The g-Drazin invertibility in a Banach algebra

Abstract

We present necessary and sufficient conditions under which the anti-triangular matrix $\left(\begin{array}{ccc}a& b1& 0\end{array}\right)$ over a Banach algebra has g-Drazin inverse. New additive results for g-Drazin inverse are obtained. Then we apply our results to $2\times 2$ operator matrices and generalize many known results, e.g.,~\cite[Theorem 2.2]{D}, ~\cite[Theorem 2.1]{YL} and \cite[Theorem 4.1]{Y}.