Emergent Cosmological Constant from Self-Organized Quantum Vacuum Boundary Conditions

his paper presents an emergent formulation of the cosmological constant (Λ) derived from macroscopic quantum vacuum boundary conditions at the Hubble horizon. Regulated by a critical acceleration threshold a₀ ≈ 1.2 × 10⁻¹⁰ m/s², the model yields an exact vacuum energy density ρvac = 3a₀ H₀ / (8π G c) ≈ 5.3 × 10⁻²⁷ kg/m³, perfectly matching Planck observational data without fine-tuning. Includes a 5-test quantitative numerical validation suite and full code reproducibility.