notes about quasi-mixing operators

In this article, we introduce quasi-mixing operators and construct various examples. we prove that quasi-mixing operators exist on all finite-dimensional and infinite-dimensional  banach spaces. we also prove that an invertible operator $t$ is quasi-mixing if and only if $t^{-1}$ is quasi-mixing. we state some sufficient conditions  under which an operator is quasi-mixing. moreover, we prove that the direct sum of two operators is quasi-mixing if and only if any of them is quasi-mixing.