ECM is a classical-field extension in which the vacuum is a real physical medium capable of storing phase potential that manifests as gravitational mass.
Negative Apparent Mass (NAM) is the stored phase potential of the vacuum. It produces gravity, redshift, inertia and cosmological acceleration.
Light loses frequency when it deposits energy into the vacuum Phase-Kernel. Redshift is therefore vacuum mass creation.
All forces arise from gradients in Phase-Kernel mass density. Spacetime curvature is not required.
Inertia arises because accelerating matter must reconfigure the surrounding Phase-Kernel mass. If the gradient is removed, inertia vanishes.