Department of Mathematics and Mechanics, St. Petersburg State University, 28, Universitetskii pr., St. Petersburg, 198504, Russia
Abstract:
We study boundedness of the differentiation and embedding operators in the shift-coinvariant subspaces generated by Blaschke products with sparse zeros, that is, in the spaces of meromorphic functions with fixed poles in the lower half-plane endowed with -norm. We answer negatively the question of K.M. Dyakonov about the necessity of the condition for the boundedness of the differentiation on . Our main tool is a construction of an unconditional basis of rational fractions in .