  Under a Lorentz-transformation, Mie's 1912 gravitational mass behaves
identical as de Broglie's 1923 clock-like frequency. The same goes for Mie's
inertial mass and de Broglie's wave-like frequency. This allows the
interpretation of de Broglie's "Harmony of the Phases" as a "Principle of
Equivalence" for Quantum Gravity. Thus, the particle-wave duality can be given
a realist interpretation. The "Mie-de Broglie" interpretation suggests a
correction of Hamilton's variational principle in the quantum domain. The
equivalence of the masses can be seen as the classical "limit" of the quantum
equivalence of the phases.
