International Journal of Mathematics and Mathematical Sciences
Volume 2003 (2003), Issue 29, Pages 1855-1866

On a certain class of nonstationary sequences in Hilbert space

Berrabah Bendoukha

Department of Mathematics, University of Mostaganem, Mostaganem 27000, Algeria

Received 8 January 2002

Copyright © 2003 Berrabah Bendoukha. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


We study the functions of correlation K(n,m)=X(n),X(m) of certain sequences: X(n)=Tnx0, x0H where T is a contraction in Hilbert space H. By using the spectral methods of the nonunitary operators we give the general form of K(n,m) and its asymptotic behaviour limp+K(n+p,m+p).