Structural Differentiation Cosmology (SDC) v1.2: Cosmic Expansion as a Projection of Internal Relational Reconfiguration

We present Structural Differentiation Cosmology (SDC), a minimal and falsifiableframework in which the observed cosmic expansion is interpreted as an observationalprojection of irreversible internal relational reconfiguration in an externallyclosed universe. The model introduces a bounded structural density C(t) as the sole dynamical statevariable. An effective expansion rate emerges through projection, without invokingdark energy, modified gravity, or additional fields. We demonstrate that SDC produces structured residuals and characteristic growthbehavior, and we outline a clear observational criterion distinguishing it fromΛCDM using precision cosmological data.