Further results on the group inverses and Drazin inverses of anti-triangular block matrices

In this paper, the sufficient and necessary conditions for the existence of the group inverse for a class of 2 x 2 anti-triangular block matrices M with some certain conditions satisfied, and representations of the group inverse of M are obtained, which can be regarded as the extension of Bu et al. [C. Bu, J. Zhao, J. Zheng, Group inverse for a class 2 x 2 block matrices over skew fields, Appl. Math. Comput. 204 (2008) 45-49] and [C. Bu, J. Zhao, K. Zhang, Some results on group inverses of block matrices over skew fields, Electron. J. Linear Algebra, 18 (2009) 117-125]. Further, we use these results to determine the expressions of the Drazin inverse of M. Finally, two numerical examples are given to illustrate our results. (C) 2012 Elsevier Inc. All rights reserved.