Böttcher Coordinate & External Rays

Mathematics Calculus & Analysis Foundation for Douady-Hubbard proof Cite
Primary: L. E. Boettcher
Publication: External rays in complex dynamics
Year: early 20th c.
URL: Wikipedia

Description

Böttcher coordinate: near infinity, f_c(z) = z² + c is conjugate to w maps to w². Conformal map Φ_c on basin of infinity satisfying Φ_c(f_c(z)) = (Φ_c(z))². Equipotentials: level sets |Φ_c(z)| = const. External rays: curves arg(Φ_c(z)) = θ. For parameter space: Φ(c) = lim (f_cⁿ(c))^(1/2ⁿ) defines Böttcher map on complement of M. External rays of M: R_M(θ) = {c : arg Φ(c) = 2πθ}. Key for Douady-Hubbard connectedness proof.

Source: Wikipedia; Böttcher; Douady-Hubbard

Dependency Flowchart

graph TD Quad["Quadratic Julia and Mandelbrot"] DefBott["Def: Böttcher coordinate Φ_c"] DefFuncEq["Def: Functional equation Φ_c(f_c(z)) = (Φ_c(z))²"] DefEquip["Def: Equipotential |Φ_c(z)| = const"] DefExtRay["Def: External ray R(θ) arg Φ_c(z) = 2πθ"] DefPhiParam["Def: Parameter Böttcher Φ(c) lim (f_cⁿ(c))^(1/2ⁿ)"] ThmBott["Thm: Böttcher-Fatou Φ analytic on basin of infinity"] LemLand["Lem: Ray landing Rays land on J_c or M"] Quad --> DefBott DefBott --> DefFuncEq DefBott --> DefEquip DefBott --> DefExtRay DefBott --> DefPhiParam DefPhiParam --> ThmBott DefExtRay --> LemLand classDef axiom fill:#ff6b6b,color:#fff,stroke:#c0392b classDef definition fill:#b197fc,color:#fff,stroke:#9775fa classDef theorem fill:#51cf66,color:#fff,stroke:#40c057 classDef lemma fill:#74c0fc,color:#fff,stroke:#4dabf7 class Quad axiom class DefBott,DefFuncEq,DefEquip,DefExtRay,DefPhiParam definition class ThmBott theorem class LemLand lemma

Color Scheme

Red Prerequisite
Blue Definitions
Teal Theorems
Purple Lemmas

Process Statistics

  • Nodes: 9
  • Edges: 10
  • Axioms: 1
  • Definitions: 5
  • Lemmas: 1
  • Theorems: 1