The essential norm of a composition operator mapping intoQktype spaces

摘要

An asymptotic formula for the essential norm of the composition operatorCφ(f):=f°φ, induced by an analytic self-mapφof the unit disc, mapping from theα-Bloch space?αor the Dirichlet type spaceDαpintoQk(p,q)is established in terms of an integral condition.