Radii of convexity associated with various subclasses of analytic functions for functions related to Kaplan classes

A normalized analytic function $f$ defined on the open unit disc $\mathbb{D}$ is called Ma-Minda convex if $ 1+zf''(z)/f'(z)$ is subordinate to the function $\varphi$. For $ 0\leqslant\alpha\leqslant\beta$, the Kaplan class $\mathcal{K}(\alpha,\beta)$ of type $\alpha$ and $\beta$ consists of normalized analytic functions of the form $p^\alpha g$ defined on $\mathbb{D}$ where $p$ with $p(0)=1$ is an analytic function taking values in the right half-plane and $g$ is an analytic function with $g(0)=1$ satisfying Re$(zg'(z)/g(z))>(\alpha-\beta)/2$. For functions $f$ with $f'\in \mathcal{K}(\alpha,\beta)$, we obtain the radius of Ma-Minda convexity for various choices of $\varphi$. The radius of lemniscate convexity, lune convexity, nephroid convexity, exponential convexity and several other radius estimates are examined. The results obtained are sharp.

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Publication Details

Journal
Hacettepe Journal of Mathematics and Statistics
Published
2025-01-27
DOI
https://doi.org/10.15672/hujms.1471427
Primary Topic
Analytic and geometric function theory
Type
article
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article

Radii of convexity associated with various subclasses of analytic functions for functions related to Kaplan classes

V. Ravichandran, Nisha Bohra, Baskar Babujee Janani
Hacettepe Journal of Mathematics and Statistics
Analytic and geometric function theory
article

Radii of convexity associated with various subclasses of analytic functions for functions related to Kaplan classes

V. Ravichandran, Nisha Bohra, Baskar Babujee Janani
article en

Abstract

A normalized analytic function $f$ defined on the open unit disc $\mathbb{D}$ is called Ma-Minda convex if $ 1+zf''(z)/f'(z)$ is subordinate to the function $\varphi$. For $ 0\leqslant\alpha\leqslant\beta$, the Kaplan class $\mathcal{K}(\alpha,\beta)$ of type $\alpha$ and $\beta$ consists of normalized analytic functions of the form $p^\alpha g$ defined on $\mathbb{D}$ where $p$ with $p(0)=1$ is an analytic function taking values in the right half-plane and $g$ is an analytic function with $g(0)=1$ satisfying Re$(zg'(z)/g(z))>(\alpha-\beta)/2$. For functions $f$ with $f'\in \mathcal{K}(\alpha,\beta)$, we obtain the radius of Ma-Minda convexity for various choices of $\varphi$. The radius of lemniscate convexity, lune convexity, nephroid convexity, exponential convexity and several other radius estimates are examined. The results obtained are sharp.

Hacettepe Journal of Mathematics and StatisticsVol. 54(4)
University of Delhi (IN), National Institute of Technology Tiruchirappalli (IN), Sri Venkateswara University (IN)
Openalex Percentile: Top 96%
Analytic and geometric function theory
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