Invariant Subspaces for Positive Operators Acting on a Banach Space with Markushevich Basis

Abstract

We introduce ‘weak quasinilpotence’ for operators. Then, by substituting ‘Markushevich basis’ and ‘weak quasinilpotence at a nonzero vector’ for ‘Schauder basis’ and ‘quasinilpotence at a nonzero vector’, respectively, we answer a question on the invariant subspaces of positive operators in [3].