Documentation

LeanPool.ArnoldKAM.Arnold1963.Analysis.Taylor

Taylor remainder estimates obtained by integration along a contained segment, with explicit operator and coordinate Hessian bounds.

theorem KamProject.Arnold1963.norm_taylor_remainder_le {E : Type u_1} {F : Type u_2} [NormedAddCommGroup E] [NormedSpace ℝ E] [NormedSpace ℂ E] [IsScalarTower ℝ ℂ E] [NormedAddCommGroup F] [NormedSpace ℝ F] [NormedSpace ℂ F] [IsScalarTower ℝ ℂ F] [CompleteSpace F] {f : E → F} {U : Set E} {a b : E} {C : ℝ} (hab : segment ℝ a b ⊆ U) (hf : AnalyticOnNhd ℂ f U) (hC : NormBoundOn (fderiv ℂ (fderiv ℂ f)) U C) :
‖f b - f a - (fderiv ℂ f a) (b - a)‖ ≤ C / 2 * ‖b - a‖ ^ 2
theorem KamProject.Arnold1963.norm_taylor_remainder_le_of_coordinate_bound {n : ℕ} {f : ComplexSpace n → ℂ} {U : Set (ComplexSpace n)} {a b : ComplexSpace n} {Θ : ℝ} (hab : segment ℝ a b ⊆ U) (hf : AnalyticOnNhd ℂ f U) (hΘ : 0 ≤ Θ) (hbound : ∀ x ∈ U, ∀ (i j : Fin n), ‖((fderiv ℂ (fderiv ℂ f) x) (Pi.single i 1)) (Pi.single j 1)‖ ≤ Θ) :
‖f b - f a - (fderiv ℂ f a) (b - a)‖ ≤ 1 / 2 * ↑n ^ 2 * Θ * ‖b - a‖ ^ 2