On the Double Commutator Algebra of QF-3 Algebras

Abstract

Introduction and Preliminaries. Nakayama [9] suggested that algebras be classified according to the length of a right projective, injective resolution of the algebra as a left module. Tachikawa [10] showed that an algebra is QF-3 (see [12] for definition) if and only if the length is at least one. He [11] also gave some estimations of the length of the resolution besides relating the length to the size of the double commutator algebra of a faithful projective, injective left ideal.