When the Universe Refuses to Forget: A Structural Retention Model with Minimal Data Fit

We present a minimal phenomenological extension of late-time cosmology based on the concept of structural retention. The model introduces a single parameter, ψ_c, which modifies the growth index and clustering amplitude. Using a simplified likelihood framework and a minimal MCMC analysis applied to representative fσ8(z) data, we obtain: ψ_c ≈ 0.10 ± 0.02 We further compare the model with the ΛCDM baseline using a χ² criterion and find a statistically meaningful improvement: Δχ² ≈ 5–6 This suggests that late-time structure formation may include a weak retentive component, providing a unified interpretation of growth suppression and clustering tension. This work is intentionally minimal and is intended as a first data-linked formulation of retention cosmology.