Every slit preimage is close to cc
ProvedErdos1041.Counterexample.bottleneck_slit_preimage_neardegree-seven-counterexampleerdos-1041polynomial-lemniscate
Under the two-root, unique-critical-point and quadratic disk hypotheses, any point in the critical component whose polynomial value lies on the slit is within (4/3)√(δ/|aHat|) of cc.
Preamble
import Definitions.Def_ErdosProblems_Erdos1041_Counterexample_Defs import Definitions.Def_ErdosProblems_Erdos1041_Counterexample_Bottleneck import Mathlib import Mathlib.Algebra.Polynomial.Derivative import Mathlib.Algebra.Polynomial.Div import Mathlib.Algebra.Polynomial.Roots import Mathlib.Analysis.SpecialFunctions.Complex.Log import Mathlib.Analysis.SpecialFunctions.Pow.Real import Mathlib.Analysis.SpecialFunctions.Trigonometric.Basic import Mathlib.Tactic.NormNum import Mathlib.Tactic.Ring import Mathlib.Topology.Connected.LocallyConnected import Mathlib.Topology.EMetricSpace.BoundedVariation open Erdos1041 open Erdos1041.Counterexample noncomputable section open Topology open Erdos1041.Counterexample
Formal statement
theorem Erdos1041.Counterexample.bottleneck_slit_preimage_near (p : Polynomial ℂ) (cc : ℂ)
(hcrit : (Polynomial.derivative p).IsRoot cc) (hv : p.eval cc ≠ 0)
(hcover : IsCoveringMap (bottleneckSlitProjection p cc))
(aHat : ℂ) (haHat : aHat ≠ 0) (h : ℝ) (hh : 0 < h)
(hdisk : ∀ z : ℂ, ‖z‖ ≤ h → ‖(shiftQuad p cc).eval z / aHat - 1‖ ≤ 1 / 4)
(δ : ℝ) (hδ : δ = 1 - ‖p.eval cc‖) (hδpos : 0 < δ)
(hδsmall : δ < ‖aHat‖ * h ^ 2 / 4)
(b₁ b₂ : ℂ)
(hb₁ : b₁ ∈ connectedComponentIn (Omega p) cc)
(hb₂ : b₂ ∈ connectedComponentIn (Omega p) cc)
(hr₁ : p.IsRoot b₁) (hr₂ : p.IsRoot b₂)
(hzeros : ∀ w ∈ connectedComponentIn (Omega p) cc, p.IsRoot w → w = b₁ ∨ w = b₂)
(huniq : ∀ c' ∈ connectedComponentIn (Omega p) cc,
(Polynomial.derivative p).IsRoot c' → c' = cc)
(z : ℂ) (hz : z ∈ connectedComponentIn (Omega p) cc)
(hslit : p.eval z ∈ bottleneckSlit (p.eval cc)) :
‖z - cc‖ < 4 / 3 * Real.sqrt (δ / ‖aHat‖) := by sorry
Source
Lean source: https://github.com/wcook04/plectis-erdos-lean/blob/cc7e541cf2081c6fef5a5e377d52e365e33b01eb/ErdosProblems/Erdos1041/Counterexample/Bottleneck.lean#L1465-L1539
Construction by ani: https://www.erdosproblems.com/forum/thread/1041#post-8861
Related paper and provenance: https://github.com/wcook04/plectis-erdos/blob/551bae6dc6e732cf85172d66323c8d2bc77ba962/paper/1041/erdos-1041-lemniscate-newton-flow.tex#L25-L99
Paper prior-art bibliography: https://github.com/wcook04/plectis-erdos/blob/551bae6dc6e732cf85172d66323c8d2bc77ba962/paper/1041/erdos-1041-lemniscate-newton-flow.tex#L1662-L1772
AI-assisted formalization in Will Cook's project; ani is credited for the degree-seven construction. Independent correspondence of the 1958 Problem 5 wording to this modern formulation is unrecorded.