ψ-Retention Cosmology and Neutrinos: A Structural Suppression Mechanism Beyond Mass-Driven Damping

This article (ψ-Architecture Research Series, Vol. IV, Article 5) examines the relationship between ψ-Retention Cosmology and neutrino-induced structure suppression in the late Universe. It demonstrates that the ψ-retentive mechanism is structurally distinct from mass-driven neutrino damping and cannot be reproduced by any effective neutrino mass parameter Σmν. While massive neutrinos suppress structure through scale-dependent free-streaming, ψ-Retention produces a scale-invariant fixed point in the growth observable fσ₈(z), a constant anomalous growth index, null gravitational slip (η = 1), and uniform void-lensing suppression. The work derives clear degeneracy-breaking conditions and shows that neutrinos and ψ-Retention occupy orthogonal explanatory axes in late-time cosmology. The article provides falsifiable predictions for Euclid DR1 and establishes ψ-Retention as a minimal, non-dynamical structural framework for understanding late-time growth saturation, fully consistent with General Relativity and current observational constraints.