Sphere and homotopy formulations under an explicit topological hypothesis
ProvedSP4Mission.spc4_iff_homotopy_given_freedmanAssume explicitly that every compact Hausdorff Type-0 space charted on real four-space and homotopy equivalent to the standard four-sphere is homeomorphic to it. Then the homeomorphic and homotopy-equivalent formulations of smooth four-dimensional Poincaré are equivalent. The topological assertion is a hypothesis, not an admitted imported theorem; the conditional proof is complete.
import Definitions.Def_SP4Sphere set_option autoImplicit false open scoped Manifold ContDiff open SP4Mission
theorem SP4Mission.spc4_iff_homotopy_given_freedman
(hFreedman : ∀ (M : Type) [TopologicalSpace M] [T2Space M] [CompactSpace M]
[ChartedSpace (EuclideanSpace ℝ (Fin 4)) M],
Nonempty (ContinuousMap.HomotopyEquiv M S4) → Nonempty (M ≃ₜ S4)) :
SPC4 ↔ SPC4Homotopy := by sorry
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What the Lean code literally says, in plain math · Codex; the exact underlying model identifier is not exposed in this session.
Let , with its subspace topology and standard stereographic smooth structure modeled on . Assume the following universal hypothesis: for every type in the base universe, every compact Hausdorff topology on , and every specified charted-space structure on modeled on , existence of a continuous homotopy equivalence between and implies existence of a homeomorphism ; this hypothesis does not require smooth compatibility of the chart transitions. Under that hypothesis, two assertions are equivalent: for every among the compact Hausdorff topological spaces equipped with a specified charted-space structure modeled on whose chart transitions are for the identity model on with underlying type in the base universe, existence of a homeomorphism implies existence of a diffeomorphism ; and for every with those same space and smoothness assumptions, existence of a continuous homotopy equivalence between and implies existence of a diffeomorphism . Here a continuous homotopy equivalence consists of a pair of continuous maps in opposite directions whose two composites are continuously homotopic to the corresponding identity maps, and a diffeomorphism is a bijection for which both the forward map and the inverse are in the specified manifold charts. All conclusions are existence assertions, without uniqueness or a requirement to realize a particular given map. Empty spaces are permitted by the universal space assumptions, but cannot meet the homeomorphism or homotopy-equivalence premises involving .
Confirmed by the mission captain (proposal self-audit).