Abstract
This paper extends the theory of Zen spaces (weighted Hardy/Bergman spaces on the right-hand half-plane) to the Hilbert-space valued case, and describes the multipliers on them; it is shown that the methods of H-infinity control can therefore be extended to a family of weighted L-2 input and output spaces. Next, the particular case of retarded delay systems with operator-valued transfer functions is analysed, and the dependence of H-infinity structure on the delay is determined by developing an extension of the Walton-Marshall technique used in the scalar case. The method is illustrated with examples.