Let R be a commutative Noetherian local ring and let M and N be nonzero finitely generated R-modules. In this paper, we investigate how the finiteness of the homological dimension of Ext modules between M and N affects that of M and N. One of our main result states that if ExtⁱR (M, N) has finite projective dimension for any 0 i RfdR M, where RfdR M is the (large) restricted flat dimension of M, then M has finite projective or injective dimension if and only if N does.
Kaito Kimura (Mon,) studied this question.