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A feasible point can be rounded to a parent vertex preserving all closed-face memberships

Proved
Hirsch.feasible_point_has_face_preserving_parent_vertex

by jjosh · Sep 10, 2026 · Mathlib c5ea003 (Lean v4.30.0)

extreme-faceshirsch-conjecturepath-repairpolyhedra

For a compact parent and any family of closed extreme faces, every feasible point has a parent extreme vertex that lies in every supplied face containing the point; the face family need not be finite.

Preamble
import Mathlib
import Mathlib.Analysis.Convex.KreinMilman
import Definitions.Def_Hirsch_model

open scoped BigOperators RealInnerProductSpace
open Set Hirsch
Formal statement
namespace Hirsch

theorem feasible_point_has_face_preserving_parent_vertex
    {d : ℕ} {ι : Type*} (P : Set (EuclideanSpace ℝ (Fin d)))
    (F : ι → Set (EuclideanSpace ℝ (Fin d)))
    (hP : IsCompact P) (hF : ∀ i, IsExtreme ℝ P (F i))
    (hclosed : ∀ i, IsClosed (F i))
    (x : EuclideanSpace ℝ (Fin d)) (hx : x ∈ P) :
    ∃ v, v ∈ extremePoints ℝ P ∧ ∀ i, x ∈ F i → v ∈ F i := by sorry

end Hirsch
Source
Kernel-verified theorem from jjoshua2/prove2me-work PR #48/#50.

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