Structural Differentiation Cosmology (SDC) is a minimal cosmological framework in which the observed acceleration of the universe is interpreted as an observational projection of irreversible internal structural differentiation within an externally closed universe. Rather than introducing dark energy or additional cosmological components, SDC describes cosmic evolution through the monotonic increase of structural differentiation. The central observational criterion proposed in this work is the geometry–growth relationship. If cosmic acceleration is not a physical expansion of spacetime but instead a projection effect, the relationship between the expansion history and the growth of cosmic structure should deviate from the trajectory predicted by the ΛCDM model. This work introduces the Geometry–Growth Projection Test (GGPT), a single observational diagnostic designed to distinguish structural projection cosmology from physical acceleration models. This release presents version 1.9 of the SDC framework, including the geometry–growth separation test and an analysis of the observational detectability of the predicted deviations. The figures included in this repository illustrate the predicted background evolution, the growth divergence, and the geometry–growth diagnostic plane that provides a decisive observational test distinguishing SDC from ΛCDM.
Koji Okino (2026) studied this question.