Homological behavior of idempotent subalgebras and Ext algebras

Colin Ingalls, Charles Paquette

Let $A$ be a (left and right) Noetherian ring that is semiperfect. Let $e$ be an idempotent of $A$ and consider the ring $\Gamma :=(1-e)A(1-e)$ and the semi-simple right $A$-module $S_e…