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Theorems · Theorem · complex analysis

Complex.norm_deriv_le_div_of_mapsTo_ball

∀ {E : Type u_1} [inst : NormedAddCommGroup E] [inst_1 : NormedSpace ℂ E] {R₁ R₂ : ℝ} {f : ℂ → E} {c : ℂ},
  DifferentiableOn ℂ f (Metric.ball c R₁) →
    Set.MapsTo f (Metric.ball c R₁) (Metric.closedBall (f c) R₂) → 0 < R₁ → ‖deriv f c‖ ≤ R₂ / R₁

The Schwarz Lemma: if f : ℂ → E is complex analytic on an open disk with center c and a positive radius R₁, and it sends this disk to a closed ball with center f c and radius R₂, then the norm of the derivative of f at c is at most the ratio R₂ / R₁.

Defined in
Mathlib.Analysis.Complex.Schwarz
Cited by
2 results in Mathlib
Foundations
Depth 295 from the axioms · uses propext, Classical.choice, Quot.sound
Assumes
NormedAddCommGroupNormedSpace

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