Spiral Galaxy Rotation Curves in Stiffness Field Cosmology

We present a quantitative test of Stiffness Field Cosmology (SFC) using rotation curve data
from four spiral galaxies: the Milky Way, M33, NGC 2403, and NGC 3198. In SFC, gravity
emerges from spatial gradients of a physical vacuum stiffness field K(x), rather than from
non-baryonic dark matter. Starting from a Poisson-type equation for the logarithmic stiffness
sourced by baryonic matter, we derive the stiffness profile of an exponential disk and obtain an
analytic expression for circular velocities. With one universal coupling constant and observed
baryonic disk parameters, the model reproduces rising, quasi-flat, and gently declining rotation
curves. Gravitational lensing and cluster-scale phenomena are explained consistently through
photon refraction and the viscoelastic persistence of the stiffness field.