Claims that experiments confirm the many-worlds interpretation often conflate evidence for quantum coherence, universal unitarity, the absence of objective collapse, decoherence-defined branches, and the reality of every branch. This paper develops a contrast-relative architecture that separates those targets. A complete theory package includes dynamics, ontology, state and parameter assumptions, and a probability or typicality rule that generates empirical likelihoods. Four formal results follow. Operationally equivalent theories have a Bayes factor of one for every fixed or adaptive protocol in the domain of equivalence. Evidence can redistribute probability toward a theoretical family while leaving the odds among equivalent members unchanged. An exact decomposition identifies the bridge factors required when support is inherited from shared dynamics by stronger structural or ontological claims. Finally, an inheritance-attenuation formula quantifies how evidence for unitarity weakens when Everett is compared with a complement containing other unitary theories. Applications include massive matter-wave interference, XENONnT collapse constraints, experimental quantum Darwinism, Local Friendliness tests, and proposed interbranch communication. Current results extend the tested domain of coherent quantum dynamics, constrain specified collapse models, and support mechanisms for stable, redundant records. They do not supply an outcome distribution favoring Everett over all operationally equivalent unitary rivals or directly establish the reality of every decohered component. Everett can therefore receive indirect, family-mediated confirmation while its distinctive ontology remains underdetermined within a predictive equivalence class.
Claims that experiments confirm the many-worlds interpretation often conflate evidence for quantum coherence, universal unitarity, the absence of objective collapse, decoherence-defined branches, and the reality of every branch. This paper develops a contrast-relative architecture that separates those targets. A complete theory package includes dynamics, ontology, state and parameter assumptions, and a probability or typicality rule that generates empirical likelihoods. Four formal results follow. Operationally equivalent theories have a Bayes factor of one for every fixed or adaptive protocol in the domain of equivalence. Evidence can redistribute probability toward a theoretical family while leaving the odds among equivalent members unchanged. An exact decomposition identifies the bridge factors required when support is inherited from shared dynamics by stronger structural or ontological claims. Finally, an inheritance-attenuation formula quantifies how evidence for unitarity weakens when Everett is compared with a complement containing other unitary theories. Applications include massive matter-wave interference, XENONnT collapse constraints, experimental quantum Darwinism, Local Friendliness tests, and proposed interbranch communication. Current results extend the tested domain of coherent quantum dynamics, constrain specified collapse models, and support mechanisms for stable, redundant records. They do not supply an outcome distribution favoring Everett over all operationally equivalent unitary rivals or directly establish the reality of every decohered component. Everett can therefore receive indirect, family-mediated confirmation while its distinctive ontology remains underdetermined within a predictive equivalence class.
Despite quantum mechanics’ unrivalled empirical success, its unrestricted formal applicability does not by itself establish that it provides a physically self-sufficient account of an entirely quantum world. This paper argues that the common operational core of quantum mechanics is not a complete theory of purely quantum reality. It is an interface architecture: it connects quantum states and transformations to physical preparations, measurement contexts, stable records, and definite outcomes. The argument distinguishes formal universality, conditional predictive adequacy, and physical self-sufficiency. Quantizing the apparatus extends the chain of quantum correlations but does not derive a single outcome from unitary dynamics; decoherence explains interference suppression, pointer stability, and record proliferation, but does not by itself convert an improper mixture into the actuality of one alternative. A closed universe provides the decisive test because preparation, subsystem decomposition, time, probability, and records can no longer be assigned to an external domain. Decoherent histories, Everettian quantum mechanics, Bohmian mechanics, objective-collapse theories, relational quantum mechanics, and contextual approaches are accordingly analysed as distinct strategies for closing or redefining the interface. The diagnosis extends to quantum field theory and quantum gravity: quantizing matter, apparatuses, reference frames, or geometry does not alone close the record interface. A fundamental theory must derive, constrain, or replace the conditions under which determinate empirical reality becomes possible. The measurement problem is therefore a local manifestation of a broader problem concerning the physical domain of quantum mechanics. This is a preprint version of a manuscript currently under journal review.
Abstract Much of the evidence for quantum mechanics is statistical in nature. Relative frequency data summarizing the results of repeated experiments is compared to probabilities calculated from the theory; close agreement between the observed relative frequencies and calculated probabilities is taken as evidence in favour of the theory. The Everett interpretation, if it is to be a candidate for serious consideration, must be capable of doing justice to this sort of reasoning. Since, on the Everett interpretation, all outcomes with non-zero amplitude are actualized on different branches, it is not obvious that sense can be made of ascribing probabilities to outcomes of experiments, and this poses a prima facie problem for statistical inference. It is incumbent on the Everettian either to make sense of ascribing probabilities to outcomes of experiments in the Everett interpretation, or to find a substitute on which the usual statistical analysis of experimental results continues to count as evidence for quantum mechanics, and, since it is the very evidence for quantum mechanics that is at stake, this must be done in a way that does not presuppose the correctness of Everettian quantum mechanics. This requires an account of theory confirmation that applies to branching-universe theories but does not presuppose the correctness of any such theory. This chapter supplies and defends such an account. The account has the consequence that statistical evidence can confirm a branching-universe theory such as Everettian quantum mechanics in the same way in which it can confirm a non-branching probabilistic theory.
Quantum interpretations differ in ontology, dynamics, and the meaning of quantum states, but these differences become empirical alternatives only when they yield different records for a com-mon experiment. Two worked comparisons establish where discrimination succeeds and fails. In a trapped-particle arrival-time model, paired spin ensembles have identical density operators but detector-free first-entry laws separated by an exactly calculable total-variation distance. A common quantum instrument nevertheless gives them identical record laws, with a sharp obstruction to re-producing both free-arrival distributions. A second comparison places universal unitary evolution and genuine collapse in the same coherent-memory experiment. An echo removes constant detuning but leaves ordinary Markov dephasing exactly confounded with collapse when their total rates co-incide. Independent noise and readout bounds yield a discrimination gap, an optimal observation time for equal trial cost, and a finite-sample guarantee. Comparisons involving GRW ontologies, relational quantum mechanics, and QBism clarify the roles of record formation and conditioning. Recent nanoparticle-interference and spontaneous-radiation experiments constrain specified collapse dynamics without uniquely favoring an ontology. A Bayesian analysis separates these constraints from posterior comparisons and from theoretical preferences based on scope, economy, and definite out-comes. It identifies the conditional case for Everett alongside the relevant Bohmian counterpoints. The resulting assessment permits unequal empirical support without claiming either universal equivalence or an experimentally established ranking of the surviving interpretations.
Working philosophical/foundational draft.This paper extends the logic of the companion BCT paper The A=A Problem for Everettian Branching from subject-individuation to observer-world individuation. Its central claim is that branch or microphysical multiplicity should not automatically be counted as observer-world multiplicity unless it induces observer-relevant record differentiation. The paper does not deny decoherence, emergent branch structure, or the universal quantum state. It argues instead for an observer-equivalence constraint: physically distinct realizations that agree on all accessible, persistent, update-constraining records for a finite observer A do not define distinct observer-worlds for A.Related companion paper: The A=A Problem for Everettian Branching, available in the recently published BCT philosophical working-papers record (DOI: 10.5281/zenodo.19649860).Background: independent researcher.Web site: https://bit-collapse-theory.netlify.app/Main DOI: 10.5281/zenodo.18496128 AbstractEverettian quantum mechanics is often presented as ontologically economical because it preserves unitary dynamics and avoids physical collapse. This paper argues that such economy remains incomplete unless Everettian realism supplies a principled criterion for counting worlds, branches, histories, or observer-relevant realities. The central worry is not mathematical branching, but ontological overcounting: the move from branch-level or microphysical multiplicity to full world-multiplicity may assign ontological weight to distinctions that make no difference to any observer-constituting record. The paper introduces an observer-equivalence constraint: two physical or branch-relative realizations are equivalent for a finite observer A if they agree with respect to all physically accessible, persistent, update-constraining records available to A within its finite integration window. In the conscious case, the relevant record-structure is understood as temporally integrated over a finite window rather than as an instantaneous observer-slice. The resulting picture does not refute Everettian quantum mechanics, nor does it deny decoherence or branch structure. It instead challenges the interpretation of branch multiplicity as unpriced ontological multiplicity and proposes a record-based constraint on ontological economy: worlds should not be counted more finely than the record-structures that make them difference-making for observers. Keywordsquantum foundations; Everett interpretation; observer-equivalence; ontological economy; branching worlds; records; subject-individuation; informational identity
Abstract There is a compelling intellectual case for exploring whether purely unitary quantum theory defines a sensible and scientifically adequate theory, as Everett originally proposed. Many different and incompatible attempts to define a coherent Everettian quantum theory have been made over the past fifty years. However, no known version of the theory (unadorned by extra ad hoc postulates) can account for the appearance of probabilities and explain why the theory it was meant to replace — Copenhagen quantum theory — appears to be confirmed, or more generally why our evolutionary history appears to be Born-rule typical. This chapter reviews some ingenious and interesting recent attempts in this direction by Wallace, Greaves–Myrvold, and others, and explains why they don't work. An account of one-world randomness, which appears scientifically satisfactory, and has no many-worlds analogue, is proposed. A fundamental obstacle to confirming many-worlds theories is illustrated by considering some toy many-worlds models. These models show that branch weights can exist without having any role in either rational decision-making or theory confirmation, and also that the latter two roles are logically separate. Wallace's proposed decision theoretic axioms for rational agents in a multiverse and claimed derivation of the Born rule are examined. It is argued that Wallace's strategy of axiomatizing a mathematically precise decision theory within a fuzzy Everettian quasiclassical ontology is incoherent. Moreover, Wallace's axioms are not constitutive of rationality either in Everettian quantum theory or in theories in which branchings and branch weights are precisely defined. In both cases, there exist coherent rational strategies that violate some of the axioms.
This record contains version 2 of the preprint “Identifiability Limits in Experimental Tests of Quantum Collapse.” It supersedes the conceptually broader first version deposited under DOI 10.5281/zenodo.19617199 and substantially revises the framing, formal results and experimental analysis. The paper formulates experimental tests of objective-collapse dynamics as an operational identifiability problem. It shows that finite accessible CPTP process statistics cannot uniformly distinguish fundamental nonunitarity from an unrestricted unitary-environment dilation. It then separates visibility loss, record formation and global measurement access, and derives a nuisance-profiled Fisher-information criterion for determining when complementary measurement channels jointly identify a shared collapse-parameter vector. A four-arm matched-control architecture is proposed that combines baseline stability, coherent reversibility, calibrated decoherence, durable-record formation and at least one independent side-effect channel. The result is a falsifiable experimental decision framework and a boundary on what accessible data can establish; it is not presented as an ontological solution of the quantum measurement problem. A major technical revision is available as version 3 under DOI 10.5281/zenodo.22072199. This record contains version 2 of the preprint “Identifiability Limits in Experimental Tests of Quantum Collapse.” It supersedes the conceptually broader first version deposited under DOI 10.5281/zenodo.19617199 and substantially revises the framing, formal results and experimental analysis. The paper formulates experimental tests of objective-collapse dynamics as an operational identifiability problem. It shows that finite accessible CPTP process statistics cannot uniformly distinguish fundamental nonunitarity from an unrestricted unitary-environment dilation. It then separates visibility loss, record formation and global measurement access, and derives a nuisance-profiled Fisher-information criterion for determining when complementary measurement channels jointly identify a shared collapse-parameter vector. A four-arm matched-control architecture is proposed that combines baseline stability, coherent reversibility, calibrated decoherence, durable-record formation and at least one independent side-effect channel. The result is a falsifiable experimental decision framework and a boundary on what accessible data can establish; it is not presented as an ontological solution of the quantum measurement problem. Files in this record:1. Main preprint PDF.2. Reproducibility package containing the journal-neutral source, editable manuscript, original figures, deterministic calculation and figure-generation code, machine-readable results, citation metadata and SHA-256 checksums. The included calculations are deterministic mathematical and synthetic checks; they are not experimental validation.