Every category gives rise to an arrow category such that the objects of are the morphisms (or arrows, hence the name) of .
For any category, its arrow category is the category such that:
in ;
This is isomorphic to the functor category
for the interval category . is also written , , , or , since and (for the -simplex) are common notations for the interval category.
The arrow category is equivalently the comma category for the case that is the identity functor.
plays the role of a directed path object for categories in that functors
are the same as natural transformations between functors between and .
(arrow category is Grothendieck construction on slice categories)
For any category, let
be the pseudofunctor which sends
an object to the slice category ,
a morphism to the left base change functor given by post-composition in .
The Grothendieck construction on this functor is the arrow category of :
This follows readily by unwinding the definitions. In the refinement to the Grothendieck construction for model categories (here: slice model categories and model structures on functors) this equivalence is also considered for instance in Harpaz & Prasma (2015), above Cor. 6.1.2.
The correponding Grothendieck fibration is also known as the codomain fibration.
Last revised on April 1, 2023 at 16:23:38. See the history of this page for a list of all contributions to it.