Semigroups of holomorphic functions; rectifiability and Lipschitz properties of the orbits

Abstract

Let $({\varphi }_t)$ be a semigroup of holomorphic functions in the unit disk. We prove that all its orbits are rectifiable and that its forward orbits are Lipschitz curves. Moreover, we find a necessary and sufficient condition in terms of hyperbolic geometry so that a backward orbit is a Lipschitz curve. We further explore the Lipschitz condition for forward orbits lying on the unit circle and then for semigroups of holomorphic functions in general simply connected domains.

arXiv comment31 pages, 2 figures, to appear in Canadian Journal of Mathematics