English
If there exists an isomorphism making the given diagram universal, then the base category is finitary extensive.
Русский
Если существует изоморфизм, делающий данный диаграмм универсальным, то базовая категория — конечная расширяемая.
LaTeX
$$$FinitaryExtensive\; C$ if a certain universal isomorphism exists for diagrams.$$
Lean4
theorem finitaryExtensive_of_preserves_and_reflects_isomorphism (F : C ⥤ D) [FinitaryExtensive D]
[HasFiniteCoproducts C] [HasPullbacks C] [PreservesLimitsOfShape WalkingCospan F]
[PreservesColimitsOfShape (Discrete WalkingPair) F] [F.ReflectsIsomorphisms] : FinitaryExtensive C :=
by
haveI : ReflectsLimitsOfShape WalkingCospan F := reflectsLimitsOfShape_of_reflectsIsomorphisms
haveI : ReflectsColimitsOfShape (Discrete WalkingPair) F := reflectsColimitsOfShape_of_reflectsIsomorphisms
exact finitaryExtensive_of_preserves_and_reflects F