The Nature of Mass: Deriving the Koide Mass Formula Axiomatically from Xinzi Field Theory

The Koide mass formula Q = (m_e+m_mu+m_tau)/(sqrt(m_e)+sqrt(m_mu)+sqrt(m_tau))^2 has held to 10^-5 precision since 1981, yet lacks a theoretical explanation. This paper presents an axiomatic derivation within Xinzi Field Theory: the charged-lepton mass spectrum is decomposed into a DC component and a triple-phase fluctuation component, and it is shown that the Koide relation holds exactly when the fluctuation component equals the DC component in strength (Q = 2/3). The derivation yields the prediction m_tau = 1776.969 MeV, within ~0.1 MeV of the experimental value 1776.86 +/- 0.12 MeV, and proves that the electron mass is the structural lower bound of the lepton spectrum. All numerical results can be independently reproduced via the script in Appendix C.