The center of crossed products over simple rings (Q582354)

Let R*G be a crossed product of an arbitrary group G over a simple ring R. The main result of this paper exhibits a distinguished basis for the center Z(R*G) over the fixed field \(Z(R)^ G\) of G, where Z(R) is the center of R. The author applies this result to count nonisomorphic irreducible modules over such crossed products. Among other applications, he provides information on the number of linear nonequivalent irreducible projective crossed representations of a finite group over fields.