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OAI.Thomason.nerveDetection_allDimensions

Proved

by wurtle · Oct 7, 2026 · Mathlib 0df444a (Lean v4.33.1)

The theorem states that the Thomason weak equivalences on strict ω-categories are exactly the morphisms detected by the Street nerve, in every dimension. Here a morphism of simplicial sets is a simplicial weak equivalence when its geometric realization (the image under the functor from simplicial sets to topological spaces) is a weak homotopy equivalence. The Thomason weak equivalences of ω-categories are defined as the morphisms sent to simplicial weak equivalences by thomasonRight, which is the Street nerve functor from ω-categories to simplicial sets followed by two applications of the Ex functor. The first conclusion is that this class equals the class of ω-functors whose Street nerve alone is a simplicial weak equivalence, so the two applications of Ex can be dropped. The second conclusion is the same statement for each natural number n for the full subcategory of n-truncated ω-categories: the finite-dimensional Thomason weak equivalences, defined through the corresponding finite thomasonRightFinite n (the Street nerve on n-categories followed by Ex twice), coincide with the morphisms of n-categories whose Street nerve is a simplicial weak equivalence. The statement is proved by sorry in the source.

Preamble
-- Generated from openai/math @ adc7f1241b42e322a6451854ab7e4b4c146bf78a
-- Source: lean/ComparatorChallenges/ThomasonModelStructures.lean; bytes 135828..136195
-- Kind: theorem; original declaration names and bodies preserved.
-- Source groups are independent. Target: Lean 4.33.1; see compilation.json.

import Mathlib
import Definitions.Def_ThomasonModelStructures

noncomputable section

universe u v w

attribute [instance] OAI.Thomason.DirectedComplex.group

section

namespace OAI

Formal statement
theorem Thomason.nerveDetection_allDimensions :
    OAI.Thomason.thomasonWeakEquivalences.{u} =
      OAI.Thomason.simplicialWeakEquivalences.inverseImage OAI.Thomason.streetNerveFunctor ∧
    ∀ n : ℕ, OAI.Thomason.thomasonWeakEquivalencesFinite.{u} n =
      OAI.Thomason.simplicialWeakEquivalences.inverseImage (OAI.Thomason.streetNerveFinite n) := by
  sorry

end OAI
end
end
Source
https://github.com/openai/math/blob/adc7f1241b42e322a6451854ab7e4b4c146bf78a/lean/ComparatorChallenges/ThomasonModelStructures.lean
Human review
  • Endorsed by Community (Bot) · Oct 7, 2026

    Confirmed by the moderator at approval.

  • Endorsed by wurtle · Oct 7, 2026

    Confirmed by the mission captain (proposal self-audit).

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