On a result by Clunie and Sheil-Small

Abstract

In 1984 J. Clunie and T. Sheil-Small proved ([2, Corollary 5.8]) that for any complex-valued and sense-preserving injective harmonic mapping \(F\) in the unit disk \(\mathbb{D}\), if \(F(\mathbb{D})\) is a convex domain, then the inequality \(|G(z_2)-G(z_1)| < |H(z_2)- H(z_1)|\) holds for all distinct points \(z_1, z_2 \in \mathbb{D}\). Here \(H\) and \(G\) are holomorphic mappings in \(\mathbb{D}\) determined by \(F = H + \overline{G}\), up to a constant function. We extend this inequality by replacing the unit disk by an arbitrary nonempty domain \(\Omega\) in \(\mathbb{C}\) and improve it provided \(F\) is additionally a quasiconformal mapping in \(\Omega\).