Boundary Rigidity: A Cross-Domain Structural Pattern of Confinement and Regularity

We describe a recurring structural pattern observed across several independent domains: when a system is constrained by a complete and rigid boundary (cosmological horizon, spectral cutoff, critical line), bulk defects are suppressed and regularity emerges as a structural consequence rather than a numerical coincidence. This paper does not claim formal proofs of open conjectures. It proposes a cross-domain structural analogy and provides explicit falsifiability criteria within each domain. The pattern appears in: Generalized Universe Holography (GUH), structural analysis of the Riemann zeta function, band-limited Navier–Stokes equations, an emergent Hilbert–Pólya operator interpretation. A fifth meta-layer treats the framework's own scope as an object of falsifiability: applying the schema to additive number theory (Goldbach, twin primes) yields no structural gain, and this negative invariance is treated as evidence of a genuine scope boundary rather than a technical limitation. We emphasize that structural similarity does not imply mathematical equivalence between domains. Each case remains independently falsifiable. This whitepaper is a macro-level synthesis companion to ARG's domain-specific publications on GUH, Riemann zeta structural analysis, band-limited Navier–Stokes regularity, the Hilbert–Pólya operator interpretation, and the AI governance track (Chimera, AGI Stability Conditions).