Properties of morphisms #
We provide the basic framework for talking about properties of morphisms. The following meta-property is defined
RespectsLeft P Q
:P
respects the propertyQ
on the left ifP f → P (i ≫ f)
wherei
satisfiesQ
.RespectsRight P Q
:P
respects the propertyQ
on the right ifP f → P (f ≫ i)
wherei
satisfiesQ
.Respects
:P
respectsQ
ifP
respectsQ
both on the left and on the right.
A MorphismProperty C
is a class of morphisms between objects in C
.
Equations
- CategoryTheory.MorphismProperty C = (⦃X Y : C⦄ → (X ⟶ Y) → Prop)
Instances For
Equations
- CategoryTheory.instInhabitedMorphismProperty C = { default := ⊤ }
The morphism property in Cᵒᵖ
associated to a morphism property in C
Equations
- P.op f = P f.unop
Instances For
The morphism property in C
associated to a morphism property in Cᵒᵖ
Equations
- P.unop f = P f.op
Instances For
The inverse image of a MorphismProperty D
by a functor C ⥤ D
Equations
- P.inverseImage F f = P (F.map f)
Instances For
The image (up to isomorphisms) of a MorphismProperty C
by a functor C ⥤ D
Equations
- P.map F f = ∃ (X' : C) (Y' : C) (f' : X' ⟶ Y') (_ : P f'), Nonempty (CategoryTheory.Arrow.mk (F.map f') ≅ CategoryTheory.Arrow.mk f)
Instances For
A morphism property P
satisfies P.RespectsRight Q
if it is stable under post-composition
with morphisms satisfying Q
, i.e. whenever P
holds for f
and Q
holds for i
then P
holds for f ≫ i
.
- postcomp : ∀ {X Y Z : C} (i : Y ⟶ Z), Q i → ∀ (f : X ⟶ Y), P f → P (CategoryTheory.CategoryStruct.comp f i)
Instances
A morphism property P
satisfies P.RespectsLeft Q
if it is stable under
pre-composition with morphisms satisfying Q
, i.e. whenever P
holds for f
and Q
holds for i
then P
holds for i ≫ f
.
- precomp : ∀ {X Y Z : C} (i : X ⟶ Y), Q i → ∀ (f : Y ⟶ Z), P f → P (CategoryTheory.CategoryStruct.comp i f)
Instances
A morphism property P
satisfies P.Respects Q
if it is stable under composition on the
left and right by morphisms satisfying Q
.
- precomp : ∀ {X Y Z : C} (i : X ⟶ Y), Q i → ∀ (f : Y ⟶ Z), P f → P (CategoryTheory.CategoryStruct.comp i f)
- postcomp : ∀ {X Y Z : C} (i : Y ⟶ Z), Q i → ∀ (f : X ⟶ Y), P f → P (CategoryTheory.CategoryStruct.comp f i)
Instances
Equations
- ⋯ = ⋯
Equations
- ⋯ = ⋯
Equations
- ⋯ = ⋯
Equations
- ⋯ = ⋯
Equations
- ⋯ = ⋯
The MorphismProperty C
satisfied by isomorphisms in C
.
Equations
Instances For
The MorphismProperty C
satisfied by monomorphisms in C
.
Equations
Instances For
The MorphismProperty C
satisfied by epimorphisms in C
.
Equations
Instances For
P
respects isomorphisms, if it respects the morphism property isomorphisms C
, i.e.
it is stable under pre- and postcomposition with isomorphisms.
Equations
- P.RespectsIso = P.Respects (CategoryTheory.MorphismProperty.isomorphisms C)
Instances For
Equations
- ⋯ = ⋯
Equations
- ⋯ = ⋯
Equations
- ⋯ = ⋯
The closure by isomorphisms of a MorphismProperty
Equations
- P.isoClosure f = ∃ (Y₁ : C) (Y₂ : C) (f' : Y₁ ⟶ Y₂) (_ : P f'), Nonempty (CategoryTheory.Arrow.mk f' ≅ CategoryTheory.Arrow.mk f)
Instances For
Equations
- ⋯ = ⋯
Equations
- ⋯ = ⋯
Equations
- ⋯ = ⋯
Equations
- ⋯ = ⋯
Equations
- ⋯ = ⋯
Equations
- ⋯ = ⋯
Alias of CategoryTheory.MorphismProperty.cancel_left_of_respectsIso
.
Alias of CategoryTheory.MorphismProperty.cancel_right_of_respectsIso
.
Alias of CategoryTheory.MorphismProperty.isoClosure_eq_self
.
If W₁
and W₂
are morphism properties on two categories C₁
and C₂
,
this is the induced morphism property on C₁ × C₂
.
Instances For
If W j
are morphism properties on categories C j
for all j
, this is the
induced morphism property on the category ∀ j, C j
.
Equations
- CategoryTheory.MorphismProperty.pi W f = ∀ (j : J), W j (f j)
Instances For
The morphism property on J ⥤ C
which is defined objectwise
from W : MorphismProperty C
.
Equations
- W.functorCategory J f = ∀ (j : J), W (f.app j)
Instances For
Given W : MorphismProperty C
, this is the morphism property on Arrow C
of morphisms
whose left and right parts are in W
.