > actually proposes. The number of observer instances experiencing each > sequence scales with the amplitude squared > > But that doesn't follow from the measurements which just produce one > branch for every possible result. It only follows from assuming the > branches have a probability measure equal to the square modulus of the > amplitude, aka the Born rule. The concept of "observer instances" and > their "experiences" is a fantasy. The number of observers of a particular > result can be anything once the result in recorded. > > Brent > You keep assuming that one branch corresponds to one observer, but that’s simply not what MWI proposes. Everett’s framework is about relative states, not discrete worlds with single, isolated observers. If you treat branches as coarse-grained partitions of an underlying continuous wavefunction, then observer instances scale with amplitude, and that’s what leads to the Born rule. The fact that all 2^N sequences exist doesn’t mean they contain the same number of observer copies. If you disagree, you need to justify why unitary evolution should produce equal weighting when the amplitudes explicitly define the structure of the wavefunction. Quentin > -- > You received this message because you are subscribed to the Google Groups > "Everything List" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to everything-list+unsubscr...@googlegroups.com. > To view this discussion visit > https://groups.google.com/d/msgid/everything-list/dbbf4367-b996-42db-8a4d-7eb9d5507bb3%40gmail.com > <https://groups.google.com/d/msgid/everything-list/dbbf4367-b996-42db-8a4d-7eb9d5507bb3%40gmail.com?utm_medium=email&utm_source=footer> > . > -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To view this discussion visit https://groups.google.com/d/msgid/everything-list/CAMW2kAqz7mTg26K7uL-X9jtJ1W2zmYuPPV_io3NeVzTEM%3Dn2oQ%40mail.gmail.com.
