A Concrete Metric for Boundary Pressure FB

This paper introduces a measurable formulation for boundary pressure (FB) within the Theory of Non-Derivable Admissibility (TNA) framework. We define FB as a quantifiable metric derived from three observable components: reliability degradation (R), prediction uncertainty (U), and structural instability (D). The proposed integral and discrete models allow for the localization of structural tension at the system's boundary (∂Ω), providing a domain-independent tool to identify expansion triggers (Ω → Ω⁺). By instantiating this metric in physics, machine learning, and cognition, we demonstrate its utility in predicting system adaptation or failure. This formalization transforms the qualitative concept of boundary pressure into a rigorous analytical parameter for assessing the structural health and evolutionary potential of complex systems.