On $n$th roots of normal operators

Abstract

For $n$-normal operators $A$, equivalently $n$th roots $A$ of normal Hilbert space operators, both $A$ and $A^*$ satisfy the Bishop--Eschmeier--Putinar property $(\beta)_{\epsilon}$, $A$ is decomposable and the quasi-nilpotent part $H_0(A-\lambda)$ of $A$  satisfies $H_0(A-\lambda)^{-1}(0)=(A-\lambda)^{-1}(0)$ for every non-zero complex $\lambda$. $A$ satisfies every Weyl and Browder type theorem, and a sufficient condition for $A$ to be normal is that either $A$ is dominant or $A$ is a class ${\mathcal A}(1,1)$ operator.