English
If F preserves colimits of a given size after forgetting, then F preserves colimits of that size.
Русский
Если F сохраняет колимиты заданного размера после забывания, то F сохраняет колимиты этого размера.
LaTeX
$$$\operatorname{PreservesColimitsOfSize}(F) \Leftarrow \operatorname{PreservesColimitsOfSize}(F \circ \mathrm{forget}).$$$
Lean4
/-- `F : C ⥤ Action V G` preserves colimits of some size
if it does after postcomposing with the forgetful functor `Action V G ⥤ V`. -/
theorem preservesColimitsOfSize_of_preserves (F : C ⥤ Action V G)
(h : PreservesColimitsOfSize.{w₂, w₁} (F ⋙ Action.forget V G)) : PreservesColimitsOfSize.{w₂, w₁} F :=
by
constructor
intro J _
apply Action.preservesColimitsOfShape_of_preserves
exact PreservesColimitsOfSize.preservesColimitsOfShape