### On $g_{z}$-Kato decomposition and generalization of Koliha Drazin invertibility

#### Abstract

In \cite{koliha}, Koliha proved that $T\in L(X)$ is generalized Drazin invertible operator is equivalent to there exists a commuting operator $S$ with $T$ such that $STS = S$ and $\sigma(T^{2}S - T)\subset\{0\}$ which is equivalent to say that $0\not\in \mbox{acc}\,\sigma(T).$ Later, in \cite{rwassa,rwassa1} the authors extended the class of generalized Drazin invertible operators and they also extended the class of pseudo-Fredholm operators introduced by Mbekhta \cite{mbekhta} and other classes of semi-Fredholm operators.

As a continuation of these works, we introduce and study the class of $g_{z}$-invertible (resp., $g_{z}$-Kato) operators which generalizes the class of generalized Drazin invertible operators (resp., the class of generalized Kato-meromorphic operators introduced by \v{Z}ivkovi\'{c}-Zlatanovi\'{c} and Duggal in \cite{rwassa2}). Among other results, we prove that $T$ is $g_{z}$-invertible if and only if $T$ is $g_{z}$-Kato with $\tilde{p}(T)=\tilde{q}(T)<\infty$ which is equivalent to there exists a commuting operator $S$ with $T$ such that $STS = S$ and $\mbox{acc}\,\sigma(T^{2}S - T)\subset\{0\}$ which in turn is equivalent to say that $0\not\in \mbox{acc}\,(\mbox{acc}\,\sigma(T)).$ As applications, using the concept of the Weak SVEP introduced at the end of this paper, we give new characterizations of Browder-type theorems.

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