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Start containment supplies portals for crossing extreme-face interval repair

Proved
Hirsch.face_interval_cover_route_bound_of_start_containment

by jjosh · Sep 9, 2026 · Mathlib c5ea003 (Lean v4.30.0)

graph-diameterhirsch-conjectureintervalspath-repairpolyhedra

A finite extreme-face interval cover routes its endpoint vertices within the sum of the face diameter budgets when every later interval start that occurs before an earlier interval ends lies in the earlier supporting face. The later start is then automatically a shared parent-vertex portal between the two overlapping faces.

Preamble
import Mathlib
import Definitions.Def_Hirsch_model

open scoped BigOperators RealInnerProductSpace
open Set Hirsch
Formal statement
namespace Hirsch

theorem face_interval_cover_route_bound_of_start_containment
    {d : ℕ} {ι : Type*} [Fintype ι]
    (P : Set (EuclideanSpace ℝ (Fin d)))
    (F : ι → Set (EuclideanSpace ℝ (Fin d))) (B : ι → ℕ)
    (hF : ∀ i, IsExtreme ℝ P (F i)) (hD : ∀ i, DiamLE (F i) (B i))
    (s t : ι → ℕ) (w : ℕ → EuclideanSpace ℝ (Fin d)) (L : ℕ)
    (hbound : ∀ i, t i ≤ L)
    (hverts : ∀ i, w (s i) ∈ extremePoints ℝ P ∧ w (t i) ∈ extremePoints ℝ P)
    (hends : ∀ i, w (s i) ∈ F i ∧ w (t i) ∈ F i)
    (hcover : ∀ k < L, ∃ i, s i ≤ k ∧ k + 1 ≤ t i)
    (hcontain : ∀ i j, s i ≤ s j → s j ≤ t i → w (s j) ∈ F i) :
    ∃ q : ℕ → EuclideanSpace ℝ (Fin d),
      q 0 = w 0 ∧ q (∑ i, B i) = w L ∧
      ∀ r < ∑ i, B i,
        q r = q (r + 1) ∨ Adj P (q r) (q (r + 1)) := by sorry

end Hirsch
Source
Verified Lean theorem from jjoshua2/prove2me-work PR #48.

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