Points of objects tensor without vanishing #
In the setting of Deligne's theorem the tensor unit is simple, so a nonzero morphism out of it is a monomorphism; whiskering is exact, so the tensor of two nonzero points is again a monomorphism, and in particular nonzero. This is the input that makes a tensor product of nonzero algebras nonzero.
theorem
RS.mono_of_point_ne_zero
{A : Type u}
[CategoryTheory.Category.{v, u} A]
[CategoryTheory.Abelian A]
[CategoryTheory.Linear ℂ A]
[CategoryTheory.MonoidalCategory A]
[CategoryTheory.MonoidalPreadditive A]
[CategoryTheory.RigidCategory A]
(hu : HasScalarUnit A)
{X : A}
{u : CategoryTheory.MonoidalCategoryStruct.tensorUnit A ⟶ X}
(h : u ≠ 0)
:
A nonzero point is a monomorphism: the unit is simple.
theorem
RS.mono_tensorHom_point
{A : Type u}
[CategoryTheory.Category.{v, u} A]
[CategoryTheory.Abelian A]
[CategoryTheory.Linear ℂ A]
[CategoryTheory.MonoidalCategory A]
[CategoryTheory.MonoidalPreadditive A]
[CategoryTheory.RigidCategory A]
(hu : HasScalarUnit A)
{X Y : A}
{u : CategoryTheory.MonoidalCategoryStruct.tensorUnit A ⟶ X}
{v : CategoryTheory.MonoidalCategoryStruct.tensorUnit A ⟶ Y}
(hu0 : u ≠ 0)
(hv0 : v ≠ 0)
:
The tensor of two nonzero points is a monomorphism.
theorem
RS.tensorHom_point_ne_zero
{A : Type u}
[CategoryTheory.Category.{v, u} A]
[CategoryTheory.Abelian A]
[CategoryTheory.Linear ℂ A]
[CategoryTheory.MonoidalCategory A]
[CategoryTheory.MonoidalPreadditive A]
[CategoryTheory.RigidCategory A]
(hu : HasScalarUnit A)
{X Y : A}
{u : CategoryTheory.MonoidalCategoryStruct.tensorUnit A ⟶ X}
{v : CategoryTheory.MonoidalCategoryStruct.tensorUnit A ⟶ Y}
(hu0 : u ≠ 0)
(hv0 : v ≠ 0)
:
The tensor of two nonzero points is nonzero.