Unitary couplings,scattering suboperators and regular factorizations of bounded operator valued functions II

In the paper bilateral shifts are studied which generate factorizations of unitary couplings (in the system theory they play the part of channels). Subspaces of L²(??), reducing the multiplication operator by e^it, are investigated in the channel language. New criteria for regular divisibility of contractive operator functions in the class L^∞ are obtained. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)