Additive perturbation results for the Drazin inverse Original Research Article

In this paper some new additive results for the Drazin inverse are presented. We give a formula for the Drazin inverse of a sum of two matrices under conditions on the matrices less restrictive than those imposed in the corresponding theorem given by Hartwig et al. (Linear Algebra Appl. 322 (2001) 207–217). We consider some aplications of our results to the perturbation of the Drazin inverse and analyze a number of special cases.