It is well-know that for a Hermitian matrix the diagonal elements are majorized by the eigenvalues. Let M be a Hermitian matrix with eigenvalues \lambda_1, ..., \lambda_n and x a real eigenvector of M associated with the eigenvalue \lambda_k. Let y be any row vector in real field. It is not difficult to prove that M+xy has eigenvalues \lambda_1,... \lambda_{k-1}, \lambda_k+yx, \lambda_{k+1},... ,\lambda_n.
Simlar to Hermitian matrix, whether the majorization betweeen diagonal lements and eigenvalues of M+xy still holds.