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split_epi_category_imp_of_is_equivalence [is_equivalence F] [split_epi_category C] : split_epi_category D
⟨λ X Y f, begin introI, rw ← F.inv.is_split_epi_iff f, apply is_split_epi_of_epi, end⟩
def
category_theory.functor.split_epi_category_imp_of_is_equivalence
category_theory.functor
src/category_theory/functor/epi_mono.lean
[ "category_theory.epi_mono", "category_theory.limits.shapes.strong_epi", "category_theory.lifting_properties.adjunction" ]
[]
If `F : C ⥤ D` is an equivalence of categories and `C` is a `split_epi_category`, then `D` also is.
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
strong_epi_map_of_strong_epi (adj : F ⊣ F') (f : A ⟶ B) [h₁ : F'.preserves_monomorphisms] [h₂ : F.preserves_epimorphisms] [strong_epi f] : strong_epi (F.map f)
⟨infer_instance, λ X Y Z, by { introI, rw adj.has_lifting_property_iff, apply_instance, }⟩
lemma
category_theory.adjunction.strong_epi_map_of_strong_epi
category_theory.functor
src/category_theory/functor/epi_mono.lean
[ "category_theory.epi_mono", "category_theory.limits.shapes.strong_epi", "category_theory.lifting_properties.adjunction" ]
[ "adj" ]
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
strong_epi_map_of_is_equivalence [is_equivalence F] (f : A ⟶ B) [h : strong_epi f] : strong_epi (F.map f)
F.as_equivalence.to_adjunction.strong_epi_map_of_strong_epi f
instance
category_theory.adjunction.strong_epi_map_of_is_equivalence
category_theory.functor
src/category_theory/functor/epi_mono.lean
[ "category_theory.epi_mono", "category_theory.limits.shapes.strong_epi", "category_theory.lifting_properties.adjunction" ]
[]
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
strong_epi_map_iff_strong_epi_of_is_equivalence [is_equivalence F] : strong_epi (F.map f) ↔ strong_epi f
begin split, { introI, have e : arrow.mk f ≅ arrow.mk (F.inv.map (F.map f)) := arrow.iso_of_nat_iso F.as_equivalence.unit_iso (arrow.mk f), rw strong_epi.iff_of_arrow_iso e, apply_instance, }, { introI, apply_instance, }, end
lemma
category_theory.functor.strong_epi_map_iff_strong_epi_of_is_equivalence
category_theory.functor
src/category_theory/functor/epi_mono.lean
[ "category_theory.epi_mono", "category_theory.limits.shapes.strong_epi", "category_theory.lifting_properties.adjunction" ]
[]
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
to_diagram : J ⥤ structured_arrow c.X K
{ obj := λ j, structured_arrow.mk (c.π.app j), map := λ j k g, structured_arrow.hom_mk g (by simpa) }
def
category_theory.structured_arrow_cone.to_diagram
category_theory.functor
src/category_theory/functor/flat.lean
[ "category_theory.limits.filtered_colimit_commutes_finite_limit", "category_theory.limits.preserves.functor_category", "category_theory.limits.bicones", "category_theory.limits.comma", "category_theory.limits.preserves.finite", "category_theory.limits.shapes.finite_limits" ]
[]
Given a cone `c : cone K` and a map `f : X ⟶ c.X`, we can construct a cone of structured arrows over `X` with `f` as the cone point. This is the underlying diagram.
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
diagram_to_cone {X : D} (G : J ⥤ structured_arrow X F) : cone (G ⋙ proj X F ⋙ F)
{ X := X, π := { app := λ j, (G.obj j).hom } }
def
category_theory.structured_arrow_cone.diagram_to_cone
category_theory.functor
src/category_theory/functor/flat.lean
[ "category_theory.limits.filtered_colimit_commutes_finite_limit", "category_theory.limits.preserves.functor_category", "category_theory.limits.bicones", "category_theory.limits.comma", "category_theory.limits.preserves.finite", "category_theory.limits.shapes.finite_limits" ]
[]
Given a diagram of `structured_arrow X F`s, we may obtain a cone with cone point `X`.
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
to_cone {X : D} (f : X ⟶ F.obj c.X) : cone (to_diagram (F.map_cone c) ⋙ map f ⋙ pre _ K F)
{ X := mk f, π := { app := λ j, hom_mk (c.π.app j) rfl, naturality' := λ j k g, by { ext, dsimp, simp } } }
def
category_theory.structured_arrow_cone.to_cone
category_theory.functor
src/category_theory/functor/flat.lean
[ "category_theory.limits.filtered_colimit_commutes_finite_limit", "category_theory.limits.preserves.functor_category", "category_theory.limits.bicones", "category_theory.limits.comma", "category_theory.limits.preserves.finite", "category_theory.limits.shapes.finite_limits" ]
[]
Given a cone `c : cone K` and a map `f : X ⟶ F.obj c.X`, we can construct a cone of structured arrows over `X` with `f` as the cone point.
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
representably_flat (F : C ⥤ D) : Prop
(cofiltered : ∀ (X : D), is_cofiltered (structured_arrow X F))
class
category_theory.representably_flat
category_theory.functor
src/category_theory/functor/flat.lean
[ "category_theory.limits.filtered_colimit_commutes_finite_limit", "category_theory.limits.preserves.functor_category", "category_theory.limits.bicones", "category_theory.limits.comma", "category_theory.limits.preserves.finite", "category_theory.limits.shapes.finite_limits" ]
[]
A functor `F : C ⥤ D` is representably-flat functor if the comma category `(X/F)` is cofiltered for each `X : C`.
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
representably_flat.id : representably_flat (𝟭 C)
begin constructor, intro X, haveI : nonempty (structured_arrow X (𝟭 C)) := ⟨structured_arrow.mk (𝟙 _)⟩, rsufficesI : is_cofiltered_or_empty (structured_arrow X (𝟭 C)), { constructor }, constructor, { intros Y Z, use structured_arrow.mk (𝟙 _), use structured_arrow.hom_mk Y.hom (by erw [functor....
instance
category_theory.representably_flat.id
category_theory.functor
src/category_theory/functor/flat.lean
[ "category_theory.limits.filtered_colimit_commutes_finite_limit", "category_theory.limits.preserves.functor_category", "category_theory.limits.bicones", "category_theory.limits.comma", "category_theory.limits.preserves.finite", "category_theory.limits.shapes.finite_limits" ]
[]
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
representably_flat.comp (F : C ⥤ D) (G : D ⥤ E) [representably_flat F] [representably_flat G] : representably_flat (F ⋙ G)
begin constructor, intro X, haveI : nonempty (structured_arrow X (F ⋙ G)), { have f₁ : structured_arrow X G := nonempty.some infer_instance, have f₂ : structured_arrow f₁.right F := nonempty.some infer_instance, exact ⟨structured_arrow.mk (f₁.hom ≫ G.map f₂.hom)⟩ }, rsufficesI : is_cofiltered_or_empty...
instance
category_theory.representably_flat.comp
category_theory.functor
src/category_theory/functor/flat.lean
[ "category_theory.limits.filtered_colimit_commutes_finite_limit", "category_theory.limits.preserves.functor_category", "category_theory.limits.bicones", "category_theory.limits.comma", "category_theory.limits.preserves.finite", "category_theory.limits.shapes.finite_limits" ]
[ "nonempty.some" ]
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
cofiltered_of_has_finite_limits [has_finite_limits C] : is_cofiltered C
{ cone_objs := λ A B, ⟨limits.prod A B, limits.prod.fst, limits.prod.snd, trivial⟩, cone_maps := λ A B f g, ⟨equalizer f g, equalizer.ι f g, equalizer.condition f g⟩, nonempty := ⟨⊤_ C⟩ }
lemma
category_theory.cofiltered_of_has_finite_limits
category_theory.functor
src/category_theory/functor/flat.lean
[ "category_theory.limits.filtered_colimit_commutes_finite_limit", "category_theory.limits.preserves.functor_category", "category_theory.limits.bicones", "category_theory.limits.comma", "category_theory.limits.preserves.finite", "category_theory.limits.shapes.finite_limits" ]
[]
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
flat_of_preserves_finite_limits [has_finite_limits C] (F : C ⥤ D) [preserves_finite_limits F] : representably_flat F
⟨λ X, begin haveI : has_finite_limits (structured_arrow X F) := begin apply has_finite_limits_of_has_finite_limits_of_size.{v₁} (structured_arrow X F), intros J sJ fJ, resetI, constructor end, exact cofiltered_of_has_finite_limits end⟩
lemma
category_theory.flat_of_preserves_finite_limits
category_theory.functor
src/category_theory/functor/flat.lean
[ "category_theory.limits.filtered_colimit_commutes_finite_limit", "category_theory.limits.preserves.functor_category", "category_theory.limits.bicones", "category_theory.limits.comma", "category_theory.limits.preserves.finite", "category_theory.limits.shapes.finite_limits" ]
[]
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
lift : s.X ⟶ F.obj c.X
let s' := is_cofiltered.cone (to_diagram s ⋙ structured_arrow.pre _ K F) in s'.X.hom ≫ (F.map $ hc.lift $ (cones.postcompose ({ app := λ X, 𝟙 _, naturality' := by simp } : (to_diagram s ⋙ pre s.X K F) ⋙ proj s.X F ⟶ K)).obj $ (structured_arrow.proj s.X F).map_cone s')
def
category_theory.preserves_finite_limits_of_flat.lift
category_theory.functor
src/category_theory/functor/flat.lean
[ "category_theory.limits.filtered_colimit_commutes_finite_limit", "category_theory.limits.preserves.functor_category", "category_theory.limits.bicones", "category_theory.limits.comma", "category_theory.limits.preserves.finite", "category_theory.limits.shapes.finite_limits" ]
[ "lift" ]
(Implementation). Given a limit cone `c : cone K` and a cone `s : cone (K ⋙ F)` with `F` representably flat, `s` can factor through `F.map_cone c`.
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
fac (x : J) : lift F hc s ≫ (F.map_cone c).π.app x = s.π.app x
by simpa [lift, ←functor.map_comp]
lemma
category_theory.preserves_finite_limits_of_flat.fac
category_theory.functor
src/category_theory/functor/flat.lean
[ "category_theory.limits.filtered_colimit_commutes_finite_limit", "category_theory.limits.preserves.functor_category", "category_theory.limits.bicones", "category_theory.limits.comma", "category_theory.limits.preserves.finite", "category_theory.limits.shapes.finite_limits" ]
[ "lift" ]
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
uniq {K : J ⥤ C} {c : cone K} (hc : is_limit c) (s : cone (K ⋙ F)) (f₁ f₂ : s.X ⟶ F.obj c.X) (h₁ : ∀ (j : J), f₁ ≫ (F.map_cone c).π.app j = s.π.app j) (h₂ : ∀ (j : J), f₂ ≫ (F.map_cone c).π.app j = s.π.app j) : f₁ = f₂
begin -- We can make two cones over the diagram of `s` via `f₁` and `f₂`. let α₁ : to_diagram (F.map_cone c) ⋙ map f₁ ⟶ to_diagram s := { app := λ X, eq_to_hom (by simp [←h₁]), naturality' := λ _ _ _, by { ext, simp } }, let α₂ : to_diagram (F.map_cone c) ⋙ map f₂ ⟶ to_diagram s := { app := λ X, eq_to_hom (by...
lemma
category_theory.preserves_finite_limits_of_flat.uniq
category_theory.functor
src/category_theory/functor/flat.lean
[ "category_theory.limits.filtered_colimit_commutes_finite_limit", "category_theory.limits.preserves.functor_category", "category_theory.limits.bicones", "category_theory.limits.comma", "category_theory.limits.preserves.finite", "category_theory.limits.shapes.finite_limits" ]
[]
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
preserves_finite_limits_of_flat (F : C ⥤ D) [representably_flat F] : preserves_finite_limits F
begin apply preserves_finite_limits_of_preserves_finite_limits_of_size, intros J _ _, constructor, intros K, constructor, intros c hc, exactI { lift := preserves_finite_limits_of_flat.lift F hc, fac' := preserves_finite_limits_of_flat.fac F hc, uniq' := λ s m h, by { apply preserves_finite_limits_...
def
category_theory.preserves_finite_limits_of_flat
category_theory.functor
src/category_theory/functor/flat.lean
[ "category_theory.limits.filtered_colimit_commutes_finite_limit", "category_theory.limits.preserves.functor_category", "category_theory.limits.bicones", "category_theory.limits.comma", "category_theory.limits.preserves.finite", "category_theory.limits.shapes.finite_limits" ]
[ "lift" ]
Representably flat functors preserve finite limits.
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
preserves_finite_limits_iff_flat [has_finite_limits C] (F : C ⥤ D) : representably_flat F ≃ preserves_finite_limits F
{ to_fun := λ _, by exactI preserves_finite_limits_of_flat F, inv_fun := λ _, by exactI flat_of_preserves_finite_limits F, left_inv := λ _, proof_irrel _ _, right_inv := λ x, by { cases x, unfold preserves_finite_limits_of_flat, dunfold preserves_finite_limits_of_preserves_finite_limits_of_size, congr } }
def
category_theory.preserves_finite_limits_iff_flat
category_theory.functor
src/category_theory/functor/flat.lean
[ "category_theory.limits.filtered_colimit_commutes_finite_limit", "category_theory.limits.preserves.functor_category", "category_theory.limits.bicones", "category_theory.limits.comma", "category_theory.limits.preserves.finite", "category_theory.limits.shapes.finite_limits" ]
[ "inv_fun" ]
If `C` is finitely cocomplete, then `F : C ⥤ D` is representably flat iff it preserves finite limits.
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
Lan_evaluation_iso_colim (F : C ⥤ D) (X : D) [∀ (X : D), has_colimits_of_shape (costructured_arrow F X) E] : Lan F ⋙ (evaluation D E).obj X ≅ ((whiskering_left _ _ E).obj (costructured_arrow.proj F X)) ⋙ colim
nat_iso.of_components (λ G, colim.map_iso (iso.refl _)) begin intros G H i, ext, simp only [functor.comp_map, colimit.ι_desc_assoc, functor.map_iso_refl, evaluation_obj_map, whiskering_left_obj_map, category.comp_id, Lan_map_app, category.assoc], erw [colimit.ι_pre_assoc (Lan.diagram F H X) (costructured_ar...
def
category_theory.Lan_evaluation_iso_colim
category_theory.functor
src/category_theory/functor/flat.lean
[ "category_theory.limits.filtered_colimit_commutes_finite_limit", "category_theory.limits.preserves.functor_category", "category_theory.limits.bicones", "category_theory.limits.comma", "category_theory.limits.preserves.finite", "category_theory.limits.shapes.finite_limits" ]
[]
(Implementation) The evaluation of `Lan F` at `X` is the colimit over the costructured arrows over `X`.
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
Lan_preserves_finite_limits_of_flat (F : C ⥤ D) [representably_flat F] : preserves_finite_limits (Lan F.op : _ ⥤ (Dᵒᵖ ⥤ E))
begin apply preserves_finite_limits_of_preserves_finite_limits_of_size.{u₁}, intros J _ _, resetI, apply preserves_limits_of_shape_of_evaluation (Lan F.op : (Cᵒᵖ ⥤ E) ⥤ (Dᵒᵖ ⥤ E)) J, intro K, haveI : is_filtered (costructured_arrow F.op K) := is_filtered.of_equivalence (structured_arrow_op_equivalence F (...
instance
category_theory.Lan_preserves_finite_limits_of_flat
category_theory.functor
src/category_theory/functor/flat.lean
[ "category_theory.limits.filtered_colimit_commutes_finite_limit", "category_theory.limits.preserves.functor_category", "category_theory.limits.bicones", "category_theory.limits.comma", "category_theory.limits.preserves.finite", "category_theory.limits.shapes.finite_limits" ]
[]
If `F : C ⥤ D` is a representably flat functor between small categories, then the functor `Lan F.op` that takes presheaves over `C` to presheaves over `D` preserves finite limits.
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
Lan_flat_of_flat (F : C ⥤ D) [representably_flat F] : representably_flat (Lan F.op : _ ⥤ (Dᵒᵖ ⥤ E))
flat_of_preserves_finite_limits _
instance
category_theory.Lan_flat_of_flat
category_theory.functor
src/category_theory/functor/flat.lean
[ "category_theory.limits.filtered_colimit_commutes_finite_limit", "category_theory.limits.preserves.functor_category", "category_theory.limits.bicones", "category_theory.limits.comma", "category_theory.limits.preserves.finite", "category_theory.limits.shapes.finite_limits" ]
[]
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
Lan_preserves_finite_limits_of_preserves_finite_limits (F : C ⥤ D) [preserves_finite_limits F] : preserves_finite_limits (Lan F.op : _ ⥤ (Dᵒᵖ ⥤ E))
begin haveI := flat_of_preserves_finite_limits F, apply_instance end
instance
category_theory.Lan_preserves_finite_limits_of_preserves_finite_limits
category_theory.functor
src/category_theory/functor/flat.lean
[ "category_theory.limits.filtered_colimit_commutes_finite_limit", "category_theory.limits.preserves.functor_category", "category_theory.limits.bicones", "category_theory.limits.comma", "category_theory.limits.preserves.finite", "category_theory.limits.shapes.finite_limits" ]
[]
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
flat_iff_Lan_flat (F : C ⥤ D) : representably_flat F ↔ representably_flat (Lan F.op : _ ⥤ (Dᵒᵖ ⥤ Type u₁))
⟨λ H, by exactI infer_instance, λ H, begin resetI, haveI := preserves_finite_limits_of_flat (Lan F.op : _ ⥤ (Dᵒᵖ ⥤ Type u₁)), haveI : preserves_finite_limits F := begin apply preserves_finite_limits_of_preserves_finite_limits_of_size.{u₁}, intros, resetI, apply preserves_limit_of_Lan_preserves_lim...
lemma
category_theory.flat_iff_Lan_flat
category_theory.functor
src/category_theory/functor/flat.lean
[ "category_theory.limits.filtered_colimit_commutes_finite_limit", "category_theory.limits.preserves.functor_category", "category_theory.limits.bicones", "category_theory.limits.comma", "category_theory.limits.preserves.finite", "category_theory.limits.shapes.finite_limits" ]
[]
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
preserves_finite_limits_iff_Lan_preserves_finite_limits (F : C ⥤ D) : preserves_finite_limits F ≃ preserves_finite_limits (Lan F.op : _ ⥤ (Dᵒᵖ ⥤ Type u₁))
{ to_fun := λ _, by exactI infer_instance, inv_fun := λ _, begin apply preserves_finite_limits_of_preserves_finite_limits_of_size.{u₁}, intros, resetI, apply preserves_limit_of_Lan_preserves_limit end, left_inv := λ x, begin cases x, unfold preserves_finite_limits_of_flat, dunfold preserves_fi...
def
category_theory.preserves_finite_limits_iff_Lan_preserves_finite_limits
category_theory.functor
src/category_theory/functor/flat.lean
[ "category_theory.limits.filtered_colimit_commutes_finite_limit", "category_theory.limits.preserves.functor_category", "category_theory.limits.bicones", "category_theory.limits.comma", "category_theory.limits.preserves.finite", "category_theory.limits.shapes.finite_limits" ]
[ "category_theory.Lan_preserves_finite_limits_of_flat", "category_theory.Lan_preserves_finite_limits_of_preserves_finite_limits", "inv_fun" ]
If `C` is finitely complete, then `F : C ⥤ D` preserves finite limits iff `Lan F.op : (Cᵒᵖ ⥤ Type*) ⥤ (Dᵒᵖ ⥤ Type*)` preserves finite limits.
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
full (F : C ⥤ D)
(preimage : ∀ {X Y : C} (f : (F.obj X) ⟶ (F.obj Y)), X ⟶ Y) (witness' : ∀ {X Y : C} (f : (F.obj X) ⟶ (F.obj Y)), F.map (preimage f) = f . obviously)
class
category_theory.full
category_theory.functor
src/category_theory/functor/fully_faithful.lean
[ "category_theory.natural_isomorphism", "logic.equiv.defs" ]
[]
A functor `F : C ⥤ D` is full if for each `X Y : C`, `F.map` is surjective. In fact, we use a constructive definition, so the `full F` typeclass contains data, specifying a particular preimage of each `f : F.obj X ⟶ F.obj Y`. See <https://stacks.math.columbia.edu/tag/001C>.
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
faithful (F : C ⥤ D) : Prop
(map_injective' [] : ∀ {X Y : C}, function.injective (@functor.map _ _ _ _ F X Y) . obviously)
class
category_theory.faithful
category_theory.functor
src/category_theory/functor/fully_faithful.lean
[ "category_theory.natural_isomorphism", "logic.equiv.defs" ]
[]
A functor `F : C ⥤ D` is faithful if for each `X Y : C`, `F.map` is injective. See <https://stacks.math.columbia.edu/tag/001C>.
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
map_injective (F : C ⥤ D) [faithful F] : function.injective $ @functor.map _ _ _ _ F X Y
faithful.map_injective F
lemma
category_theory.functor.map_injective
category_theory.functor
src/category_theory/functor/fully_faithful.lean
[ "category_theory.natural_isomorphism", "logic.equiv.defs" ]
[]
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
map_iso_injective (F : C ⥤ D) [faithful F] : function.injective $ @functor.map_iso _ _ _ _ F X Y
λ i j h, iso.ext (map_injective F (congr_arg iso.hom h : _))
lemma
category_theory.functor.map_iso_injective
category_theory.functor
src/category_theory/functor/fully_faithful.lean
[ "category_theory.natural_isomorphism", "logic.equiv.defs" ]
[]
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
preimage (F : C ⥤ D) [full F] (f : F.obj X ⟶ F.obj Y) : X ⟶ Y
full.preimage.{v₁ v₂} f
def
category_theory.functor.preimage
category_theory.functor
src/category_theory/functor/fully_faithful.lean
[ "category_theory.natural_isomorphism", "logic.equiv.defs" ]
[]
The specified preimage of a morphism under a full functor.
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
image_preimage (F : C ⥤ D) [full F] {X Y : C} (f : F.obj X ⟶ F.obj Y) : F.map (preimage F f) = f
by unfold preimage; obviously
lemma
category_theory.functor.image_preimage
category_theory.functor
src/category_theory/functor/fully_faithful.lean
[ "category_theory.natural_isomorphism", "logic.equiv.defs" ]
[]
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
map_surjective (F : C ⥤ D) [full F] : function.surjective (@functor.map _ _ _ _ F X Y)
λ f, ⟨F.preimage f, F.image_preimage f⟩
lemma
category_theory.functor.map_surjective
category_theory.functor
src/category_theory/functor/fully_faithful.lean
[ "category_theory.natural_isomorphism", "logic.equiv.defs" ]
[]
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
full_of_exists (F : C ⥤ D) (h : ∀ (X Y : C) (f : F.obj X ⟶ F.obj Y), ∃ p, F.map p = f) : full F
by { choose p hp using h, exact ⟨p, hp⟩ }
def
category_theory.functor.full_of_exists
category_theory.functor
src/category_theory/functor/fully_faithful.lean
[ "category_theory.natural_isomorphism", "logic.equiv.defs" ]
[]
Deduce that `F` is full from the existence of preimages, using choice.
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
full_of_surjective (F : C ⥤ D) (h : ∀ (X Y : C), function.surjective (@functor.map _ _ _ _ F X Y)) : full F
full_of_exists _ h
def
category_theory.functor.full_of_surjective
category_theory.functor
src/category_theory/functor/fully_faithful.lean
[ "category_theory.natural_isomorphism", "logic.equiv.defs" ]
[]
Deduce that `F` is full from surjectivity of `F.map`, using choice.
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
preimage_id : F.preimage (𝟙 (F.obj X)) = 𝟙 X
F.map_injective (by simp)
lemma
category_theory.preimage_id
category_theory.functor
src/category_theory/functor/fully_faithful.lean
[ "category_theory.natural_isomorphism", "logic.equiv.defs" ]
[]
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
preimage_comp (f : F.obj X ⟶ F.obj Y) (g : F.obj Y ⟶ F.obj Z) : F.preimage (f ≫ g) = F.preimage f ≫ F.preimage g
F.map_injective (by simp)
lemma
category_theory.preimage_comp
category_theory.functor
src/category_theory/functor/fully_faithful.lean
[ "category_theory.natural_isomorphism", "logic.equiv.defs" ]
[]
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
preimage_map (f : X ⟶ Y) : F.preimage (F.map f) = f
F.map_injective (by simp)
lemma
category_theory.preimage_map
category_theory.functor
src/category_theory/functor/fully_faithful.lean
[ "category_theory.natural_isomorphism", "logic.equiv.defs" ]
[]
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
preimage_iso (f : (F.obj X) ≅ (F.obj Y)) : X ≅ Y
{ hom := F.preimage f.hom, inv := F.preimage f.inv, hom_inv_id' := F.map_injective (by simp), inv_hom_id' := F.map_injective (by simp), }
def
category_theory.functor.preimage_iso
category_theory.functor
src/category_theory/functor/fully_faithful.lean
[ "category_theory.natural_isomorphism", "logic.equiv.defs" ]
[]
If `F : C ⥤ D` is fully faithful, every isomorphism `F.obj X ≅ F.obj Y` has a preimage.
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
preimage_iso_map_iso (f : X ≅ Y) : F.preimage_iso (F.map_iso f) = f
by { ext, simp, }
lemma
category_theory.functor.preimage_iso_map_iso
category_theory.functor
src/category_theory/functor/fully_faithful.lean
[ "category_theory.natural_isomorphism", "logic.equiv.defs" ]
[]
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
is_iso_of_fully_faithful (f : X ⟶ Y) [is_iso (F.map f)] : is_iso f
⟨⟨F.preimage (inv (F.map f)), ⟨F.map_injective (by simp), F.map_injective (by simp)⟩⟩⟩
lemma
category_theory.is_iso_of_fully_faithful
category_theory.functor
src/category_theory/functor/fully_faithful.lean
[ "category_theory.natural_isomorphism", "logic.equiv.defs" ]
[]
If the image of a morphism under a fully faithful functor in an isomorphism, then the original morphisms is also an isomorphism.
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
equiv_of_fully_faithful {X Y} : (X ⟶ Y) ≃ (F.obj X ⟶ F.obj Y)
{ to_fun := λ f, F.map f, inv_fun := λ f, F.preimage f, left_inv := λ f, by simp, right_inv := λ f, by simp }
def
category_theory.equiv_of_fully_faithful
category_theory.functor
src/category_theory/functor/fully_faithful.lean
[ "category_theory.natural_isomorphism", "logic.equiv.defs" ]
[ "inv_fun" ]
If `F` is fully faithful, we have an equivalence of hom-sets `X ⟶ Y` and `F X ⟶ F Y`.
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
iso_equiv_of_fully_faithful {X Y} : (X ≅ Y) ≃ (F.obj X ≅ F.obj Y)
{ to_fun := λ f, F.map_iso f, inv_fun := λ f, F.preimage_iso f, left_inv := λ f, by simp, right_inv := λ f, by { ext, simp, } }
def
category_theory.iso_equiv_of_fully_faithful
category_theory.functor
src/category_theory/functor/fully_faithful.lean
[ "category_theory.natural_isomorphism", "logic.equiv.defs" ]
[ "inv_fun" ]
If `F` is fully faithful, we have an equivalence of iso-sets `X ≅ Y` and `F X ≅ F Y`.
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
nat_trans_of_comp_fully_faithful (α : F ⋙ H ⟶ G ⋙ H) : F ⟶ G
{ app := λ X, (equiv_of_fully_faithful H).symm (α.app X), naturality' := λ X Y f, by { dsimp, apply H.map_injective, simpa using α.naturality f, } }
def
category_theory.nat_trans_of_comp_fully_faithful
category_theory.functor
src/category_theory/functor/fully_faithful.lean
[ "category_theory.natural_isomorphism", "logic.equiv.defs" ]
[]
We can construct a natural transformation between functors by constructing a natural transformation between those functors composed with a fully faithful functor.
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
nat_iso_of_comp_fully_faithful (i : F ⋙ H ≅ G ⋙ H) : F ≅ G
nat_iso.of_components (λ X, (iso_equiv_of_fully_faithful H).symm (i.app X)) (λ X Y f, by { dsimp, apply H.map_injective, simpa using i.hom.naturality f, })
def
category_theory.nat_iso_of_comp_fully_faithful
category_theory.functor
src/category_theory/functor/fully_faithful.lean
[ "category_theory.natural_isomorphism", "logic.equiv.defs" ]
[]
We can construct a natural isomorphism between functors by constructing a natural isomorphism between those functors composed with a fully faithful functor.
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
nat_iso_of_comp_fully_faithful_hom (i : F ⋙ H ≅ G ⋙ H) : (nat_iso_of_comp_fully_faithful H i).hom = nat_trans_of_comp_fully_faithful H i.hom
by { ext, simp [nat_iso_of_comp_fully_faithful], }
lemma
category_theory.nat_iso_of_comp_fully_faithful_hom
category_theory.functor
src/category_theory/functor/fully_faithful.lean
[ "category_theory.natural_isomorphism", "logic.equiv.defs" ]
[]
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
nat_iso_of_comp_fully_faithful_inv (i : F ⋙ H ≅ G ⋙ H) : (nat_iso_of_comp_fully_faithful H i).inv = nat_trans_of_comp_fully_faithful H i.inv
by { ext, simp [←preimage_comp], dsimp, simp, }
lemma
category_theory.nat_iso_of_comp_fully_faithful_inv
category_theory.functor
src/category_theory/functor/fully_faithful.lean
[ "category_theory.natural_isomorphism", "logic.equiv.defs" ]
[]
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
nat_trans.equiv_of_comp_fully_faithful : (F ⟶ G) ≃ (F ⋙ H ⟶ G ⋙ H)
{ to_fun := λ α, α ◫ 𝟙 H, inv_fun := nat_trans_of_comp_fully_faithful H, left_inv := by tidy, right_inv := by tidy, }
def
category_theory.nat_trans.equiv_of_comp_fully_faithful
category_theory.functor
src/category_theory/functor/fully_faithful.lean
[ "category_theory.natural_isomorphism", "logic.equiv.defs" ]
[ "inv_fun" ]
Horizontal composition with a fully faithful functor induces a bijection on natural transformations.
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
nat_iso.equiv_of_comp_fully_faithful : (F ≅ G) ≃ (F ⋙ H ≅ G ⋙ H)
{ to_fun := λ e, nat_iso.hcomp e (iso.refl H), inv_fun := nat_iso_of_comp_fully_faithful H, left_inv := by tidy, right_inv := by tidy, }
def
category_theory.nat_iso.equiv_of_comp_fully_faithful
category_theory.functor
src/category_theory/functor/fully_faithful.lean
[ "category_theory.natural_isomorphism", "logic.equiv.defs" ]
[ "inv_fun" ]
Horizontal composition with a fully faithful functor induces a bijection on natural isomorphisms.
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
full.id : full (𝟭 C)
{ preimage := λ _ _ f, f }
instance
category_theory.full.id
category_theory.functor
src/category_theory/functor/fully_faithful.lean
[ "category_theory.natural_isomorphism", "logic.equiv.defs" ]
[]
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
faithful.id : faithful (𝟭 C)
by obviously
instance
category_theory.faithful.id
category_theory.functor
src/category_theory/functor/fully_faithful.lean
[ "category_theory.natural_isomorphism", "logic.equiv.defs" ]
[]
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
faithful.comp [faithful F] [faithful G] : faithful (F ⋙ G)
{ map_injective' := λ _ _ _ _ p, F.map_injective (G.map_injective p) }
instance
category_theory.faithful.comp
category_theory.functor
src/category_theory/functor/fully_faithful.lean
[ "category_theory.natural_isomorphism", "logic.equiv.defs" ]
[]
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
faithful.of_comp [faithful $ F ⋙ G] : faithful F
{ map_injective' := λ X Y, (F ⋙ G).map_injective.of_comp }
lemma
category_theory.faithful.of_comp
category_theory.functor
src/category_theory/functor/fully_faithful.lean
[ "category_theory.natural_isomorphism", "logic.equiv.defs" ]
[]
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
full.of_iso [full F] (α : F ≅ F') : full F'
{ preimage := λ X Y f, F.preimage ((α.app X).hom ≫ f ≫ (α.app Y).inv), witness' := λ X Y f, by simp [←nat_iso.naturality_1 α], }
def
category_theory.full.of_iso
category_theory.functor
src/category_theory/functor/fully_faithful.lean
[ "category_theory.natural_isomorphism", "logic.equiv.defs" ]
[]
If `F` is full, and naturally isomorphic to some `F'`, then `F'` is also full.
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
faithful.of_iso [faithful F] (α : F ≅ F') : faithful F'
{ map_injective' := λ X Y f f' h, F.map_injective (by rw [←nat_iso.naturality_1 α.symm, h, nat_iso.naturality_1 α.symm]) }
lemma
category_theory.faithful.of_iso
category_theory.functor
src/category_theory/functor/fully_faithful.lean
[ "category_theory.natural_isomorphism", "logic.equiv.defs" ]
[]
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
faithful.of_comp_iso {H : C ⥤ E} [ℋ : faithful H] (h : F ⋙ G ≅ H) : faithful F
@faithful.of_comp _ _ _ _ _ _ F G (faithful.of_iso h.symm)
lemma
category_theory.faithful.of_comp_iso
category_theory.functor
src/category_theory/functor/fully_faithful.lean
[ "category_theory.natural_isomorphism", "logic.equiv.defs" ]
[]
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
faithful.of_comp_eq {H : C ⥤ E} [ℋ : faithful H] (h : F ⋙ G = H) : faithful F
@faithful.of_comp _ _ _ _ _ _ F G (h.symm ▸ ℋ)
lemma
category_theory.faithful.of_comp_eq
category_theory.functor
src/category_theory/functor/fully_faithful.lean
[ "category_theory.natural_isomorphism", "logic.equiv.defs" ]
[]
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
faithful.div (F : C ⥤ E) (G : D ⥤ E) [faithful G] (obj : C → D) (h_obj : ∀ X, G.obj (obj X) = F.obj X) (map : Π {X Y}, (X ⟶ Y) → (obj X ⟶ obj Y)) (h_map : ∀ {X Y} {f : X ⟶ Y}, G.map (map f) == F.map f) : C ⥤ D
{ obj := obj, map := @map, map_id' := begin assume X, apply G.map_injective, apply eq_of_heq, transitivity F.map (𝟙 X), from h_map, rw [F.map_id, G.map_id, h_obj X] end, map_comp' := begin assume X Y Z f g, apply G.map_injective, apply eq_of_heq, transitivity F.map (f ≫ ...
def
category_theory.faithful.div
category_theory.functor
src/category_theory/functor/fully_faithful.lean
[ "category_theory.natural_isomorphism", "logic.equiv.defs" ]
[]
“Divide” a functor by a faithful functor.
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
faithful.div_comp (F : C ⥤ E) [faithful F] (G : D ⥤ E) [faithful G] (obj : C → D) (h_obj : ∀ X, G.obj (obj X) = F.obj X) (map : Π {X Y}, (X ⟶ Y) → (obj X ⟶ obj Y)) (h_map : ∀ {X Y} {f : X ⟶ Y}, G.map (map f) == F.map f) : (faithful.div F G obj @h_obj @map @h_map) ⋙ G = F
begin casesI F with F_obj _ _ _, casesI G with G_obj _ _ _, unfold faithful.div functor.comp, unfold_projs at h_obj, have: F_obj = G_obj ∘ obj := (funext h_obj).symm, substI this, congr, funext, exact eq_of_heq h_map end
lemma
category_theory.faithful.div_comp
category_theory.functor
src/category_theory/functor/fully_faithful.lean
[ "category_theory.natural_isomorphism", "logic.equiv.defs" ]
[ "functor.comp" ]
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
faithful.div_faithful (F : C ⥤ E) [faithful F] (G : D ⥤ E) [faithful G] (obj : C → D) (h_obj : ∀ X, G.obj (obj X) = F.obj X) (map : Π {X Y}, (X ⟶ Y) → (obj X ⟶ obj Y)) (h_map : ∀ {X Y} {f : X ⟶ Y}, G.map (map f) == F.map f) : faithful (faithful.div F G obj @h_obj @map @h_map)
(faithful.div_comp F G _ h_obj _ @h_map).faithful_of_comp
lemma
category_theory.faithful.div_faithful
category_theory.functor
src/category_theory/functor/fully_faithful.lean
[ "category_theory.natural_isomorphism", "logic.equiv.defs" ]
[]
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
full.comp [full F] [full G] : full (F ⋙ G)
{ preimage := λ _ _ f, F.preimage (G.preimage f) }
instance
category_theory.full.comp
category_theory.functor
src/category_theory/functor/fully_faithful.lean
[ "category_theory.natural_isomorphism", "logic.equiv.defs" ]
[]
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
full.of_comp_faithful [full $ F ⋙ G] [faithful G] : full F
{ preimage := λ X Y f, (F ⋙ G).preimage (G.map f), witness' := λ X Y f, G.map_injective ((F ⋙ G).image_preimage _) }
def
category_theory.full.of_comp_faithful
category_theory.functor
src/category_theory/functor/fully_faithful.lean
[ "category_theory.natural_isomorphism", "logic.equiv.defs" ]
[]
If `F ⋙ G` is full and `G` is faithful, then `F` is full.
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
full.of_comp_faithful_iso {F : C ⥤ D} {G : D ⥤ E} {H : C ⥤ E} [full H] [faithful G] (h : F ⋙ G ≅ H) : full F
@full.of_comp_faithful _ _ _ _ _ _ F G (full.of_iso h.symm) _
def
category_theory.full.of_comp_faithful_iso
category_theory.functor
src/category_theory/functor/fully_faithful.lean
[ "category_theory.natural_isomorphism", "logic.equiv.defs" ]
[]
If `F ⋙ G` is full and `G` is faithful, then `F` is full.
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
fully_faithful_cancel_right {F G : C ⥤ D} (H : D ⥤ E) [full H] [faithful H] (comp_iso: F ⋙ H ≅ G ⋙ H) : F ≅ G
nat_iso.of_components (λ X, H.preimage_iso (comp_iso.app X)) (λ X Y f, H.map_injective (by simpa using comp_iso.hom.naturality f))
def
category_theory.fully_faithful_cancel_right
category_theory.functor
src/category_theory/functor/fully_faithful.lean
[ "category_theory.natural_isomorphism", "logic.equiv.defs" ]
[]
Given a natural isomorphism between `F ⋙ H` and `G ⋙ H` for a fully faithful functor `H`, we can 'cancel' it to give a natural iso between `F` and `G`.
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
fully_faithful_cancel_right_hom_app {F G : C ⥤ D} {H : D ⥤ E} [full H] [faithful H] (comp_iso: F ⋙ H ≅ G ⋙ H) (X : C) : (fully_faithful_cancel_right H comp_iso).hom.app X = H.preimage (comp_iso.hom.app X)
rfl
lemma
category_theory.fully_faithful_cancel_right_hom_app
category_theory.functor
src/category_theory/functor/fully_faithful.lean
[ "category_theory.natural_isomorphism", "logic.equiv.defs" ]
[]
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
fully_faithful_cancel_right_inv_app {F G : C ⥤ D} {H : D ⥤ E} [full H] [faithful H] (comp_iso: F ⋙ H ≅ G ⋙ H) (X : C) : (fully_faithful_cancel_right H comp_iso).inv.app X = H.preimage (comp_iso.inv.app X)
rfl
lemma
category_theory.fully_faithful_cancel_right_inv_app
category_theory.functor
src/category_theory/functor/fully_faithful.lean
[ "category_theory.natural_isomorphism", "logic.equiv.defs" ]
[]
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
functorial (F : C → D) : Type (max v₁ v₂ u₁ u₂)
(map : Π {X Y : C}, (X ⟶ Y) → ((F X) ⟶ (F Y))) (map_id' : ∀ (X : C), map (𝟙 X) = 𝟙 (F X) . obviously) (map_comp' : ∀ {X Y Z : C} (f : X ⟶ Y) (g : Y ⟶ Z), map (f ≫ g) = (map f) ≫ (map g) . obviously)
class
category_theory.functorial
category_theory.functor
src/category_theory/functor/functorial.lean
[ "category_theory.functor.basic" ]
[]
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
map (F : C → D) [functorial.{v₁ v₂} F] {X Y : C} (f : X ⟶ Y) : F X ⟶ F Y
functorial.map.{v₁ v₂} f
def
category_theory.map
category_theory.functor
src/category_theory/functor/functorial.lean
[ "category_theory.functor.basic" ]
[]
If `F : C → D` (just a function) has `[functorial F]`, we can write `map F f : F X ⟶ F Y` for the action of `F` on a morphism `f : X ⟶ Y`.
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
map_as_map {F : C → D} [functorial.{v₁ v₂} F] {X Y : C} {f : X ⟶ Y} : functorial.map.{v₁ v₂} f = map F f
rfl
lemma
category_theory.map_as_map
category_theory.functor
src/category_theory/functor/functorial.lean
[ "category_theory.functor.basic" ]
[]
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
functorial.map_id {F : C → D} [functorial.{v₁ v₂} F] {X : C} : map F (𝟙 X) = 𝟙 (F X)
functorial.map_id' X
lemma
category_theory.functorial.map_id
category_theory.functor
src/category_theory/functor/functorial.lean
[ "category_theory.functor.basic" ]
[]
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
functorial.map_comp {F : C → D} [functorial.{v₁ v₂} F] {X Y Z : C} {f : X ⟶ Y} {g : Y ⟶ Z} : map F (f ≫ g) = map F f ≫ map F g
functorial.map_comp' f g
lemma
category_theory.functorial.map_comp
category_theory.functor
src/category_theory/functor/functorial.lean
[ "category_theory.functor.basic" ]
[]
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
of (F : C → D) [I : functorial.{v₁ v₂} F] : C ⥤ D
{ obj := F, ..I }
def
category_theory.functor.of
category_theory.functor
src/category_theory/functor/functorial.lean
[ "category_theory.functor.basic" ]
[]
Bundle a functorial function as a functor.
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
map_functorial_obj (F : C ⥤ D) {X Y : C} (f : X ⟶ Y) : map F.obj f = F.map f
rfl
lemma
category_theory.map_functorial_obj
category_theory.functor
src/category_theory/functor/functorial.lean
[ "category_theory.functor.basic" ]
[]
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
functorial_id : functorial.{v₁ v₁} (id : C → C)
{ map := λ X Y f, f }
instance
category_theory.functorial_id
category_theory.functor
src/category_theory/functor/functorial.lean
[ "category_theory.functor.basic" ]
[]
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
functorial_comp (F : C → D) [functorial.{v₁ v₂} F] (G : D → E) [functorial.{v₂ v₃} G] : functorial.{v₁ v₃} (G ∘ F)
{ ..(functor.of F ⋙ functor.of G) }
def
category_theory.functorial_comp
category_theory.functor
src/category_theory/functor/functorial.lean
[ "category_theory.functor.basic" ]
[]
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
hom : Cᵒᵖ × C ⥤ Type v
{ obj := λ p, unop p.1 ⟶ p.2, map := λ X Y f, λ h, f.1.unop ≫ h ≫ f.2 }
def
category_theory.functor.hom
category_theory.functor
src/category_theory/functor/hom.lean
[ "category_theory.products.basic", "category_theory.types" ]
[]
`functor.hom` is the hom-pairing, sending `(X, Y)` to `X ⟶ Y`, contravariant in `X` and covariant in `Y`.
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
comp_inv_iso [h : is_equivalence H] (i : F ≅ G ⋙ H) : F ⋙ H.inv ≅ G
iso_whisker_right i H.inv ≪≫ (associator G H H.inv) ≪≫ iso_whisker_left G h.unit_iso.symm ≪≫ eq_to_iso (functor.comp_id G)
def
category_theory.comp_inv_iso
category_theory.functor
src/category_theory/functor/inv_isos.lean
[ "category_theory.eq_to_hom" ]
[]
Construct an isomorphism `F ⋙ H.inv ≅ G` from an isomorphism `F ≅ G ⋙ H`.
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
iso_comp_inv [h : is_equivalence H] (i : G ⋙ H ≅ F) : G ≅ F ⋙ H.inv
(comp_inv_iso i.symm).symm
def
category_theory.iso_comp_inv
category_theory.functor
src/category_theory/functor/inv_isos.lean
[ "category_theory.eq_to_hom" ]
[]
Construct an isomorphism `G ≅ F ⋙ H.inv` from an isomorphism `G ⋙ H ≅ F`.
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
inv_comp_iso [h : is_equivalence G] (i : F ≅ G ⋙ H) : G.inv ⋙ F ≅ H
iso_whisker_left G.inv i ≪≫ (associator G.inv G H).symm ≪≫ iso_whisker_right h.counit_iso H ≪≫ eq_to_iso (functor.id_comp H)
def
category_theory.inv_comp_iso
category_theory.functor
src/category_theory/functor/inv_isos.lean
[ "category_theory.eq_to_hom" ]
[]
Construct an isomorphism `G.inv ⋙ F ≅ H` from an isomorphism `F ≅ G ⋙ H`.
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
iso_inv_comp [h : is_equivalence G] (i : G ⋙ H ≅ F) : H ≅ G.inv ⋙ F
(inv_comp_iso i.symm).symm
def
category_theory.iso_inv_comp
category_theory.functor
src/category_theory/functor/inv_isos.lean
[ "category_theory.eq_to_hom" ]
[]
Construct an isomorphism `H ≅ G.inv ⋙ F` from an isomorphism `G ⋙ H ≅ F`.
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
functor.left_derived (F : C ⥤ D) [F.additive] (n : ℕ) : C ⥤ D
projective_resolutions C ⋙ F.map_homotopy_category _ ⋙ homotopy_category.homology_functor D _ n
def
category_theory.functor.left_derived
category_theory.functor
src/category_theory/functor/left_derived.lean
[ "category_theory.preadditive.projective_resolution" ]
[ "homotopy_category.homology_functor" ]
The left derived functors of an additive functor.
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
functor.left_derived_obj_iso (F : C ⥤ D) [F.additive] (n : ℕ) {X : C} (P : ProjectiveResolution X) : (F.left_derived n).obj X ≅ (homology_functor D _ n).obj ((F.map_homological_complex _).obj P.complex)
(homotopy_category.homology_functor D _ n).map_iso (homotopy_category.iso_of_homotopy_equiv (F.map_homotopy_equiv (ProjectiveResolution.homotopy_equiv _ P))) ≪≫ (homotopy_category.homology_factors D _ n).app _
def
category_theory.functor.left_derived_obj_iso
category_theory.functor
src/category_theory/functor/left_derived.lean
[ "category_theory.preadditive.projective_resolution" ]
[ "homology_functor", "homotopy_category.homology_factors", "homotopy_category.homology_functor", "homotopy_category.iso_of_homotopy_equiv" ]
We can compute a left derived functor using a chosen projective resolution.
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
functor.left_derived_obj_projective_zero (F : C ⥤ D) [F.additive] (X : C) [projective X] : (F.left_derived 0).obj X ≅ F.obj X
F.left_derived_obj_iso 0 (ProjectiveResolution.self X) ≪≫ (homology_functor _ _ _).map_iso ((chain_complex.single₀_map_homological_complex F).app X) ≪≫ (chain_complex.homology_functor_0_single₀ D).app (F.obj X)
def
category_theory.functor.left_derived_obj_projective_zero
category_theory.functor
src/category_theory/functor/left_derived.lean
[ "category_theory.preadditive.projective_resolution" ]
[ "chain_complex.homology_functor_0_single₀", "chain_complex.single₀_map_homological_complex", "homology_functor" ]
The 0-th derived functor of `F` on a projective object `X` is just `F.obj X`.
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
functor.left_derived_obj_projective_succ (F : C ⥤ D) [F.additive] (n : ℕ) (X : C) [projective X] : (F.left_derived (n+1)).obj X ≅ 0
F.left_derived_obj_iso (n+1) (ProjectiveResolution.self X) ≪≫ (homology_functor _ _ _).map_iso ((chain_complex.single₀_map_homological_complex F).app X) ≪≫ (chain_complex.homology_functor_succ_single₀ D n).app (F.obj X) ≪≫ (functor.zero_obj _).iso_zero
def
category_theory.functor.left_derived_obj_projective_succ
category_theory.functor
src/category_theory/functor/left_derived.lean
[ "category_theory.preadditive.projective_resolution" ]
[ "chain_complex.homology_functor_succ_single₀", "chain_complex.single₀_map_homological_complex", "homology_functor" ]
The higher derived functors vanish on projective objects.
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
functor.left_derived_map_eq (F : C ⥤ D) [F.additive] (n : ℕ) {X Y : C} (f : X ⟶ Y) {P : ProjectiveResolution X} {Q : ProjectiveResolution Y} (g : P.complex ⟶ Q.complex) (w : g ≫ Q.π = P.π ≫ (chain_complex.single₀ C).map f) : (F.left_derived n).map f = (F.left_derived_obj_iso n P).hom ≫ (homology_functor D _...
begin dsimp only [functor.left_derived, functor.left_derived_obj_iso], dsimp, simp only [category.comp_id, category.id_comp], rw [←homology_functor_map, homotopy_category.homology_functor_map_factors], simp only [←functor.map_comp], congr' 1, apply homotopy_category.eq_of_homotopy, apply functor.map_homot...
lemma
category_theory.functor.left_derived_map_eq
category_theory.functor
src/category_theory/functor/left_derived.lean
[ "category_theory.preadditive.projective_resolution" ]
[ "chain_complex.single₀", "homology_functor", "homotopy.trans", "homotopy_category.eq_of_homotopy", "homotopy_category.homology_functor_map_factors", "homotopy_category.homotopy_out_map" ]
We can compute a left derived functor on a morphism using a lift of that morphism to a chain map between chosen projective resolutions.
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
nat_trans.left_derived {F G : C ⥤ D} [F.additive] [G.additive] (α : F ⟶ G) (n : ℕ) : F.left_derived n ⟶ G.left_derived n
whisker_left (projective_resolutions C) (whisker_right (nat_trans.map_homotopy_category α _) (homotopy_category.homology_functor D _ n))
def
category_theory.nat_trans.left_derived
category_theory.functor
src/category_theory/functor/left_derived.lean
[ "category_theory.preadditive.projective_resolution" ]
[ "homotopy_category.homology_functor" ]
The natural transformation between left-derived functors induced by a natural transformation.
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
nat_trans.left_derived_id (F : C ⥤ D) [F.additive] (n : ℕ) : nat_trans.left_derived (𝟙 F) n = 𝟙 (F.left_derived n)
by { simp [nat_trans.left_derived], refl, }
lemma
category_theory.nat_trans.left_derived_id
category_theory.functor
src/category_theory/functor/left_derived.lean
[ "category_theory.preadditive.projective_resolution" ]
[]
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
nat_trans.left_derived_comp {F G H : C ⥤ D} [F.additive] [G.additive] [H.additive] (α : F ⟶ G) (β : G ⟶ H) (n : ℕ) : nat_trans.left_derived (α ≫ β) n = nat_trans.left_derived α n ≫ nat_trans.left_derived β n
by simp [nat_trans.left_derived]
lemma
category_theory.nat_trans.left_derived_comp
category_theory.functor
src/category_theory/functor/left_derived.lean
[ "category_theory.preadditive.projective_resolution" ]
[]
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
nat_trans.left_derived_eq {F G : C ⥤ D} [F.additive] [G.additive] (α : F ⟶ G) (n : ℕ) {X : C} (P : ProjectiveResolution X) : (nat_trans.left_derived α n).app X = (F.left_derived_obj_iso n P).hom ≫ (homology_functor D _ n).map ((nat_trans.map_homological_complex α _).app P.complex) ≫ (G.left_derive...
begin symmetry, dsimp [nat_trans.left_derived, functor.left_derived_obj_iso], simp only [category.comp_id, category.id_comp], rw [←homology_functor_map, homotopy_category.homology_functor_map_factors], simp only [←functor.map_comp], congr' 1, apply homotopy_category.eq_of_homotopy, simp only [nat_trans....
lemma
category_theory.nat_trans.left_derived_eq
category_theory.functor
src/category_theory/functor/left_derived.lean
[ "category_theory.preadditive.projective_resolution" ]
[ "homology_functor", "homotopy.comp_left_id", "homotopy_category.eq_of_homotopy", "homotopy_category.homology_functor_map_factors" ]
A component of the natural transformation between left-derived functors can be computed using a chosen projective resolution.
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
reflects_isomorphisms (F : C ⥤ D) : Prop
(reflects : Π {A B : C} (f : A ⟶ B) [is_iso (F.map f)], is_iso f)
class
category_theory.reflects_isomorphisms
category_theory.functor
src/category_theory/functor/reflects_isomorphisms.lean
[ "category_theory.balanced", "category_theory.functor.epi_mono", "category_theory.functor.fully_faithful" ]
[]
Define what it means for a functor `F : C ⥤ D` to reflect isomorphisms: for any morphism `f : A ⟶ B`, if `F.map f` is an isomorphism then `f` is as well. Note that we do not assume or require that `F` is faithful.
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
is_iso_of_reflects_iso {A B : C} (f : A ⟶ B) (F : C ⥤ D) [is_iso (F.map f)] [reflects_isomorphisms F] : is_iso f
reflects_isomorphisms.reflects F f
lemma
category_theory.is_iso_of_reflects_iso
category_theory.functor
src/category_theory/functor/reflects_isomorphisms.lean
[ "category_theory.balanced", "category_theory.functor.epi_mono", "category_theory.functor.fully_faithful" ]
[]
If `F` reflects isos and `F.map f` is an iso, then `f` is an iso.
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
of_full_and_faithful (F : C ⥤ D) [full F] [faithful F] : reflects_isomorphisms F
{ reflects := λ X Y f i, by exactI ⟨⟨F.preimage (inv (F.map f)), ⟨F.map_injective (by simp), F.map_injective (by simp)⟩⟩⟩ }
instance
category_theory.of_full_and_faithful
category_theory.functor
src/category_theory/functor/reflects_isomorphisms.lean
[ "category_theory.balanced", "category_theory.functor.epi_mono", "category_theory.functor.fully_faithful" ]
[]
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
reflects_isomorphisms_of_reflects_monomorphisms_of_reflects_epimorphisms [balanced C] (F : C ⥤ D) [reflects_monomorphisms F] [reflects_epimorphisms F] : reflects_isomorphisms F
{ reflects := λ A B f hf, begin resetI, haveI : epi f := epi_of_epi_map F infer_instance, haveI : mono f := mono_of_mono_map F infer_instance, exact is_iso_of_mono_of_epi f end }
instance
category_theory.reflects_isomorphisms_of_reflects_monomorphisms_of_reflects_epimorphisms
category_theory.functor
src/category_theory/functor/reflects_isomorphisms.lean
[ "category_theory.balanced", "category_theory.functor.epi_mono", "category_theory.functor.fully_faithful" ]
[ "balanced" ]
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
is_thin_iff : quiver.is_thin C ↔ ∀ c : C, subsingleton (c ⟶ c)
begin refine ⟨λ h c, h c c, λ h c d, subsingleton.intro $ λ f g, _⟩, haveI := h d, calc f = f ≫ (inv g ≫ g) : by simp only [inv_eq_inv, is_iso.inv_hom_id, category.comp_id] ... = f ≫ (inv f ≫ g) : by congr ... = g : by simp only [inv_eq_inv, is_iso.hom_inv_id_assoc], end
lemma
category_theory.groupoid.is_thin_iff
category_theory.groupoid
src/category_theory/groupoid/basic.lean
[ "category_theory.groupoid", "combinatorics.quiver.basic" ]
[ "quiver.is_thin" ]
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
is_totally_disconnected
∀ (c d : C), (c ⟶ d) → c = d
def
category_theory.groupoid.is_totally_disconnected
category_theory.groupoid
src/category_theory/groupoid/basic.lean
[ "category_theory.groupoid", "combinatorics.quiver.basic" ]
[ "is_totally_disconnected" ]
A subgroupoid is totally disconnected if it only has loops.
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
quiver.hom.to_pos_path {X Y : V} (f : X ⟶ Y) : ((category_theory.paths.category_paths $ quiver.symmetrify V).hom X Y)
f.to_pos.to_path
abbreviation
category_theory.groupoid.free.quiver.hom.to_pos_path
category_theory.groupoid
src/category_theory/groupoid/free_groupoid.lean
[ "category_theory.category.basic", "category_theory.functor.basic", "category_theory.groupoid", "tactic.nth_rewrite", "category_theory.path_category", "category_theory.quotient", "combinatorics.quiver.symmetric" ]
[ "category_theory.paths.category_paths", "quiver.symmetrify" ]
Shorthand for the "forward" arrow corresponding to `f` in `paths $ symmetrify V`
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
quiver.hom.to_neg_path {X Y : V} (f : X ⟶ Y) : ((category_theory.paths.category_paths $ quiver.symmetrify V).hom Y X)
f.to_neg.to_path
abbreviation
category_theory.groupoid.free.quiver.hom.to_neg_path
category_theory.groupoid
src/category_theory/groupoid/free_groupoid.lean
[ "category_theory.category.basic", "category_theory.functor.basic", "category_theory.groupoid", "tactic.nth_rewrite", "category_theory.path_category", "category_theory.quotient", "combinatorics.quiver.symmetric" ]
[ "category_theory.paths.category_paths", "quiver.symmetrify" ]
Shorthand for the "forward" arrow corresponding to `f` in `paths $ symmetrify V`
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
red_step : hom_rel (paths (quiver.symmetrify V)) | step (X Z : quiver.symmetrify V) (f : X ⟶ Z) : red_step (𝟙 X) (f.to_path ≫ (quiver.reverse f).to_path)
inductive
category_theory.groupoid.free.red_step
category_theory.groupoid
src/category_theory/groupoid/free_groupoid.lean
[ "category_theory.category.basic", "category_theory.functor.basic", "category_theory.groupoid", "tactic.nth_rewrite", "category_theory.path_category", "category_theory.quotient", "combinatorics.quiver.symmetric" ]
[ "hom_rel", "quiver.reverse", "quiver.symmetrify", "to_path" ]
The "reduction" relation
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
_root_.category_theory.free_groupoid (V) [Q : quiver V]
quotient (@red_step V Q)
def
category_theory.free_groupoid
category_theory.groupoid
src/category_theory/groupoid/free_groupoid.lean
[ "category_theory.category.basic", "category_theory.functor.basic", "category_theory.groupoid", "tactic.nth_rewrite", "category_theory.path_category", "category_theory.quotient", "combinatorics.quiver.symmetric" ]
[ "quiver" ]
The underlying vertices of the free groupoid
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
congr_reverse {X Y : paths $ quiver.symmetrify V} (p q : X ⟶ Y) : quotient.comp_closure red_step p q → quotient.comp_closure red_step (p.reverse) (q.reverse)
begin rintro ⟨XW, pp, qq, WY, _, Z, f⟩, have : quotient.comp_closure red_step (WY.reverse ≫ 𝟙 _ ≫ XW.reverse) (WY.reverse ≫ (f.to_path ≫ (quiver.reverse f).to_path) ≫ XW.reverse), { apply quotient.comp_closure.intro, apply red_step.step, }, simpa only [category_struct.comp, category_struct.id, quiver.p...
lemma
category_theory.groupoid.free.congr_reverse
category_theory.groupoid
src/category_theory/groupoid/free_groupoid.lean
[ "category_theory.category.basic", "category_theory.functor.basic", "category_theory.groupoid", "tactic.nth_rewrite", "category_theory.path_category", "category_theory.quotient", "combinatorics.quiver.symmetric" ]
[ "quiver.path.comp_assoc", "quiver.path.nil_comp", "quiver.path.reverse", "quiver.path.reverse_comp", "quiver.path.reverse_to_path", "quiver.reverse", "quiver.reverse_reverse", "quiver.symmetrify", "to_path" ]
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
congr_comp_reverse {X Y : paths $ quiver.symmetrify V} (p : X ⟶ Y) : quot.mk (@quotient.comp_closure _ _ red_step _ _) (p ≫ p.reverse) = quot.mk (@quotient.comp_closure _ _ red_step _ _) (𝟙 X)
begin apply quot.eqv_gen_sound, induction p with _ _ q f ih, { apply eqv_gen.refl, }, { simp only [quiver.path.reverse], fapply eqv_gen.trans, { exact q ≫ q.reverse, }, { apply eqv_gen.symm, apply eqv_gen.rel, have : quotient.comp_closure red_step (q ≫ (𝟙 _) ≫ q.reverse) ...
lemma
category_theory.groupoid.free.congr_comp_reverse
category_theory.groupoid
src/category_theory/groupoid/free_groupoid.lean
[ "category_theory.category.basic", "category_theory.functor.basic", "category_theory.groupoid", "tactic.nth_rewrite", "category_theory.path_category", "category_theory.quotient", "combinatorics.quiver.symmetric" ]
[ "ih", "quiver.path.comp_assoc", "quiver.path.reverse", "quiver.reverse", "quiver.symmetrify", "to_path" ]
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
congr_reverse_comp {X Y : paths $ quiver.symmetrify V} (p : X ⟶ Y) : quot.mk (@quotient.comp_closure _ _ red_step _ _) (p.reverse ≫ p) = quot.mk (@quotient.comp_closure _ _ red_step _ _) (𝟙 Y)
begin nth_rewrite 1 ←quiver.path.reverse_reverse p, apply congr_comp_reverse, end
lemma
category_theory.groupoid.free.congr_reverse_comp
category_theory.groupoid
src/category_theory/groupoid/free_groupoid.lean
[ "category_theory.category.basic", "category_theory.functor.basic", "category_theory.groupoid", "tactic.nth_rewrite", "category_theory.path_category", "category_theory.quotient", "combinatorics.quiver.symmetric" ]
[ "quiver.symmetrify" ]
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83
quot_inv {X Y : free_groupoid V} (f : X ⟶ Y) : Y ⟶ X
quot.lift_on f (λ pp, quot.mk _ $ pp.reverse) (λ pp qq con, quot.sound $ congr_reverse pp qq con)
def
category_theory.groupoid.free.quot_inv
category_theory.groupoid
src/category_theory/groupoid/free_groupoid.lean
[ "category_theory.category.basic", "category_theory.functor.basic", "category_theory.groupoid", "tactic.nth_rewrite", "category_theory.path_category", "category_theory.quotient", "combinatorics.quiver.symmetric" ]
[ "con" ]
The inverse of an arrow in the free groupoid
https://github.com/leanprover-community/mathlib
65a1391a0106c9204fe45bc73a039f056558cb83