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Mathlib.CategoryTheory.Adjunction.Opposites

Opposite adjunctions #

This file contains constructions to relate adjunctions of functors to adjunctions of their opposites.

Tags #

adjunction, opposite, uniqueness

If G is adjoint to F then F.unop is adjoint to G.unop.

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    def CategoryTheory.Adjunction.op {C : Type u₁} [Category.{v₁, u₁} C] {D : Type uā‚‚} [Category.{vā‚‚, uā‚‚} D] {F : Functor C D} {G : Functor D C} (h : G ⊣ F) :

    If G is adjoint to F then F.op is adjoint to G.op.

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      If F is adjoint to G.leftOp then G is adjoint to F.leftOp.

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        If F.rightOp is adjoint to G then G.rightOp is adjoint to F.

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          If F and F' are both adjoint to G, there is a natural isomorphism F.op ā‹™ coyoneda ≅ F'.op ā‹™ coyoneda. We use this in combination with fullyFaithfulCancelRight to show left adjoints are unique.

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            @[deprecated "Use `(Adjunction.conjugateIsoEquiv adj1 adj2).symm` (requires `import Mathlib.CategoryTheory.Adjunction.Mates`)." (since := "2026-01-31")]
            def CategoryTheory.Adjunction.natIsoOfRightAdjointNatIso {C : Type u₁} [Category.{v₁, u₁} C] {D : Type uā‚‚} [Category.{vā‚‚, uā‚‚} D] {F F' : Functor C D} {G G' : Functor D C} (adj1 : F ⊣ G) (adj2 : F' ⊣ G') (r : G ≅ G') :
            F ≅ F'

            Deprecated: prefer (Adjunction.conjugateIsoEquiv adj1 adj2).symm.

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              @[deprecated "Use `Adjunction.conjugateIsoEquiv adj1 adj2` (requires `import Mathlib.CategoryTheory.Adjunction.Mates`)." (since := "2026-01-31")]
              def CategoryTheory.Adjunction.natIsoOfLeftAdjointNatIso {C : Type u₁} [Category.{v₁, u₁} C] {D : Type uā‚‚} [Category.{vā‚‚, uā‚‚} D] {F F' : Functor C D} {G G' : Functor D C} (adj1 : F ⊣ G) (adj2 : F' ⊣ G') (l : F ≅ F') :
              G ≅ G'

              Deprecated: prefer Adjunction.conjugateIsoEquiv adj1 adj2.

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