Abstract. In this note we give conditions for the invertibility of a bounded linear operator $T$ defined on a Banach space $X$ such that $X$ decomposes into a (non direct) sum of two closed $T$-invariant subspaces.
AMS Subject Classification
(1991): 47A10, 47A15,47A05, 15A29
spectrum of an operator
Received May 13, 2015, and in final form April 6, 2016. (Registered under 34/2015.)