theorem liquidity_trap {J : ℕ} {ρ : ℝ}
{T_new T_old Tstar : ℝ} (hTs : 0 < Tstar)
(hNew : Tstar ≤ T_new) (hOld : Tstar ≤ T_old) :
policyResponse J ρ T_new T_old Tstar = 0 := by
simp only [policyResponse]
rw [effectiveCurvatureKeff_above_critical J ρ T_new Tstar hTs hNew,
effectiveCurvatureKeff_above_critical J ρ T_old Tstar hTs hOld]
ringMonetary Policy and the Liquidity Trap