On Monday, November 18, 2024 at 7:03:02 AM UTC+1 Bruce Kellett wrote:
On Mon, Nov 18, 2024 at 4:17 PM PGC <[email protected]> wrote: Bruce, let’s directly address the epistemic interpretation of the wavefunction. While this view neatly avoids ontological commitments and sidesteps issues like FTL action, it doesn’t fully account for experimentally observed phenomena such as violations of Bell’s inequalities. The violation of Bell inequalities implies non-locality, and the epistemic interpretation of the wave function is perfectly compatible with non-locality. These correlations are not just statistical artifacts of knowledge updates; they point to an underlying structure that resists dismissal as mere epistemic bookkeeping. The wavefunction’s role in consistently modeling entanglement and its statistical implications suggests questioning the existence of a deeper reality, challenging the sufficiency of an epistemic-only framework. Unfortunately, Everettian QM, or MWI, cannot even account for the correlations, much less the violations of the Bell inequalities. I have made this argument before, but failed to make any impact. Let me try again. The essence of Everett, as I see it, is that every possible outcome is realized on every experiment, albeit on separate branches, or in disjoint worlds. Given this interpretation, when Alice and Bob each separately measure their particles, say spin one-half particles, they split at random on to two branches, one getting spin-up and the other branch seeing spin-down. This happens for both Alice and Bob, independent of their particular polarization orientations. If this were not so, the correlations could be used to send messages at spacelike separations, i.e, FTL. If N entangled pairs are exchanged, each of Alice and Bob split into 2^N branches, covering all possible combinations of UP and DOWN. When Alice and Bob meet, there is no control over which Alice-branch meets which Bob-branch. If the branch meet-up is random, then in general there will be zero correlation, since out of the 2^N Bob branches for each Alice branch, only one will give the observed correlations -- a 1/2^N chance. In the literature, some attempts have been made to solve this problem: for instance, it is sometimes claimed that Alice and Bob interact when they meet, and this interaction sorts out the relevant branches. But no account of any suitable interaction has ever been given, and also, one can reduce the possible interaction between Alice and Bob to as little as desired, say by having them exchange their data by email, or some such. Another suggestion has been that since the original particles are entangled, some magic keeps everything straight. I do not find either line of attempted explanation in the least convincing, so I conclude that Everettian QM cannot account for any correlations, much less those that are observed to violate the Bell inequalities. Attempts to relate Everettian many worlds to computationalism, or theories of everything, are just disingenuous. There is no reason why these many-worlds theories should have anything in common. Bruce, your assertion that the epistemic interpretation of the wavefunction is compatible with non-locality and capable of addressing Bell inequality violations deserves attention. While it is true that an epistemic interpretation can align with non-local correlations, it struggles to explain the coherence and structure underlying these correlations. If the wavefunction is purely a representation of knowledge, what enforces the observed statistical regularities that persist independently of the observer? These correlations suggest a deeper reality to the wavefunction itself, beyond an epistemic framework. You critique MWI on the basis of a "branch meet-up" problem, suggesting that the coherence of correlations collapses due to arbitrary branch matching. However, this interpretation mischaracterizes the role of the wavefunction in Everettian QM. The wavefunction evolves unitarily, preserving coherence across all branches. Correlations between Alice and Bob emerge from the shared history of their entangled particles, embedded in the global structure of the wavefunction. The branches are not randomly assigned but are intrinsically connected through their common origin in the unitary evolution. This global coherence ensures the persistence of correlations without requiring post-measurement sorting. MWI is, at its core, a “local theory” with no faster-than-light action. The violation of Bell’s inequalities becomes a natural consequence of the wavefunction’s structure, serving as confirmation, softer than evidence, of the "other histories" that MWI posits. These violations do not indicate FTL signaling but instead highlight the fundamentally relational nature of quantum mechanics as described by the universal wavefunction. In this way, MWI addresses non-local correlations without the need for external collapse mechanisms or epistemic assumptions. It also provides a cure for what can be termed a form of Cosmo-solipsism—a worldview that limits reality to a single trajectory while dismissing the explanatory power of other branches. Your argument implies that randomness in branch matching undermines MWI’s explanatory capacity, but this critique relies on a rather superficial misunderstanding of the global coherence of the wavefunction, uncharacteristic of your reasoning. The correlations are not artifacts of randomness but emerge from the mathematical structure of the wavefunction itself. Dismissing MWI on the grounds that it fails to account for these correlations requires evidence of mathematical or empirical failure, yet MWI has consistently matched experimental predictions, including Bell inequality violations. The connections between computationalism and MWI are not disingenuous; they arise naturally from their shared reliance on universality and formal systems. Both frameworks explore branching realities—MWI through the wavefunction's evolution and computationalism through the interplay of self-reference and arithmetic. These are not disparate domains but overlapping ones, addressing the same fundamental questions of structure, indeterminacy, and coherence. Your dismissal of computationalism as speculative philosophy overlooks its grounding in formal logic, arithmetic, and modal systems, which are as rigorous and predictive as the mathematical framework of quantum mechanics itself. The scientific method, which studies observable phenomena, is not in opposition to computationalism but is enriched by its insights into the structures that generate those phenomena. Computationalism extends the explanatory scope of science, bridging physical observations with deeper metaphysical questions. I’ll admit that my perspective on this matter is rooted not only in logic and evidence but in an enduring curiosity shaped by personal experience, not merely by this list. Since childhood, I’ve been struck by the inadequacies of both hard and soft sciences when it comes to reconciling the physical and the subjective. Hard sciences have captivated me with their explanatory precision but often falter when addressing consciousness and first-person experience. Soft sciences offer insight into the subjective but lack the rigor to engage with physical phenomena in a truly predictive way. This bias has shaped my openness to frameworks like computationalism, which strive to bridge these domains instead of the dull compartmentalization that is standard. Who can finally prove some absolute notion of domain-specificity? You're arguments are in constant danger of slipping into ideological certitude here. Perhaps this is my own version of taste, cultivated not just by logic but by a personal journey through wonder, doubt, and staying globally naive. The notion of “taste” is apt—it underscores the need to engage with these ideas experientially, not dismissively. Whether one prefers beans from an epistemic or Everettian can, the richness lies in savoring the flavor, not in rejecting the dish outright. -- You received this message because you are subscribed to the Google Groups "Everything List" group. 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