Department of Mathematics, Faculty of Philosophy, University of Nis, Cirila i Metodija 2, 18000 Nis, Yugoslavia
Abstract:
A Hilbert space operator is called the EP operator if the range of is equal to the range of its adjoint . In this article necessary and sufficient conditions are given for a product of two EP operators with closed ranges to be an EP operator with a closed range. Thus, a generalization of the well-known result of Hartwig and Katz (Linear Algebra Appl. 252 (1997), 339-345) is given.