Dynamic Vacuum Viscosity as the Unified Origin of Cosmic Expansion

Update 03-08-2026 The AEGIS framework demonstrates a self-consistent pathway from early-universe hydrodynamics to present-day expansion. By replacing the static cosmological constant with a dynamic, phase-transitioning vacuum viscosity, I have closed the loop between the theoretical 'impedance' of the early vacuum and the observed acceleration of the late-time universe. The standard $\Lambda$CDM model of cosmology faces mounting observational tensions, most prominently the discovery of massive, mature galaxies at redshifts $z>10$ by the James Webb Space Telescope (JWST). These objects appear to have formed far earlier than the limited time available in the standard 13.79~Gyr cosmic timeline would allow. In this work we present the \textbf{AEGIS model} (Active Expansion via Geometric Injection System), a phenomenological yet physically motivated extension of the Friedmann equations that treats the vacuum itself as a viscous fluid. We introduce a dynamic viscosity coefficient $\eta(z)$ whose sign reverses across a geometric phase transition at $z\approx1.0$. In the early universe ($\eta>0$) the vacuum exerts a positive drag that slows expansion and “buys” extra time for structure formation. After the transition ($\eta<0$) the same vacuum fluid provides a negative pressure that naturally drives the observed late-time acceleration. This single mechanism replaces the cosmological constant entirely.