Λψ Beyond Negative Pressure: Structural Retention as a Post-Dynamical Cosmological Regime

This work introduces the Λψ term as a non-dynamical equilibrium component in retentive cosmology, formalizing a post-dynamical regime in which large-scale cosmic structure remains coherent under asymptotic conditions where expansion-driven dynamics and energy flux diminish. Λψ is shown to be neither a form of negative pressure nor a substitute for dark energy, but a complementary structural term extending cosmological description beyond purely dynamical evolution. The paper provides a minimal formal definition, establishes compatibility with the Friedmann context without modification, and identifies observational signatures accessible through long-duration, non-perturbative integration.