DOUBLE ORE EXTENSIONS VERSUS ITERATED ORE EXTENSIONS

Motivated by the construction of new examples of Artin-Schelter regular algebras of global dimension four, Zhang and Zhang [6] introduced an algebra extension A(P)[y(1),y(2);sigma, delta, tau] of A, which they called a double Ore extension. This construction seems to be similar to that of a two-step iterated Ore extension over A. The aim of this article is to describe those double Ore extensions which can be presented as iterated Ore extensions of the form A[y(1);sigma(1),delta(1)][y(2);sigma(2),delta(2)]. We also give partial answers to some questions posed in Zhang and Zhang [6].