The third selected physical root is a root
ProvedErdos1041.Counterexample.s4_b3_isRootdegree-seven-counterexampleerdos-1041polynomial-lemniscate
The physical root with index 3 is a zero of f.
Preamble
import Definitions.Def_ErdosProblems_Erdos1041_Counterexample_Defs import Definitions.Def_ErdosProblems_Erdos1041_Counterexample_InstanceCritical import Mathlib.Algebra.Polynomial.Derivative import Mathlib.Algebra.Polynomial.Div import Mathlib.Algebra.Polynomial.Roots import Mathlib.Analysis.Real.Pi.Bounds import Mathlib.Analysis.SpecialFunctions.Complex.Log import Mathlib.Analysis.SpecialFunctions.Pow.Real import Mathlib.Analysis.SpecialFunctions.Trigonometric.Basic import Mathlib.Tactic import Mathlib.Tactic.ComputeDegree import Mathlib.Tactic.NormNum import Mathlib.Tactic.Ring import Mathlib.Topology.Connected.LocallyConnected import Mathlib.Topology.EMetricSpace.BoundedVariation import Mathlib.Topology.MetricSpace.Contracting import Mathlib.Topology.Order.IntermediateValue open Erdos1041 open Erdos1041.Counterexample noncomputable section open scoped ComplexConjugate NNReal set_option maxHeartbeats 4000000 set_option maxRecDepth 10000 open Erdos1041.Counterexample
Formal statement
theorem Erdos1041.Counterexample.s4_b3_isRoot : f.IsRoot (S4Proofs.physicalRoot 3) := by sorry
Source
Lean source: https://github.com/wcook04/plectis-erdos-lean/blob/cc7e541cf2081c6fef5a5e377d52e365e33b01eb/ErdosProblems/Erdos1041/Counterexample/InstanceCritical.lean#L960-L962
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.