Abstract: | We study the derived functors of Hom that are computed by using flat resolutions of Hom. These are denoted n. We compare these with the usual Extn's and show that 1? Ext1and indicate (using MacLane's terminology) why the class of associated short exact sequences is a proper class. When the ring is a Dedekind domain we classify the N such that n(–, N) = 0 and show that unlike the situation for other classically defined right derived functors of Hom, Hom is not balanced relative to the two classes of modules that make 1 vanish. |