The MOND Acceleration Scale from Rindler-de Sitter Thermodynamics

We derive the MOND acceleration scale from Rindler–de Sitter thermodynamics. If the Rindler horizon distance of a uniformly accelerated observer equals the Gibbons–Hawking thermal de Broglie wavelength λₓ₇ = 2πc/H, then a₀ = cH/2π. The factor 2π arises directly from the KMS period of the Euclidean de Sitter propagator and is not fitted. The Deser–Levin quadratic temperature addition law then supplies the interpolating function μ (x) = x/√ (1 + x²). These two inputs uniquely determine a ghost-free covariant AQUAL action F (Q) = √ (Q + Q²) − arcsinh (√Q) that satisfies the null and weak energy conditions, reduces to Newtonian gravity at high acceleration, yields the exact BTFR exponent 4 in the deep-MOND limit, and enforces constant a₀ as a structural consequence of vacuum selection on Rᵥac = 4Λ (not an extra assumption). The predicted value cH₃ₒ/2π ≈ 0. 94 × 10^-10 m s^-2 (using the asymptotic de Sitter Hubble rate) lies 22 % below the SPARC best-fit of 1. 20 × 10^-10 m s^-2; the residual is comparable to the present-day departure from exact de Sitter expansion. Gravitational-wave speed remains exactly c. Gravitational lensing requires a disformal metric completion and is deferred to future work. The central matching condition dR = λₓ₇ is a physically motivated postulate; a first-principles derivation (possibly from the holographic mode spectrum of the de Sitter boundary) remains the principal open problem of the framework.