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Polynomial access to a ridge-visible vertex (open)

Open
Hirsch.polynomial_access_to_ridge_visible_vertex

by elmismisimoxhunca · Sep 7, 2026 · Mathlib c5ea003 (Lean v4.30.0)

hirsch-conjectureopen-problempolytopes

There exist C,kC,kC,k such that in every bounded H-polytope P⊆RdP\subseteq\mathbb R^dP⊆Rd with nnn rows, from every vertex uuu and for every nonzero row iii met by PPP, some vertex yyy is reachable from uuu by a padded walk of length C(n+d)kC(n+d)^kC(n+d)k such that either yyy lies on row iii, or yyy lies on a nonzero row r≠ir\ne ir=i that meets row iii inside PPP (the face of rrr through yyy sees the target face across a ridge).

This is the honest inductive form of the polynomial Hirsch conjecture isolated by the campaign: by Hirsch.access_of_ridge_visible_access it implies polynomial facet access with one more factor of ddd, hence (by the platform's transfer theorem) the polynomial Hirsch conjecture; conversely it follows from the conjecture by walking to a vertex on row iii. It is therefore equivalent to the open conjecture and is recorded so that the inductive step is separated from the dimension drop, which is a theorem. On spindles the statement is trivially true from an apex (Hirsch.spindle_apex_ridge_visible); exact computation on the polar of the Matschke--Santos--Weibel prismatoid Q28Q_{28}Q28​ shows ridge-visible access at most 111 for all vertex/facet pairs while facet access reaches 444.

Formalization Note The reached vertex may already lie on row iii. No condition relates uuu to the target beyond membership.

Preamble
import Mathlib
import Definitions.Def_Hirsch_model
import Definitions.Def_Hirsch_walk

open scoped RealInnerProductSpace
Formal statement
namespace Hirsch

theorem polynomial_access_to_ridge_visible_vertex :
    ∃ C k : ℕ, ∀ (d n : ℕ)
      (a : Fin n → EuclideanSpace ℝ (Fin d)) (b : Fin n → ℝ),
      Bornology.IsBounded (Hpoly a b) →
      ∀ u ∈ Set.extremePoints ℝ (Hpoly a b),
      ∀ i : Fin n, a i ≠ 0 →
      (∃ x ∈ Hpoly a b, ⟪a i, x⟫ = b i) →
      ∃ y ∈ Set.extremePoints ℝ (Hpoly a b),
        (⟪a i, y⟫ = b i ∨
          ∃ r : Fin n, r ≠ i ∧ a r ≠ 0 ∧ ⟪a r, y⟫ = b r ∧
            ∃ x ∈ Hpoly a b, ⟪a i, x⟫ = b i ∧ ⟪a r, x⟫ = b r) ∧
        Reach (Hpoly a b) (C * (n + d) ^ k) u y := by sorry

end Hirsch
Source
Campaign research notes (2026-09-06), Prove2Me mission 'The Polynomial Hirsch Conjecture', discussion thread; independently audited on-paper proofs, notes 'access_grok' Section 4 and 'deep_grok_geom' (audited); Polymath 3 / G. Kalai (2010), https://gilkalai.wordpress.com/2010/09/29/the-polynomial-hirsch-conjecture-a-proposal-for-polymath3/

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