BU03 Boundary Drift and Ontological Fragmentation

This paper develops Boundary Drift and Ontological Fragmentation as the negative morphism of single-universe boundary axiomatics. Its central claim is precise: once global boundary consistency fails, single-universe standing fails with it. Formally, the paper expands the implication \neg B_U \Rightarrow \neg S, where B_U denotes the global invariance of physical boundary conditions over the total domain U, and S denotes ontological single-universe standing. In this framework, fragmentation is not defined by spatial separation, visual discontinuity, or numerical multiplicity. It is defined by the loss of a unique globally shared boundary set. The paper shows that even minimal boundary drift is structurally decisive. If boundary conditions cease to remain identical across U, then the universe no longer preserves a single admissibility background. This immediately destabilizes global law-level unity, constant-level unity, and settlement-level unity. The consequence is not merely local irregularity, but a collapse of global physical admissibility itself. Theoretical constructions that tolerate branching boundary conditions, region-dependent validity, or independent ontological subdomains are therefore reclassified as fragmentation structures rather than single-universe physics. The aim of the paper is diagnostic and disciplinary. It provides a rigorous negative criterion for distinguishing local effective success from universe-level standing, and for identifying when explanatory expansion has already crossed into ontological fracture.