On Wed, Feb 12, 2025 at 9:51 AM Quentin Anciaux <[email protected]> wrote:
> Bruce, > > You argue that quantum mechanics follows the Born rule, but MWI does not. > However, this assumes that MWI should reproduce the Born rule directly from > the Schrödinger equation without additional structure. The issue is not > whether the Born rule holds in quantum mechanics—it clearly does—but > whether MWI can account for it without collapse. > > You say that deriving the Born rule in MWI requires additional > assumptions, but that’s not a valid objection—it’s an open question that > multiple approaches are trying to address. Decision theory, envariance, and > self-locating uncertainty all attempt to show why observers should expect > probabilities to follow . Dismissing them outright ignores that they > provide serious motivation for why the Born rule emerges from unitary > evolution > But the point is that no matter what you add to MWI, the basic structure of the theory makes any attempt to draft in the Born rule impossible. Your argument rests on the claim that all sequences exist independently of > their amplitudes, meaning that counting sequences alone should determine > probabilities. > Where on earth did you get this idea? I don't even know what it might mean to count sequences. The idea is that in any observed sequence of zeros and ones, the proportion of zeros gives an estimate of the probability of finding a zero. This is basic statistics 101. But this contradicts experimental results. If naive sequence counting were > correct, we would observe a uniform distribution of outcomes across > experiments, which we do not. The fact that quantum mechanics consistently > follows suggests that something in the structure of MWI must explain why > high-measure branches dominate experience. > This is just incoherent rubbish. You dismiss measure as a "made-up surrogate" for probability, but this > ignores that measure is a mathematical property of the wavefunction, not an > arbitrary postulate. Amplitudes determine the structure of the quantum > state, and decoherence ensures that branches remain effectively > independent. The question is whether measure also determines the relative > frequency with which observers find themselves in different branches. If it > did not, we would expect deviations from the Born rule, yet we see none. > Explain to me why it is that in the binary case under discussion, with N trials, you get the same 2^N binary sequences of length N for any combination of initial amplitudes. The fact that multiple approaches attempt to derive the Born rule within > MWI—decision theory, envariance, self-locating uncertainty—shows that this > is an open question, not a settled failure. Simply asserting that MWI "does > not follow the Born rule" ignores the very problem that these derivations > attempt to solve. The Born rule is an observed fact, and MWI needs to > explain it—but dismissing all attempts to do so does not make the problem > go away. > > You frame your argument as avoiding "spurious additional assumptions." But > you are making an assumption yourself: that all branches contribute equally > to experience. > I do not know what such an assumption could mean, and I challenge you to point out exactly where I make such an assumption. If you mean no more than that the same conclusion is reached regardless of which binary sequence one looks at, then I agree. But that is not an assumption, it is a conclusion of the argument. Bruce -- 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 [email protected]. To view this discussion visit https://groups.google.com/d/msgid/everything-list/CAFxXSLQfoiMf-L%3DUT7af2PL_h9easFWDDAzHaVfOx8-Ns-p35A%40mail.gmail.com.
