A Spectral Commutant Lifting Theorem
Hari Bercovici, Ciprian Foiaş, Allen Tannenbaum · Transactions of the American Mathematical Society · 1991
The commutant lifting theorem of [24] may be regarded as a very general interpolation theorem from which a number of classical interpolation results may be deduced. In this paper we prove a spectral version of the commutant lifting theorem in which one bounds the spectral radius of the interpolant and not the norm. We relate this to a spectral analogue of classical matricial Nevanlinna-Pick interpolation.