theorem effectiveAlpha_monotone_J {rho : ℝ} {J1 J2 : ℕ}
(hrho_pos : 0 < rho) (hrho_lt : rho < 1)
(_hJ1 : 1 ≤ J1) (_hJ2 : 1 ≤ J2) (hJ : J1 ≤ J2) :
(1 - rho) / rho * ((↑J1 - 1) / ↑J1) ≤
(1 - rho) / rho * ((↑J2 - 1) / ↑J2) := by
apply mul_le_mul_of_nonneg_left _ (div_nonneg (by linarith) (le_of_lt hrho_pos))
have hJ1_pos : (0 : ℝ) < ↑J1 := by positivity
have hJ2_pos : (0 : ℝ) < ↑J2 := by positivity
rw [div_le_div_iff₀ hJ1_pos hJ2_pos]
have hJ_cast : (↑J1 : ℝ) ≤ ↑J2 := Nat.cast_le.mpr hJ
nlinarithPaper 6: Endogenous Decentralization and the AI Transition