Radion Stabilization and Dark Matter Consistency in Scalar–Vector–Spinor Effective Field Theory

A compact spectrum can generate a radion potential without determining a viable dark matter history. We make this distinction quantitative in a one-time, spacelike-circle realization of scalar-vector-spinor effective field theory organized by . The finite five-dimensional determinant contains a kernel and a massless limit; transforming to the Einstein frame introduces an additional inverse-volume factor. For periodic massive fermions competing with massless bosons, we prove existence and uniqueness of a finite Minkowski minimum after one bulk vacuum-energy tuning and derive its positive radion curvature. A benchmark containing the five graviton polarizations and two Dirac fields gives and , corresponding to at . We solve the radiation-era oscillation problem and obtain a two-component response to a specified thermal trace source. One component cannot be removed by adjusting a single frozen initial displacement, giving a conditional lower bound on the relic density. We also prove that the common-mass spectrum realizing the extremal gauge threshold in the companion study cannot simultaneously achieve Minkowski stabilization and its required one-loop gauge matching using only a bulk vacuum term. These results supply calculable masses and compatibility tests, while leaving the initial state, thermal history and additional matching operators explicit.