English

On a relation between harmonic measure and hyperbolic distance on planar domains

Complex Variables 2019-09-02 v1

Abstract

Let ψ\psi be a conformal map of D\mathbb{D} onto an unbounded domain and, for α>0\alpha >0, let Fα={zD:ψ(z)=α}{F_\alpha }=\left\{ {z \in \mathbb{D}:\left| {\psi \left( z \right)} \right| = \alpha } \right\}. If ωD(0,Fα)\omega _\mathbb{D}\left( {0,{F_\alpha }} \right) denotes the harmonic measure at 00 of FαF_\alpha and dD(0,Fα)d_\mathbb{D} {\left( {0,{F_\alpha }} \right)} denotes the hyperbolic distance between 00 and FαF_\alpha in D\mathbb{D}, then an application of the Beurling-Nevanlinna projection theorem implies that ωD(0,Fα)2πedD(0,Fα){\omega _\mathbb{D}}\left( {0,{F_\alpha }} \right) \ge \frac{2}{\pi }{e^{ - {d_\mathbb{D}}\left( {0,{F_\alpha }} \right)}}. Thus a natural question, first stated by P. Poggi-Corradini, is the following: Does there exist a positive constant KK such that for every α>0\alpha >0, ωD(0,Fα)KedD(0,Fα){\omega _\mathbb{D}}\left( {0,{F_\alpha }} \right) \le K{e^{ - {d_\mathbb{D}}\left( {0,{F_\alpha }} \right)}}? In general, we prove that the answer is negative by means of two different examples. However, under additional assumptions involving the number of components of FαF_\alpha and the hyperbolic geometry of the domain ψ(D)\psi \left( \mathbb{D} \right), we prove that the answer is positive.

Keywords

Cite

@article{arxiv.1908.11830,
  title  = {On a relation between harmonic measure and hyperbolic distance on planar domains},
  author = {Christina Karafyllia},
  journal= {arXiv preprint arXiv:1908.11830},
  year   = {2019}
}

Comments

24 pages, 23 figures

R2 v1 2026-06-23T11:01:28.831Z