Characterizations of normal, hyponormal and EP operators ✩

In this paper normal and hyponormal operators with closed ranges, as well as EP operators, are characterized in arbitrary Hilbert spaces. All characterizations involve generalized inverses. Thus, recent results of S. Cheng and Y. Tian [S. Cheng, Y. Tian, Two sets of new characterizations for normal and EP matrices, Linear Algebra Appl. 375 (2003) 181–195] are extended to infinite-dimensional settings. © 2006 Elsevier Inc. All rights reserved.