On the differentiability of T(r,f)

It is well known that T(r,f) is differentiable at least for r>r0. We show that, in fact, T(r,f) is differentiable for all but at most one value of r, and if T(r,f) fails to have a derivative for some value of r, then f is a constant times a quotient of finite Blaschke products.

Bibliographic Details
Main Author: Douglas W. Townsed
Format: Article
Language:English
Published: Hindawi Limited 1982-01-01
Series:International Journal of Mathematics and Mathematical Sciences
Subjects:
Online Access:http://dx.doi.org/10.1155/S0161171282000337