On Variability Regions and Coefficient Inequalities for Exponentially Convex Janowski Functions

The current study concerns explicitly obtaining regions of variability described as \(\mathcal{R}_{\rho}[\alpha,A,B;z_0]:=\{\log f'(z_0)+\alpha f(z_0):f\in\mathcal{E}_{\rho}[\alpha,A,B]\}\) for the subclass \(\mathcal{E}[\alpha,A,B]\) of \(\alpha\)-exponentially convex Janowski analytic functions. Also, sharp initial coefficient bounds are obtained, and the corresponding Fekete-Szegö functional is solved to answer a recently posed open problem partially. The work presented herein generalizes and unifies various known results reported earlier. Geometric illustrations for various involved parameters support the current findings.

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Publication Details

Journal
Analysis in Theory and Applications
Published
2026-10-30
DOI
https://doi.org/10.4208/ata.oa-2025-0019
Primary Topic
Analytic and geometric function theory
Type
article
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article

On Variability Regions and Coefficient Inequalities for Exponentially Convex Janowski Functions

Manzoor Hussain
Analysis in Theory and Applications
Analytic and geometric function theory
article

On Variability Regions and Coefficient Inequalities for Exponentially Convex Janowski Functions

Manzoor Hussain
article en

Abstract

The current study concerns explicitly obtaining regions of variability described as \(\mathcal{R}_{\rho}[\alpha,A,B;z_0]:=\{\log f'(z_0)+\alpha f(z_0):f\in\mathcal{E}_{\rho}[\alpha,A,B]\}\) for the subclass \(\mathcal{E}[\alpha,A,B]\) of \(\alpha\)-exponentially convex Janowski analytic functions. Also, sharp initial coefficient bounds are obtained, and the corresponding Fekete-Szegö functional is solved to answer a recently posed open problem partially. The work presented herein generalizes and unifies various known results reported earlier. Geometric illustrations for various involved parameters support the current findings.

Analysis in Theory and Applications
University of Azad Jammu and Kashmir (PK), Women University of Azad Jammu & Kashmir Bagh (PK)
Openalex Percentile: Top 7%
Analytic and geometric function theory
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