The c‐Entropy optimality of Donoghue classes

Abstract In this paper, we evaluate c‐Entropy of perturbed L‐systems introduced in Belyi and Tsekanovskii [Complex Anal. Oper. Theory 13 (2019), no. 3, 1227–1311]. Explicit formulas relating the c‐Entropy of the L‐systems and the perturbation parameter are established. We also show that c‐Entropy attains its maximum value (finite or infinite) whenever the perturbation parameter vanishes so that the impedance function of such a L‐system belongs to one of the generalized (or regular) Donoghue classes.