Opposite adjunctions #
This file contains constructions to relate adjunctions of functors to adjunctions of their opposites. These constructions are used to show uniqueness of adjoints (up to natural isomorphism).
Tags #
adjunction, opposite, uniqueness
If G.op is adjoint to F.op then F is adjoint to G.
Equations
- category_theory.adjunction.adjoint_of_op_adjoint_op F G h = category_theory.adjunction.mk_of_hom_equiv {hom_equiv := λ (X : C) (Y : D), ((h.hom_equiv (opposite.op Y) (opposite.op X)).trans (category_theory.op_equiv (opposite.op Y) (F.op.obj (opposite.op X)))).symm.trans (category_theory.op_equiv (G.op.obj (opposite.op Y)) (opposite.op X)), hom_equiv_naturality_left_symm' := _, hom_equiv_naturality_right' := _}
If G is adjoint to F.op then F is adjoint to G.unop.
If G.op is adjoint to F then F.unop is adjoint to G.
If G is adjoint to F then F.unop is adjoint to G.unop.
If G is adjoint to F then F.op is adjoint to G.op.
Equations
- category_theory.adjunction.op_adjoint_op_of_adjoint F G h = category_theory.adjunction.mk_of_hom_equiv {hom_equiv := λ (X : Cᵒᵖ) (Y : Dᵒᵖ), (category_theory.op_equiv (F.op.obj X) Y).trans ((h.hom_equiv (opposite.unop Y) (opposite.unop X)).symm.trans (category_theory.op_equiv X (opposite.op (G.obj (opposite.unop Y)))).symm), hom_equiv_naturality_left_symm' := _, hom_equiv_naturality_right' := _}
If G is adjoint to F.unop then F is adjoint to G.op.
If G.unop is adjoint to F then F.op is adjoint to G.
If G.unop is adjoint to F.unop then F is adjoint to G.
If F and F' are both adjoint to G, there is a natural isomorphism
F.op ⋙ coyoneda ≅ F'.op ⋙ coyoneda.
We use this in combination with fully_faithful_cancel_right to show left adjoints are unique.
Equations
- adj1.left_adjoints_coyoneda_equiv adj2 = category_theory.nat_iso.of_components (λ (X : Cᵒᵖ), category_theory.nat_iso.of_components (λ (Y : D), ((adj1.hom_equiv (opposite.unop X) Y).trans (adj2.hom_equiv (opposite.unop X) Y).symm).to_iso) _) _
If F and F' are both left adjoint to G, then they are naturally isomorphic.
Equations
If G and G' are both right adjoint to F, then they are naturally isomorphic.
Equations
Given two adjunctions, if the left adjoints are naturally isomorphic, then so are the right adjoints.
Equations
- adj1.nat_iso_of_left_adjoint_nat_iso adj2 l = adj1.right_adjoint_uniq (adj2.of_nat_iso_left l.symm)
Given two adjunctions, if the right adjoints are naturally isomorphic, then so are the left adjoints.
Equations
- adj1.nat_iso_of_right_adjoint_nat_iso adj2 r = adj1.left_adjoint_uniq (adj2.of_nat_iso_right r.symm)