English
Proof of the second corepresentable-by construction, showing how extended diagrams produce a corepresentable by structure.
Русский
Доказательство второй конструкции corepresentableBy, демонстрирующее построение корпредставляющей структуры через расширенные диаграммы.
LaTeX
$$$\\text{corepresentableBy₂'} \\text{ proof }$$
Lean4
/-- Since a convolution unit is a pointwise left Kan extension, maps out of it at
any object are uniquely characterized. -/
theorem hom_ext {c : C} {v : V} {g h : U.obj c ⟶ v} (e : ∀ f : 𝟙_ C ⟶ c, can ≫ U.map f ≫ g = can ≫ U.map f ≫ h) :
g = h := by
apply (isPointwiseLeftKanExtensionCan c).hom_ext
intro j
simpa using e j.hom