Radiation-Dependent Scalar Coupling: Deriving the Baryonic Tully–Fisher Relation without Dark Matter

This work presents a refined and extended formulation of my earlier scalar–gravity framework (Zenodo record: https://zenodo.org/records/15870352). Building upon the original idea of gravity emerging from baryonic matter density gradients, the present thesis introduces a radiation-dependent regulatory mechanism that dynamically controls the coupling between the scalar field and matter. This refinement resolves key theoretical limitations of the earlier model by providing a physically motivated screening mechanism that restores General Relativity in high-radiation environments such as the Solar System and the early universe, while allowing modified gravitational dynamics in low-radiation galactic halos. The updated framework derives the Baryonic Tully–Fisher Relation directly from baryonic matter without invoking non-baryonic dark matter, incorporates a consistent action-based formulation, and clarifies the thermodynamic and horizon-scale implications. As such, this work should be regarded as a consolidated, mathematically complete, and observationally focused advancement of the earlier preprint rather than a separate or unrelated proposal.