Gravity Field Dynamics and Bimetric Gravity: Dual Tetrahedral Field Chambers as the Key to the General Parameters

Bimetric gravity provides a theoretically robust, ghost-free framework for interacting spin-2 fields, yet its interaction potential has remained phenomenologically underdetermined for over a decade: the five coefficients betaₙ have been treated as continuous free parameters to be fitted to cosmological data. We show that Gravity Field Dynamics (GFD), the derivation of gravitational coupling laws from the discrete combinatorial geometry of the local tetrad frame, resolves this underdetermination. The GFD coupling polynomial f (k, s) = 1 + k² + ks, evaluated at k = 4 tetrahedral faces, encodes the full interaction structure: its static skeleton at the symmetric point (s = 0) yields the locked integer coefficients betaₙ = 1, 0, 16, 0, 1, while its dynamic body under the conformal map s (x) = (x-1) / (x+1) produces the continuous topological capacity f (x) = (21x + 13) / (x + 1). Normalizing this capacity recovers the constitutive law mu (x) = x/ (x+1) and determines the scalar-tensor action without fitted parameters. Within GFD, the UV bimetric potential and the IR scalar-tensor action are projections of a single geometric object: the topological capacity of the dual tetrahedral field chamber. The locked potential lies within the ghost-free Hassan-Rosen class by construction.