Cross-Domain Validation of Viability Metrology: Testing the Invariant Measurement Core Across Systems of Different Nature

This article develops a framework for cross-domain validation of viability metrology within Vitology. Building on the interdisciplinary pilot testing conducted in G34, indicator standardization in G35, standardized retesting in G36, and the external-transferability framework proposed in G37, the study asks which components of viability measurement can remain operationally invariant across systems of different nature. The article distinguishes between an invariant metrological layer and a domain-specific operational layer. The invariant layer contains the functional positions occupied by system state, disturbance, response, recovery or adaptation, change, profile, and trajectory. The domain-specific layer contains the observable variables, units, reference conditions, timescales, causal mechanisms, uncertainty structures, and interpretation rules required in particular scientific domains. G38 introduces the concepts of Invariant Metrological Core of Viability (IMCV), Cross-Domain Viability Validation (CDVV), Functional Metrological Equivalence (FME), Invariant Layer (IL), Domain-Specific Layer (DSL), Cross-Domain Viability Invariance Hypothesis (CDVIH), Metrological Transferability Boundary (MTB), and the Invariant–Domain Model of Viability (IDMV). Four levels of cross-domain validation are proposed: Structural Invariance, Operational Equivalence, Metrological Comparability, and Interpretive Stability. The framework explicitly rejects the assumption that physical identity of indicators is required for functional comparison, while also rejecting the opposite assumption that any domain-specific measure can be normalized into meaningful cross-domain equivalence. The article further formulates the Doctrine of the Invariant Core of Viability Metrology and the working Theory of Invariant–Domain Viability Metrology (TIDVM). These constructs are presented as testable methodological propositions rather than established universal laws. The central conclusion is that the strongest currently defensible form of interdisciplinary universality in viability metrology is likely to be partial and structural rather than complete and numerical. A common architecture may be preserved while domain-specific measurement content remains irreducible. This distinction provides a basis for future empirical cross-domain validation, independent replication, sensitivity analysis, and systematic identification of the boundaries within which viability metrology retains scientific meaning. Keywords: Vitology; viability; viability metrology; cross-domain validation; invariant metrological core; structural invariance; functional equivalence; metrological comparability; domain specificity; standardization; normalization; measurement uncertainty; regeneration; adaptation; viability trajectory; interdisciplinary research; transferability.