Author here. This explores identifying the second variation of the Einstein-Hilbert action (δ²S_total) as physical inertia. In the weak-field limit, this reduces to ½mv² and derives F=ma from geometric principles rather than postulating it. Key implications:

Explains equivalence principle (m_i = m_g automatically) Makes testable predictions for ACES mission

Uses only standard GR formalisms. Seeking technical feedback on mathematical errors or prior work I may have missed.

Full paper:https://doi.org/10.5281/zenodo.17672563