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Diff — Hahn–Banach theorem

Revision #1858 → #2736 · back to history

modifiedFunctional problem (general)a8ec41c25c92
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mathlib.declexists_extension_of_le_sublinear
mathlib.match_kindexact
mathlib.moduleMathlib.Analysis.Convex.Cone.Extension
noteThis is the standard Hahn–Banach extension formalized as `exists_extension_of_le_sublinear`.Helly-style characterization of a continuous linear functional attaining prescribed values; not exposed as a standalone Mathlib lemma.
provenanceaiai-moderated
statusformalizednot_formalized
modifiedEvery sublinear function is convex29d0e0575ac0
FieldFrom #1858To #2736
noteMathlib lacks an `IsSublinear` predicate but proves `Seminorm.convexOn`, the seminorm special case of the same fact.Mathlib lacks an `IsSublinear` predicate but proves `Seminorm.convexOn`, the seminorm special case.
modifiedReal sublinear is seminorm iff symmetric9a645eb5b2cb
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noteSame — without a sublinear-function class this real-case characterization is absent.Without a sublinear-function class this real-case characterization is absent.
modifiedHahn–Banach theorem (seminorm version)96398359ae34
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noteExactly `Module.Dual.exists_extension_of_le_seminorm` for fields satisfying `IsRCLikeNormedField`.Exactly `Module.Dual.exists_extension_of_le_seminorm` for RCLike fields.
modifiedOne-dimensional dominated extension lemma1d205e192d61
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noteThe one-dimensional step is inlined inside the Zorn argument of `RieszExtension.step`/`exists_extension_of_le_sublinear` and not exposed as a separate lemma.The one-dimensional step is inlined inside the Zorn argument of `exists_extension_of_le_sublinear` and not exposed as a separate lemma.
modifiedSeparation of convex sets (locally convex TVS)6fca749fe9f0
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noteStrict separation in a locally convex space is `geometric_hahn_banach_compact_closed` (compact/closed) with companion `geometric_hahn_banach_open` variants.Strict separation in a locally convex space is `geometric_hahn_banach_compact_closed`.
modifiedMazur's theorem4a52c02e8fd2
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noteMazur's theorem on weak closure of convex sets does not appear in Mathlib (only Gelfand–Mazur and Mazur–Ulam exist).Mazur's theorem on hyperplane containment for a subspace and an open convex set is not formalized as a standalone result in Mathlib.
modifiedSmooth normed space3b6756ff9d07
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noteThe notion of a (point-) smooth normed space (unique supporting functional) is not defined in Mathlib.The notion of a (point-)smooth normed space (unique supporting functional) is not defined in Mathlib.
modifiedLinear subspaces characterized by continuous functionalse4461b86f54a
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noteNo standalone statement that closed subspaces equal the intersection of zero-sets of continuous functionals appears in Mathlib (only `iInter_halfSpaces_eq` for closed convex sets).No standalone statement that closed subspaces equal the intersection of zero-sets of continuous functionals appears in Mathlib.
modifiedCharacterization of reflexive Banach spaces via separation48d49ac3e929
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noteMathlib has no notion of reflexive Banach space, so this characterization is not formalized.Mathlib has `Module.IsReflexive` but not this separation-based characterization of reflexivity for real Banach spaces.
provenanceaiai-moderated
modifiedHahn–Banach theorem for seminorms42f23592f66a
FieldFrom #1858To #2736
mathlib.declModule.Dual.exists_extension_of_le_seminorm
mathlib.match_kindexact
mathlib.moduleMathlib.Analysis.LocallyConvex.HahnBanach
note`Module.Dual.exists_extension_of_le_seminorm` is the seminorm-bounded extension.The seminorm-extends-seminorm form is not formalized; Mathlib's `Module.Dual.exists_extension_of_le_seminorm` instead extends a linear functional bounded by a seminorm.
provenanceaiai-moderated
statusformalizednot_formalized
modifiedVector-valued Hahn–Banach theorem8b5cd8bca526
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noteOnly the finite-dimensional-codomain special case is in Mathlib via `ContinuousLinearMap.exist_extension_of_finiteDimensional_range`.The closest exposed result is the finite-dimensional-codomain continuous-linear case; the plain vector-space statement is not exposed as a single named lemma.
addedDominated extension holds with convex pb43185a48120