A Universal Three-Regime Sequence in Galaxy Dynamics Predicted by a Quantum Vacuum Composite Stiffness Response

This paper presents an observational classification of galaxy dynamics predicted by the Quantum Vacuum Composite Stiffness Response (QVCSR) framework. Rather than attributing low-acceleration phenomena to dark matter particles, QVCSR proposes that the quantum vacuum itself exhibits a nonlinear stiffness response below a universal acceleration scale. Using the total effective acceleration g_tot=g_bar + g_ext, where g_bar is the baryonic acceleration and g_ext is the external (environmental) gravitational field), the framework predicts that galaxies separate naturally into three regimes: (1) a high-acceleration suppression regime with baryon-dominated dynamics, (2) a shallow-activation regime with weak, diffuse vacuum response, and (3) a full-activation regime in which the vacuum response produces dark-matter-like gravitational effects. The paper shows that all three regimes are already populated by well-studied galaxies across a wide range of environments, including dark-matter-deficient satellites, baryon-dominated ultra-diffuse galaxies, and isolated low-surface-brightness dwarfs. This tripartite structure is not predicted by ΛCDM or MOND but emerges naturally from the QVCSR transition law. The work provides falsifiable observational predictions linking galaxy dynamics to their acceleration environments and offers a unified, environment-dependent interpretation of several long-standing anomalies in galaxy rotation curves.