Asymptotic behavior of orbits of holomorphic semigroups

Abstract

Let $({\varphi }_t)$ be a holomorphic semigroup of the unit disc (i.e., the flow of a semicomplete holomorphic vector field) without fixed points in the unit disc and let $\Omega$ be the starlike at infinity domain image of the Koenigs function of $({\varphi }_t)$. In this paper we completely characterize the type of convergence of the orbits of $({\varphi }_t)$ to the Denjoy-Wolff point in terms of the shape of $\Omega$. In particular we prove that the convergence is non-tangential if and only if the domain $\Omega$ is `quasi-symmetric with respect to vertical axes'. We also prove that such conditions are equivalent to the curve $[0,\infty )\ni t\mapsto {\varphi }_t(z)$ being a quasi-geodesic in the sense of Gromov. Also, we characterize the tangential convergence in terms of the shape of $\Omega$.

25 pages, 3 figures