BU45 Space under B_U Projection Settlement Stratum, Physically Admissible Domain, and Boundary-Locked Dimensional Readout

Abstract Space under B_U: Projection Settlement Stratum, Physically Admissible Domain, and Boundary-Locked Dimensional Readout reclassifies space as a boundary-locked projection settlement stratum rather than a passive container, empty background, or unlimited geometric stage. Under B_U, space is the physically admissible domain in which total reality becomes readable, auditable, and settleable in the projection stratum. The paper argues that spatial standing is not granted by coordinate description alone: paths, fields, local fluctuations, and geometric structures must pass boundary consistency and dynamic admissibility before they obtain physical qualification. The dynamically complete interface D(M) is positioned as the qualification-audit interface that filters admissible projection structures and prevents microscopic fast disturbances from entering the macroscopic spatial ledger as lawful nonzero net items. Through zero-mean projection and fast-slow orthogonal decomposition, microscopic disturbance is cleared into background, allowing stable macroscopic geometry and repeatable physical law to stand. The paper further distinguishes space and time as complementary projection-layer outputs: space delivers the settlement field, while time delivers the settlement sequence. The final claim is that space is the boundary-admitted field of reality-carriage: a structured admissible domain where objects, paths, measurements, causal chains, and macroscopic geometry receive stable spatial standing.