Measurement as Coherence under Single-Universe Boundary Consistency

Abstract This paper develops Measurement as Coherence under Single-Universe Boundary Consistency as a structural rewriting of the quantum measurement problem. Its central claim is that measurement is not a mysterious transition from indeterminacy to reality, nor a branching into parallel worlds, but a coherence operation performed within one single-universe admissibility background. Let B_U denote global boundary consistency over the total domain U, let B_0 denote the unique fixed boundary set, and let measurement be defined as the operation that forces previously unrelated degrees of freedom into one causal chain under B_0. Under this definition, measurement immediately generates causal linkage, requires information-update cost, and yields single-valued settlement. The framework therefore replaces collapse-language with boundary-grounded settlement language. No coherence implies no new causal standing; coherence implies causal-chain generation, cost payment, and unique result. Apparent probabilistic uncertainty is reclassified as local ignorance of path expansion rather than ontological multiplicity. Branching interpretations lose standing because they require boundary drift or parallel result-spaces incompatible with B_U. The paper further shows that Schrödinger’s cat is not a paradox but a macroscopic illustration of the same rule: without coherence, no shared causal standing is established; with coherence, field-state matching enforces one admissible outcome. Measurement is thus recast as a lawful structural act of coherence, not a metaphysical mystery.