Irreversible Accessibility Loss in Dissipative Systems: A Time-Scale Criterion for Structural Irreversibility in Systems Governance

Irreversibility in complex systems is typically identified through instability, bifurcation, or entropy production. We propose a structurally distinct operational criterion: irreversible loss of future accessibility under locally admissible dynamics. We formalize an Accessibility Loss Index (ALI) based on contraction of reachable state-space subsets and demonstrate that irreversible contraction emerges when forcing intervals are shorter than intrinsic recovery times. We provide explicit regime inequalities and a fully traceable demonstrator. The framework extends viability theory and resilience analysis by introducing time-scale misalignment as a governance-relevant irreversibility mechanism. The criterion is measurable, falsifiable, and independent of local instability. Irreversibility; Accessibility; Systems governance; Viability theory; Time-scale dynamics; Regime shift