The perturbation theory for the Drazin inverse and its applications

Abstract Let A and E be n × n matrices and B = A + E. Denote the Drazin inverse of A by AD. We give an upper bound for the relative error ∥B D − A D ∥ ∥A D ∥ under certain circumstances. An error bound for the solution for the singular equations Ax = b [b ∈ R(A)] is also considered.