Riesz and Kolmogorov inequality for harmonic quasiregular mappings

Abstract

Let $K\ge 1$ and $p\in(1,2]$. We obtain asymptotically sharp constant $c(K,p)$, when $K\to 1$ in the inequality $$\|\Im f\|_{p}\le c(K,p)\|\Re(f)\|_p$$ where $f\in \mathbf{h}^p$ is a $K-$quasiregular harmonic mapping in the unit disk belonging to the Hardy space $\mathbf{h}^p$, under the conditions $\arg(f(0))\in (-\pi/(2p),\pi/(2p))$ and $f(\mathbb{D})\cap(-\infty,0)=\emptyset$. The paper improves a recent result by Liu and Zhu in \cite{aimzhu}. We also extend this result for the quasiregular harmonic mappings in the unit ball in $\mathbb{R}^n$. We also extend Kolmogorov theorem for quasiregular harmonic mappings in the plane.