Observable Signatures of Structural Differentiation Cosmology: The Geometry–Growth Projection Test (GGPT)

This work presents a minimal and reproducible figure set demonstrating the observable signatures of Structural Differentiation Cosmology (SDC). SDC interprets cosmic acceleration not as a consequence of dark energy, but as a projection effect arising from irreversible structural differentiation in a closed universe. The included figures illustrate a key prediction of the framework:a near-degeneracy with ΛCDM in the background expansion history H(z), accompanied by a systematic and measurable suppression in the growth observable fσ₈(z). This separation is quantified through a monotonic residual and unified in the Geometry–Growth Projection Test (GGPT), which provides a single observable plane where SDC produces a characteristic trajectory. The GGPT serves as a clear and falsifiable diagnostic for distinguishing projection-based cosmological acceleration from physically driven models such as ΛCDM. All figures are fully reproducible using the included Python script.