Adjoint mates for explicit exact pairings #
Mathlib's CategoryTheory.rightAdjointMate sends f : X ⟶ Y to fᘁ : Yᘁ ⟶ Xᘁ, where the duals
are the ambient HasRightDual choices. Several right duals are not of that form: the tensor
product pairing ExactPairing (X ⊗ Y) (Yᘁ ⊗ Xᘁ), the self-pairing of the unit, or a pairing
transported along an isomorphism. This file takes the exact pairings as explicit arguments
instead: for pX : ExactPairing X X' and pY : ExactPairing Y Y', the mate of f : X ⟶ Y is
ExactPairing.rightMate pX pY f : Y' ⟶ X'. This is Mathlib's rightAdjointMate with the given
pairings made ambient, and its basic properties are Mathlib's; what the definition adds is the
type Y' ⟶ X', so that rewriting sees X' and Y' rather than projections out of HasRightDual
records.
A morphism into a right dual is determined by its composite with the evaluation
(CategoryTheory.ExactPairing.rightHom_ext), and the mate is characterized by
CategoryTheory.ExactPairing.rightMate_comp_evaluation. From these we compute the mates of the
monoidal structure morphisms with respect to the tensor product pairings: the mate of a
tensor product of morphisms is the reversed tensor product of their mates, and the mates of the
associator and the unitors are again an associator and unitors. These are the identities that
make the right dual functor C ⥤ (Cᵒᵖ)ᴹᵒᵖ monoidal.
The same is done for left duals: for pX : ExactPairing X' X and pY : ExactPairing Y' Y, the
left mate of f : X ⟶ Y is ExactPairing.leftMate pX pY f : Y' ⟶ X', Mathlib's
leftAdjointMate with the given pairings made ambient. A morphism into a left dual is
determined by its composite with the evaluation (CategoryTheory.ExactPairing.leftDualHom_ext),
and the left mates of tensor products and of the structure morphisms are computed in the same
way. These are the identities that make the left dual functor C ⥤ (Cᵒᵖ)ᴹᵒᵖ monoidal.
Taking a left adjoint mate and then a right adjoint mate, or conversely, recovers the original morphism.
Main declarations #
CategoryTheory.ExactPairing.rightHom_ext: morphisms into a right dual agree once they agree after evaluation, andCategoryTheory.ExactPairing.leftHom_ext: morphisms out of a left member agree once they agree after coevaluation;CategoryTheory.leftAdjointMate_rightAdjointMateandCategoryTheory.rightAdjointMate_leftAdjointMate: taking the opposite-handed mate recovers the original morphism, soCategoryTheory.rightAdjointMate_injective;CategoryTheory.Iso.rightAdjointMate: the isomorphismYᘁ ≅ Xᘁinduced byX ≅ Y;CategoryTheory.ExactPairing.rightMate: the right adjoint mate with respect to explicit exact pairings, characterized byCategoryTheory.ExactPairing.rightMate_comp_evaluation(and its whiskered formCategoryTheory.ExactPairing.whiskerRight_rightMate_evaluation) andCategoryTheory.ExactPairing.coevaluation_comp_rightMate, withrightMate_idandcomp_rightMate;CategoryTheory.ExactPairing.rightMate_whiskerLeft,CategoryTheory.ExactPairing.rightMate_whiskerRightandCategoryTheory.ExactPairing.rightMate_tensorHom: mates with respect to tensor product pairings;CategoryTheory.ExactPairing.rightMate_associator_hom,CategoryTheory.ExactPairing.rightMate_leftUnitor_homandCategoryTheory.ExactPairing.rightMate_rightUnitor_hom: mates of the structure morphisms;CategoryTheory.ExactPairing.rightMate_evaluationandCategoryTheory.ExactPairing.rightMate_coevaluation: the mate of an evaluation is a coevaluation, and conversely;TauCeti.rightAdjointMate_eq_rightMate,CategoryTheory.ExactPairing.rightDualIso_homandCategoryTheory.ExactPairing.rightDualIso_inv: Mathlib'srightAdjointMateandrightDualIsoas mates, with the evaluation identitiesrightDualIso_hom_whiskerRight_evaluationandrightDualIso_inv_whiskerRight_evaluation;CategoryTheory.ExactPairing.leftDualHom_ext: morphisms into a left dual agree once they agree after evaluation;CategoryTheory.ExactPairing.leftMate: the left adjoint mate with respect to explicit exact pairings, characterized byCategoryTheory.ExactPairing.leftMate_comp_evaluationandCategoryTheory.ExactPairing.coevaluation_comp_leftMate, withleftMate_id,comp_leftMate, the tensor product formulasleftMate_whiskerLeft,leftMate_whiskerRightandleftMate_tensorHom, and the structure-morphism formulasleftMate_associator_hom,leftMate_leftUnitor_homandleftMate_rightUnitor_hom;TauCeti.leftAdjointMate_eq_leftMate,CategoryTheory.ExactPairing.leftDualIso_homandCategoryTheory.ExactPairing.leftDualIso_inv: Mathlib'sleftAdjointMateandleftDualIsoas left mates;CategoryTheory.ExactPairing.leftMate_rightDualIso_homandCategoryTheory.ExactPairing.rightMate_leftDualIso_hom: the opposite-handed mate of the comparison between two duals is an identity;CategoryTheory.ExactPairing.leftMate_rightDualIso_invandCategoryTheory.ExactPairing.rightMate_leftDualIso_inv: the opposite-handed mate of the inverse comparison between two duals is the comparison between the two opposite-handed duals.
References #
- [P. Etingof, S. Gelaki, D. Nikshych, V. Ostrik, Tensor categories][egno15], §2.10
- leanprover-community/mathlib4#42145,
for the explicit-pairing form of
CategoryTheory.ExactPairing.leftHom_extand the two mate-inverse lemmas
Two morphisms into a right dual Y of X agree as soon as they agree after evaluation
against X.
Two morphisms out of the left member X of an exact pairing agree as soon as they agree
after the coevaluation of the pairing.
The right adjoint mate Y' ⟶ X' of f : X ⟶ Y, with respect to explicitly given exact
pairings (X, X') and (Y, Y'): Mathlib's CategoryTheory.rightAdjointMate with the given
pairings made ambient. Stating it with the type Y' ⟶ X' keeps the duals X' and Y' visible
to rewriting: as a term @rightAdjointMate C _ _ X Y ⟨X'⟩ ⟨Y'⟩ f, its source and target are the
projections HasRightDual.rightDual ⟨Y'⟩ and HasRightDual.rightDual ⟨X'⟩, and Mathlib's lemmas
about it do not rewrite against the evaluation ε_ X X' of the given pairing.
Instances For
The characteristic property of the right adjoint mate: evaluating it against X is the
same as evaluating against Y after applying f.
The characteristic property of the right adjoint mate: evaluating it against X is the
same as evaluating against Y after applying f.
The characteristic property of the right adjoint mate, after a morphism a : W ⟶ Y' into the
dual of the target: evaluating a followed by the mate of f : X ⟶ Y against X is evaluating
a against Y after applying f to X. Morphisms into a right dual are compared in this form
via CategoryTheory.ExactPairing.rightHom_ext.
The dual characterization of the right adjoint mate: applying it after the coevaluation of
(Y, Y') is the same as applying f after the coevaluation of (X, X').
The dual characterization of the right adjoint mate: applying it after the coevaluation of
(Y, Y') is the same as applying f after the coevaluation of (X, X').
The mate of an identity is an identity.
Taking mates reverses composition.
The mate of f ▷ Z with respect to the tensor product pairings is Z' ◁ fᘁ.
The mate of Z ◁ f with respect to the tensor product pairings is fᘁ ▷ Z'.
The mate of a tensor product of morphisms with respect to the tensor product pairings is the tensor product of their mates, in the reverse order.
The mate of the associator of X, Y, Z with respect to the tensor product pairings is the
associator of their duals.
The mate of the left unitor of X with respect to the tensor product of the self-pairing
of the unit with (X, X') is the inverse right unitor of X'.
The mate of the right unitor of X with respect to the tensor product of (X, X') with the
self-pairing of the unit is the inverse left unitor of X'.
The comparison rightDualIso p₁ p₂ : Y₁ ≅ Y₂ between two right duals of X is the mate of
the identity of X.
The inverse of the comparison rightDualIso p₁ p₂ : Y₁ ≅ Y₂ is the mate of the identity of
X taken in the other direction.
Through the comparison rightDualIso p₁ p₂ : Y₁ ≅ Y₂, the evaluation of p₂ is the
evaluation of p₁.
Through the comparison rightDualIso p₁ p₂ : Y₁ ≅ Y₂, the evaluation of p₂ is the
evaluation of p₁.
Through the inverse comparison (rightDualIso p₁ p₂).inv : Y₂ ⟶ Y₁, the evaluation of p₁ is
the evaluation of p₂.
Through the inverse comparison (rightDualIso p₁ p₂).inv : Y₂ ⟶ Y₁, the evaluation of p₁ is
the evaluation of p₂.
The mate of the evaluation ε_ X X' : X' ⊗ X ⟶ 𝟙_ C, taken with respect to the tensor product
pairing of (X', X'') with (X, X') and the self-pairing of the unit, is the coevaluation
η_ X' X'' : 𝟙_ C ⟶ X' ⊗ X''.
The mate of the coevaluation η_ X X' : 𝟙_ C ⟶ X ⊗ X', taken with respect to the self-pairing
of the unit and the tensor product pairing of (X, X') with (X', X''), is the evaluation
ε_ X' X'' : X'' ⊗ X' ⟶ 𝟙_ C.
Left adjoint mates #
Two morphisms into the left member X of an exact pairing (X, Y), that is into a left dual
of Y, agree as soon as they agree after evaluation against Y.
The left adjoint mate Y' ⟶ X' of f : X ⟶ Y, with respect to explicitly given exact
pairings (X', X) and (Y', Y): Mathlib's CategoryTheory.leftAdjointMate with the given
pairings made ambient. As for CategoryTheory.ExactPairing.rightMate, the type Y' ⟶ X' keeps
the left duals X' and Y' visible to rewriting.
Instances For
The characteristic property of the left adjoint mate: evaluating it against X is the
same as evaluating against Y after applying f.
The characteristic property of the left adjoint mate: evaluating it against X is the
same as evaluating against Y after applying f.
The dual characterization of the left adjoint mate: applying it after the coevaluation of
(Y', Y) is the same as applying f after the coevaluation of (X', X).
The dual characterization of the left adjoint mate: applying it after the coevaluation of
(Y', Y) is the same as applying f after the coevaluation of (X', X).
The left mate of an identity is an identity.
Taking left mates reverses composition.
The left mate of Z ◁ f with respect to the tensor product pairings is ᘁf ▷ Z'.
The left mate of f ▷ Z with respect to the tensor product pairings is Z' ◁ ᘁf.
The left mate of a tensor product of morphisms with respect to the tensor product pairings is the tensor product of their left mates, in the reverse order.
The left mate of the associator of X, Y, Z with respect to the tensor product pairings
is the associator of their left duals.
The left mate of the left unitor of X with respect to the tensor product of the
self-pairing of the unit with (X', X) is the inverse right unitor of X'.
The left mate of the right unitor of X with respect to the tensor product of (X', X)
with the self-pairing of the unit is the inverse left unitor of X'.
The comparison leftDualIso p₁ p₂ : X₁ ≅ X₂ between two left duals of Y is the left mate
of the identity of Y.
The inverse of the comparison leftDualIso p₁ p₂ : X₁ ≅ X₂ is the left mate of the identity
of Y taken in the other direction.
If X has two right duals Y₁ and Y₂, then taking the left mate with respect to (X, Y₁)
turns the comparison rightDualIso p₁ p₂ : Y₁ ≅ Y₂ into the identity, transported to the pairing
(X, Y₂). With q = p₂, the left mate of the comparison is 𝟙 X.
If Y has two left duals X₁ and X₂, then taking the right mate with respect to (X₁, Y)
turns the comparison leftDualIso p₁ p₂ : X₁ ≅ X₂ into the identity, transported to the pairing
(X₂, Y). With q = p₂, the right mate of the comparison is 𝟙 Y.
If X has two right duals Y₁ and Y₂ and Z is a left dual of Y₁, then the left mate
of the inverse comparison Y₂ ⟶ Y₁ is the comparison leftDualIso q p₁ : Z ≅ X of the two left
duals of Y₁.
If Y has two left duals X₁ and X₂ and Z is a right dual of X₁, then the right mate
of the inverse comparison X₂ ⟶ X₁ is the comparison rightDualIso q p₁ : Z ≅ Y of the two
right duals of X₁.
Taking the left adjoint mate of a right adjoint mate recovers the original morphism.
Taking the right adjoint mate of a left adjoint mate recovers the original morphism.
Taking right adjoint mates is injective: the left adjoint mate is a left inverse.
An isomorphism X ≅ Y induces an isomorphism Yᘁ ≅ Xᘁ of right duals, whose components are
the right adjoint mates of those of X ≅ Y.
Instances For
The component of Iso.rightAdjointMate e is the right adjoint mate of that of e.
The inverse of Iso.rightAdjointMate e is the right adjoint mate of the inverse of e.
Mathlib's right adjoint mate is the mate with respect to the ambient right duals.
Mathlib's left adjoint mate is the left mate with respect to the ambient left duals.