In our companion paper (Paygachkin, 2026, V2. 0), we demonstrated that a vacuum viscosity of η ≈ 0. 10 naturally resolves the Hubble Tension and explains the dispersion of Gravitational Waves (GW150914). However, microphysical experiments suggest that massive particles interact with the vacuum differently than massless waves. In this study, we extend the Primary Energy framework to the "Matter Regime" of high energy densities. We postulate that vacuum viscosity is not a constant but saturates near massive particles. Analyzing the Muon g-2 anomaly, we derive a saturation limit of viscosity ηₘicro ≈ 0. 14. We calculate that this phase transition occurs when the local energy density exceeds a critical magnetic field threshold of Bcrit ≈ 17. 25 T. Prediction: We propose a falsifiable experiment to verify this saturation. A stationary muon placed in a static magnetic field B > 20 T should exhibit a non-kinematic lifetime extension (Time Dilation) due to the local thickening of the vacuum. This "Static Time Dilation" is predicted to exceed standard relativistic calculations, confirming the material nature of the vacuum.
Sergey Yurevich Paygachkin (Sun,) studied this question.