On an argument of J.--F. Cardoso dealing with perturbations of joint   diagonalizers
  B. Afsari has recently proposed a new approach to the matrix joint diagonalization, introduced by J.--F. Cardoso in 1994, in order to investigate the independent component analysis and the blind signal processing in a wider prospective. Delicate notions of linear algebra and differential geometry are involved in the works of B. Afsari and the present paper continues such a line of research, focusing on a theoretical condition which has significant consequences in the numerical applications. 
Francesco G. Russo (Universita' degli Studi di Palermo, Palermo,   Italy)
math.RA