We prove that Dlab and Ringel's result in Citation5, Thm. 1 can be generalized to affine quasi-hereditary algebras. To be precise, under particular conditions, for an algebra H and an idempotent e∈H, H is affine quasi-hereditary if and only if eHe and H/HeH are affine quasi-hereditary. As an application, we give a new proof that triangular matrix algebras over affine quasi-hereditary algebras are affine quasi-hereditary.
Guiyu Yang (Fri,) studied this question.