Let D denote the unit disk of C and let Λ α (D) denote the scale of holomorphic Lipschitz spaces extended to all α ∈ R. For arbitrary α, β ∈ R, we characterize the bounded weighted composition operators from Λ β (D) into Λ α (D) and estimate their essential norms.
IntroductionLet H(D) denote the space of holomorphic functions on the unit disk D of C.It is well known that the definition of the space Λ α (D) does not depend on J whenever J > α. For α ∈ R, J ∈ Z + and J > α, Λ α (D) is a Banach space with respect to the following norm:where the first summand is defined to be zero for J = 0. The above norms are equivalent for different parameters J, J > α, so in what follows, we use the brief notation · Λ α in the place of · Λ α,J (D) with the smallest J, J > α.Holomorphic Lipschitz spaces. If α > 0, then each f ∈ Λ α (D) extends to a Lipschitz function on the unit circle ∂D. So, we say that Λ α (D), α > 0, is a holomorphic Lipschitz space. The standard holomorphic Lipschitz spaces Λ α (D) are those with 0 < α < 1. Also, Λ α (D) with α < 1 are often called Bloch type spaces because the Bloch space Λ 0 (D) is defined with J = 1 (see, for example, [7,9]). One has J = 2 in the definition of the classical Zygmund space Λ 1 (D), so Λ α (D), 1 ≤ α < 2 or α < 2, are sometimes called Zygmund type spaces (see, for example, [4]).The scale Λ α (D) splits at the point α = 0. Indeed, Λ 0 (D) is the classical Bloch space; Λ α (D), α < 0, is the growth space defined by the following condition: |f (z)| ≤ C(1 − |z|) α , z ∈ D.1991 Mathematics Subject Classification. Primary 47B33; Secondary 30H30, 30H99, 46E15, 47B38.