Commun. Korean Math. Soc. 1997 Vol. 12, No. 3, 561-569
Eungil Ko Ewha Women's University
Abstract : In this paper we shall characterize a finite triangular operator matrix with $M$-hyponormal operators on main diagonal. This shows in particular that such an operator is subscalar, i.e., is similar to the restriction to a closed invariant subspace of a scalar operator. As a corollary, we get that every algebraic operator is subscalar.
Keywords : $M$-hyponormal, Subscalar, and Scalar operators, Putinar's theorem