In this paper, several equivalent conditions on the Drazin invertibility of product and difference of idempotents are obtained in a ring. Some results in Banach algebras are extended to the ring case.

In this paper we investigate the connection between relations among various invariants of number fields L coresponding to subgroups H acting on L and of linear relations among norm idempotents.

Let G be a possibly disconnected algebraic group over an algebraically closed field k of characteristic p > 0, such that its neutral connected component, H = G0, is a unipotent group. We recall that an algebraic group over k is defined to be a smooth group scheme of finite type over k. Let us fix a prime number l 6= p. If X is a k-scheme, we use D(X) to denote the bounded derived category of Ql...