Abstract

We present a covariant scalar–vector–tensor framework in which late-time cosmic acceleration arises from a dynamical coupling between spacetime expansion and a scalar–aether sector rather than from a fundamental cosmological constant. The theory reduces to General Relativity in local and strong-field regimes but introduces a linear correction in the Hubble parameter at cosmological scales. We derive the field equations from the action, explicitly show how the interaction term generates the linear-H modification, analyze background and perturbation stability, and compute observable consequences for the expansion rate, structure growth, and effective dark energy equation of state. A constrained parameter window produces small correlated shifts in H0, fσ8, and w0 while preserving early-universe physics.