Subcategories of comma categories defined by morphism properties #
Given functors L : A ⥤ T
and R : B ⥤ T
and morphism properties P
, Q
and W
on T
, Aand
Brespectively, we define the subcategory
P.Comma L R Q Wof
`Comma L R` where
- objects are objects of
Comma L R
with the structural morphism satisfyingP
, and - morphisms are morphisms of
Comma L R
where the left morphism satisfiesQ
and the right morphism satisfiesW
.
For an object X : T
, this specializes to P.Over Q X
which is the subcategory of Over X
where the structural morphism satisfies P
and where the horizontal morphisms satisfy Q
.
Common examples of the latter are e.g. the category of schemes étale (finite, affine, etc.)
over a base X
. Here Q = ⊤
.
Implementation details #
P.Comma L R Q W
is the subcategory of Comma L R
consisting of
objects X : Comma L R
where X.hom
satisfies P
. The morphisms are given by
morphisms in Comma L R
where the left one satisfies Q
and the right one satisfies W
.
Instances For
A morphism in P.Comma L R Q W
is a morphism in Comma L R
where the left
hom satisfies Q
and the right one satisfies W
.
- w : CategoryTheory.CategoryStruct.comp (L.map self.left) Y.hom = CategoryTheory.CategoryStruct.comp X.hom (R.map self.right)
- prop_hom_left : Q self.left
- prop_hom_right : W self.right
Instances For
The underlying morphism of objects in Comma L R
.
Equations
- f.hom = f.toCommaMorphism
Instances For
See Note [custom simps projection]
Equations
Instances For
The identity morphism of an object in P.Comma L R Q W
.
Equations
- X.id = { left := CategoryTheory.CategoryStruct.id X.left, right := CategoryTheory.CategoryStruct.id X.right, w := ⋯, prop_hom_left := ⋯, prop_hom_right := ⋯ }
Instances For
Composition of morphisms in P.Comma L R Q W
.
Equations
- f.comp g = { left := CategoryTheory.CategoryStruct.comp f.left g.left, right := CategoryTheory.CategoryStruct.comp f.right g.right, w := ⋯, prop_hom_left := ⋯, prop_hom_right := ⋯ }
Instances For
Equations
If i
is an isomorphism in Comma L R
, it is also a morphism in P.Comma L R Q W
.
Equations
- CategoryTheory.MorphismProperty.Comma.homFromCommaOfIsIso i = { toCommaMorphism := i, prop_hom_left := ⋯, prop_hom_right := ⋯ }
Instances For
Any isomorphism between objects of P.Comma L R Q W
in Comma L R
is also an isomorphism
in P.Comma L R Q W
.
Equations
- One or more equations did not get rendered due to their size.
Instances For
Constructor for isomorphisms in P.Comma L R Q W
from isomorphisms of the left and right
components and naturality in the forward direction.
Equations
Instances For
The forgetful functor.
Equations
- One or more equations did not get rendered due to their size.
Instances For
The forgetful functor from the full subcategory of Comma L R
defined by P
is
fully faithful.
Equations
- One or more equations did not get rendered due to their size.
Instances For
Lift a functor F : C ⥤ Comma L R
to the subcategory P.Comma L R Q W
under
suitable assumptions on F
.
Equations
- One or more equations did not get rendered due to their size.
Instances For
A natural transformation L₁ ⟶ L₂
induces a functor P.Comma L₂ R Q W ⥤ P.Comma L₁ R Q W
.
Equations
- One or more equations did not get rendered due to their size.
Instances For
A natural transformation R₁ ⟶ R₂
induces a functor P.Comma L R₁ Q W ⥤ P.Comma L R₂ Q W
.
Equations
- One or more equations did not get rendered due to their size.
Instances For
Given a morphism property P
on a category C
and an object X : C
, this is the
subcategory of Over X
defined by P
where morphisms satisfy Q
.
Equations
- P.Over Q X = CategoryTheory.MorphismProperty.Comma (CategoryTheory.Functor.id T) (CategoryTheory.Functor.fromPUnit X) P Q ⊤
Instances For
The forgetful functor from the full subcategory of Over X
defined by P
to Over X
.
Equations
Instances For
Construct a morphism in P.Over Q X
from a morphism in Over.X
.
Equations
- CategoryTheory.MorphismProperty.Over.Hom.mk f hf = { toCommaMorphism := f, prop_hom_left := hf, prop_hom_right := trivial }
Instances For
Make an object of P.Over Q X
from a morphism f : A ⟶ X
and a proof of P f
.
Equations
- CategoryTheory.MorphismProperty.Over.mk Q f hf = { left := A, right := { as := PUnit.unit }, hom := f, prop := hf }
Instances For
Make a morphism in P.Over Q X
from a morphism in T
with compatibilities.
Equations
- CategoryTheory.MorphismProperty.Over.homMk f w hf = { toCommaMorphism := CategoryTheory.Over.homMk f w, prop_hom_left := hf, prop_hom_right := trivial }
Instances For
Make an isomorphism in P.Over Q X
from an isomorphism in T
with compatibilities.
Equations
Instances For
Given a morphism property P
on a category C
and an object X : C
, this is the
subcategory of Under X
defined by P
where morphisms satisfy Q
.
Equations
- P.Under Q X = CategoryTheory.MorphismProperty.Comma (CategoryTheory.Functor.fromPUnit X) (CategoryTheory.Functor.id T) P ⊤ Q
Instances For
The forgetful functor from the full subcategory of Under X
defined by P
to Under X
.
Equations
Instances For
Construct a morphism in P.Under Q X
from a morphism in Under.X
.
Equations
- CategoryTheory.MorphismProperty.Under.Hom.mk f hf = { toCommaMorphism := f, prop_hom_left := trivial, prop_hom_right := hf }
Instances For
Make an object of P.Under Q X
from a morphism f : A ⟶ X
and a proof of P f
.
Equations
- CategoryTheory.MorphismProperty.Under.mk Q f hf = { left := { as := PUnit.unit }, right := A, hom := f, prop := hf }
Instances For
Make a morphism in P.Under Q X
from a morphism in T
with compatibilities.
Equations
- CategoryTheory.MorphismProperty.Under.homMk f w hf = { toCommaMorphism := CategoryTheory.Under.homMk f w, prop_hom_left := trivial, prop_hom_right := hf }
Instances For
Make an isomorphism in P.Under Q X
from an isomorphism in T
with compatibilities.