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Pre-Schwarzian and Schwarzian norm Estimates for Robertson class

2025/11/19 by Ahamed, Molla Basir, Hossain, Rajesh, Wang, Xiaoyuan · 1 citation
#30C45 #30C55 #Complex Variables (math.CV) #FOS: Mathematics

paper · doi:10.48550/arxiv.2511.16702

Abstract

Let A denote the class of analytic functions f on the unit disk \mathbbD=\z∈ℂ : |z|<1\, normalized by f(0)=0 and f(0)=1. For -π/2<α<π/2, let Sα be the subclass of A consisting of functions f that satisfy the relation Re\e(1+zf′′(z)/f(z))\>0 for z∈\mathbbD. In this paper, we first give an equivalent characterization for a subclass of Robertson functions; then we present the distortion and growth theorems and obtain the pre-Schwarzian and Schwarzian norms for the subclass Sα. In addition, a sharp upper bound of the Schwarzian norm for the subclass is given in terms of the value f′ ′(0).

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