PORTUGALIAE MATHEMATICA Vol. 51, No. 4, pp. 617628 (1994) 

On Operators of Saphar TypeChristoph SchmoegerMathematisches Institut I, Universität Karlsruhe,Postfach 6980, D7500 Karlsruhe 1  GERMANY Abstract: A bounded linear operator $T$ on a complex Banach space $X$ is called an operator of Saphar type, if $T$ is relatively regular and if its null space is contained in its generalized range $\displaystyle\bigcap^{\infty}_{n=1}T^n(X)$. This paper contains some characterizations of operators of Saphar type. Furthermore, for a function $f$ admissible in the analytic calculus, we obtain a necessary and sufficient condition in order that $f(T)$ is an operator of Saphar type. Full text of the article:
Electronic version published on: 29 Mar 2001. This page was last modified: 27 Nov 2007.
© 1994 Sociedade Portuguesa de Matemática
