THE DRAZIN AND MOORE{PENROSE INVERSE IN C-ALGEBRAS

In this paper we give an explicit representation of the Moore{Penrose inverse in a C-algebra in terms of the Drazin inverse of a quasipolar element, and derive properties of the Moore{Penrose inverse from the theory of the Drazin inverse. Results include an alternative proof that regularity implies Moore{Penrose invertibility, and a simplied proof of the continuity theorem for the Moore{Penrose inverse.