AUTOMORPHISMS AND DERIVATIONS OF SKEW POLYNOMIAL-RINGS

For a prime ring R and sigma is-an-element-of Aut(R), we determine the group of R-stabilizing automorphisms of the skew polynomial ring R[x;sigma]. In the case where R is simple, we characterize the X-inner automorphisms of R[x;sigma]. We also provide necessary and sufficient conditions for a sigma-commuting derivation of a prime ring R to extend to a derivation of R[x;sigma].