Brent, That’s exactly the key issue—standard QM introduces a non-unitary projection, while MWI seeks to replace it with purely unitary evolution. The challenge is whether probability and the Born rule can emerge naturally from that evolution rather than being postulated.
Self-locating uncertainty is an attempt to bridge that gap, but as you point out, it risks assuming the very thing it tries to explain. That’s why I lean toward computational approaches to consciousness and measure, where probability could emerge from constraints on information processing rather than from an explicit collapse rule. If the projection postulate is just a practical tool and not a fundamental physical process, then something else must explain why we observe the Born rule. Whether that’s self-locating uncertainty, decision theory, or something entirely different remains an open question—but dismissing all attempts without a working alternative doesn’t resolve the problem either. Quentin Le mar. 25 févr. 2025, 07:31, Brent Meeker <meekerbr...@gmail.com> a écrit : > > > On 2/24/2025 6:09 PM, Quentin Anciaux wrote: > > Bruce, > > Your response assumes that unitary evolution inherently produces "one > observer per branch" in a discrete way, but that’s not what follows from > the wavefunction’s continuous structure. Everett’s relative state > formulation does not propose discrete worlds but rather an evolving > superposition where decoherence prevents interference. The fact that we > describe macroscopic branches as "splitting" is a convenient approximation, > not a fundamental aspect of the theory. > > The key point you keep ignoring is that amplitudes are not just "carried > along" without meaning—they define the structure of the wavefunction, and > decoherence prevents low-amplitude branches from significantly contributing > to observer experiences. Your claim that "one observer per branch" follows > directly from unitary evolution is an assumption, not a derivation. > > If you insist that unitary evolution cannot produce probability weights, > then your argument applies equally to any interpretation of quantum > mechanics. The Born rule is a fact of experiment, and any valid > interpretation must explain it. If you believe MWI cannot do so, you must > show why—not just assert that it "hasn’t been done" while dismissing > attempts to derive it. Assume your pride, publish and get the glory. > > A measurement in QM conforms to the Born rule, but it's not unitary, it's > a projection operator. That's how it produces probabilities, it projects > the unitarily evolved state vector onto the basis eigenvectors of the > operator. That's pretty much the problem MWI wants to solve: "How can we > replace that projection operation with some unitary evolution." And it > comes up with "self-locating uncertainty" which postulates the Born rule > for "selfs". > > Brent > > -- > 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/ec74a2f2-cfc8-4015-9141-5a3f6d444bb2%40gmail.com > <https://groups.google.com/d/msgid/everything-list/ec74a2f2-cfc8-4015-9141-5a3f6d444bb2%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/CAMW2kApe1y8hU6%2Bu0VCs%2BoheWmr-bvX2H6RwrJtVF5F-wwngbQ%40mail.gmail.com.
