English

Semigroup-fication of univalent self-maps of the unit disc

Complex Variables 2020-02-20 v1 Dynamical Systems

Abstract

Let ff be a univalent self-map of the unit disc. We introduce a technique, that we call {\sl semigroup-fication}, which allows to construct a continuous semigroup (ϕt)(\phi_t) of holomorphic self-maps of the unit disc whose time one map ϕ1\phi_1 is, in a sense, very close to ff. The semigrup-fication of ff is of the same type as ff (elliptic, hyperbolic, parabolic of positive step or parabolic of zero step) and there is a one-to-one correspondence between the set of boundary regular fixed points of ff with a given multiplier and the corresponding set for ϕ1\phi_1. Moreover, in case ff (and hence ϕ1\phi_1) has no interior fixed points, the slope of the orbits converging to the Denjoy-Wolff point is the same. The construction is based on holomorphic models, localization techniques and Gromov hyperbolicity. As an application of this construction, we prove that in the non-elliptic case, the orbits of ff converge non-tangentially to the Denjoy-Wolff point if and only if the Koenigs domain of ff is "almost symmetric" with respect to vertical lines.

Keywords

Cite

@article{arxiv.2002.08252,
  title  = {Semigroup-fication of univalent self-maps of the unit disc},
  author = {Filippo Bracci and Oliver Roth},
  journal= {arXiv preprint arXiv:2002.08252},
  year   = {2020}
}