For any category, its arrow category is the functor category
for the interval category . is also written or or , since 2 and (the 1-simplex) etc. are common notation for the interval category.
This means that the objects of are the morphisms (the “arrows”, therefore the name) of , while the morphisms of are pairs of morphisms constituting commuting square diagrams in .
Revised on March 21, 2013 09:13:06
by Chris Waggoner?