Toward a Covariant Extension of Relational Information Dynamics: The Einstein-Langevin Route to Q_μν

Paper 1 derived the galactic acceleration floor g† = 2cH₀, dS/π² from the synchronisation cost of quantum correlations across the de Sitter cosmological horizon. The central claim is that the de Sitter horizon is not merely a boundary condition but an active participant in local physics through the entanglement structure of the vacuum. The scale g† ~ cH₀, dS is structurally inevitable from de Sitter geometry — it is the only acceleration constructible from c and H₀, dS alone. What Paper 1 contributes beyond dimensional analysis is the exact coefficient 2/π², derived from the mode structure of the horizon. The present paper provides three things. First, a derivation of the 1/n² spectral scaling from the published de Sitter noise kernel, replacing the heuristic with a result grounded in stochastic semiclassical gravity. Second, a physical mechanism — the Planck cancellation — showing that Planck-suppressed per-cell fluctuations sum incoherently over the Nbits = (lH/lP) ² horizon cells to produce a macroscopic acceleration threshold g† = cH₀, dS × (2/π²), with ℏ and G cancelling exactly. Third, a comparison with Verlinde emergent gravity showing that three independent frameworks all converge on g† ~ cH₀, dS, confirming that this scale is structurally forced by de Sitter geometry. The remaining open problem — deriving the exact coefficient from the Pérez-Nadal noise kernel bitensor — is resolved in Paper 3 via the KMS condition and canonical normalisation of de Sitter mode functions.