TCIE–MSSM v1.5: A Froggatt–Nielsen Origin for Yukawa Couplings in a Unifying Scalar Framework

We present TCIE–MSSM v1.5, a complete effective field theory framework in which a single light scalar field controls the cosmological variation of gauge couplings through a universal scalar–gauge interaction, while remaining consistent with all local tests of gravity via a Damour–Polyakov screening mechanism. The model embeds naturally within an SU(5)-unified extension of the MSSM and incorporates a Froggatt–Nielsen origin for the scalar dependence of Yukawa couplings. This construction replaces a previously fine-tuned continuous electroweak parameter with a discrete integer Froggatt–Nielsen charge, improving the theoretical naturalness of the framework. The theory predicts a relative variation of the fine-structure constant at redshift two of order minus two times ten to the minus seven, accompanied by correlated variations of the strong coupling and a suppressed but calculable variation of the proton-to-electron mass ratio. All current constraints from equivalence principle tests and fifth-force searches are satisfied. The model is predictive and falsifiable by next-generation spectroscopic surveys and high-precision atomic clock experiments.