Structural Differentiation Cosmology (SDC): Observational Decision Framework

This paper presents version 2.0 of Structural Differentiation Cosmology (SDC), focusing on an observational decision framework designed to distinguish SDC from the standard ΛCDM cosmological model. Rather than introducing new physical components such as dark energy, SDC interprets the observed cosmic acceleration as an observational projection of irreversible internal structural differentiation in a closed universe. The purpose of this document is not to provide a complete cosmological model, but to define a minimal and falsifiable observational criterion capable of discriminating between two interpretations of cosmic acceleration: • ΛCDM: acceleration driven by dark energy • SDC: acceleration arising as a projection of internal structural differentiation The central discriminator is the geometry–growth relation between the expansion history H(z) and the growth observable fσ₈(z). In ΛCDM these quantities follow a single trajectory, while SDC predicts systematic deviations caused by projection effects. A conceptual geometry–growth plane is presented to illustrate how future observations may distinguish these two frameworks. This work explicitly defines falsification conditions. If observations fail to satisfy the predicted criterion, SDC is rejected. The goal of this framework is therefore not to protect a model, but to state clearly where observations may confirm or refuse it. Relevant observational programs include: DESI Euclid Roman Space Telescope CMB-S4 This document serves as an observational decision framework for evaluating whether cosmic acceleration should be interpreted as a physical expansion component or as a structural projection phenomenon.