def npvOptimalBound (η D₀ δ_gap : ℝ) : ℝ := δ_gap / (8 * η ^ 2 * (D₀ + δ_gap / (2 * η)))
thesis/CESProofs/Macro/GrowthTax.lean:79
Growth and Dynamic Tax Revenue (Layer 4-5 of Macro Extension)