Time Field Theory (TFT): Axiomatic Foundations, Flat-Spacetimes Gravity, and Velocity-Dependent Gravitational Acceleration — Complete Series I, II, IX

This collection contains three core papers of Time Field Theory (TFT), a self-consistent, axiomatic, flat-spacetime framework for gravity based on the universal total speed conservation: 1. Time Field Theory I: Gravitational Effects in Flat Spacetime 2. Time Field Theory II: Fundamental Axioms and Geometric Foundations 3. Time Field Theory IX: Velocity-Dependent Gravity and Parameter-Free Unified Fitting of Experimental Data TFT is built on the invariant spacetime speed relation c² = vₜ² + vₛ², where gravity arises from the gradient of the time field = vₜ/c. The theory reproduces all classic gravitational tests (gravitational time dilation, light deflection, Mercury perihelion precession, gravitational waves), is singularity-free, linear, quantizable, and provides a definitive experimental test using cold-atom interferometry to distinguish TFT from general relativity. All results are derived rigorously without free parameters or ad hoc assumptions.