摘要

For any n x n complex matrix A, let A(g) be the group inverse of A. When A is singular, a matrix B = A + E is said to be an acute perturbation of A, if parallel to E parallel to is small and the spectral radius rho(BgB - A(g)A) < 1. The acute perturbation coincides with the stable perturbation of the group inverse, if the matrix B satisfies condition. R(B) boolean AND N(A) = {0}, N(B) boolean AND R(A) = {0} which was introduced by Castro-Gonzalez et al. (2008) [8]. Furthermore, several examples are provided to illustrate the acute perturbation of the group inverse.