Vacuum Phase Coherence and the MOND Acceleration Scale

The characteristic acceleration scale a0 ≈ 1.2×10^-10 m/s² appearing in Modified Newtonian Dynamics (MOND) is numerically close to cH0/2, where H0 is the Hubble parameter. This paper derives the relationship a0 = cH0/2 from the assumption that the vacuum possesses a coherent phase field extending to the Hubble radius. The factor of 2 arises necessarily from the periodicity of the phase field and the requirement of single-valuedness, not from dimensional analysis or numerical fitting. The derivation shows that if the vacuum has a compact phase field with period 2π that is coherent over cosmological scales, then the characteristic acceleration scale a0 = cH0/2 emerges naturally. Part I establishes this fundamental connection without addressing galaxy rotation curves, interpolation functions, or cosmological dynamics, which are deferred to subsequent work.