BU83 Global Physical Admissibility Theorem under B_U Boundary Consistency, Retained-Term Qualification, Resolution-Gap Audit, and Macro-Readout Standing

BU83 Global Physical Admissibility Theorem under B_U Boundary Consistency, Retained-Term Qualification, Resolution-Gap Audit, and Macro-Readout Standing BU83-B No-Free-Variable Universe under B_U Guardrail against Fatalistic Misreading, Parameter-Free Settlement Surface, Source-Level Dynamic Completeness, and Low-Entropy Trial Evolution BU83 establishes the Global Physical Admissibility Theorem under B_U as a source-level criterion for determining whether any candidate physical term, effective model, averaging contribution, residual structure, or macroscopic readout can obtain retained standing inside the single-universe settlement surface. Its central entry point is the failure of backward-mirror cosmology to derive a strict, closed, domain-independent FLRW + \Lambda macro-behavior from full GR with arbitrary inhomogeneous initial data. FLRW + \Lambda remains a self-consistent macroscopic model under imposed symmetry, but symmetry-based success does not by itself deliver global physical admissibility. The paper reclassifies Buchert backreaction, Green-Wald-style negligibility claims, attractor results, gauge dependence, and domain selection as symptoms of a deeper retained-term qualification problem. A term does not acquire macroscopic standing merely by appearing inside an averaging equation. It must first pass the admissible domain fixed by M, D(M), B_U, and B_0. The decisive theorem states that microscopic feedback contribution is not merely small. Within the physically admissible microscopic domain, its spatial average is exactly zero. This exact zero does not arise from random-phase cancellation, statistical smoothing, or heuristic averaging. It follows from two structural operations: the microscopic entropy-gradient is projected into a zero-mean fast subspace, and the covariance between the fast projected component and the slow residual-driving sector vanishes by orthogonal decomposition. The first cut eliminates the mean; the second cut eliminates the covariance. BU83 therefore shifts the problem from averaging closure to admissibility closure. It does not add another empirical closure ansatz to cosmology. It supplies a prior physical qualification rule: only terms that survive boundary consistency, dynamic completeness, zeroing, residual audit, and settlement can enter the retained macro-ledger. Global physical admissibility precedes macroscopic model closure.