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Add missing hypotheses to mem_relint_dual and its sibling - #85

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martinwintermath merged 5 commits into
ooovi:mainfrom
mo271:fix-relint-dual
Sep 7, 2026
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Add missing hypotheses to mem_relint_dual and its sibling#85
martinwintermath merged 5 commits into
ooovi:mainfrom
mo271:fix-relint-dual

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@mo271

@mo271 mo271 commented Aug 29, 2026

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Both relint duality lemmas were false as stated:

  • mem_relint_iff_forall_dual_zero_le_mem_lineal_of_eq_zero fails in infinite dimensions (for the lexicographic cone on ⊕ℕ R the dual cone is trivial, making the right hand side vacuous while the relint is empty); it now assumes C.FinRank. Its forward direction holds unconditionally and is proven separately as mem_lineal_dual_of_mem_relint.
  • mem_relint_dual fails already in for non-dual-closed cones; it now assumes C.DualClosed p and (dual p C).FinSalRank. The exists_dual_pos example inherits the dual closedness assumption.

Both relint duality lemmas were false as stated:

* `mem_relint_iff_forall_dual_zero_le_mem_lineal_of_eq_zero` fails in infinite
  dimensions (for the lexicographic cone on `⊕ℕ R` the dual cone is trivial,
  making the right hand side vacuous while the relint is empty); it now assumes
  `C.FinRank`. Its forward direction holds unconditionally and is proven
  separately as `mem_lineal_dual_of_mem_relint`.
* `mem_relint_dual` fails already in `R²` for non-dual-closed cones; it now
  assumes `C.DualClosed p` and `(dual p C).FinSalRank`. The
  `exists_dual_pos` example inherits the dual closedness assumption.
@mo271

mo271 commented Aug 29, 2026

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Before #82 one could give much easier disproofs for these

Comment thread Polyhedral/Mathlib/Geometry/Convex/Cone/Pointed/Relint.lean
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mo271 requested a review from YaelDillies September 2, 2026 19:58
Comment thread Polyhedral/Mathlib/Geometry/Convex/Cone/Pointed/Relint.lean Outdated
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mo271 requested a review from YaelDillies September 4, 2026 06:17

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LGTM!

@mo271

mo271 commented Sep 4, 2026

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@martinwintermath

Comment thread Polyhedral/Mathlib/Geometry/Convex/Cone/Pointed/Relint.lean
Comment thread Polyhedral/Mathlib/Geometry/Convex/Cone/Pointed/Relint.lean Outdated
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martinwintermath merged commit 7c272f7 into ooovi:main Sep 7, 2026
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3 participants